Electrochemical cell stack with cr-getter material

Abstract

The invention relates to an electrochemical cell stack (10), comprising a plurality of cell units (12), wherein each cell unit comprises an electrochemically active cell region (26) on a first side (38) thereof and an electrical connection region (72) on a second side (40) thereof. The cell units are stacked upon one another along a stacking direction (14) such that the electrical connection region of a first cell unit overlies at least part of the electrochemically active cell region of a second, neighbouring cell unit. Between two neighbouring cell units, there is provided a chromium-getter material (76).

Description

[0001] R.415892

[0002] - 1 -

[0003] Description

[0004] Title

[0005] Electrochemical cell stack with Cr-getter material

[0006] Technical Field and Background Art

[0007] The invention relates to the field of electrochemical cell stacks, in particular, fuel cell stacks and electrolyser cell stacks.

[0008] Fuel cell units and electrolyser cell units are examples of electrochemical cell units. Fuel cell units are energy conversion devices that allow for conversion of electrochemical fuel to electricity. Electrolyser cell units may be considered fuel cell units running in reverse mode, i.e. using electricity to decompose a compound into its constituent parts, for example water into hydrogen and oxygen. Reversible cell units are capable of operating in both modes.

[0009] Electrochemical cells of this kind typically comprise cell chemistry layers in an electrochemically active region of the cell, said cell chemistry layers comprising a fuel electrode (anode), an electrolyte and an air electrode (cathode).

[0010] The present invention specifically relates to solid oxide cell units (SOCs). Solid oxide cell units (SOCs) typically comprise an electrolyte layer formed from a solid oxide, e.g. from Yttria-stabilised Zirconia (YSZ), Gadolinia-doped Ceria, or Cerium Gadolinium Oxide (CGO). SOCs can be run as solid oxide fuel cell units (SOFC) or as solid oxide electrolyser cell units (SOEC).

[0011] In SOC systems, chromium containing stainless steels are widely used as part of the fluid supply system (e.g., as heat exchanger, tubes, housings) or even as part of the individual cell units. In particular, so-called metal-supported SOCs typically comprise an interconnector formed from a chromium containing stainless steel.

[0012] During operation of such SOC systems at elevated temperatures, chromium (Cr) tends to evaporate from the steel, thus possibly leading to degradation of the electrochemically active cell region, in particular of the cathode (referred to as 'Cr-poisoning'). R.415892

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[0014] As a measure to reduce Cr-poisoning, it has therefore been proposed to include Cr-getter materials in the fluid supply system in order to reduce the chromium concentration in the gas entering the cell stack. However, for systems comprising a chromium steel in the individual cell unit, e.g. for metal-supported SOCs comprising an interconnector made of stainless steel, this solution has proven not to be sufficient. For such metal-supported SOCs, it has been proposed, e.g., in WO 2023 / 052780 A1 , to include a Cr-getter material directly into the electrode materials.

[0015] It is an object of the invention to improve stability and performance of an electrochemical cell stack. It is a further object of the invention to increase flexibility and reduce manufacturing costs.

[0016] Summary of Invention

[0017] According to a first aspect, there is provided an electrochemical cell stack, preferably fuel cell stack or electrolysis cell stack. The cell stack comprises a plurality of cell units, preferably fuel cell units or electrolysis cell units, more preferably metal-supported solid oxide cell units. Each cell unit comprises an electrochemically active cell region, preferably comprising cell chemistry layers, and an electrical connection region. The electrical connection region preferably is configured for electrically connecting the cell unit to the electrochemically active cell region of a neighbouring cell unit in the stack. The (plurality of) cell units are stacked upon one another along a stacking direction such that the electrical connection region of a first cell unit overlies at least part of the electrochemically active cell region of a second, neighbouring cell unit. Preferably, the electrochemically active cell region is located on a first side of the cell unit, and the electrical connection region is located on a second side of the cell unit, said second side being opposite the first side. Thus, the electrochemically active cell region and the electrical connection region of a cell unit preferably are located on opposite sides of the cell unit. The (plurality of) cell units preferably are stacked upon one another along a stacking direction such that the first side of a first cell unit faces the second side of a second, neighbouring cell unit. Between two neighbouring cell units in the stack, there is provided a chromium-getter material (hereinafter also referred to as Cr-getter material). R.415892

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[0019] The proposed configuration reduces cell degradation due to Cr-poisoning and thus helps to extend the lifetime of the cell stack. Specifically, by applying the Cr- getter material in the space between two neighbouring cell units - and not as part of the electrode material - the Cr-getter function is separated from the function of the electrochemically active cell region, thus making it possible to select optimal materials for the respective purpose. In particular, the proposed solution allows to use relatively cheap chromium getter materials as compared to the prior art since the Cr-getter material does not need to be compatible to the cathode characteristics in terms of electrocatalytic, electrochemical, redox stability, etc. Further, as in the proposed configuration gettering of chromium will take place outside the electrochemically active region (but still in close proximity thereto), effective Cr-capturing is achieved before the gas enters the cell chemistry layers. By this, the electrochemically active region has proven more robust, e.g. in terms of its electro- and electrocatalytic characteristics, compared to the prior art where Cr-gettering occurs inside the electrochemically active cell region, in particular in the air or oxidant electrode layer. In summary, the proposed configuration provides for a specifically robust cell function and thus extended lifetime of the stack.

[0020] As used herein, the term "Cr-getter material" refers to a material that is capable of capturing chromium. Specifically, the Cr-getter material may be configured for capturing, on its surface or bulk, chromium and / or chromium gas molecules. Capturing chromium may comprise chemically or physically bonding the chromium gas molecules to the Cr-getter material.

[0021] Different types of Cr-getter materials are known in the art. For example, the Cr- getter material may comprise a Pr-Sr-Co perovskite material. Further examples of Cr-getter materials include other perovskite compounds like LaCaFeCh or modifications of those as well as alkaline earth metals like CaO, MgO, and ZnO. Preferably, the Cr-getter material comprises a Sr-Ni-0 material.

[0022] Preferably, the Cr-getter material is provided as a separate component within the stack.

[0023] As used herein, the term "electrochemically active cell region" refers to the region of the cell unit wherein electrochemical processes occur during cell operation. Preferably, each cell comprises cell chemistry layers (also referred to as R.415892

[0024] - 4 - electrochemically active layers) in said electrochemically active cell region. More preferably, the electrochemically active cell region is defined by said cell chemistry layers. Preferably, the cell chemistry layers comprise a fuel electrode layer, in particular anode, an air or oxidant electrode layer, in particular cathode, and an electrolyte layer located between the fuel electrode layer and the air or oxidant electrode layer.

[0025] Preferably, the Cr-getter material contacts the cell chemistry layers, more preferably the air or oxidant electrode layer (cathode in fuel cell mode). This has proven advantageous for reducing Cr-poisoning of the cell chemistry layers.

[0026] The chromium-getter material may be placed at various positions between the two neighbouring cell units.

[0027] Preferably, the Cr-getter material is provided in a fluid pathway between an air or oxidant port of the cell stack for supplying air or oxidant to the cell units and the electrochemically active cell region of a cell unit, in particular in a fluid pathway between an air or oxidant port of the cell stack and the air or oxidant electrode layer of the cell chemistry layers.

[0028] In some embodiments, the cell units are stacked upon one another such that between two adjacent cell units a fluid volume is defined. Preferably, the Cr- getter material is disposed in said fluid volume.

[0029] In some embodiments, the Cr-getter material may be provided at a fluid inlet portion of said fluid volume. Said fluid inlet portion preferably is a portion of said fluid volume defined between two neihgbouring cell units through which - during operation of the cell stack - fluid, preferably air or oxidant, is supplied between two neighbouring cell units.

[0030] In some embodiments, the cell units are stacked upon one another such that between the electrical connection region of a first cell unit and the electrochemically active layer of a second, neighbouring cell unit, i.e. in the overlap region, a fluid volume is defined, and the Cr-getter material is disposed in said fluid volume R.415892

[0031] - 5 -

[0032] In some preferred embodiments, the chromium-getter material is provided between the electrical connection region of a first cell unit and the electrochemically active cell region, preferably the cell chemistry layers, of a second, neighbouring cell unit.

[0033] In some embodiments, the electrical connection region comprises a plurality of spatially separated connection portions. The connection portions preferably are configured for electrical connection to the electrochemically active cell region of a neighbouring cell unit in the stack. In such embodiments, preferably, the Cr-getter material is, in particular selectively, disposed between at least some of said connection portions and the electrochemically active region of a neighbouring cell unit. This has proven advantageous with regards to reduced cell degradation and thus extended lifetime of the stack, as the Cr-getter material is provided close to the region that is prone to Cr-poisoning, i.e. the electrochemically active cell region.

[0034] In the stack, the connection portions of a cell unit may directly contact, i.e. touchcontact, the electrochemically active cell region of a neighbouring cell unit. Thus, the connection portions may form contact portions. Alternatively, there may be provided a separate contact material, e.g. contact paste, between the connection portions of a cell unit and the electrochemically active cell region of a neighbouring cell unit.

[0035] The connection portions may be formed in various ways. Preferably, each cell unit, on its second side, comprises a plurality of outwardly extending (i.e. in a direction away from the cell unit) protrusions, preferably in the form of dimples. Preferably, the connection portions are formed by portions of said protrusions. Thus, the electrical connection region may comprise a plurality of outwardly, preferably dimpled, protrusions, wherein the Cr-getter material is, preferably selectively, disposed between at least some of said protrusions and the electrochemically active region of a neighbouring cell unit. Preferably, the Cr- getter material is provided on the tips of said protrusions.

[0036] The cell unit may have different architectures. The cell unit may be a metal- supported, anode-supported, electrolyte-supported, or cathode-supported cell unit. R.415892

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[0038] In some preferred embodiments, each cell unit comprises a cell layer and an interconnector (also referred to as interconnector plate or separator plate) overlying the cell layer. The cell layer preferably comprises the electrochemically active cell region. The interconnector preferably comprises the electrical connection region.

[0039] Preferably, the interconnector comprises or is formed by a metal sheet, in particular formed from a stainless steel, e.g. from a Crofer steel. In such embodiments, the electrical connection region may be formed by a selectively shaped three-dimensional region, in which the metal sheet has been deformed into a plurality of outwardly extending, preferably dimpled, protrusions. The Cr- getter material may be disposed between said protrusions and a neighbouring cell unit in the stack.

[0040] Thus, according to a second aspect, there is provided an electrochemical cell stack preferably fuel cell stack or electrolysis cell stack, comprising a plurality of cell units, wherein each cell unit comprises a cell layer comprising an electrochemically active cell region, and an interconnector overlying the cell layer and comprising a metal sheet; the interconnector comprises a selectively shaped electrical connection region, in which the metal sheet has been deformed, preferably pressed, into a plurality of outwardly extending, preferably dimpled, protrusions, the cell units are stacked upon one another along a stacking direction such that the electrical connection region of a first cell unit overlies at least part, preferably all, of the electrochemically active cell region of a second, neighbouring cell unit; between at least some of said protrusions and the electrochemically active cell region of a neighbouring cell unit, there is provided a Cr-getter material.

[0041] Thus, the Cr-getter material is provided in close proximity to the interconnector. This has proven advantageous as the deformation of the metal sheet may lead to local defects, in particular cracks, of the metal sheet and thus to increased Cr- evaporation. Specifically, such defects may occur at the tips of the protrusions. Therefore, advantageously, the Cr-getter material may be provided at the tips of said protrusions. R.415892

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[0043] The interconnector, in particular the metal sheet, may have been deformed into a second plurality of dimpled protrusions extending towards the cell layer.

[0044] The cell layer may comprise a metal support plate carrying, on a first side thereof, the electrochemically active cell region, preferably provided over a porous region. In such embodiments, preferably, at least one of the interconnector and the metal support plate may comprise flanged perimeter features formed by pressing the plate to a concave configuration. The interconnector and the metal support plate may directly be adjoined at the flanged perimeter features, optionally by welding.

[0045] The interconnector, in particular the metal sheet, may comprise a coating on at least part of its surface. In some embodiments, the interconnector, in particular the metal sheet, comprises a protective coating, preferably of a Co-Ce-O- material, on a side facing away from the cell layer. Such a coating may further reduce chromium evaporation.

[0046] According to a general aspect, the Cr-getter material may be applied in various ways. For example, the Cr-getter material may be applied as a coating.

[0047] In some preferred embodiments, the Cr-getter material is applied in the form of a paste. Preferably, the Cr-getter material may form part of a contact paste disposed between two neighbouring cell units for establishing electrical connection therebetween. In other words, between two neighbouring cell units, in particular between the electrical connection region of a first cell unit and the electrochemically active cell region of a second, neighbouring cell unit, there may be provided a contact paste for establishing electrical connection between the cell units, wherein the Cr-getter material forms part of said contact paste.

[0048] Thus, according to a third aspect, there is provided an electrochemical cell stack, preferably fuel cell stack or electrolysis cell stack, comprising a plurality of cell units, wherein each cell unit comprises an electrochemically active cell region on a first side thereof and an electrical connection region on a second side thereof, the cell units are stacked upon one another along a stacking direction such that the electrical connection region of a first cell unit overlies at least part of the electrochemically active cell region of a second, neighbouring cell unit; R.415892

[0049] - 8 - between two neighbouring cell units, in particular between the electrical connection region of a first cell unit and the electrochemically active cell region of a second, neighbouring cell unit, there is provided a contact paste for establishing electrical connection between the cell units, said contact comprising a Cr-getter material.

[0050] Further embodiments are derivable from the following description and the drawings

[0051] Brief Description of Drawings

[0052] Figure 1 shows a perspective view of an electrochemical cell stack;

[0053] Figure 2 shows an exploded perspective top view of a cell unit of the stack of Figure 1 ;

[0054] Figure 3 shows an exploded perspective bottom view of the cell unit of Figure 2;

[0055] Figure 4 shows a cross-sectional view of a cell stack; and

[0056] Figure 5 shows a detail of Figure 4.

[0057] Referring to Figure 1, there is shown an exemplary configuration of an electrochemical cell stack 10 (hereinafter referred to as 'stack 10'). The stack 10 comprises a plurality of electrochemical cell units 12 that are stacked upon one another along a stacking direction 14. The electrochemical cell units 12 may be fuel cell units or electrolyser cell units.

[0058] In the following, an exemplary configuration of a cell unit 12 will be explained in more detail with reference to Figures 2 and 3.

[0059] The cell unit 12 comprises a cell layer 16 and an interconnector (also referred to as interconnector plate) 18.

[0060] The cell layer 16 comprises a metal support plate 20. The support plate 20 carries cell chemistry layers 22 (also referred to as electrochemically active R.415892

[0061] - 9 - layers) over a porous area 24 (see Fig. 3). The cell chemistry layers 22 define an electrochemically active cell region 26 of the cell unit 12.

[0062] The interconnector 18 comprises a metal sheet 28. The metal sheet 28 comprises a structured region 30 (also referred to as selectively shaped three- dimensional region 30). The structured region 30 comprises a plurality of first (outward) protrusions 32 protruding away from the cell layer 16 (see Fig. 3). In the example, the structured region 30 further comprises optional second (inward) protrusions 34 protruding towards the cell layer 16 (see Fig. 2).

[0063] Figures 2 and 3 depict only a reduced number of protrusions 32, 34 for clarity of the Figures. It will be understood that there will typically be many more protrusions 32, 34 than those depicted.

[0064] The protrusions 32, 34 are typically pressed or formed in the metal sheet 28 forming the interconnector 18. For example, a first protrusion 32 on one side of the interconnector 18, facing away from the support plate 20, typically forms a depression on the other side of the interconnector 18, facing towards the support plate 20 (and similarly for second protrusions 34). The first and second protrusions 32, 34 typically have a circular cross section. In this way, the protrusions 32, 34 may be referred to as dimples.

[0065] In some embodiments, the interconnector 18 may comprise a protective coating (not shown) on a surface 36 of the interconnector 18, said surface 36 facing away from the cell layer 16.

[0066] In the assembled cell unit 12 (see Figure 4), the support plate 20 and the interconnector 18 are stacked upon one another along the stacking direction 14 such that the porous area 24 of the support plate 20 carrying the cell chemistry layers 22 and the structured region 30 of the interconnector 18 overlap. Referring to Fig. 4 it can be seen that the cell chemistry layers 22 are located on a first side 38 of the cell unit 12 and the first protrusions 32 are located on a second side 40 of the cell unit 12 opposite the first side 38. That is, the electrochemically active cell region 26 and the first protrusions 32 are located at opposite sides 38, 40 of the cell unit 12. R.415892

[0067] - 10 -

[0068] Preferably, a periphery 42 of the support plate 20 is sealingly attached to a periphery 44 of the interconnector 18. Preferably, the periphery 42 of the support plate 20 is welded to the periphery 44 of the interconnector 18 around part or all of their perimeter.

[0069] In the specific example, the interconnector 18 is configured tub-shaped. Thus, the interconnector 18 comprises a bottom 46 and a flange portion 48 forming the periphery 44 of the interconnector 18. The bottom 46 and the flange portion 48 (periphery 44) are connected by a circumferential wall 50. Thus, as shown in Fig. 2, the periphery 44 of the interconnector 18 is elevated with respect to the bottom 46. In this regard, the periphery 44 of the interconnector 18 is also referred to as "flanged perimeter".

[0070] In the assembled state of the cell unit 12, the support plate 20 and the interconnector 18 define or enclose an internal fluid volume 52 (internal cell volume, see Fig. 4) therebetween. The internal fluid volume 52 is in fluid communication with the cell chemistry layers 22 via the porous region 24. Thus, during operation of the cell unit 12 a fluid, e.g. a fuel, may exit the internal fluid volume 52 through pores formed in the porous area 24 and reach to a layer of the cell chemistry layers 22 that is closest to the support plate 20 (e.g. a fuel electrode layer, see below).

[0071] To transport fluid between the internal fluid volume 52 and the exterior of the cell unit 12, the cell unit 12 further comprises at least one fluid port. In the example, each cell unit 12 comprises one fluid inlet port 54 and one fluid outlet port 56 (see Fig. 1). The fluid inlet port 54 and the fluid outlet port 56 are formed by respective through-holes 58, that extend through the cell unit 12 along the stacking direction 14 (in the example through the support plate 20 and the interconnector 18).

[0072] In the assembled stack 10 of cell units 12, the fluid inlet ports 54 and the fluid outlet ports 56 of the cell units 12 are aligned with each other along the stacking direction 14, thus forming a fluid inlet manifold 60 or a fluid outlet manifold 62, respectively (see Fig. 4).

[0073] Referring to Figure 1, it can be seen that the fluid inlet port 54 and the fluid outlet port 56 are located at opposite ends of the cell unit 12. Thus, the electrochemically active cell region 26 of the cell layer 12 and the structured R.415892

[0074] - 11 - region 30 of the interconnector 18 are located between the fluid inlet port 54 and the fluid outlet port 56. Thus, a fluid, e.g. a fuel, that flows from the fluid inlet port 54 to the fluid outlet port 56 through the internal fluid volume 52 may pass through the structured region 30 and reach to the cell chemistry layers 22 through the porous area 24.

[0075] In the stack 10, each fluid port 54, 56 preferably is associated with a respective gasket 64 (see Fig. 4). In the assembled stack 10, the gaskets 64 contribute to forming the fluid inlet manifold 60 and the fluid outlet manifold 62 and prevent loss of fluid between adjacent / neighbouring cell units 12.

[0076] Figure 4 shows a cross-sectional view of a cell stack 10 comprising a plurality of cell units 12. The cell units 12 are stacked upon one another along the stacking direction 14 such the structured region 30 of a cell unit 12 overlies the cell chemistry layers 22 of a neighbouring cell unit 12.

[0077] Referring to Fig. 5, it can be seen that the structured region 30 of a cell unit 12 and the cell chemistry layers 22 of a neighbouring cell unit define a second fluid volume 66 therebetween for second fluid, in particular air or oxidant.

[0078] As set out above, the tips 68 of the first protrusions 32 form connection portions 70 for electrically connecting the cell unit 12 to the electrochemically active cell region 26 of a neighbouring cell unit 12 in the stack 10. Thus, the structured region 30 of a cell unit 12 forms an electrical connection region 72 of the cell unit 12.

[0079] In this way, electrical connection is provided between adjacent cell units 12 in the stack 10, while maintaining fluid passageways between the cell units 12 (i.e. between the protrusions 32).

[0080] The protrusions 32, specifically the tips 68 of the protrusions (connection portions 70) of a cell unit 12 may directly contact the cell chemistry layers 22 of an adjacent cell unit 12 for establishing electrical connection between two neighbouring cell units 12.

[0081] Preferably, however, between at least some of the tips 68 of the first protrusions 32 of a cell unit 12 and the cell chemistry layers 22 of an adjacent cell unit 10 in R.415892

[0082] - 12 - the stack 10, there is provided a contact paste 74 for providing electrical connection (see Fig. 5).

[0083] As set out above, in the second fluid volume 66 defined between two adjacent cell units 12 of the stack 10, there is provided a Cr-getter material 76, e.g. a Sr- Ni-0 material.

[0084] In the specific example shown in Fig. 5, the Cr-getter material 76 forms part of the contact paste 74 disposed between the first protrusions 32 and the cell chemistry layers 22. As such, the Cr-getter material 76 is provided in close proximity to, preferably in touch-contact with, the cell chemistry layers 22.

[0085] More specifically, as shown in Fig. 5, the cell chemistry layers 22 comprise a fuel electrode layer 78 disposed on the support plate 20, an electrolyte layer 80 disposed on the fuel electrode layer 78 and an air or oxidant electrode layer 82 disposed on the electrolyte layer 80. As such, the Cr-getter material 76, preferably, is in close proximity to, more preferably in touch-contact with, the air or oxidant electrode layer 82.

[0086] In other embodiments not shown, the Cr-getter material 76 may be provided as a coating on the tips 68 of the first protrusions 32. In even further embodiments, the Gr-getter material 76 may be provided as a separate component in the second fluid volume 66, e.g. in the valleys 84 formed by the backsides of the second protrusions 34 or in the fluid volume between the tips 68 of the first protrusions 32 and the cell chemistry layers 22 of an adjacent cell unit 12. In even further embodiments, the Cr-getter material 76 may be provided between the peripheries of two adjacent cell units.

Claims

R.415892- 13 -Claims1. An electrochemical cell stack (10), comprising a plurality of cell units (12), wherein each cell unit (12) comprises an electrochemically active cell region (26) on a first side (38) thereof and an electrical connection region (72) on a second side (40) thereof for electrically connecting to the electrochemically active cell region (26) of a neighbouring cell unit (12) in the stack (10), the cell units (12) are stacked upon one another along a stacking direction (14) such that the electrical connection region (72) of a first cell unit (12) overlies at least part of the electrochemically active cell region (26) of a second, neighbouring cell unit (12) between two neighbouring cell units (12), there is provided a chromium-getter material (76).

2. The electrochemical cell stack (10) according to claim 1 , wherein the chromium-getter material (76) is disposed in a fluid volume (66) defined between the electrochemically active cell region (26) of a cell unit (12) and the electrical connection region (72) of a neighbouring cell unit (12).

3. The electrochemical cell stack (10) according to any one of the preceding claims, wherein the electrical connection region (72) comprises a plurality of spatially separated connection portions (70), preferably in the form of outwardly extending, preferably dimpled, protrusions (32), the chromium-getter material (76) is, preferably selectively, disposed between at least some of said connection portions (70) and the electrochemically active cell region (26) of a neighbouring cell unit (12).

4. The electrochemical cell stack (10) according to the preceding claim, wherein the connection portions (70) are coated with the chromium-getter material (76).

5. The electrochemical cell stack (10) according to any one of the preceding claims, whereinR.415892- 14 - each cell unit (12) comprises a cell layer (16) comprising the electrochemically active cell region (26) and an interconnector (18) overlying the cell layer (16); the interconnector (18) comprises the electrical connection region (72).

6. The electrochemical cell stack (10) according to the preceding claim, wherein the interconnector (18) comprises a metal sheet (28), said metal sheet (28) having a selectively shaped three-dimensional region (30), in which the metal sheet (28) has been deformed into a plurality of outwardly extending protrusions (32).

7. The electrochemical cell stack (10) according to the preceding claim when referring to claim 3 or claim 4, wherein the connection portions (70) are formed by portions of said protrusions (32).

8. The electrochemical cell stack (10) according to claim 6, wherein the chromium-getter material (76) is disposed on the tips (68) of at least some of said protrusions (32).

9. The electrochemical cell stack (10) according to any one of claims 5 to 8, wherein the interconnector (18) comprises a protective coating, preferably of a Co-Ce-O-material, on a surface (36) facing away from the cell layer (16).

10. The electrochemical cell stack (10) according to any one of the preceding claims, wherein the chromium-getter material (76) is applied in the form of a paste, preferably as part of a contact paste (74) for establishing electrical connection between two neighbouring cell units (12).

11. An electrochemical cell stack (10) comprising a plurality of cell units (12), wherein each cell unit (12) comprises an electrochemically active cell region (26) on a first side (38) thereof and an electrical connection region (72) on a second side (40) thereof, the cell units (12) are stacked upon one another along a stacking direction (14) such that the electrical connection region (72) of a first cell unitR.415892- 15 -(12) overlies at least part of the electrochemically active cell region (26) of a second, neighbouring cell unit (12); between two neighbouring cell units (12), in particular between the electrical connection region (72) of a first cell unit (12) and the electrochemically active cell region (26) of a second, neighbouring cell unit (12), there is provided a contact paste (74) for establishing electrical connection between the cell units (12), said contact paste (74) comprising a chromium-getter material (76).

12. The electrochemical cell stack (10) according to any one of the preceding claims, wherein each cell unit (12) comprises cell chemistry layers (22) in the electrochemically active cell region (26), the chromium-getter material (76) contacts the cell chemistry layers (22).

13. The electrochemical cell stack (10) according to the preceding claim, wherein the cell chemistry layers (22) comprise a fuel electrode layer (78), in particular anode layer, an air or oxidant electrode layer (82), in particular cathode layer, and an electrolyte layer (80) located between the fuel electrode layer (78) and the air or oxidant electrode layer (82), the chromium-getter material (76) contacts the air or oxidant electrode layer (82).

14. The electrochemical cell stack (10) according to any one of the preceding claims, wherein the chromium-getter material (76) comprises a Sr-Ni-0 material.

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