Electrochemical cell assembly

Abstract

The invention pertains to an electrochemical cell assembly (10), comprising a stack (12) of cell units (14) that are stacked upon one another along a stacking direction (16), and a current transmission device (54) for electrically contacting the stack of cell units, said current transmission device spanning the stack along the stacking direction and being electrically connected to a first end of the stack, wherein the current transmission device comprises at least one spring member (56) that is configured to be elastically deformable along the stacking direction in order to compensate for relative thermal expansion of the stack and the current transmission device during operation of the electrochemical cell assembly.

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 to electricity. Electrolyser cells may be considered fuel cells running in reverse mode, i.e. using electricity to decompose a compound into its constituent parts, for example H2O into hydrogen and oxygen. Reversible cells are capable of operating in both modes. Such electrochemical cells typically comprise electrochemically active layers that may be configured to allow for conversion of electrochemical fuel to electricity (fuel cells) or for decomposing a compound into its constituent parts using electricity (electrolyser cells).

[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- stabilised Zirconia (YSZ), Gadolinia-doped Ceria, or Cerium Gadolinium Oxide (CGO). SOCs can be run as solid oxide fuel cells (SOFC) or as solid oxide electrolyser cells (SOEC).

[0008] Typically, multiple of such electrochemical cell units are stacked upon one another to form a stack of cell units, also referred to as "cell repeat units". A touch contact between adjacent cell units may provide an electrical connection between the cell units. Thus, the cell units of the stack may be electrically connected in series.

[0009] Commonly, one or more current transmission devices are allocated to the stack of cell units. The current transmission device or current transmission devices may be used to electrically connect the stack of cell units to an external device, e.g. an electrical energy storage device or a work machine to be driven by the stack of cell units.

[0010] It is an object of the invention to improve long-term performance of an electrochemical cell assembly. Description of the Invention

[0011] According to the invention, there is provided an electrochemical cell assembly with the features of claim 1. The cell assembly comprises a stack of cell units, said stack of cell units comprising a plurality of cell units that are stacked upon one another along a stacking direction. The cell assembly further comprises an electrically conductive current transmission device for electrically contacting the stack of cell units. The current transmission device is spanning the stack of cell units along the stacking direction. Thus, the current transmission device is extending along the entire height extent of the stack of cell units, i.e. the extent of the stack of cell units along the stacking direction. The current transmission device is electrically connected to a first end of the stack of cell units. Thus, the current transmission device may serve to electrically connect the stack of cell units to an external device. Preferably, the current transmission device is electrically connected to a first outermost cell unit located at the first end of the stack of cell units. The first outermost cell unit may be the lowermost cell unit of the stack of cell units. The current transmission device comprises at least one spring member, i.e. only one spring member or several spring members, that is configured to be elastically deformable along the stacking direction in order to compensate for relative thermal expansion between the stack of cell units and the current transmission device during operation of the electrochemical cell assembly.

[0012] During operation of an electrochemical cell assembly, the temperature of the components of the cell assembly is typically elevated (fuel cell units can reach an operating temperature of 600 °C, for example). This elevated temperature may result in thermal expansion of the components of the cell assembly, e.g., an expansion along the stacking direction. Particularly, the current transmission device and the stack of cell units may be affected by thermal expansion to different extents, e.g., the current transmission device may thermally expand to a greater extent than the stack of cell units. The difference in thermal expansion between the current transmission device and the stack of cell units may result from the current transmission device and the stack of cell units having different coefficients of thermal expansion. Additionally or alternatively, the difference in thermal expansion between the current transmission device and the stack of cell units may result from the current transmission device and the stack of cell units being heated to different temperatures during operation. The proposed at least one spring member may compensate for the relative thermal expansion between the stack of cell units and the current transmission device. Particularly, should the current transmission device thermally expand to a greater extent than the stack of cell units, the at least one spring member may be elastically deformed to compensate for this difference in thermal expansion. Consequently, the at least one spring member may limit forces, e.g. compression forces, that act on components of the cell assembly and / or on connections between different components of the cell assembly. This may secure a desired configuration of the cell assembly over its life-time. In some embodiments, the current transmission device comprises only one spring member that is configured to be elastically deformable along the stacking direction.

[0013] In some other embodiments, the current transmission device comprises several spring members that are each configured to be elastically deformable along the stacking direction. Where the current transmission device comprises several spring members, the several spring members may be spring members of the same type, e.g., regarding their arrangement in the cell assembly and / or their mode of elastic deformation. Alternatively, the several spring members may be spring members of at least two different types, e.g., regarding the arrangement of the spring members in the cell assembly and / or regarding the mode of elastic deformation of the spring members.

[0014] The cell units may be configured flat or planar. Thus, the length extent and the width extent of the cell units may be significantly larger than their height extent. Preferably, the cell units are arranged such that the length extent and the width extent are perpendicular to the stacking direction.

[0015] In some embodiments, the cell units are fuel cell units. In some embodiments, the cell units are electrolyser cell units. Preferably, the cell units are solid oxide cell units, e.g. solid oxide fuel cell units (SOFC) or solid oxide electrolyser cell units (SOEC). Preferably, the cell units are metal- supported solid-oxide cell units, e.g. metal-supported solid oxide fuel cell units or metal- supported solid oxide electrolyser cell units.

[0016] In some embodiments, the spring member or at least one of the spring members is electrically conductive and arranged in a current flow path of the current transmission device. Thus, during operation of the cell assembly, an electrical current may flow through that spring member.

[0017] In some embodiments, the cell assembly comprises a further current transmission device for electrically contacting the stack of cell units. Said further current transmission device may be electrically connected to a second end of the stack of cell units. That is, the stack of cell units comprises a first end and an opposite second end. The current transmission device is electrically connected to the first end of the stack and the further current transmission device is electrically connected to the second end of the stack. Thus, the current transmission device, the stack of cell units and the further current transmission device may be electrically connected in series in this order. Preferably, the further current transmission device is electrically connected to a second outermost cell unit located at the second end of the stack. The second outermost cell unit may be an uppermost cell unit of the stack of cell units. During operation of the cell assembly the current transmission device and the further current transmission device may be used as electrodes with opposite polarity. Since the current transmission device spans the stack of cell units along the stacking direction, a pole of the current transmission device and a pole of the further current transmission device may be arranged on the same side of the stack of cell units. This may facilitate the overall construction of the cell assembly and / or the electrical connection of the stack of cell units to an external device.

[0018] In some embodiments, the cell assembly comprises a housing that is provided around the stack of cell units. The current transmission device may extend through a fluid volume between the housing and the stack of cell units.

[0019] In some embodiments, the spring member or at least one spring member is configured to be elastically compressible and / or elastically expandable along the stacking direction. A spring member of this kind can be integrated into the cell assembly in a space-saving manner.

[0020] Preferably, in these embodiments, the spring member is configured elongate and arranged such that the longitudinal extent of the spring member is parallel to the stacking direction.

[0021] In some embodiments, the spring member or at least one spring member extends in a direction that is perpendicular to the stacking direction or at an angle to the stacking direction, said spring member being configured to be elastically bendable along the stacking direction. Thus, the elastic deformation of the spring member may be an elastic bending deformation along the stacking direction. The spring member may be elastically bendable in the stacking direction and / or in a direction that is opposite to the stacking direction. In some embodiments, the spring member may be elastically bendable around an axis that is perpendicular to the stacking direction.

[0022] In some preferred embodiments, the spring member or at least one spring member is configured as a compression spring (e.g., coil spring or folded spring). A compression spring can be integrated into the cell assembly in a particularly space-saving manner. Additionally, a compression spring has the advantage that it may typically change its length to a large extent. Thus, a compression spring may effectively compensate for relative thermal expansion between the current transmission device and the stack of cell units. In some preferred embodiments, the spring member or at least one spring member is configured as a flat spring. A flat spring is a spring that is formed from a band of material, e.g., steel or spring steel. A flat spring has the advantage that it may be provided in various shapes, e.g. elongate or curved. Thus, a flat spring may be easily adjusted to the specific circumstances provided in the cell assembly. In some preferred embodiments, the spring member or at least one spring member is arranged such that, when seen along a viewing direction that is parallel to the stacking direction, at least a portion of the spring member is positioned offset to the stack of cell units. Thus, an elastic deformation of at least said portion of the spring member along the stacking direction is not hindered by the stack of cell units. Preferably, the spring member is arranged such that, when seen along a viewing direction that is parallel to the stacking direction, the entire spring member is positioned offset to the stack of cell units.

[0023] In some preferred embodiments, the current transmission device comprises at least one busbur, i.e. only one busbar or several busbars, that extends in the stacking direction or at on angle to the stacking direction from the first end of the stack of cell units alongside the stack of cell units. Thus, the busbar of the current transmission device spans or partly spans the stack of cell units along the stacking direction. Preferably, the busbar is positioned beyond the stack of cell units in the stacking direction and in the direction opposite to the stacking direction. The busbar may be provided in a plurality of shapes. In some embodiments, the busbar is configured flat or plateshaped. In other embodiments, the busbar is configured cylindrical.

[0024] In some preferred embodiments, the busbar comprises a first end that is electrically connected to the first end of the stack of cell units and a second end that is electrically connected to a pole which acts as an electrical terminal of the electrochemical cell assembly. In such cases, the spring member or at least one spring member may be arranged between the first end of the stack of cell units and the pole to provide compliance. The pole may be rigidly held at the second end of the busbar (such that it may pass through a hole in a vessel for electrical communication outwith the assembly). The electrochemical cell assembly may comprise a vessel that encloses the stack of cell units. The vessel may be formed by the above-mentioned housing and first and second end plates that are arranged on opposite sides of the stack of cell units. The pole which acts as an electrical terminal may pass through a hole in the vessel, e.g. a hole in the housing, the first end plate or the second end plate.

[0025] In some preferred embodiments, the current transmission device comprises a first current transmission plate that forms the electrical connection to the first end of the stack of cell units and is electrically connected to the first end of the busbar. The first current transmission plate may provide a reliable electrical connection to the first end of the stack of cell units. Preferably, the first current transmission plate is stacked with the stack of cell units. The electrical connection between the first current transmission plate and the first end of the stack of cell units may be provided by a direct contact between the first current transmission plate and the first end of the stack of cell units, e.g. a direct contact with the first outermost cell unit. In some preferred embodiments, the current transmission device comprises a second current transmission plate that is electrically connected to the second end of the busbar and electrically connected to the pole. Preferably, the second current transmission plate is stacked with the stack of cell units. The first and second current transmission plates may be located on opposite sides of the stack of cell units. Thus, the stack of cell units may be located between the first and second current transmission plates. An insulating member, e.g. an insulating plate, may be interposed between the stack of cell units and the second current transmission plate.

[0026] In some preferred embodiments, the first current transmission plate is rigidly connected to the first end of the busbar. This may provide a mechanically stable connection between the first current transmission plate and the busbar. In these embodiments, the spring member may be provided in at least one of the busbar, the second current transmission plate and the connection of the busbar to the second current transmission plate.

[0027] In some preferred embodiments, the second current transmission plate is rigidly connected to the second end of the busbar. This may provide a mechanically stable connection between the second current transmission plate and the busbar. In these embodiments, the spring member may be provided in at least one of the busbar, the first current transmission plate and the connection of the busbar to the first current transmission plate.

[0028] In some preferred embodiments, the busbar comprises a first busbar portion and a second busbar portion that are electrically connected in series, wherein the spring member or at least one of the several spring members is arranged between the first busbar portion and the second busbar portion. Thus, the spring member may be integrated into the busbar. This allows for an especially effective compensation of thermal expansion. This is due to the fact that the busbar is typically affected most by thermal expansion. The first busbar portion may comprise the first end of the busbar. The second busbar portion may comprise the second end of the busbar. Preferably, the spring member is a separate unit that is fixedly attached to the first busbar portion and to the second busbar portion, most preferably by welding. Alternatively, the spring member may be integrally formed with the first busbar portion and / or with the second busbar portion. Preferably, the first and second busbar portions are axially offset, i.e. spaced apart from one another along the stacking direction. Alternatively, the first and second busbar portions may be arranged such that they axially overlap.

[0029] In some preferred embodiments, the spring member arranged between the first and second busbar portions is located centrally, based on the extent of the stack of cell units in the stacking direction. Consequently, the first and second busbar portions are located off-center, based on the extent of the stack of cell units in the stacking direction. In some preferred embodiments, the spring member or at least one spring member is configured as a separate unit and arranged between the busbar and one of the first current transmission plate and the second current transmission plate. That is to say, the spring member is not integrally formed with the busbar nor with the current transmission plate. In some embodiments, the spring member is arranged between the busbar and the first current transmission plate. In some embodiments, the spring member is arranged between the busbar and the second current transmission plate. In some embodiments, a first spring member is arranged between the busbar and the first current transmission plate and a second spring member is arranged between the busbar and the second current transmission plate.

[0030] In some preferred embodiments, the spring member is fixedly attached to the busbar, preferably by welding. This may provide a robust mechanical and particularly electrical connection between the busbar and the spring member. In some preferred embodiments, the spring member is fixedly attached to the respective current transmission plate, preferably by welding. This may provide a robust mechanical and particularly electrical connection between the current transmission plate and the spring member.

[0031] In some preferred embodiments, the spring member or at least one spring member is formed by the first current transmission plate. Thus, a portion of the first current transmission plate may constitute the spring member. This has the advantage that the overall number of separate units may be decreased which may in turn facilitate the manufacture of the electrochemical cell assembly. Preferably, the spring member is formed by a machined feature of the first current transmission plate. Different measures may be provided to enhance the elastic deformability of the part of the current transmission plate forming the spring member. Preferably, the thickness of the first current transmission plate, i.e. the extent of the first current transmission plate along the stacking direction, may be reduced in this part of the first current transmission plate.

[0032] In some preferred embodiments, the spring member formed by the first current transmission plate is formed by an extension (also referred to as a tab) of the first current transmission plate. Thus, the extension of the first current transmission plate is elastically deformable in order to compensate for relative thermal expansion between the stack of cell units and the current transmission device. An extension of a component is a part of the component that structurally stands out from a main body of that component. Preferably, the extension of the first current transmission plate is elongate. This may facilitate an elastic deformation of the extension. Preferably, the thickness of the first current transmission plate, i.e. the extent of the first current transmission plate along the stacking direction, is reduced in the extension compared to the main body of the first current transmission plate. This may also facilitate an elastic deformation of the extension. The extension is preferably configured as a flat spring or bent to form a compression spring.

[0033] In some preferred embodiments, the extension extends in a direction that is perpendicular to the stacking direction or at an angle to the stacking direction such that, when seen along a viewing direction that is parallel to the stacking direction, at least a portion of the extension is positioned offset to the stack of cell units (i.e. , the extension extends past the plan view extent of the stack of cell units). Thus, an elastic deformation of at least that portion of the extension along the stacking direction is not hindered by the stack of cell units.

[0034] In some preferred embodiments, the electrochemical cell assembly comprises at least one fluid manifold that extends through the first current transmission plate and through the stack of cell units along the stacking direction. During operation said fluid manifold may be used to supply a fluid, e.g. a fuel, from the exterior to the cell units, i.e. to internal cell volumes of the cell units, or to remove a fluid, e.g. a consumed or partly consumed fuel, from the cell units to the exterior. In some preferred embodiments, at the level of the first current transmission plate the fluid manifold is formed by a, preferably sleeve-shaped, sealing device that extends through the first current transmission plate without contacting the first current transmission plate. Since the sealing device does not contact the first current transmission plate, the sealing device and the first current transmission plate are mechanically decoupled. This increases the flexibility of portions of the first current transmission plate that are adjacent to the sealing device. Preferably, the extension extends from a portion of the first current transmission plate that is adjacent to the sealing device. Thus, the extension may be provided in an area of the first current transmission plate that allows for a higher flexibility. This may facilitate elastic deformation of the extension, i.e. the spring member.

[0035] In some preferred embodiments, the sealing device is positioned in a cut-out provided in the first current transmission plate, said cut-out extending through the first current transmission plate along the stacking direction. In some embodiments, the cut-out is configured as a through-hole extending through the first current transmission plate. Thus, the first current transmission plate may fully surround the sealing device in a plane that is perpendicular to the stacking direction. In some embodiments, the cut-out is located at the outer perimeter of the first current transmission plate. Thus, the first current transmission plate may partly surrounds the sealing device in a plane that is perpendicular to the stacking direction.

[0036] In some preferred embodiments, the electrochemical cell assembly comprises an end plate that is arranged on a side of the first current transmission plate that is facing away from the stack of cell units. Preferably, said end plate comprises a fluid port that extends through the end plate along the stacking direction. Thus, during operation of the electrochemical cell assembly, the end plate may be used as an access point to supply a fluid to the stack of cell units or to remove a fluid from the stack of cell units. Preferably, the fluid port is fluidical ly connected with the fluid volume between the housing and the stack of cell units. In some preferred embodiments, when seen along a viewing direction that is parallel to the stacking direction, the extension extends along an outer contour of the fluid port. This has the advantage that the extension may be cooled by fluid flowing through the fluid port, without obstructing the flow path of the fluid.

[0037] In some preferred embodiments, the first current transmission plate comprises a first extension forming a first spring member and a second extension forming a second spring member. Preferably, when seen along the viewing direction that is parallel to the stacking direction, the first and second extensions extend along the outer contour of the fluid port on opposite sides of the fluid port (i.e., across the diameter or width of the fluid port). However, the presence of the first and second extensions, i.e. two extensions, is not limited to the extensions extending along the outer contour of the fluid port on opposite sides of the fluid port. Particularly, the first and second extensions may also be provided without the extensions extending along a fluid port.

[0038] In some preferred embodiments, a first busbar is electrically connected to the first extension and a second busbar is electrically connected to the second extension. Thus, the current transmission device may comprise two busbars that are electrically connected in parallel with the first current transmission plate having the first and second extensions.

[0039] In some other preferred embodiments, the first and second extensions are electrically connected to a common busbar. In these embodiments, the common busbar preferably overlaps with the fluid port, when seen along a viewing direction that is parallel to the stacking direction.

[0040] In some preferred embodiments, at least one electrically insulating inner member is arranged between the busbar and the stack of cell units. In these embodiments, the busbar is preferably configured flat or plate-shaped. The insulating inner member may prevent an electrical short circuit beween the busbar and the cell units. Preferably, the insulating inner member is configured flat or plate-shaped. Preferably, the insulating inner member is formed from a mica material.

[0041] In some other embodiments, the electrochemical cell assembly may comprise a tubular insulating member that surrounds the busbar. In these embodiments, the busbar is preferably configured cylindrical. In some preferred embodiments, the busbar comprises a hook portion that reaches behind the electrically insulating inner member. Thus, the busbar extends around the insulating inner member such that a portion of the busbar is positioned on a side of the insulating inner member that is facing towards the stack of cell units. This may restrict or prevent a displacement of the insulating inner member relative to the busbar.

[0042] In some preferred embodiments, at least one electrically insulating outer member is arranged on a side of the busbar that faces away from the stack of cell units. The insulating outer member may prevent an electrical connection beween the busbar and the housing. Preferably, the insulating outer member is configured flat or plate-shaped. Preferably, the insulating outer member is formed from a mica material.

[0043] In some preferred embodiments, both, the insulating inner member and the insulating outer member are provided. Thus, the busbar may be sandwiched between the insulating inner member and the insulating outer member.

[0044] Further embodiments are derivable from the following description and the drawings.

[0045] In the drawings:

[0046] Figure 1 shows a cross-sectional view of an electrochemical cell assembly according to a first embodiment;

[0047] Figure 2 shows a top-view of an end plate of the electrochemical cell assembly shown in Figure 1 ;

[0048] Figure 3 shows a cross-sectional view of an electrochemical cell assembly according to a second embodiment;

[0049] Figure 4 shows a cross-sectional view of an electrochemical cell assembly according to a third embodiment;

[0050] Figure 5 shows a top-view of components of the electrochemical cell assembly shown in Figure 4;

[0051] Figure 6 shows a top-view of components of an electrochemical cell assembly according to a fourth embodiment; and

[0052] Figure 7 shows a top-view of components of an electrochemical cell assembly according to a fifth embodiment.

[0053] Referring to Figure 1 , there is shown an exemplary configuration of an electrochemical cell assembly 10. The cell assembly 10 comprises a stack 12 having a plurality of cell units 14 that are stacked upon one another along a stacking direction 16. The cell units 14 may be configured as fuel cell units or as electrolyser cell units, for example. The cell units 14 may be electrically connected in series. In this example, an electrical connection between the cell units 14 is established by a direct contact between adjacent cell units 14.

[0054] The stack 12 further comprises gaskets 18 that are interposed between adjacent cell units 14. In this example, the gaskets 18 are configured as annular sealing rings having a central opening 20.

[0055] In this example, the cell assembly 10 further comprises a first end plate assembly 22 having a first end plate 24 and a second end plate assembly 26 having a second end plate 28. Figure 2 shows a top-view of the first end plate 24. The stack 12 of cell units 14 is arranged between the first end plate 24 and the second end plate 28. That is to say, the first end plate 24 and the second end plate 28 are arranged on opposite sides of the stack 12 of cell units. In this example, the first end plate 24 forms a lower end plate or base plate of the cell assembly 10. The second end plate 28 forms an upper end plate of the cell assembly 10.

[0056] Preferably, the stack 12 is held in compression between the first end plate 24 and the second end plate 28. That is to say, the end plates 24 and 28 may be biased towards each other such that a compression force acts on the stack 12 of cell units 14 along the stacking direction 16. This improves the sealing effect of the gaskets 18 and secures the direct contact between adjacent cell units 14.

[0057] The electrochemical cell assembly 10 further comprises a housing 30 that is provided around the stack 12 of cell units 14. The housing 30 extends around the outer perimeters of the cell units 14. In this example, the housing 30 is fixedly attached to the first end plate 24 and to the second end plate 28, preferably by welding, and biases the end plates 24 and 28 towards each other.

[0058] The first end plate 24, the second end plate 28 and the housing 30 together define or enclose a fluid volume 32. The stack 12 of cell units 14 is arranged within said fluid volume 32.

[0059] In this example, the first end plate 24 comprises at least one fluid inlet port 34 for first fluid, e.g., fuel. The fluid inlet port 34 is provided by a through-hole 36 formed in the first end plate 24. The fluid inlet port 34 is fluidically connected with internal cell volumes of the cell units 14 (not shown in the Figures) via an inlet manifold 38 that extends through the stack 12 of cell units 14 along the stacking direction 16. The inlet manifold 38 is defined by the gasket openings 20 and through-holes 40 that are formed in the cell units 14 and aligned with the openings 20. During operation of the electrochemical cell assembly 10, the fluid inlet port 34 may be used to provide a fluid, e.g. fuel such as hydrogen, to the cell units 14, i.e. to their internal cell volume. In this example, the first end plate 24 comprises two fluid inlet ports 34 or through-holes 36 for first fluid (see Figure 2).

[0060] In this example, the first end plate 24 comprises at least one fluid outlet port 42 for first fluid, e.g. fuel. The fluid outlet port 42 is provided by a through-hole 44 formed in the first end plate 24. The fluid outlet port 42 is fluidically connected with the internal cell volumes of the cell units 14 via an outlet manifold 46 that extends through the stack 12 of cell units 14 along the stacking direction 16. The outlet manifold 46 is provided by the gasket openings 20 and through-holes 48 that are formed in the cell units 14 and aligned with the openings 20. During operation of the electrochemical cell assembly 10, the fluid outlet port 42 may be used to remove fluid, e.g. a consumed or partly consumed fuel, from the cell units 14 to the exterior. In this example, the first end plate 24 comprises two fluid outlet ports 42 or through-holes 44 for first fluid (see Figure 2).

[0061] The first end plate 24 may further comprise at least one second fluid inlet port 50 for second fluid, e.g. oxidant / air (see Figure 2). The second fluid inlet port 50 is not visible in Figure 1 due to the position of the sectional plane that extends through one of the fluid inlet ports 34 and one of the fluid outlet ports 42 instead. The second fluid inlet port 50 may be fluidically connected with a first portion of the fluid volume 32 between the housing 30 and the stack 12 of cell units 14. During operation of the electrochemical cell assembly 10, the second fluid inlet port 50 may be used to supply second fluid, e.g. oxidant such as air or oxygen, to the first portion of the fluid volume 32.

[0062] The first end plate 24 may further comprise at least one second fluid outlet port 52 for second fluid, e.g., oxidant / air (see Figure 2). The second fluid outlet port 52 is not visible in Figure 1 due to the position of the sectional plane. The second fluid outlet port 52 may be fluidically connected with a second portion of the fluid volume 32 between the housing 30 and the stack 12 of cell units 14. The first and second portions of the fluid volume 30 may be on opposite sides of the stack 12 of cell units 14. During operation of the cell assembly 10, the second fluid outlet port 52 may be used to remove fluid, e.g. a consumed or partly consumed oxidant, from the fluid volume 32.

[0063] The electrochemical cell assembly 10 further comprises a current transmission device 54 for electrically contacting the stack 12 of cell units 14. The current transmission device 54 may be used to electrically connect the stack 12 of cell units 14 to an external device such as an electrical energy storage device or a work machine to be driven by the stack 12 of cell units 14. The current transmission device 54 spans the stack 12 of cell units 14 along the stacking direction 16 and is electrically connected to a first end of the stack 12 of cell units 14. A first outermost cell unit 14a of the plurality of cell units 14 is located at the first end of the stack 12 of cell units 14. In this example, the first outermost cell unit 14a is the lowermost cell unit 14 of the stack 12, i.e. the one that is located closest to the first end plate 24.

[0064] In this example, the current transmission device 54 comprises a busbar 58. The busbar 58 extends in the stacking direction 16 alongside the stack 12 of cell units 14. In the example of Figure 1 , the busbar 58 comprises a first busbar portion 60 and a second busbar portion 62. The first and second busbar portions 60 and 62 are electrically connected in series.

[0065] The current transmission device 54 comprises a spring member 56 that is arranged between the first and second busbar portions 60 and 62. The spring member 56 is configured to be elastically deformable along the stacking direction 16. Thus, the spring member 56 may compensate for relative thermal expansion between the stack 12 of cell units 14 and the current transmission device 54 during operation of the electrochemical cell assembly 10. For example, should the current transmission device 54 expand along the stacking direction 16 to a greater extent than the stack 12 of cell units 14, the spring member 56 may compensate this difference in thermal expansion by being elastically deformed.

[0066] In this example, the spring member 56 is configured as a compression spring (e.g., coil spring or metal section folded into a serpentine shape). The spring member 56 is configured to be elastically compressible and elastically expandable along the stacking direction 16. Thus, the spring member 56 may compensate for differences in thermal expansion by being elastically compressed or expanded.

[0067] In this example, the spring member 56 is located centrally, based on the extent of the stack 12 of cell units 14 in the stacking direction 16.

[0068] In this example, the current transmission device 54 further comprises a first current transmission plate 64. The first current transmission plate 64 is interposed between the stack 12 of cell units 14 and the first end plate 24. The first current transmission plate 64 is in direct contact with the first outermost cell unit 14a of the cell units 14. In this example, this direct contact provides the electrical connection between the current transmission device 54 and the first end of the stack The busbar 58 may be electrically (and mechanically) connected to the first current transmission plate 64. In the example shown in Figure 1, the first busbar portion 60 is in direct contact with the first current transmission plate 64. The first busbar portion 60 and the first current transmission plate 64 may be rigidly connected to one another, preferably by welding.

[0069] In this example, a first insulating plate 66 is interposed between the first end plate 24 and the first current transmission plate 64. The first insulating plate 66 is in direct contact with the first end plate 24 and the first current transmission plate 64. Preferably, the first insulating plate 66 is formed from a mica material.

[0070] In this example, the current transmission device 54 further comprises a second current transmission plate 68. The second current transmission plate 68 is interposed between the stack 12 of cell units 14 and the second end plate 28. Thus, the first and second current transmission plates 64 and 68 are arranged on opposite sides of the stack 12 of cell units 14.

[0071] The busbar 58 may be electrically connected to the second current transmission plate 68. In the example shown in Figure 1, the second busbar portion 62 is in direct contact with the second current transmission plate 68. The second busbar portion 62 and the second current transmission plate 68 may be rigidly connected to one another, preferably by welding.

[0072] In this example, the electrochemical cell assembly 10 comprises a further current transmission device 70 for electrically contacting the stack 12 of cell units 14. The further current transmission device 70 is electrically connected to a second end of the stack 12 of cell units 14. In this example, a second outermost cell unit 14b is located at the second end of the stack 12 of cell units 14. That is to say, the first outermost cell unit 14a and the second outermost cell unit 14b are forming the first and second ends of the stack 12 of cell units 14. In this example, the further current transmission device 70 comprises a third current transmission plate 72 that is interposed between the stack 12 of cell units 14 and the second current transmission plate 68. The third current transmission plate 72 is in direct contact with the second outermost cell unit 14b of the stack 12 of cell units 14. In this example, this direct contact provides the electrical connection between the further current transmission device 70 and the second end of the stack 12 of cell units 14.

[0073] Thus, the first current transmission device 54, the stack 12 of cell units 14 and the further current transmission device 70 are electrically connected in series, i.e. the current transmission device 54 is electrically connected to the further current transmission device 70 via the stack 12 of cell units 14. During operation of the electrochemical cell assembly 10, there exists a potential difference between the current transmission devices 54, 70 (one being positive the other negative).

[0074] In this example, a second insulating plate 74 is interposed between the second current transmission plate 68 and the third current transmission plate 72. Preferably, the second insulating plate 74 is formed from a mica material.

[0075] In this example, a third insulating plate 76 is interposed between the second current transmission plate 68 and the second end plate 28. Preferably, the third insulating plate 76 is formed from a mica material.

[0076] Preferably, the current transmission device 54 and the further current transmission device 70 each comprise a pole / terminal (not shown in the Figures) that is located on a side of the second end plate 28 that is facing away from the stack 12 of cell units 14. Said pole / terminal may be used to electrically connect the stack 12 of cell units 14 to an external device. The pole / terminal of the current transmission device 54 may extend through the second end plate 28 and the third insulating plate 76 along the stacking direction 16 and may be in direct contact with (and extend from) the second current transmission plate 68. The pole / terminal of the further current transmission device 70 may extend through the second end plate 28, the third insulating plate 76, the second current transmission plate 68 and the second insulating plate 74 along the stacking direction 16 and may be in direct contact with (and extend from) the third current transmission plate 72.

[0077] In this example, an insulating inner member 78 is arranged between the busbar 58 and the stack 12 of cell units 14, i.e. the outer perimeter of the cell units 14. Thus, the insulating inner member 78 may prevent an electrical short circuit between the busbar 58 and the cell units 14. In this example, the insulating inner member 78 is configured plate-shaped. Preferably, the insulating inner member 78 is formed form a mica material.

[0078] Figure 3 shows another embodiment of the electrochemical cell assembly 10. In the following, only differences between the cell assembly 10 of Figure 1 and the cell assembly 10 of Figure 3 will be described.

[0079] In the embodiment shown in Figure 3, the current transmission device 54 comprises a spring member 56 that is arranged between the busbar 58 and the second current transmission plate 68. Said spring member 56 is configured elastically deformable along the stacking direction 16 in order to compensate for relative thermal expansion between the current transmission device 54 and the stack 12 of cell units 14. In this example, the spring member 56 is a separate unit that is fixedly attached to the busbar 58 and to the second current transmission plate 68, preferably by welding. Alternatively, the spring member 56 may be unitary with the busbar or with the current transmission plate. Preferably, the spring member 56 is configured as a compression spring (e.g., a coil spring or metal section folded into a serpentine shape).

[0080] In the example shown in Figure 3, the busbar 58 is configured as a unitary structure. The busbar 58 is in direct contact with the first current transmission plate 64. The busbar 58 may be rigidly connected to the first current transmission plate 64, preferably by welding.

[0081] In other examples, the spring member 56 is arranged between the busbar 58 and the first current transmission plate 64. In these examples, the busbar 58 may be in direct contact with the second current transmission plate 68.

[0082] Figure 4 shows another embodiment of the electrochemical cell assembly 10. Figure 5 is a topview of components of the electrochemical cell assembly 10 shown in Figure 4. In the following, only differences between the cell assembly 10 of Figure 1 and the cell assembly 10 of Figures 4 and 5 will be described.

[0083] In the embodiment shown in Figures 4 and 5, the current transmission device 54 comprises a first spring member 56a and a second spring member 56b. The spring members 56a, 56b are formed by the first current transmission plate 64. The spring members 56a, 56b are configured to be elastically bendable along the stacking direction 16. Thus, the spring members 56a, 56b may elastically deflect along the stacking direction 16 (parallel or antiparallel thereto) in order to compensate for relative thermal expansion between the stack 12 of cell units 14 and the current transmission device 54 (specifically, for different thermal expansions of the stack of cell units and current transmission device (specifically busbar) due to differing coefficients of thermal expansion and / or different temperature of the components).

[0084] In other examples, the spring members 56a, 56b are formed by the second current transmission plate 68. In further examples, spring members may be formed by both current transmission plates.

[0085] In this example, the spring members 56a, 56b are formed by a respective extension 80a, 80b of the first current transmission plate 64. Said extensions 80a, 80b extend in a direction that is perpendicular to the stacking direction 16.

[0086] In this example, the extensions 80a, 80b extend beyond the stack 12 of cell units 14 and the first insulating plate 64. Thus, when seen along a viewing direction that is parallel to the stacking direction 16, at least a part of the extensions 80a, 80b is offset from the stack 12 of cell units 14 and from the first insulating plate 64. This increases the space that is available for the elastic deformation of the extensions 80a, 80b.

[0087] In this example, the current transmission device 54 comprises a common busbar 58. The common busbar 58 is electrically connected to both spring members 56a, 56b, i.e. the extensions 80a, 80b. In this example, the common busbar 58 is in direct contact with both spring members 56a, 56b. Preferably, the busbar 58 is fixedly attached to the spring members 56a, 56b, most preferably by welding.

[0088] With reference to Figure 5, when seen along a viewing direction that is parallel to the stacking direction 16, the first and second spring members 56a, 56b or first and second extensions 80a and 80b extend along an outer contour 90 (i.e. part of the circumference) of the second fluid inlet port 50 on opposite sides (e.g., across the diameter) of the second fluid inlet port 50. The common busbar 58 partially overlaps with, preferably surrounds, the second fluid inlet port 50, when seen along the viewing direction that is parallel to the stacking direction 16.

[0089] In this example, the thickness of the first current transmission plate 64 is reduced in the area of the first and second extensions 80a and 80b (see Figure 4). This has the advantage that the force required for elastic deformation of the first and second extensions 80a and 80b may be reduced. In other examples, the thickness may not be reduced.

[0090] With reference to Figure 5 and the inset shown in Figure 4, at the level of the first current transmission plate 64 the inlet manifolds 38 are formed by a respective sleeve-shaped sealing device 82 that extends through the first current transmission plate 64 without contacting the first current transmission plate 64. Thus, the sealing devices 82 and the first current transmission plate 64 are mechanically decoupled. This may increase the flexibility of parts of the first current transmission plate 64 that are adjacent to the location of the sealing devices 82. This may in turn facilitate the deformation of the spring members 56a, 56b, i.e. the extensions 80a, 80b.

[0091] The sealing devices 82 are positioned in a respective cut-out 84 of the first current transmission plate 64, said cut-out 84 extending through the first current transmission plate 64 along the stacking direction 16. In the example shown in Figure 5, the cut-outs 84 are configured as through-holes formed in the first current transmission plate 64. Thus, the first current transmission plate 64 fully surrounds the sealing devices 82 in a plane that is perpendicular to the stacking direction 16. Figure 6 shows a top-view of components of another embodiment of the electrochemical cell assembly. In the following, only differences between the embodiment shown in Figures 4 and 5 and the embodiment shown in Figure 6 will be described.

[0092] In the example shown in Figure 6, the cut-outs 84 are positioned at the outer edge of the first current transmission plate 64. The cut-outs 84 of Fig. 6 have an open perimeter. Thus, the first current transmission plate 64 only partly surrounds the sealing devices 82 in a plane that is perpendicular to the stacking direction 16. This may further increase the flexilibility of the spring members 56a, 56b, i.e. the extensions 80a and 80b.

[0093] In the example shown in Figure 6, the current transmission device 54 comprises a first busbar 58a and a second busbar 58b, wherein the first busbar 58a is electrically connected to the first extension 80a, and wherein the second busbar 58b is electrically connected to the second extension 80b. Thus, the first and second busbars 58a and 58b are electrically connected in parallel to the first current transmission plate 64.

[0094] Figure 7 shows a top-view of components of the electrochemical cell assembly 10 according to another embodiment.

[0095] In the example shown in Figure 7, the current transmission device 54 comprises a busbar 58 that is configured flat or plate-shaped. The electrically insulating inner member 78 is arranged between the busbar 58 and the cell units 14. In the example shown in Figure 7, the busbar 58 comprises a hook portion 86 that reaches behind the insulating inner member 78. Thus, the busbar 58 extends around the insulating inner member 78 such that it is positioned on or rests on a side of the insulating inner member 78 that is facing towards the stack 12 of cell units 14. This may restrict or prevent a displacement of the insulating inner member 78 relative to the busbar 58.

[0096] In the example shown in Figure 7, an electrically insulating outer member 88 is arranged on a side of the busbar 58 that is facing away from the stack 12 of cell units 14, i.e. towards the housing 30. Thus, the busbar 58 is sandwiched between the electrically insulating inner member 78 and the electrically insulating outer member 88. The insulating outer member 88 may be held in compression between the busbar 58 and the housing 30.

[0097] In the example of Figure 7, the spring member 56 is not shown. However, the concept of Figure 7 may be combined with any one of the spring members 56 discussed above in connection with one of the other embodiments. The current transmission devices 54 discussed above in connection with the Figures always comprise just one spring member 56 or several spring members 56 of the same type. However, the different spring members 56 discussed above may also be combined in the same embodiment. For example, a current transmission device 54 may be provided that comprises one or more of: a spring member that is formed by a current transmission plate, a spring member that is arranged between a current transmission plate and a busbar, and a spring member that is arranged between a first busbar portion and a second busbar portion. Such use of multiple different spring members further increases compliance in the current transmission device improving reliability of the assembly.

Claims

Claims1. An electrochemical cell assembly (10), preferably fuel cell assembly or electrolyser cell assembly, comprising: a stack (12) of cell units (14), comprising a plurality of cell units (14) that are stacked upon one another along a stacking direction (16), and a current transmission device (54) for electrically contacting the stack (12) of cell units (14), said current transmission device (54) spanning the stack (12) of cell units (14) along the stacking direction (16) and being electrically connected to a first end of the stack (12) of cell units (14), wherein: the current transmission device (54) comprises at least one spring member (56) that is elastically deformable along the stacking direction (16) in order to compensate for relative thermal expansion between the stack (12) of cell units (14) and the current transmission device (54) during operation of the electrochemical cell assembly (10).

2. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the spring member (56) or at least one spring member (56) is configured as a compression spring, and / or wherein the spring member (56) or at least one spring member (56) is configured as a flat spring.

3. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the spring member (56) or at least one spring member (56) is arranged such that, when seen along a viewing direction that is parallel to the stacking direction (16), at least a portion of the spring member (56) is positioned offset to the stack (12) of cell units (14).

4. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the current transmission device (54) comprises at least one busbar (58) that extends in the stacking direction (16) or at an angle to the stacking direction (16) from the first end of the stack (12) of cell units (14) and alongside the stack (12) of cell units (14).

5. The electrochemical cell assembly (10) according to the preceding claim, wherein the busbar (58) comprises a first end that is electrically connected to the first end of thestack (12) of cell units (14) and a second end that is electrically connected to a pole which acts as an electrical terminal of the electrochemical cell assembly (10).

6. The electrochemical cell assembly (10) according to the preceding claim, wherein the current transmission device (54) comprises a first current transmission plate (64) that forms the electrical connection to the first end of the stack (12) of cell units (14) and is electrically connected to the first end of the busbar (58).

7. The electrochemical cell assembly (10) according to any one of claims 5 and 6, wherein the current transmission device (54) comprises a second current transmission plate (68) that is electrically connected to the second end of the busbar (58) and electrically connected to the pole.

8. The electrochemical cell assembly (10) according to any one of claims 6 and 7, wherein the first end of the busbar (58) is rigidly connected to the first current transmission plate (64), and / or wherein the second end of the busbar (58) is rigidly connected to the second current transmission plate (68).

9. The electrochemical cell assembly (10) according any one of claims 4 to 8, wherein the busbar (58) comprises a first busbar portion (60) and a second busbar portion (62) that are electrically connected in series, and wherein the spring member (56) or at least one spring member (56) is arranged between the first busbar portion (60) and the second busbar portion (62).

10. The electrochemical cell assembly (10) according to any one of claims 6 to 9, wherein the spring member (56) or at least one spring member (56) is configured as a separate unit and arranged between the busbar (56) and one of the first current transmission plate (64) and the second current transmission plate (68).

11. The electrochemical cell assembly (10) according to the preceding claim, wherein the spring member (56) is fixedly attached to the busbar (58), and / or wherein the spring member (56) is fixedly attached to the respective current transmission plate (64, 68).

12. The electrochemical cell assembly (10) according to any one of claims 6 to 11, wherein the spring member (56) or at least one of the spring members (56) is formed by the first current transmission plate (64).

13. The electrochemical cell assembly (10) according to the preceding claim, wherein the spring member (56) formed by the first current transmission plate (64) is formed by an extension (80a, 80b) of the first current transmission plate (64).

14. The electrochemical cell assembly (10) according to the preceding claim, wherein: the electrochemical cell assembly (10) comprises at least one fluid manifold (38) that extends through the first current transmission plate (64) and through the stack (12) of cell units (14) along the stacking direction (16), at the level of the first current transmission plate (64) the fluid manifold (38) is formed by a sealing device (82) that extends through the first current transmission plate (64) without contacting the first current transmission plate (64), and the extension (80a, 80b) extends from a portion of the first current transmission plate (64) that is adjacent to the sealing device (82).

15. The electrochemical cell assembly (10) according to the preceding claim, wherein the sealing device (82) is positioned in a cut-out (84) provided in the first current transmission plate (64), said cut-out (84) extending through the first current transmission plate (64) along the stacking direction (16).

16. The electrochemical cell assembly (10) according to any one of claims 13 to 15, wherein: the electrochemical cell assembly (10) comprises an end plate (24) that is arranged on a side of the first current transmission plate (64) that faces away from the stack (12) of cell units (14), the end plate (24) comprises a fluid port (50) that extends through the end plate (24) along the stacking direction (16), and when seen along a viewing direction that is parallel to the stacking direction (16), the extension (80a, 80b) extends along an outer contour (90) of the fluid port (50).

17. The electrochemical cell assembly (10) according to the preceding claim, wherein the first current transmission plate (64) comprises a first extension (80a) forming a first spring member (56a) and a second extension (80b) forming a second spring member (56b), and wherein, when seen along the viewing direction that is parallel to the stacking direction (16), the first and second extensions (80a, 80b) extend along the outer contour (90) of the fluid port (50) on opposite sides of the fluid port (50).

18. The electrochemical cell assembly (10) according to the preceding claim, wherein a first busbar (58a) is electrically connected to the first extension (80a) and a second busbar (58b) is electrically connected to the second extension (80b).

19. The electrochemical cell assembly (10) according to claim 17, wherein the first extension (80a) and the second extension (80b) are electrically connected to a common busbar (58).

20. The electrochemical cell assembly (10) according to any one of claims 4 to 19, wherein at least one electrically insulating inner member (78) is arranged between the busbar (58) and the stack (12) of cell units (14).

21. The electrochemical cell assembly (10) according to the preceding claim, wherein the busbar (58) comprises a hook portion (86) that reaches behind the electrically insulating inner member (78).

22. The electrochemical cell assembly (10) according to any one of claims 4 to 21, wherein at least one electrically insulating outer member (88) is arranged on a side of the busbar (58) that faces away from the stack (12) of cell units (14).

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