Electrochemical cell assembly

Abstract

The invention relates to an electrochemical cell assembly (10, comprising a stack (16) of cell units (18), said stack comprising a plurality of cell units stacked upon one another along a stacking direction and a plurality of gaskets (40) interposed between said cell units, said gaskets being aligned such that they overlie along the stacking direction forming a column of gaskets, and a spring device (54) being configured to exert a spring force on the column of gaskets along the stacking direction (20). The invention also relates to methods of manufacturing an electrochemical cell assembly.

Description

[0001] Title: Electrochemical cell assembly

[0002] Specification

[0003] The invention relates to the field of electrochemical cell stacks, in particular, fuel cell stacks and electrolyser cell stacks. More specifically, the invention relates to an electrochemical cell assembly, an interconnector plate for an electrochemical cell unit, a cell layer for an electrochemical cell assembly, an electrochemical cell unit, a stack of electrochemical cell units, and a method of manufacturing an electrochemical cell assembly.

[0004] Fuel cells and electrolyser cells are examples of electrochemical cells. Fuel cells are energy conversion devices that allow for conversion of electrochemical fuel (e.g. H2) to electricity. Electrolyser cells may be considered fuels cells running in reverse mode, i.e. using electricity to decompose a compound into its constituent parts, for example water into hydrogen or 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).

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

[0006] Typically, multiple of such cell units are stacked upon one another along a stacking direction, with gaskets interposed between adjacent cell units, to form a "stack" of cell units (also referred to as 'cell repeat units'). This stack is commonly arranged upon an end plate, thus forming an electrochemical cell assembly. An example of such an electrochemical cell assembly is described, for example, in WO 2020 / 126486 Al.

[0007] It is an object of the present invention to improve sealing and long-term stability of an electrochemical cell assembly.

[0008] According to the invention, there is provided an electrochemical cell assembly according to claim 1. The electrochemical cell assembly comprises a stack of cell units. The stack of cell units comprises a plurality of cell units stacked upon one another along a stacking direction. Preferably, each cell unit extends perpendicular to the stacking direction in a first direction, preferably longitudinal direction, and in a second direction, preferably width direction, perpendicular to the first direction. The stack of cell units further comprises a plurality of gaskets interposed between said cell units. Preferably, between adjacent cell units at least one of said gaskets or a group of said gasket is provided. The gaskets are aligned such that they overly along the stacking direction forming a column of gaskets. The electrochemical cell assembly further comprises a spring device. Preferably, the at least one spring member is located in a force path through the column of gaskets along the stacking direction. The spring device, in particular the at least one spring member, is configured to exert a spring force (compression force) on the column of gaskets in a direction parallel to the stacking direction, in particular for compensating loss of compression force through the stack due to creep and / or relaxation of the gaskets. Preferably, the spring device exerts a spring force on the column of gaskets.

[0009] In preferred embodiments, the electrochemical cell assembly further comprises a first end plate arranged at an end of the stack of cell units. In such embodiments, the spring device may comprise at least one spring member located between the first end plate and the stack of cell units.

[0010] Alternatively or additionally, the spring device may comprise at least one spring member located in the stack of cell units, e.g. between adjacent cell units or forming part of a cell unit.

[0011] The proposed configuration with internal spring device improves sealing of the fluid pathways inside the cell stack and, in particular, enhances a long-term stability of the cell assembly. Specifically, the spring device allows to compensate for loss of compression force in the stack, which may occur due to gasket relaxation during manufacturing of the cell assembly (e.g. during a stack baking process) or during use of the cell assembly (e.g. at elevated temperatures). Thus, manual re-adjustment of the compression force during the service life of the cell assembly can be omitted.

[0012] As used herein, the term "column" refers to the assembly of gaskets or groups of gaskets that are aligned along the stacking direction. As set out above, the gaskets are interposed between the cell units. Thus, the gaskets or groups of gaskets of said column may be separated from each other by a respective cell unit.

[0013] Preferably, the electrochemical cell assembly comprises a first end plate, a second end plate and a stack of cell units arranged, preferably held in compression, between said first end plate and said second end plate. The first end plate may be one of a base plate and top plate of the electrochemical cell assembly. The second end plate may be the other one of a base plate and a top plate of the electrochemical cell assembly.

[0014] In preferred embodiments, the stack of cell units is held in compression, preferably between the first end plate and an the second end plate, and the spring device is adapted to maintain said compression, in particular for compensating loss of compression force through the stack due to creep and / or relaxation of the gaskets (e.g. during manufacture of the electrochemical cell assembly and / or during its use).

[0015] The spring device may comprise a single spring member. The spring device may comprise a plurality of spring members. In preferred embodiments, the spring device comprises a plurality of spring members that are arranged through the stack of cell units in stacking direction, i.e. distributed along the stack of cell units. This has proven advantageous with regards to a homogeneous load distribution within the stack.

[0016] The at least one spring member may take different shapes. In some examples, the spring member or one of the spring members may take the form of a compression spring, e.g. a helical compression spring. In some examples, the spring member or one of the spring members may take the form of a disc spring (Belleville spring) or a stack of disc springs.

[0017] In preferred embodiments, the plurality of gaskets surrounds a fluid channel provided in the stack of cell units for supplying fluid to the cell units. Thus, a fluid channel (also referred to as internal fluid manifold / chimney) may be provided in the stack of cell units for supplying fluid to the cell units, wherein a plurality of gaskets is provided around said fluid channel to prevent loss of fluid. Preferably, the fluid channel extends through the stack of cell units along the stacking direction, preferably from the first end plate to the optional second end plate. Preferably, the fluid channel defines a fluid flow path from a fluid access port of the cell assembly to each of the cell units. Preferably, each gasket, or group of gaskets, delimits a section of the fluid channel. In such embodiments, the term "column" thus refers to the assembly of aligned gaskets or groups of gaskets surrounding the fluid channel.

[0018] In such embodiments having a fluid channel, the spring member or at least one of the spring members, in particular each spring member, is located adjacent to said fluid channel. Preferably, the spring member or at least one of the spring members, in particular each spring member, surrounds said fluid channel. This has proven advantageous with regards to a homogeneous force distribution around the fluid channel, thus leading to improved sealing. The at least one spring member may define a section of the fluid channel.

[0019] Preferably, the cell units and the gaskets together define, preferably delimit, the fluid channel. In some implementations, the cell units may each comprise a fluid port, preferably in the form of a through-hole, allowing for fluid entering or exiting the cell units. Said fluid port may form a section of the fluid channel. Preferably, said fluid port is in fluidic communication with electrochemically active layers of the cell unit (e.g. via respective fluid channels). Preferably, the fluid ports of the stacked cell units are aligned. Preferably, the fluid ports of the stacked cell units and the gaskets together define the fluid channel.

[0020] In preferred implementations, the gaskets of the stack of cell units are sealing rings, i.e. ring-shaped. The gaskets may be annular rings. The gasket may comprise a gasket opening. The central gasket opening preferably forms a section of the fluid channel. Preferably, the central gasket openings of the gaskets and the through-holes forming the fluid ports of the cell units together form the fluid channel.

[0021] Preferably, the gaskets are formed from a vermiculite material. The vermiculite material may comprise exfoliated vermiculite or consist of exfoliated vermiculite. An example for an exfoliated vermiculite material is the material Thermiculite (registered trademarks of the Flexitallic group).

[0022] The spring device, in particular the at least one spring member, may be located at different positions within the electrochemical cell assembly.

[0023] In some embodiments, the spring device or at least one spring member of the spring device is positioned between the optional first end plate and the stack of cell units. In such embodiments, preferably the spring device comprises a compression spring. In particular, the spring member of the spring device that is positioned between the first end plate and the stack of cell units may be a compression spring, e.g. a ceramic spring. Alternatively or additionally, a spring device or at least one spring member of the spring device, may be positioned between the optional second end plate and the stack of cell units.

[0024] In some embodiments, the electrochemical cell assembly further comprises a current transmission plate located between the optional first end plate and the stack of cell units. Preferably, the current transmission plate is in electrical contact with the stack of cell units, in particular with a neighbouring end of the stack of cell units. The current transmission plate may be a current collector plate or a current delivery plate. Preferably, the current transmission plate extends in a direction perpendicular to the stacking direction, preferably parallel to the first end plate. The current transmission plate may be formed from an electrically conductive material, preferably metal.

[0025] In such embodiments having a current transmission plate, the spring device or at least one spring member of the spring device may be positioned between the first end plate and the current transmission plate. Thus, the spring force provided by the spring device may be exerted on the stack of cell units via the current transmission plate. In other words, the current transmission plate may serve as a force distribution plate. Such a configuration aids reliable electrical contact in addition to improved sealing performance. In such embodiments, preferably the spring device comprises a compression spring. In particular, the spring member of the spring device that is positioned between the first end plate and the current transmission plate may be a compression spring, e.g. a ceramic spring.

[0026] The spring device, preferably the spring member or one of the spring members, may contact the current transmission plate. Alternatively, the spring device may act on the current transmission plate via an additional component located between the spring device and the current transmission plate.

[0027] In some embodiments, the electrochemical cell assembly further comprises an insulation plate located between the optional first end plate and the current transmission plate. In such embodiments, the spring device, in particular the at least one spring member, may act between, preferably is located between, the insulation plate and the current transmission plate.

[0028] In embodiments having a second end plate, the or an additional current transmission plate and / or the or an additional insulation plate may be located between the second end plate and the stack of cell units. In such embodiments, a spring device or at least one spring member of the spring device may be located between the second end plate and the current transmission plate, in particular between the insulation plate and the current transmission plate.

[0029] In some embodiments, the spring member or at least one of the spring members is provided between two adjacent cell units, i.e. within the stack of cell units. Thus, the spring member or at least one of the spring members may form part of the stack of cell units. In some embodiments, between at least some of the cell units, preferably between each pair of adjacent cell units, a spring member is provided. This contributes to a homogeneous load distribution inside the stack. In some embodiments, the spring member or at least one of the spring members is provided between two adjacent cell units, said spring member overlying a gasket provided between said cell units. Thus, the spring member may be stacked upon a gasket along the stacking direction. The spring member may be in direct contact with the gasket. The spring member may be separated from the gasket, e.g. by a spacer layer. Preferably, the spring member is configured such that it does not extend radially over an outer perimeter of the gasket in a plane perpendicular to the stacking direction.

[0030] The spring member or one of the spring members may be located between a gasket and an adjacent cell unit. The spring member or one of the spring members may be in touch-contact with a gasket of the stack of cell units on one side and in touch-contact with an adjacent cell unit on the other side.

[0031] In preferred embodiments, the spring member or at least one of the spring members is sandwiched between two gaskets. This allows for direct load transfer from the spring member to the gaskets, while providing reliable sealing of the fluid channel. Advantageously, between at least some of the cell units, two gaskets are provided, preferably around the fluid channel, said two gaskets overlying one another along the stacking direction, wherein at least one spring member is sandwiched between those two gaskets.

[0032] In some embodiments, the spring member or at least one of the spring members is embedded in a gasket material. Thus, the embedded spring member may be configured to provide a sealing function. The gasket material may be a vermiculite material as described above.

[0033] Preferably, the spring member or at least one of the spring members is embedded in one of said gaskets of the stack of cell units that are interposed between adjacent cell units.

[0034] In some embodiments, at least one of the gaskets of the stack of cell units that are interposed between adjacent cell units (in particular the gaskets surrounding the fluid channel) is a spring gasket, said spring gasket forming the spring member or one of the spring members. The spring gasket may comprise a spring element that is sandwiched between two layers of gasket material, preferably embedded in a gasket material. Such a configuration eases manufacturing of the electrochemical cell assembly due to reduced part count. The spring element preferably is configured to exert a spring force on adjacent cell units in a direction parallel to the stacking direction. The spring element may be a disc spring or a stack of disc springs. The gasket material may be a vermiculite material (see above). In some embodiments, at least one of the gaskets of the stack of cell units that are interposed between adjacent cell units (in particular the gaskets surrounding the fluid channel) is a beaded gasket, said beaded gasket forming the spring member or one of the spring members. A beaded gasket is a thin gasket (in some embodiments 0.1-0.3mm) with features embossed. Such gaskets are suitable for lower loads.

[0035] In some embodiments, the spring member or at least one of the spring members is (radially) offset from (i.e., not aligned with) the column of gaskets. For example, the spring device may further comprise a force distribution plate for distributing a compression force exerted on said plate by the at least one spring member to the column of gaskets. In implementations having a current transmission plate, said current transmission plate may serve as a force distribution plate (see above).

[0036] Advantageously, the spring device, preferably the at least one spring member, is more compliant than the gaskets, preferably at least 5 times as compliant, more preferably at least 10 times as compliant.

[0037] In some embodiments, the at least one spring member is formed from metal, preferably stainless steel. Metal has proven advantageous with regards to reliable spring properties even at elevated temperatures occurring during use of the cell assembly.

[0038] Alternatively, the at least one spring member may be formed from a ceramic material. Ceramics has proven particularly advantageous with regards to high-temperature stability and electrical isolation.

[0039] The spring member or at least one of the spring members may be provided separately from the cell units, i.e. be a component that is provided separately from the cell units during manufacturing of the cell assembly.

[0040] Alternatively, the spring member or at least one of the spring members may be integrally formed with a cell unit, i.e. form part of the cell unit or a component of the cell unit.

[0041] The spring device may comprise at least one spring member that is provided as separately from the cell unit and at least one spring member that is integrally formed with a cell unit.

[0042] In some embodiments, each cell unit comprises an interconnector plate (also referred to as interconnect or separator plate) and a support plate (also referred to as substrate). Preferably, the interconnector plate and the support plate are stacked upon each other along the stacking direction and are, preferably sealingly, attached to each other, preferably by welding, to define a fluid volume (also referred to as cell volume, particularly air volume) therebetween. Preferably, the interconnector plate and the support plate are formed from metal, preferably stainless steel.

[0043] Preferably, the support plate comprises electrochemically active layers (also referred to as cell chemistry layers). In particular, the support plate carries electrochemically active layers over a porous region.

[0044] Preferably, the electrochemically active layers are in fluidic communication with the fluid volume enclosed between the interconnector plate and the support plate via said porous region. The electrochemically active layers may comprise a fuel electrode layer, an electrolyte layer and an air or oxidant electrode layer. The electrochemically active layers may be deposited (e.g. as thin coatings or films) on and supported by the support plate.

[0045] Preferably, each cell unit comprises at least one fluid port, said fluid port being in fluid communication with the fluid volume defined between the interconnector plate and the support plate and forming a part of the fluid channel. In such embodiments, preferably the gaskets surround the fluid port(s) of the cell units. In preferred implementations, each fluid port takes the form of a through-hole extending through both the interconnector plate and the support plate.

[0046] In embodiments, in which the cell units each comprise a support plate and an interconnector plate, the spring member or one of the spring members may be integrally formed with the support plate and / or the interconnector plate. Thus, the support plate and / or the interconnector plate may be configured to exert a spring force along the stacking direction on the column of gasket. In some example implementations, the support plate or the interconnector plate may be shaped locally to form a spring member.

[0047] In such embodiments, preferably said spring member (that is integrally formed with the interconnector plate and / or the support plate) surrounds the fluid port of the cell unit. This allows for a homogeneous load distribution around the fluid port and, thus, for reliable sealing of the fluid port. The spring member or one of the spring members may be formed by a shaped section of the interconnector plate or the support plate surrounding the fluid port (preferably surrounding the through-hole formed therein). The shaped section may be formed by pressing the interconnector plate or the support plate.

[0048] The above-described variants of the spring members may be combined. Thus, in embodiments of the spring device comprising more than one spring member, different types of spring members, e.g. integrally formed spring members and separately formed spring members, may be combined. In addition, spring members at different locations may be combined. Thus, the spring device may, for example, comprise one or more spring members located between the first end plate and the stack of cell units and one or more spring members located within the stack.

[0049] In some embodiments, the electrochemical cell assembly comprises more than one column of gaskets that are axially offset in a direction perpendicular to the stacking direction. For example, the electrochemical cell assembly may comprise two or more (spatially separated) fluid channels, e.g. a fluid inlet channel and a fluid outlet channel, wherein each fluid channel is surrounded by a plurality of gaskets. In such implementations, the gaskets surrounding a respective fluid channel may form a respective column of gaskets. In such embodiments having more than one column of gaskets, the spring device may comprise at least one spring member for each column of gaskets, preferably associated with or at one end of each column.

[0050] The above-described concept of an electrochemical cell assembly comprising an integrated spring device is applicable to cell units of various types. Preferably, the cell units are solid oxide cell units, more preferably solid oxide fuel cell units (SOFCs) or solid oxide electrolyser cell units (SOECs). Most preferably, the cell units are metal-supported solid oxide fuel cell units or electrolyser cell units.

[0051] The cell units may be flat or planar. The cell units may each comprise multiple layers or plates overlying each other.

[0052] In some embodiments, the electrochemical cell assembly further comprises a housing surrounding the stack of cell units, preferably to define or enclose a fluid volume. The housing may be a stack enclosure defining a fluid volume containing the stack of cell units. The housing may be welded to a first end plate and optionally to a second end plate. The housing, the first end plate and, optionally, the second endplate together may form a stack enclosure defining a fluid volume containing the stack of cell units. The housing may be single piece. The housing may be formed of at least two parts, joined together at their seams, for example by welding. The housing may comprise or consist of a skirt around the cell units. Preferably, the spring device is located within said fluid volume defined by the housing and optionally the end plate(s).

[0053] The invention also relates to an interconnector plate for an electrochemical cell unit, preferably an interconnector plate for electrochemical cell units forming the stack of cell units in the electrochemical cell assembly described above. The interconnector plate has at least one fluid port adapted for fluidic communication with a fluid volume between said interconnector plate and a cell layer attached to said interconnector plate in an electrochemical cell unit, wherein the at least one fluid port is associated with a spring member integrally formed with the interconnector plate.

[0054] Preferably, the fluid port is provided by a through-hole formed in the interconnector plate. Thus, the interconnector plate may have at least one through-hole formed therein, said through-hole preferably forming a fluid port adapted for fluidic communication with a fluid volume between said interconnector plate and a cell layer attached to the interconnector plate in an electrochemical cell unit, wherein said through-hole is at least partially surrounded by a spring member integrally formed with the interconnector plate.

[0055] Preferably, the interconnector plate is formed from metal, more preferably from stainless steel. The advantages and optional features of the interconnector plate described above with respect to the electrochemical cell assembly are also applicable.

[0056] The invention also relates to a cell layer for an electrochemical cell assembly, preferably a cell layer for electrochemical cell units forming the stack of cell units in the electrochemical cell assembly described above. The cell layer comprises a, preferably metal, support plate carrying electrochemically active layers over a porous region, the support plate having at least one fluid port adapted for fluidic communication with a fluid volume between said support plate and an interconnector plate attached to the support plate in an electrochemical cell unit, wherein the at least one fluid port is associated with a spring member integrally formed with the support plate.

[0057] Preferably, the fluid port is provided by a through-hole formed in the support plate. Thus, the support plate may have at least one through-hole formed therein, said through-hole forming a fluid port adapted for fluidic communication with a fluid volume between said support plate and an interconnector plate attached to the support plate in an electrochemical cell unit, wherein said through- hole is at least partially surrounded by a spring member integrally formed with the support plate.

[0058] The invention also relates to an electrochemical cell unit for an electrochemical cell stack, the electrochemical cell unit comprising an interconnector plate and a cell layer. The cell layer comprises a support plate, preferably carrying electrochemically active layers over a porous region. The support plate and the interconnector plate are, directly or indirectly, preferably sealingly, attached to each other, preferably around their periphery, to enclose a fluid volume therebetween. The electrochemical cell unit has at least one fluid port, preferably in the form of a through-hole formed in the interconnector plate and / or the support plate, for fluidic communication with the fluid volume between said interconnector plate and said support plate. The at least one fluid port is associated with, preferably at least partially surrounded by, a spring member that is integrally formed with the interconnector plate and / or is associated with a spring member that is integrally formed with the support plate.

[0059] The invention also relates to a stack of (electrochemical) cell units, said stack of cell units comprising a plurality of cell units as described in the previous paragraph.

[0060] The invention also relates to a method of manufacturing an electrochemical cell assembly. The method comprises:

[0061] - (optionally) providing a first end plate, and optionally a second end plate,

[0062] - providing a plurality of cell units,

[0063] - providing a plurality of gaskets,

[0064] - providing at least one spring member,

[0065] - assembling the plurality of cell units, the plurality of gaskets, the at least one spring member, and optionally the first end plate, to obtain an electrochemical cell assembly, preferably of the kind described above.

[0066] Preferably, the plurality of cell units, the plurality of gaskets, and the at least one spring member are assembled such that the cell units are stacked upon the first end plate along a stacking direction to form a stack of cell units, with the gaskets being interposed between said cell units, wherein the gaskets are arranged such that they overlie along the stacking direction, thus forming a column of gaskets, wherein the at least one spring member is located so as to exert a spring force on the column of gaskets, said spring force acting along the stacking.

[0067] Preferably, the first end plate, the plurality of cell units, the plurality of gaskets, and the at least one spring member are assembled such that the cell units are stacked upon the first end plate along a stacking direction to form a stack of cell units, with the gaskets being interposed between said cell units. Preferably, the gaskets are arranged such that they overlie along the stacking direction, thus forming a column of gaskets. Preferably, at least one spring member is arranged between the first end plate and the stack of cell units and / or a spring member is arranged in the stack of cell units to exert a spring force on the column of gaskets in a direction parallel to the stacking direction.

[0068] The step of assembly may comprise stacking the cell units and the gaskets alternatingly, preferably upon the optional first end plate. In some embodiments, the method further comprises, after assembly, compressing the electrochemical cell assembly in a compression direction that is parallel to the stacking direction such that the at least one spring member is tensioned, preferably compressed, and thus exerts a spring force in a direction parallel to, preferably opposite, the compression direction.

[0069] Preferably, the method further comprises a step of fixing the electrochemical cell assembly in the compressed state. In preferred implementations, the method comprises providing a single or multipiece housing around the stack of cell units to fix the electrochemical cell assembly in the compressed state. The housing may be connected to the optional first end plate, and optionally the second end plate, by welding. Thus, the method may comprise welding a housing to the first and second end plates. Alternatively or in addition, fixing means, such as clamps, compression rods, plates or springs or bolts, may be applied to the electrochemical cell assembly in order to maintain the cell stack in the compressed state.

[0070] The invention also relates to a method of manufacturing a compressed electrochemical cell assembly, comprising:

[0071] - providing an electrochemical cell assembly, comprising a stack of cell units, said stack of cell units comprising a plurality of cell units stacked upon one another along a stacking direction and a plurality of gaskets interposed between said cell units, said gaskets being aligned such that they overlie along the stacking direction forming a column of gaskets, and a spring device comprising at least one spring member located so as to exert a spring force on the column of gaskets, said spring force acting along the stacking direction;

[0072] - compressing said electrochemical cell assembly in a compression direction parallel to the stacking direction such that the at least one spring member is tensioned, preferably compressed;

[0073] - fixing the electrochemical cell assembly in the compressed state, preferably by providing a housing around the stack of cell units.

[0074] The advantages and optional features described above in connection with the electrochemical cell assembly are also applicable to the methods of manufacturing. In order to avoid unnecessary repetition, reference is made to the above disclosure.

[0075] Further embodiments are derivable from the following description and the drawings: Fig. 1 shows a schematic perspective view of an example implementation of an electrochemical cell assembly;

[0076] Fig. 2 shows a cross-sectional view of an electrochemical cell assembly according to a first embodiment;

[0077] Fig. 3 shows a cross-sectional view of an electrochemical cell assembly according to a second embodiment comprising spring gaskets (see inset);

[0078] Fig. 4 shows a cross-sectional view of an alternative example implementation of a spring gasket;

[0079] Fig. 5 shows a cross-sectional view of an electrochemical cell assembly according to a third embodiment;

[0080] Fig. 6 shows a perspective explosion view of an example implementation of an electrochemical cell unit;

[0081] Fig. 7 shows a cross-sectional view of an electrochemical cell assembly comprising plural cell units according to Figure 6; and

[0082] Fig. 8 shows a cross-sectional view of a detail of an electrochemical cell assembly according to a fourth embodiment comprising integrally formed spring members.

[0083] Repeat use of reference symbols in the present specification and drawings is intended to represent the same or analogous features or elements.

[0084] Figure 1 schematically shows an example implementation of an electrochemical cell assembly 10. Figure 1 is intended to primarily provide an overview of the electrochemical cell assembly 10 and its components in general by way of example. The invention, however, is not limited to this specific design.

[0085] The electrochemical cell assembly 10 comprises a first end plate 12, a second end plate 14, and a stack 16 of cell units 18 (also referred to as 'cell repeat units') arranged between the first end plate 12 and the second end plate 14. In the assembled state, preferably the stack 16 is held in a compressed state between the first end plate 12 and the second end plate 14.

[0086] The stack 16 comprises a plurality of cell units 18 that are stacked upon each other along a stacking direction 20. In the example, the cell units 18 are configured essentially planar and extend perpendicular to the stacking direction 20. Adjacent cell units 18 preferably are in electrical and mechanical contact with each other.

[0087] As set out above, the cell units 18 may be fuel cell units, electrolyser cell units or reversible cell units comprising electrochemically active layers. A preferred configuration of a cell unit 18 will be described in more detail below with reference to Figure 6.

[0088] The invention, however, is not limited to such kinds of cell units 18.

[0089] In the example, the electrochemical cell assembly 10 further comprises optional insulation plates 22 located between the end plates 12, 14 and the stack 16 of cell units 18 (see Figures 1 and 2).

[0090] The electrochemical cell assembly 10 preferably also comprises a current collection or delivery system, known in the art (not shown). In the example of Figure 2, the electrochemical cell assembly 10 comprises current transmission plates 24 located between the insulation plates 22 and the stack 16 of cell units 18. In addition, the current collection or delivery system may comprise one or more electrical connection members, such as busbars, for electrically connecting said current transmission plates (not shown).

[0091] Preferably, the electrochemical cell assembly 10 further comprises a housing 26 surrounding the stack 16 of cell units 18 (see Figure 2, not shown in Figure 1). The housing 26 may be configured to maintain the stack 16 in a compressed state between the end plates 12, 14. In some examples, the housing 26 may be welded to the first end plate 12 and / or the second end plate 14.

[0092] The housing 26 may be single-piece or multi-piece. In preferred examples, the housing 26 is formed from metal, preferably steel.

[0093] The housing 26 and the end plates 12, 14 together enclose a fluid volume 28 for first fluid around the stack 16 of cell units 18. In fuel cell operation mode, preferably the first fluid is air or oxidant. During operation of the cell assembly 10, the fluid volume 28 may be supplied with first fluid via respective fluid ports provided in one of the end plates 12, 14 or in the housing 26 (not shown).

[0094] As can be seen from Figure 2, the cell assembly 10 comprises at least one fluid channel 30, 32 (also referred to as fluid manifold or chimney) for transporting second fluid (in fuel cell operation mode preferably fuel, e.g. hydrogen) between the cell units 18 and the exterior of the cell assembly 10. In the specific example shown in Figure 2, the cell assembly 10 comprises a fluid inlet channel 30 and a fluid outlet channel 32, which are axially separated in a direction perpendicular to the stacking direction 16. In other embodiments, the cell assembly 10 may comprise more or less fluid channels 30, 32.

[0095] The fluid inlet channel 30 is configured to supply second fluid, preferably fuel, to the cell units 18. The fluid outlet channel 32 is configured to remove second fluid, preferably exhaust fuel, from the cell units 18.

[0096] The fluid inlet channel 30 and the fluid outlet channel 32 are fl uidically connected via the cell units 18. Specifically, each cell unit 18 has a fluid inlet port 34, preferably in the form of a through-hole 36, and a fluid outlet port 38, preferably also in the form of a through-hole 36 (further details see below). The fluid inlet port 34 (through-hole 36) forms a section of the fluid inlet channel 30 and the fluid outlet port 38 forms a section of the fluid outlet channel 32.

[0097] Referring to Figure 2, it can be seen that the stack 16 of cell units 18 further comprises gaskets 40 that are interposed between the cell units 18 and surround the fluid ports 34, 38 (through-holes 36) of the cell units 18. Preferably, the gaskets 40 are annular sealing rings having a gasket opening 42 (see inset in Figure 2).

[0098] As shown in Figure 2, the gaskets 40 associated with a respective fluid channel 30, 32 are aligned such that they overly along the stacking direction 20, thus forming a column 44 of gaskets 40 surrounding said fluid channel 30, 32.

[0099] The aligned through-holes 36 (fluid ports 34, 38) of the cell units 18 and the associated column 44 of gaskets 40 (specifically the gasket openings 42) together form the respective fluid channel 30, 32 (see Figure 2).

[0100] The gaskets 40 may be formed from an exfoliated vermiculite material.

[0101] The fluid ports 34, 38 of a cell unit 18 are in fluidic communication with each other via an inner fluid volume 46 (cell volume) of the cell unit 18 (described in more detail below with respect to Figure 6). During use of the electrochemical cell assembly 10, second fluid, in particular fuel, may, for example, flow along the fluid inlet channel 30 in stacking direction 20 up, circulate through the cell units 18, and then flow down in a direction opposite the stacking direction 20 along the fluid outlet channel 32. As shown in Figure 2, the second end plate 14 comprises a fluid access port 48 for supplying fluid from an exterior of the cell assembly 10 to the fluid inlet channel 30, and a fluid exhaust port 50 for discharging fluid from the fluid outlet channel 32 to the exterior. In the example, the fluid access port 48 and the fluid exhaust port 50 are each formed by a respective through-hole 52 formed in the second end plate 14.

[0102] In the example, the fluid ports 48, 50 in the second end plate 14 are in fluidic communication with the associated fluid channel 30, 32 via a flow path extending through the neighbouring insulation plate 22 and current transmission plate 24. Said fluid path may, for example, be provided by a sealing device (e.g. comprising a sleeve, not shown) inserted in respective through-holes formed in the insulation plate 22 and the current transmission plate 24.

[0103] According to the invention, the electrochemical cell assembly 10 further comprises a spring device 54 that is configured to exert a spring force on the columns 44 of gaskets 40 in a direction parallel to the stacking direction 20.

[0104] Figure 2 shows an example implementation of such a spring device 54 according to a first embodiment. In this example, the spring device 54 comprises two spring members 56 (one associated with the fluid inlet channel 30 and one associated with the fluid outlet channel 32) that are located between the first end plate 12 and the neighbouring current transmission plate 24. The spring members 56 are each configured to exert a spring force on the current transmission plate 24 in a direction opposite the stacking direction 20 (illustrated by the arrows in Figure 2). The current transmission plate 24 thus serves as a force distribution plate to transfer the force applied by the spring members 56 to the gaskets 40.

[0105] As set out above, the spring device 54 aids maintaining a compression force on the stack 16, in particular on the gaskets 40, during lifetime of the cell assembly 10.

[0106] Figure 2 illustrates the spring members 56 as helical compression springs. The invention, however, is not limited to this type of springs. The spring members 56 may, for example, also each take the form of a disc spring or a stack of disc springs.

[0107] In the example, the spring members 56 are arranged in respective cut-outs 58, e.g. in the form of through-holes, formed in the insulation plate 22. Alternatively or in addition, the spring device 54 may comprise one or more spring members 56 located within the stack 16 of cell units 18, e.g. between adjacent cell units 18.

[0108] Figure 3 shows an example implementation of an embodiment comprising spring members 56 that are located between the cell units 18. Specifically, some of the gaskets of the column 44 of gaskets are spring gaskets 60 comprising a spring element 62 embedded in a gasket material 64 (see inset of Figure 3 for further details).

[0109] While Figure 3 shows such spring gaskets 60 only between some of the cell units 18, it will be understood that all gaskets can be spring gaskets 60 or only one gasket per column 44 may be a spring gasket 60.

[0110] Alternatively to such an embedded configuration, there may be two separate gaskets 40 provided between adjacent cell units 18, with a spring member 56 sandwiched between those gaskets 60. An example implementation of such a configuration is illustrate in Figure 4.

[0111] As set out above, different types of spring members 56 may be combined. For example, Figure 5 shows a further embodiment, in which the spring device 54 comprises spring members 56 located between the first end plate 12 and the stack 16 as described in connection with Figure 2 and, additionally, spring gaskets 60 interposed between the cell units 18.

[0112] The spring device 54 is applicable to various types of cell units 18. A preferred configuration of a cell units 18 will be described below with respect to Figure 6.

[0113] As shown in Figure 6, the cell unit 18 comprises an interconnector plate 66 (also referred to as interconnect or separator plate) and a support plate 68 (also referred to as substrate), which are stacked upon each other along the stacking direction 20. The interconnector plate 66 and the support plate 68 are formed from metal, preferably stainless steel.

[0114] The interconnector plate 66 and the support plate 68 each have a periphery 70, 72 and a central portion 74, 76 surrounded by the periphery 70, 72. The interconnector plate 66 and the support plate 68 are attached to each other at their peripheries 70, 72, preferably by welding, to enclose a fluid volume 46 therebetween (see Figure 7). The support plate 68, in its central portion 74, carries the electrochemically active layers 78 over a porous region. In the example, the support plate 68 is a flat component.

[0115] In the example, the interconnector plate 66 is tub-shaped having flanged perimeter features 80 around its periphery 70, preferably formed by pressing the interconnector plate 66 to a concave configuration. As can be seen from Figure 6, the flanged perimeter features 70 extend out of the predominant plane of the interconnector plate 66 to create a concavity (and a convexity to the outside surface) in the interconnector plate 66. In the assembled state of the cell unit 18, said concavity forms the fluid volume 46 enclosed between the interconnector plate 66 and the support plate 68. The fluid volume 46 is in fluid communication with the electrochemically active layers 80 via said porous region.

[0116] In the specific example, the interconnector plate 66 has a structured area 82 in its central portion 74. Specifically, the interconnector plate 66 has optional shaped inward protrusions 84 extending into the fluid volume 46. The inward protrusions 84 form a supporting structure helping to maintain the fluid volume 46 (cell space) open. The inward protrusions 84 define fluid passageways therebetween. Preferably, the inward protrusions 84 abut the support plate 68.

[0117] In the example, the interconnector plate 66, in its structured area 82, further comprises shaped outward projections 86 (see also Figure 7). Said outward projections 86 form contact portions of the cell unit 18 for contacting an adjacent cell unit 18, specifically the electrochemically active layers 78 of an adjacent cell unit 18. More specifically, the outward projections 86 engage at their ends against an outer surface of the electrochemically active layer 78 of an adjacent cell unit 18. The outward projections 86 define fluid passageways 88 for first fluid (e.g., air or oxidant) to flow between adjacent cell units 18 (see Figure 7).

[0118] In order to supply (second) fluid, in particular fuel, to the fluid volume 46 between the support plate 68 and the interconnector plate 66 (and thus to the electrochemically active layers 80) or to remove fluid from said fluid volume 46, the interconnector plate 66 and the support plate 69 each have at least one, in the specific example four, through-holes 36 formed therein, wherein an aligned pair of a through-hole formed in the interconnector plate 66 and the associated through-hole formed in the support plate 68 forms a fluid port 38 of the cell unit 18 (see also above).

[0119] As set out above, alternatively or additionally to the spring members 56 described above in connection with Figures 2 to 5, the spring device 54 may comprise spring members 56 that are integrally formed with one or both of the interconnector plate 66 and the support plate 68. Figure 8 shows (in a simplified schematic sketch) an example implementation of such an "integral" spring member 56. Specifically, the interconnector plate 66 and the support plate 68 each have a shaped portion 90 around a respective fluid port 34, 38 (through-hole 36), which acts as a spring member 56, when subject to a compression force.

[0120] It will be understood that the different types of (separate and integral) spring members 56 may be combined. Thus, for example, the gaskets 40 shown in Figure 8 may also be spring gaskets 60.

Claims

Claims1. An electrochemical cell assembly (10), preferably fuel cell assembly or electrolyser cell assembly, comprising- a stack (16) of cell units (18), said stack (16) of cell units (18) comprising a plurality of cell units (18) stacked upon one another along a stacking direction (20) and a plurality of gaskets (40) interposed between said cell units (18), said gaskets (40) being aligned such that they overlie along the stacking direction (20) forming a column (44) of gaskets (40),- a spring device (54) comprising at least one spring member (56) located so as to exert a spring force on the column (44) of gaskets (40), said spring force acting along the stacking direction (20).

2. The electrochemical cell assembly (10) according to claim 1, wherein the spring device is located between a first end plate (12) and the stack (16) of cell units (18).

3. The electrochemical cell assembly (10) according to the preceding claim, further comprising a current transmission plate (24) located between the first end plate (12) and the stack (16) of cell units (18), wherein the spring device (54) or at least one spring member (56) of the spring device (56) is positioned between the first end plate (12) and the current transmission plate (24).

4. The electrochemical cell assembly (10) according to claim 2, wherein the spring member (56) or at least one of the spring members (56) is offset from the column (44) of gaskets (40).

5. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the at least one spring member is (56) located in the stack (16) of cell units.

6. The electrochemical cell assembly (10) according to the preceding claim, wherein the spring member (56) or at least one of the spring members (56) is provided between two adjacent cell units (18).

7. The electrochemical cell assembly (10) according to the preceding claim, said spring member (56) overlying a gasket (40) provided between the cell units (18).

8. The electrochemical cell assembly (10) according to any one of claims 5 to 7, wherein the spring member (56) or at least one of the spring members (56) is integrally formed with a cell unit (18).

9. The electrochemical cell assembly (10) according to any one of claims 5 to 8, wherein each cell unit comprises a support plate (68) and an interconnector plate (66), wherein : the support plate (68) carries electrochemically active layers (78), preferably over a porous region, the support plate (68) and the interconnector plate (66) are attached to each other to define a fluid volume (46) therebetween; wherein the spring member (56) or one of the spring members (56) is integrally formed with the support plate (68) and / or the interconnector plate (66) of a cell unit (18).

10. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein said stack (16) of cell units (18) is held in compression and the spring device (54) is adapted to maintain said compression.

11. The electrochemical cell assembly according any one of the preceding claims, wherein: said plurality of gaskets (40) surrounds a fluid channel (30, 32) provided in said stack (16) of cell units (18) for supply of a fluid to the cell units (18), and said fluid channel (30, 32) extends through the stack (16) of cell units (18) along the stacking direction (20).

12. The electrochemical cell assembly (10) according to the preceding claim, wherein the at least one spring member (56) is located adjacent to or around said fluid channel (30, 32).

13. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the spring member (56) or at least one of the spring members (56) is sandwiched between two gaskets (40).

14. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the spring member (56) or at least one of the spring members (56) is embedded in a gasket material (64).

15. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein at least one of the gaskets (40) is a spring gasket (60), said spring gasket comprising a springelement (62) that is sandwiched between two layers of gasket material (64), said spring gasket (60) forming the spring member (56) or one of the spring members (56).

16. The electrochemical cell assembly according to any one of the preceding claims, wherein at least one of the gaskets (40) is a beaded gasket, said beaded gasket forming the spring member (56) or one of the spring members (56).

17. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the spring device (54), preferably the at least one spring member (56), is more compliant than the gaskets (40), preferably at least 5 times as compliant, more preferably at least 10 times as compliant.

18. The electrochemical cell assembly (10) according to any preceding claims, wherein said spring member (56) surrounds a fluid port (34, 38) of the cell unit (18).

19. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the spring device (54) comprises a plurality of spring members (56), said plurality of spring members (56) being arranged through the stack (16) of cell units (16).

20. The electrochemical cell assembly (10) according to any one of the preceding claims, comprising more than one column (44) of gaskets (40), wherein the spring device (54) comprises at least one spring member (56) for each column (44) of gaskets (40).

21. An interconnector plate (66) for an electrochemical cell unit (18), the interconnector plate (66) having at least one fluid port (34, 38), preferably in the form of a through-hole (36), adapted for fluidic communication with a fluid volume (46) between said interconnector plate (66) and a cell layer attached to said interconnector plate (66) in an electrochemical cell unit (18), wherein the at least one fluid port (34, 38) is associated with, preferably at least partially surrounded by, a spring member (56) integrally formed with the interconnector plate (66).

22. A cell layer for an electrochemical cell unit, the cell layer comprising a support plate (68) carrying electrochemically active layers (78), preferably over a porous region, the support plate (68) having at least one fluid port (34, 38), preferably in the form of a through-hole (36), adapted for fluidic communication with a fluid volume (46) between said support plate (68) and an interconnector plate (66) attached to said support plate (68) in an electrochemical cell unit(18), wherein the at least one fluid port (34, 38) is associated with, preferably at least partially surrounded by, a spring member (56) integrally formed with the support plate (68).

23. An electrochemical cell unit (18) for an electrochemical cell stack (16), the electrochemical cell unit (18) comprising an interconnector plate (66), preferably the interconnector plate (66) of claim 21, and a cell layer, preferably the cell layer of claim 22 , wherein: the cell layer comprises a support plate (68), the support plate (68) and the interconnector plate (66) are, preferably sealingly, attached to each other to enclose a fluid volume (46) therebetween the cell unit (18) has at least one fluid port (34, 38), preferably in the form of a through- hole (36) formed in the interconnector plate (66) and / or the support plate (68), for fluidic communication with the fluid volume (46) between the interconnector plate (66) and the support plate (68), the at least one fluid port (34, 38) is associated with a spring member (56) that is integrally formed with the interconnector plate (66) and / or a spring member (56) that is integrally formed with the support plate (68).

24. A stack (10) of plural electrochemical cell units (18) each according to claim 23.

25. An electrochemical cell assembly (10) according to any one of claims 1 to 20, wherein the cell units (18) are electrochemical cell units according to claim 23.

26. Method of manufacturing an electrochemical cell assembly (10), preferably according to any one of claims 1 to 20 or 25, the method comprising:- providing a plurality of cell units (18),- providing a plurality of gaskets (40),- providing at least one spring member (56),- assembling the plurality of cell units (18), the plurality of gaskets (40), and the at least one spring member (56) to obtain an electrochemical cell assembly (10), in which the cell units (18) are stacked along a stacking direction (20) to form a stack (18) of cell units (18), with the gaskets (40) being interposed between said cell units (18) such that they overlie along the stacking direction (20) forming a column (44) of gaskets (40), and in which the at least one spring member (56) is located so as to exert a spring force on the column (44) of gaskets (40), said spring force acting along the stacking direction (20).U. The method according to the preceding claim, further comprising compressing the electrochemical cell assembly (10) in a compression direction parallel to the stacking direction (20) such that the at least one spring member (56) is tensioned, preferably compressed.

28. The method according to the preceding claim, further comprising providing a housing (26) around the stack (16) of cell units (18) to fix the electrochemical cell assembly (10) in the compressed state.

29. Method of manufacturing a compressed electrochemical cell assembly (10), comprising: - providing an electrochemical cell assembly (10) according to any one of claims 1 to 20 or25,- compressing said electrochemical cell assembly (10) in a direction parallel to the stacking direction (20) such that the at least one spring member (56) is tensioned, preferably compressed; - fixing the electrochemical cell assembly (10) in the compressed state, preferably by providing a housing (26) around the stack (16) of cell units (18).

Images