ELECTROCHEMICAL CELL STACK

Abstract

An electrochemical cell assembly (1400) comprising a base plate (308) and a top plate (303) between which a stack of planar cell units (306) and at least one electrical end plate (1402, 1407) are disposed in compression. The electrical end plate (1402, 1407) comprises a two-layer construction in which a first layer (1416, 1419) and a second layer (1417, 1420) formed of different respective materials are permanently connected together to form a single conductive body. The first layer (1416, 1419) of the electrical end plate (1402, 1407) is electrically connected to an external electrical terminal (301, 505) of the cell assembly, and the second layer (1417, 1420) of the electrical end plate (1402, 1407) has an outwardly facing side having a first electrically conductive ceramic layer (1418, 1824) bonded thereto that is in face-to-face abutment with, and in electrical contact with, an adjacent cell unit (306).

Claims

1. An electrochemical cell assembly comprising: a base plate and a top plate between which a stack of planar cell units and at least one electrical end plate are disposed in compression, wherein: the electrical end plate comprises a two-layer construction in which a first layer and a second layer formed of different respective materials are permanently connected together to form a single conductive body, the first layer of the electrical end plate is electrically connected to an external electrical terminal of the cell assembly, and the second layer of the electrical end plate has an outwardly facing side having a first electrically conductive ceramic layer bonded thereto that is in face-to-face abutment with, and in electrical contact with, an adjacent cell unit.

2. The assembly according to claim 1, wherein the adjacent cell unit has a second electrically conductive ceramic layer bonded to the side which is in face-to-face abutment with the first electrically conductive ceramic layer of the electrical end plate, and the first and second electrically conductive ceramic layers are made of the same material.

3. The assembly according to claim 1, wherein the first electrically conductive ceramic layer of the electrical end plate has a thickness selected such that the spacing between the at least one electrical end plate and the adjacent cell unit is the same as the spacing between the remaining cell units of the stack.

4. The assembly according to claim 1, wherein the stack comprises electrochemically active cell units, each of which comprise a separator plate and a cell-supporting metal substrate plate.

5. The assembly according to claim 4, wherein the second layer of the electrical end plate is made of the same material as the separator plate.

6. The assembly according to claim 4, wherein the second layer of the electrical end plate has essentially the same configuration as the separator plate.

7. The assembly according to claim 1, wherein the second layer of the electrical end plate has a 3D contoured construction with a series of projections extending outwardly so as to abut the adjacent cell unit, over which projections the first electrically conductive ceramic layer extends as a discontinuous layer bonded thereto.

8. The assembly according to claim 5, wherein the first electrically conductive ceramic layer is made of the same material as a second electrically conductive ceramic layer bonded to a metal substrate plate of the adjacent cell unit that is in face-to-face abutment with the first electrically conductive ceramic layer.

9. The An assembly according to claim 8, wherein the adjacent cell unit is electrochemically active, and the second electrically conductive ceramic layer comprises an outermost electrode layer of an electrochemically active cell layer bonded to the metal substrate plate of the adjacent cell unit.

10. The assembly according to claim 8, wherein the adjacent cell unit is electrochemically inactive, and the second electrically conductive ceramic layer is an electrode material layer that is bonded to the metal substrate plate of the adjacent cell unit.

11. The assembly according to claim 4, wherein the second layer of the electrical end plate is made of the same material as the cell-supporting metal substrate plate.

12. The assembly according to claim 4, wherein the second layer of the electrical end plate has essentially the same configuration as the cell-supporting metal substrate plate.

13. The assembly according to claim 1, wherein the second layer of the electrical end plate has a flat outwardly facing side with the first electrically conductive ceramic layer comprising a continuous layer bonded thereto.

14. The assembly according to claim 4, wherein the first electrically conductive ceramic layer is made of the same material as a second electrically conductive ceramic layer bonded to a separator plate of the adjacent cell unit that is in face-to-face abutment with the first electrically conductive ceramic layer.

15. The assembly according to claim 1, comprising both a first electrical end plate at one end of the stack as defined in claim 5 and a second electrical end plate at the other end of the stack as defined in claim 14.

16-31. (canceled)

32. The assembly according to claim 1, wherein the electrochemical cells comprise planar, solid oxide, fuel cell or electrolyser cell units.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0104] FIGS. 1 and 2 are schematics of prior art cell stack arrangements.

[0105] FIG. 3 is a cross sectional view of a cell stack arrangement in accordance with a first aspect of the present invention.

[0106] FIG. 4 is a cross sectional view of a cell stack arrangement in accordance with the first aspect.

[0107] FIG. 5A is a cross sectional view of a cell stack arrangement in accordance with the first aspect and FIG. 58 is an enlarged view of a portion of the cell stack arrangement of FIG. 5A.

[0108] FIG. 6A a cross sectional view of a cell stack arrangement in accordance with the first aspect and FIGS. 6B and 6C are enlarged views of a portion of the cell stack arrangement of FIG. 6A.

[0109] FIG. 7 is a plan view of the first electrical end plate and second electrical end plate in accordance with the first aspect.

[0110] FIG. 8 is an exploded perspective view of the cell stack arrangement shown in FIG. 5A in accordance with the first aspect.

[0111] FIG. 9 is an exploded perspective view of the cell stack arrangement shown in FIG. 6A in accordance with the first aspect.

[0112] FIG. 10 is a cross sectional view of a cell stack arrangement in accordance with a second aspect the present invention.

[0113] FIG. 11 is an exploded perspective view of the cell stack arrangement shown in FIG. 10.

[0114] FIG. 12 is an exploded view of a first electrical end plate in accordance with the second aspect.

[0115] FIG. 13 is an exploded view of a second electrical end plate in accordance with the second aspect.

[0116] FIG. 14 is a cross sectional view of a portion of a cell stack arrangement in accordance with the second aspect.

[0117] FIG. 15 is a cross sectional view of a portion of a cell stack arrangement in accordance with the second aspect.

[0118] In the following figures and description like reference numerals will be used for like elements in different figures.

DETAILED DESCRIPTION OF 1ST ASPECT

[0119] Referring to FIG. 3, a cross sectional view of an electrochemical cell stack arrangement 300 is shown, the cross section is truncated at the right-hand side so as to show detail of an internal manifold (chimney), an electrical stud, and an electrical end plate. A stack of five repeating cell units 306 are shown forming the electrochemical cell stack, the number of cell units is reduced for illustrative purposes and is typically much larger (for example 30-200). The cell units 306 comprise a substrate (or metal support plate) 306a and a separator (or interconnect) 306b and may be similar to those described in the Applicant's earlier patent application WO 2015/136295. The substrate 306a carries an electrochemically active layer (or active fuel cell component layer, not shown) comprising respective anode, electrolyte and cathode layers respectively deposited (e.g. as thin coatings/films) on and supported by the metal support plate (e.g. steel plate or foil), the electrochemically active layer faces the separator 306b of the adjacent cell unit 306. The metal support plate 306a has a porous region (not shown) surrounded by a non-porous region with the active layers being deposited upon the porous region so that gases may pass through the pores from one side of the metal support plate 306a to the opposite side to access the active layers coated thereon. As shown in FIG. 3, each cell unit 306 comprises two plates or layers—the metal support plate 306a and a separator plate 306b (but a spacer plate may be sandwiched between the metal support plate 306a and the separator plate 306b). It also has fluid ports that are provided in the plates (for oxidant and/or fuel) and the plates are stacked upon one another and welded (fused together) to form a single metal-supported repeat cell unit 306 with a fluid volume in the middle defined by the space provided in between the metal support plate 306a and the separator plate 306b. The metal components of the fuel cell stack repeat layer 306 are in electrical contact with one another, with electron flow between them being primarily via the fuse/weld path, thereby avoiding surface-to-surface contact resistance losses.

[0120] As discussed in WO2015/136295, the porous region comprises small apertures (holes drilled through the metal foil substrate) (not shown) extending through the metal support plate 306a, in a location to overlie the anode (or cathode, depending on the polarity orientation of the electrochemically active layer), which is positioned under the metal support plate 306a. These are positioned in the large space or aperture between the metal support plate 306a and the separator plate 306b (and which may be defined by the spacer plate) so as to allow the fluid volume to be in fluid communication with the electrochemically active layers on the underside of the support plate 306a through the small apertures.

[0121] In the separator plate 306b, up and down corrugations are provided to extend up to the cathode (or anode, depending on the polarity orientation of the electrochemically active layers) of a subsequent (or neighboring) fuel cell unit stacked onto this fuel cell unit, and down to the metal support plate 306a of its own fuel cell unit 306. This thus electrically connects between adjacent fuel cells units 306 of a stack to put the electrochemically active layers of the stack (usually one on each fuel cell unit) in series with one another.

[0122] The stack of cell units 306 in FIG. 3 are stacked with gaskets 304 positioned between neighboring cell units 306. Each gasket 304 surrounds a fluid port of the cell unit and is electrically insulating. The stack of cell units 306, with respective gaskets 304, are positioned one atop another such that corresponding fluid ports in the cell units 306 are aligned to form an internal manifold or chimney through the stack of cell units, through which a fluid may be delivered to, and exhausted from, the cell units (specifically, to the opening between the metal support plate 306a and the separator plate 306b of each cell unit 306). The gaskets 304 provide a fluidic seal between their surface and that of the abutting surface. The gaskets 304 are preformed gaskets and are not electrically conductive. The gaskets may, for example, be made of a vermiculite (e.g. thermiculite), which may provide a superior sealing performance compared to mica or ceramic while requiring much lower load to seal.

[0123] Either or both of the metal support plate 306a and the separator plate 306b of a cell unit 306 may be provided with dimples (not shown in FIG. 3) or other 3D protrusions protruding toward and contacting the other of the metal support plate 306a and the separator plate 306b in a region surrounding the fluid port (i.e. surrounding the chimney) and in line with the gaskets 304. The dimples transfer compression through the stack of cell units, supporting compression applied to the cell unit by the gaskets (port gaskets, that is gaskets surrounding a port, the gaskets are typically annular surrounding a port of circular cross-section) 304 positioned above and below the cell unit, and maintain a separation (gap) between the metal support plate 306a and the separator plate 306b of a single cell unit 306. The dimples may be arranged in rings around the port, and allow a first fluid to enter or exit the gap between the metal support plate 306a and the separator plate 306b of a cell unit 306 (as described further with respect to FIGS. 5 and 6).

[0124] In this embodiment, positioned to each end of the stack of cell units are a power take off assembly and a top plate or baseplate. A power take off assembly comprising a first electrical end plate 302 and an electrical stud 301 is positioned to the upper end of the stack of cell units, with the first electrical end plate 302 positioned atop the stack of cell units. The first electrical end plate 302 is separated from the end of the stack by a (port) gasket 304, which is identical to the (port) gaskets used between cell units 306 in the stack. The first electrical end plate 302 blocks the chimney, by means of a base portion from which the electrical stud extends perpendicularly, such that fluid may not pass the first electrical end plate 302, as discussed further below. The first electrical end plate 302 is in electrical contact with the cell unit 306 at the upper end of the stack of cell units 306. The first electrical end plate 302 transfers electrical potential from the cell unit 306 at the upper end of the stack of cell units 306 to the electrical stud 301, which transfers the potential external to the cell stack arrangement 300, the stud acting as an electrical terminal. The first electrical end plate 302 and electrical stud 301 may be unitary; alternatively they may be two separate components which are welded, brazed, screwed, or otherwise affixed to one another.

[0125] Positioned above (i.e. outwardly of) the first electrical end plate 302 is a first electrically insulating plate 305a, so that the first electrical end plate 302 is positioned between the first electrically insulating plate 305a and the stack of cell units. The first electrically insulating plate 305a extends preferably across the stack to at least the same extent as the underlying stacked cell units and is separated from the first electrical end plate 302 by a (port) gasket 304, which is identical to the gaskets used between cell units 306 in the stack. The gasket 304 surrounds an opening in the first electrically insulating plate 305a which is coaxial with (and forms a continuation of) the chimney for internal manifold) through the stack, through which the electrical stud 301 needs to pass.

[0126] Positioned above the first electrically insulating plate 305a is a top plate 303, so that the first electrically insulating plate 305a is positioned between the top plate 303 and the first electrical end plate 302. The first electrically insulating plate 305a is separated from the top plate 303 by a (port) gasket 304, which is identical to the gaskets used between cell units 306 in the stack. The gasket 304 surrounds an opening in the top plate 303 which is coaxial with (and forms a continuation of) the chimney through the stack, through which the electrical stud 301 passes. The first electrically insulating plate 305a provides electrical insulation between the electrical end plate 302 and the top plate 303. The first electrically insulating plate 305a may be manufactured from mica or a non-conductive ceramic material.

[0127] Positioned below the stack of cell units (i.e. to the opposite end of the stack than that having the first electrical end plate 302, first electrically insulating plate 305a, and top plate 303) is a second electrical end plate 310, second electrically insulating plate 305b, and base plate 308. The second electrical end plate 310 is separated from the end of the stack by a gasket 304, which is identical to the (port) gaskets used between cell units 306 in the stack. The second electrical end plate 310 is provided with a port, which is aligned with the ports through the cell units 306, through which fluid may pass, as such, it defines part of the chimney. The second electrical end plate 310 is in electrical contact with the cell unit 306 at the lower end of the stack of cell units 306, and has opposite polarity to the first electrical end plate. The second electrical end plate 310 may be in electrical contact with a second electrical stud (not shown) to transfer electrical energy out of the cell stack arrangement 300.

[0128] Positioned below the second electrical end plate 310 is the second electrically insulating plate 305b, so that the second electrical end plate 310 is positioned between the second electrically insulating plate 305b and the stack of cell units. The second electrically insulating plate 305b is separated from the second electrical end plate 310 by a gasket 304, which is identical to the gaskets used between cell units 306 in the stack. The gasket 304 surrounds an opening in the second electrically insulating plate 305b which is coaxial with (and forms part of) the chimney through the stack, through which fluid may pass.

[0129] Positioned below the second electrically insulating plate 305b is the base plate 308, so that the second electrically insulating plate 305b is positioned between the base plate 308 and the second electrical end plate 310. The base plate 308 is separated from the second electrically insulating plate 305b by a gasket 304, which is identical to the gaskets used between cell units 306 in the stack. The gasket 304 surrounds an opening in the base plate 308 which is coaxial with (and forms part of) the chimney through the stack, through which fluid may pass, and provides a port for fluid delivery to or exhaust from the chimney and thereby the stack. The second electrically insulating plate 305b, which is similar to the first electrically insulating plate 305a, provides electrical insulation between the electrical end plate 310 and the base plate 308. The second electrically insulating plate 305b may be manufactured from mica or a non-conductive ceramic material.

[0130] Compression means 307 is provided to maintain a compression which was applied during manufacture. The compression means 307 is provided between the base plate 308 and top plate 303 and maintains a compression in components therebetween (i.e. gaskets 304, electrically insulating plates 305a, 305b, first and second electrical end plates 302, 310, and cell units 306). The compression means 307 of FIG. 3 is shown as a skirt which may be welded or otherwise permanently attached to the base plate 308 and top plate 303 while an external compression is applied between the same during manufacture. Once the external compression force is removed, a tensile force through the skirt maintains the compressive load in the stack, via the base plate 308 and top plate 303. The weld path may encircle the base plate 308 and top plate 303 and form a fluid seal to fluidically seal a (fluid) volume defined by the base plate 308, top plate 303, and skirt 307 containing the stack. The base plate 308 and top plate 303 are relatively stiff plates (stiffer than any of the other plates in the arrangement, e.g. the metal support plate, separator plate, cell unit as a whole, and the electrical end plates, and is stiffer for example by being thicker, rather than necessarily by being made of an intrinsically stiffer material), which spread the compression load over the plan area of the stack (at least over the area where they contact the gaskets 304 and the area in line with the electrochemically active layers). The compression means maintains the compressive force which provides good electrical contact between repeat units (including cell units) in the stack. The compression means also maintains compression in seals, e.g. (port) gaskets 304, to seal the chimney, and maintains structural integrity in the stack, as described in Applicant's earlier patent application WO 2019/002829A. As a result, a first fluid volume is defined in the chimney and the space between the metal support plate 306a and separator 306b of each cell unit 306. A second fluid volume, fluidically sealed from the first fluid volume, is defined by the remaining volume within the volume defined by the base plate 308, top plate 303, and skirt (compression means) 307. Thus, in this case, the compression means fulfils a further purpose of defining and sealing a fluid volume (i.e. the second fluid volume). The first fluid volume may be in fluid communication with the anode of an electrochemically active layer, and the second fluid volume may be in fluid communication with the cathode of an electrochemically active layer, or vice versa depending on how the electrochemical cell layers are laid up.

[0131] As an alternative, the compression means 307 may comprise tie bars arranged to pass through (secured with securing means, e.g. locking nuts) or screw into openings and connect the base plate 308 and top plate 303, and which maintain compression force applied to the cell stack arrangement between the base plate 308 and top plate 303. In this case, the compression means do not define and seal a fluid volume, rather the second fluid volume may be contained by a vessel in which the arrangement 300 is positioned.

[0132] In an example, the first electrical end plate 302 is in electrical contact with an outermost layer (e.g. an anode layer) of the uppermost cell unit 306 of the stack of cell units and the second electrical end plate 310 is in electrical contact with a cathode layer of the lowermost cell unit 306 of the stack of cell units (the stacked cell units being in a series connection). The anode may be in fluid communication with the first fluid volume and the cathode in contact with the second fluid volume. Operated as a fuel cell, fuel is supplied to the first fluid volume and oxidant supplied to the second fluid volume, and a potential difference is produced between the first electrical end plate 302 and the second electrical end plate 310, and a load may be connected therebetween. In this case, the first electrical end plate 302 may be referred to as a monopole and the second electrical end plate 310 may be referred to as an end pole.

[0133] Operated as an electrolyser cell, a potential difference is applied between the first electrical end plate 302 and the second electrical end plate 310 to drive the production of hydrogen gas and/or carbon monoxide and oxygen.

[0134] Referring to FIG. 4, a cross sectional view of a cell stack arrangement 400 is shown. Cell stack arrangement 400 is a variant of the cell stack arrangement 300 of FIG. 3. In the variant shown in FIG. 4, the cell unit (repeat unit) 406 includes a metal support plate 406a and a separator plate 406b. In this variant, no preformed (port) gaskets are required between cell units 406 in the stack of cell units. Instead of a (preformed) gasket, an annulus surrounding the fluid port of the metal support plate 406a is raised (downwards in the figure) by forming the annulus to protrude away from the separator plate 406b of that cell unit and toward the separator plate of the neighboring cell unit.

[0135] An in-situ seal, namely, a ring of sealant material 409 is formed on the annulus, and this material may be applied during assembly of the stack. It can be any conventional sealant material designed when hardened to withstand the operational environment of the fuel cell. It could also be replaced with a (pre-formed) gasket if needed, but the use of an in-situ seal has the significant advantage of reducing the parts count, reducing costs and simplifying assembly since the careful positioning of gaskets is no longer required.

[0136] With this arrangement, the thickness of the sealant material can be significantly less than is generally needed for a pre-formed gasket. An electrically insulating seal or in-situ seal may be used on one or both of the abutting surfaces (which form a hard stop surface, e.g. formed by the raised annulus and separator plate of the adjacent fuel cell unit) of adjacent fuel cell units to prevent electrical contact between adjacent fuel cell units via the abutting surfaces.

[0137] An annular groove (not shown, for clarity) may also be provided in the annulus, the annular groove protruding toward the separator plate 406b of that cell unit, for accommodating the insitu seal material. The annular groove may form a uniform circle in this, with a constant depth, however it would be possible to make the groove less uniform both in radius and depth, but for simplicity a uniform radius and depth is provided. The annular groove accommodates a volume (or bead) of the sealant material, and contacts the separator plate 306b of an adjacent cell unit 306, thus it functions like the gaskets 304 of FIG. 3.

[0138] The thickness of the gasket 304 of FIG. 3 helped provide a space between adjacent fuel cell units for air or fuel flow. To retain that space, shaped port features can be provided in the annular portion of the metal support plate 406a. This also ensures that the final height of the top of the gasket seal material still is the correct height to allow the outer surface of the electrochemically active layers to correctly contact the separator plate 406b of the adjacent cell unit 406.

[0139] The raised annulus is shown in FIG. 4 as part of the metal support plate 406a, but may alternatively be provided in the separator plate 406b of each cell unit 406.

[0140] As now exemplified in the embodiment that follows, any or all of the shaped features and shaped perimeter flange (through which the cell units are welded as a two piece cell) provided, as described in the arrangements of FIGS. 3 and 4, in the metal support plate 406a, could instead be provided in the separator plate 406b.

[0141] Referring to FIG. 5A, a cross sectional view of a cell stack arrangement 500 is shown, and referring to FIG. 5B an enlarged view of the area encircled in FIG. 5A is shown. FIG. 8 is an exploded perspective view of the arrangement 500 of FIG. 5.

[0142] Cell stack arrangement 500 comprises a stack of cell units 306 similar to the cell units 306 described above. FIG. 5A shows the electrochemically active layer 506, comprising respective anode, electrolyte and cathode layers respectively deposited (e.g. as thin coatings/films) on and supported by the metal support plate 306a. FIG. 5A also shows the up and down projections of the separator plate 306b which contact the metal support plate 306a of the cell unit 306 and an outermost layer of the electrochemically active layer 506 of the adjacent (neighboring) cell unit 306.

[0143] The electrical stud 301 and first electrical end plate 302 are similar to those described above. In this case an electrically insulating sleeve 503 (also referred to as a collar) surrounds the electrical stud 301. The electrical stud 301 and the openings through the first electrically insulating plate 305a and top plate 303 may be circular in cross section, and in which case the sleeve 503 is a hollow cylinder. The sleeve 503 is formed from an (electrically) insulating material, such as mica or ceramic. It provides mechanical stability to the electrical stud 301 during handling of the stack arrangement 500 and during connection of a load to the stud 301. The sleeve 503 also prevents ingress of foreign material (e.g. dirt) into the stack arrangement 500 via the opening in the top plate 303. Further mechanical stability is provided by a washer 504 which surrounds the sleeve 503 (and stud 301) and sits on the outer face of the top plate 303. The outer face of the washer 504 sits proud (i.e. protrudes from the outer face of the top plate 303 further than) the outer end of the sleeve 503 such that any mechanical forces applied to the stud are transferred through the washer 504 to the top plate 303 rather than through the sleeve 503 or through the stud 301 to the first electrical end plate 302. The washer may be formed of any suitable (electrically) insulating material, such as ceramic or mica. As seen in FIG. 5b, a busbar 509 may be affixed to the stud 301, external to the stack arrangement 500 and contacting the washer 504, by a nut 508.

[0144] Further details of the first electrical end plate 302 are apparent in FIG. 5A. The first electrical end plate 302 is (preferably) provided with a layer of material 510 deposited (e.g. as thin coatings/films) on—or attached to—and supported by the first electrical end plate 302. The layer of material 510 is an electrically conductive ceramic material, and may have a similar composition to that of the cathode of the electrochemically active layer 506, for example it may be LSCF, LCN, BSCF, eg LCN60. The layer of material 510 advantageously has a thickness which is equivalent to the thickness of the electrochemically active layer 506 of the cell units 306, which means that the protrusions in the separator plate 306b of the outermost (uppermost in FIG. 5A) cell unit 306 contact the face of the layer of material 510. This conveniently also allows all gaskets 304 to be of similar thickness. This reduces the number of different components required in the stack arrangement 500 as no special components are required to connect the stack of cell units 306 to the first electrical end plate 302. The layer of material 510 contacts the (up) protrusions in the separator plate 306b of the outermost (uppermost in FIG. 5A) cell unit in the stack of cell units and electrically connects that separator plate to the first electrical end plate 302 to allow transfer electrical energy therebetween. The electrical end plate 302 is shown as a single plate upon which the layer of material 510 is affixed, coated, or deposited, but may also be a two (or more) part construction, as described in the second aspect, for example electrical end plate 1402 of FIG. 10.

[0145] A second electrical stud 505 is shown in FIG. 5A, which is similar to the electrical stud 301 described above but has opposite polarity. The second electrical stud 505 is connected to the second electrical end plate 507, and passes through openings in the second electrically insulating plate 305b and base plate 308. The second electrical stud 505 is provided with a sleeve 503, washer 504, busbar, and nut, similar to the first electrical stud 301, but associated with the base plate 308 rather than the top plate 303.

[0146] Further details of the second electrical end plate 507 are apparent in FIG. 5A. The second electrical end plate 507 is provided with protrusions extending toward the stack of cell units to contact an outermost electrode (e.g. the cathode) of the electrochemically active layer 506 of the outermost (lowermost in FIG. 5A) cell unit 306 of the stack of cell units. The protrusions have the same height as those in the separator plates 306b which protrude (up) towards the electrochemically active layer 506 of an adjacent cell unit 306. This advantageously allows the gaskets 304 positioned between the second electrical end plate 507 and the stack of cell units to be of the same thickness (indeed, to be the same gaskets) as those used between adjacent cell units 306 in the stack of cell units.

[0147] The protrusions in the second electrical end plate 507 contact the outermost (lowermost in FIG. 5A) face of the electrochemically active layer (e.g. the cathode) of the outermost cell unit in the stack of cell units and electrically connects that face of that electrochemically active layer to the second electrical end plate 507 to allow transfer of electrical energy therebetween. The electrical end plate 507 is shown as a single plate, with integral projections, but may also be a two (or more) part construction, as described in the second aspect, for example electrical end plate 1407 of FIG. 10.

[0148] It will be noted that the electrical stud 301 and the second electrical stud 505 are positioned at opposite ends of the stack of cell units. Two chimneys are present in the arrangement 500, and an electrical stud is aligned with each (e.g., preferably coaxial with each). The chimneys are defined/formed by the gaskets 304, ports through the cell units 306, and ports through either the first electrical end plate 302, first electrically insulating plate 305a, and top plate 303 or through the second electrical end plate 507, second electrically insulating plate 305b, and base plate 308. The first electrical end plate 302 blocks a first chimney (left side of FIG. 5A, by means of a base portion from which the electrical stud extends perpendicularly) and the second electrical end plate 507 blocks a second chimney (right side of FIG. 5A, by means of a base portion from which the electrical stud extends perpendicularly).

[0149] As indicated by the arrows in FIG. 5A, the first chimney is used for delivery of a first fluid to a first fluid volume, and the second chimney is used for exhaust of the first fluid volume. The first fluid volume is enclosed between the metal support plate 306a and the separator plate 306b of a cell unit 306 and supplied/exhausted by the chimneys. The second fluid volume may be provided surrounding the cell units and chimneys, enclosed by the skirt, base plate, and end plate, and to be in fluid communication with the outermost electrode of the electrochemically active layer 506. Ports for supply and exhaust of the second fluid volume may be provided in the base and/or end plate (not shown in FIG. 5A).

[0150] Further shown in FIG. 5A are support layers 511 provided between the power take of plate 302 and the first electrically insulating plate 305a, between the first electrically insulating plate 305a and the top plate 303, between the second electrical end plate 507 and the second electrically insulating plate 305b, and between the second electrically insulating plate 305b and the base plate 308. The support layers 511 have an extent which corresponds to the extent of (are in line with, and in plan view cover a corresponding plan view area to) the electrochemically active layers 506 (and protrusions in the separator plate 306b). The support layers 511 transfer a portion of the compression force applied between the base plate 308 and top plate 303 through the stack of cell units. This ensures good (for example even across the plan view area) electrical contact within cell units 306 and between adjacent cell units in the stack of cell units (i.e. good electrical contact between the down protrusions of the separator plate 306b toward the metal support plate 306a of the same cell unit 306, and good electrical contact between the up protrusions of the separator plate 306b toward the outermost electrode of the electrochemically active layer 506 of the adjacent, or neighboring, cell unit 306 in the stack of cell units). Naturally, the same compression force, via the support layers 511, provides good electrical contact between the first and second electrical end plates 302, 507 and the outermost cell units of the stack of cell units. The support layers 511 may be formed from any conductive or non-conductive resilient material capable of transmitting the compression force to the stack, for example a mesh or expanded metal foil.

[0151] Referring to FIG. 8, a partial skirt 307 is shown for clarity. It is to be understood that the skirt 307 may include a further two side walls to connect edges of the shown skirt components 307 such that the skirt surrounds the stack. Note also that the metal support plates 306a and separators 306b are not shown exploded, and so only the separators 306b are apparent in this view. The metal support plate 306a and separator 306b of a cell unit 306 are welded or otherwise affixed to one another around their periphery.

[0152] In use as a fuel cell, an electrical load may be connected between the electrical stud 301 and the second electrical stud 505 of the arrangement 500. In an example where the anode is the electrochemically active layer closest to the metal support plate 306a, the first fluid is fuel. The fuel is supplied to the anode via the first chimney, the gap between the metal support plate 306a and the separator 306b, and the porous region of the metal support plate 306b, and fuel exhaust products are routed from the anode, via the gap between the metal support plate 306a and the separator 306b, to the second chimney. The second fluid is oxidant and is supplied to the cathode via the second fluid volume.

[0153] In use as an electrolyser cell, a potential difference may be provided between the electrical stud 301 and the second electrical stud 505 and to provide electrical energy to the arrangement 500. Relevant fluids are provided to the first and second fluid volumes, and exhausted therefrom.

[0154] Referring to FIG. 6A, a cross sectional view of a cell stack arrangement 600 is shown. Cell stack arrangement 600 is a variant of the cell stack arrangement 500 of FIG. 5A. FIGS. 6B and 6C show zoomed areas of the cell stack arrangement 600 of FIG. 6A. FIG. 7 is a plan view of the first and second electrical end plates 602, 606 of the cell stack arrangement 600, each having a stud. FIG. 9 is an exploded perspective view of the arrangement 600 of FIGS. 6 and 7. Note that the arrangement 600 (including cell units 306 in the stack of cell units) is shown rotated by 180 degrees relative to the arrangement 500 shown in FIG. 5.

[0155] In the arrangement 600 shown in FIG. 6, first electrical end plate 602 with stud 601 is connected via an additional busbar 612 to an additional electrical end plate 607, which allows both electrical studs 601 and 605 to be positioned at the same end of the stack arrangement 600. It also allows fluid entry and exhaust from the first fluid volume to be positioned at the same end of the stack arrangement 600 (the fluid entry and exhaust being positioned to the opposite end of the stack arrangement 600 to the electrical studs 601, 605). Gaskets 304 are provided between each of the additional components of the arrangement 600 to define the chimneys or continuations thereof.

[0156] The second electrical stud 605 and associated second electrical end plate 606 are similar to the second electrical stud 505 and second electrical end plate 507 of the arrangement 500, with the exception that the second electrical stud 605 passes through openings in an additional electrically insulating plate 613 (for reasons outlined below) and through the first electrical end plate 602. Thus, the second electrical end plate 606 is provided with projections 614 towards and in contact with the outermost layer of the outermost cell unit 306 of the stack of cell units, which may be an outermost electrochemically active layer of the electrochemically active layers 506. The second electrical end plate 606 is shown as a single plate, with integral projections, but may also be a two (or more) part construction, as described in the second aspect, for example electrical end plate 1407 of FIG. 10.

[0157] A support layer 511 is positioned to the opposite side of the second electrical end plate 606 to the projections, between the second electrical end plate 606 and the additional electrically insulating plate 613 to maintain the compression within the electrochemically active region of the stack.

[0158] The first electrical stud 601 is connected to or unitary with the first electrical end plate 602, similar to the electrical stud 301 and first electrical end plate 302 of the arrangement 500. Unlike arrangement 500, there is no electrically conductive ceramic layer 510 coated or deposited on the first electrical end plate 602. The first electrical end plate 602 is electrically connected to the busbar 612, which in turn is electrically connected to the additional electrical end plate 607 such that the two electrical end plates are at the same polarity and both subject to the compression forces exerted by the compression means, particularly in the vicinity of the chimneys. The additional electrical end plate 607 is positioned to the opposite end of the stack of cell units to the first electrical plate 602. The additional electrical end plate 607 is provided with a layer of material 510 deposited (e.g. as thin coatings/films) on—or attached to—and supported by the first electrical end plate 607. The layer of material 510 is otherwise similar to that described above with reference to FIG. 5.

[0159] The first electrical plate 602 is positioned between the additional electrically insulating plate 613 and the top plate 303 of the stack arrangement 600. The first electrical plate 602 is separated from the additional electrically insulating plate 613 by support layers 511 and gaskets 304. In other words, the first electrical plate 602 is positioned to the opposite side of the additional electrically insulating plate 613 from the second electrical end plate 606. The additional electrically insulating plate 613 thus provides electrical insulation between the first electrical plate 602 and the second electrical end plate 606. Similarly, the additional electrical end plate 607 is separated from the first electrically insulating plate 305a by support layers 511 and gaskets 304.

[0160] The busbar 612 is welded or otherwise affixed to (and in electrical connection with) the first electrical end plate 602 and the additional electrical end plate 607 via tabs on the ends of the busbar 612 and/or the first electrical end plate 602 and the additional electrical end plate 607. The busbar is positioned to one side of the stack of cell units, between the stack of cell units and the skirt, and is approximately parallel to a stacking direction of the same. The tabs are more flexible than (for example because they are thinner than) the busbar 612, first electrical end plate 602, and the additional electrical end plate 607, which means that differential thermal expansion between the stack and the busbar is accounted for by flexibility in the tabs, and so minimal stress is transferred to the busbar 612, first electrical end plate 602, and the additional electrical end plate 607.

[0161] The additional electrical end plate 607 is shown as a single plate upon which the layer of material 510 is affixed, coated, or deposited, but may also be a two (or more) part construction, similar to the plates described with respect to the second aspect, for example electrical end plate 1407 of FIG. 10.

[0162] It will be noted that in the example shown in FIG. 6A, the second electrical end plate 606 extends across both of the chimneys, so both end plates block the left hand side chimney and are compressed by compression forces in that chimney. In this case the first electrical plate 602 may be manufactured from the same material as the second electrical end plate 606 but may be thinner than the second electrical end plate 606 because it is not exposed to the fluid in the chimneys (typically fuel in a fuel cell application). Thus, where there are two electrical end plates, but one is exposed to dual atmospheres (two different fluids) in the stack, and the other a single atmosphere (one fluid), the latter plate may be made of a less corrosion resistant material, and/or have less or no corrosion protective coating and/or be made thinner than the former plate. Alternatively, if the second electrical end plate 606 does not additionally block the chimney to the left-hand side of FIG. 6A, the first electrical plate 602 and the second electrical end plate 606 may be manufactured from the same material and be of the same thickness, as both are exposed to similar (dual) chemical environments.

[0163] Referring to the partially exploded view of the arrangement 600 shown in FIG. 9, a partial skirt 307 is shown for clarity. It is to be understood that the skirt 307 may include a further two side walls to connect edges of the shown skirt components 307 such that the skirt surrounds the stack. Note also that the metal support plates 306a and separators 306b are not shown exploded, and so only the metal support plates 306a are apparent in this view. The metal support plate 306a and separator 306b of a cell unit 306 are welded or otherwise affixed to one another around their periphery. Note further that the additional electrical end plate 607, busbar 612, and first electrical end plate 602 are shown in their assembled (e.g. welded, brazed, or otherwise affixed together) form, dashed lines indicate the location in the exploded arrangement that the plate 607 and plate 602 occupy. Only once these plates are in position in the stack (and preferably once compression is applied to the stack) may the busbar 612 be affixed to the plate 607 and plate 602. Furthermore, electrically conductive ceramic layer 510 is shown separate to the additional electrical end plate 607, but it will be understood that frequently the electrically conductive ceramic layer 510 will be coated or deposited on the additional electrical end plate 607.

[0164] In use as a fuel cell, an electrical load may be connected between the electrical stud 601 and the second electrical stud 605 in the arrangement 600. In an example where the anode is the electrochemically active layer closest to the metal support plate 306a, the first fluid is fuel and flow within the first fluid volume is represented by the arrows in FIG. 6A. The fuel is supplied to the anode via the first chimney, the gap between the metal support plate 306a and the separator 306b, and the porous region of the metal support plate 306b, and exhaust products are routed from the anode, via the gap between the metal support plate 306a and the separator 306b, to the second chimney. The second fluid is oxidant and is supplied to the cathode via the second fluid volume.

[0165] In use as an electrolyser cell, a potential difference may be provided between the electrical stud 601 and the second electrical stud 605 and to provide electrical energy to the stack in the arrangement 600. Relevant fluids are provided to the first and second fluid volumes, and exhausted therefrom.

[0166] The arrangement 600 allows convenient electrical and fluidic connections to a system in which the cell stack arrangement 600 is positioned because all electrical connections are positioned to one end of the arrangement and all fluidic connections are positioned to the other end.

[0167] FIG. 7 shows plan views of the first electrical end plate 602 and second electrical end plate 606 of FIG. 6. The first electrical end plate 602 is provided with the electrical stud 601, to align with the first chimney in the cell stack arrangement 600. The first electrical end plate 602 is provided with an opening 704 through which the second electrical stud 605 and associated sleeve 503 passes, The end of the first electrical end plate 602 nearest to the electrical stud 601 may be straight for ease of attachment to the busbar 612.

[0168] The second electrical end plate 606 is provided with the second electrical stud 605, to align with the second chimney in the cell stack arrangement 600. A plurality of projections 614 are provided which project toward the outermost electrode of the electrochemically active layer of the outermost cell unit of the stack of cell units, to transfer power from the stack to the second electrical end plate 606. A port 706 may optionally be provided through the second electrical end plate 606. If the port 706 is provided, then it forms part of the first chimney, if the port is not provided then the second electrical end plate 606 blocks the first chimney. In the latter case, the second electrical end plate 606 blocks both chimneys.

DETAILED DESCRIPTION OF 2ND ASPECT

[0169] Referring to FIG. 10, a cross sectional view of a cell stack arrangement 1400 is shown. Cell stack arrangement 1400 is a variant of the cell stack arrangement 500 of FIG. 5. FIG. 11 is an exploded perspective view of the arrangement 1400 of FIG. 10. Note that the compression means (for example skirt 307) is not shown in arrangement 1400 for sake of clarity.

[0170] FIG. 12 is an exploded view of a first electrical end plate of the cell stack arrangement 1400. FIG. 13 is an exploded view of a second electrical end plate of the cell stack arrangement 1400.

[0171] In arrangement 1400 a first electrical end plate 1402 is shown, which may function substantially similarly to the first electrical end plate described above. The first electrical end plate 1402 comprises a two-layer construction in which a first layer 1416 is welded (or otherwise connected) to a second layer 1417 (the weld path is shown by a dashed line 1621 in FIG. 11 and FIG. 12). The first layer 1416 is a planar plate. The first layer 1416 blocks one of the chimneys of the cell stack arrangement (the electrical stud 301 exits the cell stack arrangement via a continuation of that blocked chimney) and is provided with a port which forms a part of another chimney for fluid delivery or exhaust of the first fluid volume.

[0172] It may be seen that the second layer 1417 is a planar plate. The second layer 1417 is similar to the metal support plate 306a of a cell unit 306 in the stack of cell units. The second layer 1417 is provided with (similarly positioned) ports in the same way as the metal support plates 306a in the stack of cell units. An electrically conductive ceramic layer 1418 is bonded (for example affixed to or deposited on) the opposite face of the second layer 1417 to that which faces the first layer 1416. The electrically conductive ceramic layer 1418 may be similar to the electrically conductive ceramic layer 510 described previously, and may be of a type of material suitable for use in a cathode of a fuel cell, for example LSCF, LCN, BSCF, e.g. LCN60. The thickness of the electrically conductive ceramic layer 1418 is similar to the thickness of the electrochemically active layers 506 of cell units 306 in the stack of cell units. This means that the gaskets 304 which separate the second layer 1417 from the separator plate 306b of the neighboring (outermost or uppermost) cell unit 306 of the stack of cell units can be identical to the gaskets 304 used elsewhere in the arrangement 1400.

[0173] The face of the electrically conductive ceramic layer 1418 which is opposite to the second layer 1417 contacts projections on the separator plate 306b of the neighboring (outermost or uppermost) cell unit 306 of the stack of cell units. The projections on the separator plate 306b alternate in up-and-down directions, the up projections directed toward and in contact with the electrically conductive ceramic layer 1418 and away from the metal support plate 306a of the same cell unit 306, and the down projections directed away from the electrically conductive ceramic layer 1418 and toward and in contact with metal support plate 306a of the same cell unit 306. The down projections of the separator plate 306b contact the metal support plate 306a and so are electrically connected to the layer 506, which may be electrochemically active in which case the down projections of the separator plate are electrically connected to the electrode (typically the anode) of the electrochemically active layer closest to the metal support plate 306a (those electrochemically active layers being on the other side of the substrate). That electrical connection is enhanced by the welding of the metal support plate 306a and the separator plate 306b around their periphery. As a result, the electrical stud 301 is electrically connected to the stack of cell units via the first layer 1416, second layer 1417, and electrically conductive ceramic layer 1418.

[0174] The arrangement 1400 also includes a second electrical end plate 1407, as shown in FIG. 10, which may function substantially similarly to the first electrical end plate 1402 described above. The second electrical end plate 1407 comprises a two-layer construction in which a first layer 1419 is welded (or otherwise connected) to a second layer 1420 (the weld path 1722 is shown by a dashed line in FIG. 11 and FIG. 13). The first layer 1419 is a planar plate. The first layer 1419 blocks one of the chimneys of the cell stack arrangement (the electrical stud 505 exits the cell stack arrangement via a continuation of that blocked chimney) and is provided with a port which forms a part of another chimney for fluid delivery or exhaust of the first fluid volume.

[0175] The second layer 1420 is similar to the separator plate 306b of a cell unit 306 in the stack of cell units. The second layer 1420 is provided with (similarly positioned) ports in the same way as the separator plates 306b in the stack of cell units. The second layer 1420 is welded or otherwise connected to the first layer 1419 around its periphery (and may also be welded around the ports). It may be seen that the second layer 1420 is a contoured plate (i.e. it has 3D features). The second layer 1420 is provided with projections which alternate in up-and-down directions, the up projections directed toward and in contact with the layer 506 (which may be an electrochemically active layer) of the neighboring (lowermost in the figure) cell unit 306 in the stack of cell units and away from the first layer 1419 of the electrical end plate 1407, and the down projections directed away from the neighboring (lowermost in the figure) cell unit 306 in the stack of cell units and toward and in contact with the first layer 1419 of the electrical end plate 1407. The up projections of the second layer 1420 contact the layer 506 of the neighboring (lowermost in the figure) cell unit 306 of the stack of cell units and so are electrically connected to the electrode (typically the cathode) of the neighboring (lowermost in the figure) cell unit 306. As a result, the electrical stud 505 is electrically connected to the stack of cell units via the first layer 1419 and the second layer 1420. The electrical studs 301 and 505 are affixed or otherwise connected at base portions of the respective electrical end plates in a similar manner to that described with respect to the first aspect above, the base portions being subjected to the compressions forces in the respective chimneys.

[0176] The first (1416, 1419) and second (1417, 1420) layers of the electrical end plates (1402, 1407) are iron-containing layers, for example the layers are steel (typically stainless steel, or ferritic stainless steel). Examples of suitable materials for the first layer include SS441 and Crofer 22 and examples of suitable materials for the second layer include SS441, SS444, and Crofer 22. The first and second layers are formed of different metals and are permanently connected. The first layer of the electrical end plate will have a thickness of at least 0.5 mm, for example between 0.5 mm and 5 mm, or between 0.5 and 2 mm, or between 1 and 2 mm.

[0177] The arrangement 1400 of FIG. 10 may be varied to provide both the first electrical stud 301 and second electrical stud 505 at the same end of the stack through use of a busbar and additional electrical plate, as described with respect to arrangement 600 in FIG. 6 of the first aspect.

[0178] FIG. 12 is an (artificially) exploded view of the first electrical end plate 1402. In FIG. 12, the first layer 1416 and the second layer 1417 are self-supporting rigid plates. The weld path 1621 is represented by the dashed line and follows the periphery of the second layer 1417 of the first electrical end plate 1402. Further weld path(s) (not shown) around the periphery of the fluid ports may also be present to prevent fluid flowing from the chimney formed by the respective port into the space between the first and second layers 1416, 1417 of the first electrical end plate 1420.

[0179] FIG. 13 is an (artificially) exploded view of the second electrical end plate 1407. In FIG. 13, the first layer 1419 and the second layer 1420 are self-supporting rigid plates. The weld path 1722 is represented by the dashed line and follows the periphery of the first layer 1419 and the second layer 1420 of the second electrical end plate. Also shown in FIG. 13 are the up-and-down projections 1723 of the second layer 1420 of the second electrical end plate 1407. Further weld path(s) (not shown) around the periphery of the fluid ports may also be present to prevent fluid flowing from the chimney formed by the respective port into the space between the first and second layers 1419, 1420 of the second electrical end plate 1407.

[0180] Referring to FIG. 14, a cross sectional view of a portion of a cell stack arrangement is shown. The portion of a cell stack arrangement is a variant of the electrical stud 505, second electrical end plate 1407 and neighboring (lowermost in FIG. 10) cell unit 306 in the stack of cell units in the cell stack arrangement 1400 of FIG. 10.

[0181] In the variant shown in FIG. 14, the projections 1723 of the second layer 1420 of the second electrical end plate 1407 which are directed toward the layers 506 of the neighboring cell unit 306 of the stack of cell units are provided with a conductive ceramic layer 1824. The projections of the separator plate 306b of each cell unit 306 which are directed toward the electrochemically active layers of the neighboring cell unit 306 of the stack of cell units are also provided with a conductive ceramic layer 1824. The conductive ceramic layers 1824 are bonded or deposited to said projections.

[0182] The conductive ceramic layers 1824 are in face-to-face contact with the layers 506 of the neighboring cell unit 306 of the stack of cell units, and provide improved electrical contact between the projections (and therefore separator plate 306b or second plate 1420) and the layers 506. When the layers 506 are electrochemically active layers of a cell unit, the outermost electrode of the neighboring cell unit is typically the cathode, and a cathode-type material is used for the conductive ceramic layers 1824, such as LSCF, LCN, BSCF.

[0183] FIG. 15 shows the second electrical end plate 1407 and conductive ceramic layers 1824 as part of a cell stack arrangement 1900. Cell stack arrangement 1900 is a variant of the arrangement 1400 of FIG. 10. FIG. 15 additionally shows conductive ceramic layers 1824 which are bonded to or deposited on the up projections of the separator plate 306b of the uppermost cell unit 306 in the stack of cell units contacting the electrically conductive ceramic layer 1418 of the first electrical end plate 1402. These conductive ceramic layers 1824 provide good electrical connection between the first electrical end plate 1402 and the neighboring (uppermost in FIG. 15) cell unit of the stack of cell units.

[0184] The present invention is not limited to the above examples only, and other examples will be readily apparent to one of ordinary skill in the art without departing from the scope of the appended claims.

[0185] These and other features of the present invention have been described above purely by way of example. Modifications in detail may be made to the invention within the scope of the claims.