Fluid guidance in electrochemical cells

Abstract

An electrochemical cell unit comprising a cell layer affixed to an interconnector plate, forming a fluid volume. A fluid guidance insert is provided in the fluid volume, the fluid guidance insert partially circumscribes a fluid port thereby forming a throat, the throat providing a passage for fluid between the fluid port and a fluid volume. The interconnector and / or the cell layer comprising a fluid guidance feature aligned with said throat to redirect the fluid flow.

Description

[0001] Fluid guidance in electrochemical cells

[0002] 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 cell units, to stacks of cell units, to fluid guidance inserts for use in cell units, to methods of manufacture of a cell unit and to methods of manufacture of stacks of cell units.

[0003] Fuel cell units and electrolyser cell units are examples of electrochemical cell units. Fuel cell units are energy conversion devices that allow for conversion of electrochemical fuel to electricity. Electrolyser cell units may be considered fuel cell units running in reverse mode, i.e. using electricity to decompose a compound into its constituent parts, for example water into hydrogen and oxygen. Reversible cell units are capable of operating in either mode.

[0004] The present invention specifically relates to solid oxide cell units (SOCs). Solid oxide cell units (SOCs) typically comprise an electrolyte layer formed from a solid oxide, e.g. from Yttria-stabilised Zirconia (YSZ), Gadolinia-doped Ceria, or Cerium Gadolinium Oxide (CGO). SOCs can be run as solid oxide fuel cell units (SOFC) or as solid oxide electrolyser cell units (SOEC).

[0005] Electrochemical cell units often comprise a cell layer having electrochemically active layers and an interconnector plate. The cell layer and the interconnector plate may be sealingly attached to one another and define a fluid volume therebetween. An electrochemical cell unit of this type is disclosed in WO 2020 / 126486 A1, for example. The electrochemically active layers of the cell layer 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). The fluid volume of WO 2020 / 126486 A1 is formed by at least one of the cell layer or interconnect plates having flanged perimeter features, the plates being directly adjoined at the flanged perimeter features. This fluid volume is maintained at the fluid ports by pressed shaped port features (also referred to as ‘dimples’) formed around the ports, which are spaced from one another to define fluid pathways to enable passage of fluid from the port to the fluid volume. It is an object of the invention to improve the performance of an electrochemical cell unit, specifically to improve the guidance of fluid through an electrochemical cell unit.

[0006] Statements of invention

[0007] According to the invention, there is provided an electrochemical cell unit with the features of claim 1. In particular, the electrochemical cell unit comprises a cell layer having a periphery and a central portion surrounded by the periphery, and an interconnector plate havinga peripheryand a central portion surrounded by the periphery.

[0008] The cell layer and the interconnector plate are stacked upon one another, the periphery of the cell layer is attached to the periphery of the interconnector plate, the central portion of the cell layer and the central portion of the interconnector plate define a fluid volume therebetween.

[0009] Chemistry layers are provided on the central portion of the cell layer; these include a fuel electrode (anode in fuel cell mode, cathode in electrolysis mode), electrolyte, and air electrode (cathode in fuel cell mode, anode in electrolysis mode). The interconnect acts to separate the fuel and air volumes for a given cell unit (also called a repeat unit) and electrically connect neighbouring cell units.The cell unit has at least one fluid port in fluidic communication with the fluid volume, and a fluid guidance insert is disposed in the fluid volume. The fluid guidance insert has several functions; one function is to maintain the integrity of fluid volume around the port to stop it collapsing. A stack of cell units is typically compressed to ensure electrical connection and leak prevention between cell units. This compression acts to compress the fluid volumes within each cell unit. A second function is to direct the fluid from the fluid port to the fluid volume.

[0010] The fluid guidance insert partially circumscribes the fluid porttherebyforminga throat, the throat providing a passage for fluid between the fluid port and the fluid volume.

[0011] The interconnector and / or the cell layer comprising a fluid guidance feature aligned with said throat to redirect the fluid flow.

[0012] In such a way, a structurally strong fluid guidance insert can be provided which is able to direct fluid flow in a reliable and tuneable manner. This is particularly advantageous when used in the fuel volume. The fluid guidance insert, which partially circumscribes a port (i.e. having a single throat), is a simple constriction which does not rely on three-dimensional features such as tunnels or bridges which would increase the thickness of the insert (or reducing the cross-sectional are available for fluid to flow) and / or adversely impact other fluid volumes.

[0013] Optionally, the cell unit comprises at least one fluid inlet port and at least one fluid outlet port. Optionally, for improved fluid distribution, the throat of the fluid guidance insert is positioned at an angle to a line joining the inlet and outlet ports. In some examples, the throat of the fluid guidance insert is positioned at an angle of greater than zero but less than 45 degrees to a line joining the inlet and outlet ports.

[0014] In other examples, the throat of the fluid guidance insert is positioned greater than 45 degrees to a line joining the inlet and outlet ports.

[0015] In yet further examples, the throat of the fluid guidance insert is positioned greater than 90 degrees to a line joining the inlet and outlet ports; preferably at least 135 degrees; preferably substantially directly away from the opposing port. Such an orientation improves the dispersion of fluid from the fluid port and increases the fluid flow path.

[0016] Optionally, the cell unit comprises at least two fluid guidance inserts, and the at least one fluid inlet port and the at least one fluid outlet port are associated with different ones of the at least two fluid guidance inserts.

[0017] Optionally, for improved fluid distribution, the fluid guidance insert associated with the inlet port is positioned at a different angle to the fluid guidance insert associated with the outlet port. Optionally, the fluid guidance insert associated with the inlet port is positioned away from outlet port and the fluid guidance insert associated with the outlet port is positioned towards the inlet port.

[0018] Optionally, the fluid guidance feature comprises the periphery of the cell layer; preferably the attachment of the interconnect plate and the cell layer. In such a way, the side wall of the fluid volume acts to redirect and disperse the fluid.Optionally, to improve fluid distribution, the fluid guidance feature comprises at least one dimple on the central area of the interconnect and / or cell layer adjacent to the fluid guidance insert. The least one dimple is adapted (in orientation, location and / or shape) to distribute the fluid from the fluid port.

[0019] Optionally, the width of the throat (w) is related to the thickness of the interconnector or cell layer (t), whichever smaller, by the formula: w < 15t; preferably w<11t, preferably w < 8t. The throat must be large enough to ensure sufficient fluid flow, but not too large to compromise the structural integrity of the fluid volume.

[0020] Optionally, the fluid guidance insert, the cell layer and / or the interconnect comprise a locating feature to locate the fuel guidance insert. The accurate placement and orientation of the fluid guidance insert improves the function of the insert.

[0021] In some examples, the locating feature comprises a protrusion or depression adapted to interface with a corresponding feature on the fuel guidance insert. Such an arrangement ensures accurate placement and orientation.

[0022] Optionally, the locating feature on the fluid guidance insert varying in position depending on the intended orientation of the throat. Multiple locating features may be provided corresponding to the multiple possible throat orientations.

[0023] Optionally, the locating feature comprises a tab on the fluid guidance insert adapted to engage with a periphery of the fluid port. Such an arrangement does not require any modification to the cell layer or interconnect and ensures the insert is aligned with the fluid port. The orientation of thethroat may be achieved bya machine, forexample by computervision orvia engagementwith the tool used to place the insert.

[0024] Optionally, the insert is circular in shape. Optionally, the insert is made of metal, preferably steel. Other materials such as ceramic, alumina or glass would also be appropriate depending on the conditions (e.g. temperature, chemical environment, and pressure) to which the insert is exposed.

[0025] Optionally, the electrochemical cell is a solid oxide electrolysis cell (SOEC), preferably a metal (e.g. steel) supported SOEC. The fluid guidance insert, as described herein is particularly advantage for SOEC when used in the fuel (steam) volume. This is because the air volume in SOEC can be made significantly smaller than the fuel volume, as such, any impingement on the air volume caused by a fuel insert has an exaggerated effect on the air flow in the air volume. As such, it is particularly advantageous to have a fuel guidance insert which does not have an impact on the air volume.

[0026] In a second aspect of the invention there is provided an electrochemical cell stack comprising a series of electrochemical cells as recited in claim 18. The individual cells in the stack being electrically connected and the fluid ports being in alignment.

[0027] Optionally, for improved fluid distribution, the orientation of thethroat of the fluid guidance insert for each respective cell varies based on the position of the cell within the stack. The fluid pressure may change for cell layers further away from the fluid inlet to the stack. It is possible to adjust thefluid distribution in each cell byadjustingthe orientation of the fluid guidance insert. This enables a design where fuel utilisation is more even in different cell layers, which ameliorates deleterious effects such as fuel starvation or uneven temperatures. For example, the throat may be oriented directing away from the outlet port for a cell near the stack fluid inlet (i.e. where the fluid path is shortest) and directed more towards the outlet for a cell further away from the stack fluid inlet (i.e. where fluid path is longest). This can be achieved with a single design of fluid insert, simplifying the manufacturing and assembly process.

[0028] In athird aspect ofthe invention there is provided a method of manufacturing an electrochemical cell as recited in claim 22 . The electrochemical cell comprising a cell layer having a periphery and a central portion surrounded by the periphery, and an interconnector plate havinga periphery and a central portion surrounded by the periphery. The method comprises: placingfluid guidance insert around a port of the cell layer; the fluid guidance insert partially circumscribing the fluid port thereby forming a throat, the throat providing a passage for fluid between the fluid port and the fluid volume. The method further comprises attaching an interconnect to the cell layer, the periphery of the cell layer being attached to the periphery of the interconnector plate, the central portion ofthe cell layer and the central portion ofthe interconnector plate defining a fluid volume therebetween.

[0029] In such a way, a structurally strong electrochemical cell with good fluid flow characteristics is manufactured.

[0030] Optionally, attaching the interconnect to the cell layer comprises welding. The cell layer and fluid guidance insert are made of metal, preferably both of steel, preferably both substantially the same grade of steel, and can be joined together easily by welding. This may take the form of one or more spot welds, or a weld substantially around the fluid port (excluding the throat). This latter option would ensure fluid can only pass to the fluid volume via the throat.

[0031] Additional preferred features, e.g. regarding the fluid guidance insert or the interconnector plate, may be realised as described above. The cell unit may be manufactured according to the abovedescribed method of manufacture of a cell unit.

[0032] Further embodiments are derivable from the following description and the drawings:

[0033] Figure 1 shows a perspective view of a stack of electrochemical cell units according to an embodiment;

[0034] Figure 2 shows an exploded view of a single electrochemical cell unit from above (Fig 2a) and below (Fig 2b);

[0035] Figure 3 shows a fluid guidance insert with dimension labels;

[0036] Figure 4 shows a plan view of the fluid guidance inserts in various orientations around fluid ports of an electrochemical cell;

[0037] Figure 5 shows a close up view of a fluid guidance insert oriented at an angle to a line joining the inlet and outlet ports;

[0038] Figure 6 shows a fluid guidance insert and associated fluid guidance dimples;Figure 7 shows an example fluid guidance insert orienting features;

[0039] Figure 8 shows an alternative electrochemical cell design where there are multiple inlet ports and multiple outlet ports; and

[0040] Figure 9 shows a plan view of example orientations of fluid guidance inserts where there are multiple inlet ports and multiple outlet ports.

[0041] Referring to Figure 1 , there is shown an exemplary configuration of a stack 10 of cell units 12. The stack 10 comprises a plurality of electrochemical cell units 12 that are stacked upon one another along a stacking direction 14. Neighbouring cell units 12 are in direct contact with one another, said direct contact providing an electrical connection between the cell units 12.

[0042] A fluid inlet port 16 and a fluid outlet port 18 are provided for supplying a fluid to an electrochemically active area 20.

[0043] Fluid distribution inside a Solid Oxide Cell (SOC) is important for the efficient operation and longevity of the cell. Proper fluid distribution ensures that reactants are evenly supplied to the electrochemically active layers, which maintains uniform reaction rates across the cell. This uniformity helps in preventing localized hotspots that can lead to thermal stresses and degradation of the cell materials. Additionally, effective fluid distribution minimizes concentration polarization, thereby enhancing the overall performance and efficiency of the SOC.

[0044] Pursuant to the present invention, fluid guidance inserts can be used to direct the flow of fluids, ensuring that they reach the intended areas within the cell and as such improving the cell's functionality, and longevity. In fuel cell mode, the fluid may be hydrogen or a gaseous hydrocarbon (a ‘fuel’). In electrolysis mode, the fluid may be steam (also termed ‘fuel’ in electrolysis). Similarly, the fluid may be an oxidant, such as air, in either fuel cell mode or electrolysis mode.

[0045] Figure 2 shows an electrochemical cell unit. The cell unit 12 extends in a cell plane that is perpendicular to the stacking direction 14. The cell plane is defined by a first direction 15 (see Figure 4A) and a second direction 16 that is perpendicular to the first direction 15. The first direction 15 corresponds to the length extent of the cell unit 12. The second direction 16 corresponds to the width extent of the cell unit 12.

[0046] The cell unit 12 comprises a cell layer 26 comprising electrochemically active layers 20. The cell layer 26 comprises a periphery 22 and a central portion 24 surrounded by the periphery. In this example, the periphery 22 and the central portion 24 are formed by a support plate of the cell layer 26. The electrochemically active layers 20 are carried by the central portion 24 of the support plate 26.

[0047] The cell unit 12 further comprises an interconnector plate 28 having a periphery 30 and a central portion 32 surrounded by the periphery 30.

[0048] In the assembled cell unit 12, the cell layer 26 and the interconnector plate 28 are stacked upon one another along the stacking direction 14. The periphery 22 of the cell layer 26 is sealingly attached to the periphery 30 of the interconnector plate 28 (in this case, directly attached), preferably by welding. The central portion 24 of the cell layer 26 and the central portion 32 of the interconnector plate 28 define or enclose a fluid volume 34 therebetween. The fluid volume 34 isan internal cell volume of the cell unit 12. The combination of a cell layer a nd interconnector plate is termed a ‘repeat unit’.

[0049] In this example, the electrochemically active layers 20 are arranged on a side of the central portion 24 of the cell layer 26 that faces away from the fluid volume 34 of the assembled cell unit 12.

[0050] The electrochemically active layers 20 may be carried by a porous area 38 (see Figure 2b) of the central portion 24 of the cell layer 26 such that during operation a fluid, e.g. a fuel, may exit the fluid volume 34 through pores formed in the porous area 36 and reach to a layer of the electrochemically active layers 20 that is closest to the support plate 26.

[0051] In this example, the central portion 32 of the interconnector plate 28 comprises a structured area 38. The structured area 38 comprises a plurality of first protrusions 40a protruding towards the cell layer 26 and a plurality of second protrusions 40b protruding away from the cell layer 26, i.e. in the opposite direction. A reduced number of protrusions 40a, 40b are depicted in Figure 2 for clarity of the Figures. It will be understood thatthere will typically be many more protrusions 40a, 40b than those depicted. Further, the protrusions 40a, 40b are typically pressed or formed in the sheet forming the interconnector plate 28. For example, a second protrusion 40b on one side of the interconnector plate 28, facing away from the cell layer 26, typically forms a depression on the other side of the interconnector plate 28, facing towards the cell layer 26 (and similarly for first protrusions 40a).

[0052] In the stack 10 of cell units 12, the first protrusions 40a of a given cell unit 12 contactthe cell layer 26 of that cell unit 12, and the second protrusions 40b of that cell unit 12 contact the cell layer 20 of the adjacent / neighboring cell unit 12. In this way, the protrusions 40a, 40b transfer compression forces through the stack 10, while maintaining the fluid volumes on either side of the interconnector plate 28.

[0053] The first and second protrusions 40a, 40b typically have a circular cross section. In this way, the protrusions 40a, 40b may be referred to as dimples, and do not restrict flow of fluid (first protrusions 40a do not restrict flow of fluid in the cell volume 34, second protrusions 40b do not restrict flow of fluid outside the cell volume 34). The first and second protrusions 40a, 40b may define a network of interconnected fluid channels on each side of the interconnector plate 28. The protrusions 40a, 40b are exemplary. Other means for maintaining the spacing between interconnector plate 28 and cell layer 26 (to provide the fluid volumes therebetween) maybe used in combination with the interconnector plate 28 described herein. For example, ribs which may also act to direct fluid flow.

[0054] In this example, the interconnector plate 28 is configured tub-shaped. Thus, the interconnector plate 28 comprises a bottom 102 and a circumferential wall 104 between the bottom 102 and the periphery 30. In this example, the bottom 102 is configured flat and extends parallel to the cell plane. The circumferential wall 104 is angled with respect to the cell plane and with respect to the stacking direction 14.

[0055] The cell unit 12 further comprises at least one fluid port. In this example, the cell unit 12 comprises one fluid inlet port 42 and one fluid outlet port 44. The fluid inlet port 42 and the fluid outlet port 44 are formed by a respective through-hole that extends through the cell unit 12. In the assembled stack 10 of cell units 12, the fluid inlet ports 42 and the fluid outlet ports 44 of the cell units 12 are aligned with each other along the stacking direction 14, thus forming a fluid inletmanifold or a fluid outlet manifold, respectively. During operation, a fluid, e.g. a fuel, may be supplied to the fluid volume 34 through the fluid inlet port 42.

[0056] The fluid inlet port 42 is located at a first longitudinal end 46 of the cell unit 12. The fluid outlet port 44 is located at a second longitudinal end 48 of the cell unit 12. The porous area 36 and the structured area 38 are located between the fluid inlet port 42 and the fluid outlet port 44. Thus, a fluid, e.g. a fuel, that flows from the fluid inlet port 42 to the fluid outlet port 44 may pass through the structured area 38 and reach to the electrochemically active layers 20 carried by the porous area 36.

[0057] Each fluid port is associated with a respective gasket 50. In this example, the gaskets 50 are positioned on a face of the interconnector plate 28 that faces away from the fluid volume 34. One of the gaskets 50 is associated with the fluid inlet port 42 and surrounds the fluid inlet port 42. The other one of the gaskets 50 is associated with the fluid outlet port 44 and surrounds the fluid outlet port 44. In the assembled stack 10 of cell units 12, the gaskets 50 contribute to forming the fluid inlet manifold and the fluid outlet manifold and prevent loss of fluid between adjacent / neighbouring cell units 12.

[0058] The cell unit 12 further comprises at least one fluid guidance insert 52 that is disposed in the fluid volume and associated with at least one fluid port. In this example, the cell unit 12 comprises two fluid guidance inserts 52.

[0059] The cell unit includes at least one fluid port 16 in fluidic communication with the fluid volume. A fluid guidance insert 52 is disposed within the fluid volume, partially circumscribing the fluid port to form a throat. Such an arrangement maintains the fluid volume at the port whilst providing a passage for fluid between the fluid port and the fluid volume.

[0060] A fluid guidance insert with multiple throats would require additional connecting structures, and elements which allow fluid to bypass the connecting structures. These additional features fill some of the fluid volume which would otherwise be used by the fluid. It has been surprisingly found a single slit where such connecting structures can be omitted has a similar performance in fluid distribution compared to a more complex fluid guidance insert with additional throats. Additionally, the interconnector and / or the cell layer comprises a fluid guidance feature aligned with the throat to redirect the fluid flow. This may take the form of dim pies 70 (see Figure 6) formed on the interconnect 28, cell layer 26 and / or the periphery 30 of the interconnector plate 28 itself. Alternatively, a continuous rib on the interconnector plate 28 and / or cell layer 26 can also effectively distribute fluid from the fluid guidance insert 52.

[0061] Adjacent repeat units are separated from one-another by gaskets 50 which electrically isolate the interconnect of one repeat unit from a cell layer of a neighbouring repeat unit, forcing current to pass between repeat units via the electrochemically active area 20.

[0062] Figure 2 also shows a structured area 38 (in this example, dimples) on the interconnect overlying the active area. These are described in the prior art, for example WO 2020 / 126486 A1 , and act to maintain the fluid volume when electrical cell units are stacked upon one-another and compressed.

[0063] Figure 2b shows an alternative view of the exploded repeat unit of Figure 2a. This view shows the inverse dimple pattern on the interconnector plate 38. Such dimples are most easily formed by hydroforming or pressing, which results in a protrusion on one side and a corresponding depression on the other.Figure 2b also shows a porous region formed on the cell layer 24 which allows fluid to reach the electrochemically active layers. The porous region may be formed by drilling, for example laser drilling.

[0064] Figure 3 shows an example fluid guidance insert 52. The width (w) of the throat of the fluid guidance insert 52 is influenced by several factors. One factor is the thickness (t) of the interconnector or cell layer (whichever thinner - typically the interconnect). For a steel interconnect of thickness 0.2mm, throat widths of 1.5-2.2mm withstand stacking pressures of up to 15MPa.cm-2. This corresponds to w<11t. For a steel interconnect of thickness 0.1 mm, throat widths of 0.35-0.8mm withstand stacking pressures of up to 15MPa.cm-2, this corresponds to w<8t.

[0065] A larger width may be possible depending on material selection and stacking pressure, as such, in some embodiments the width of the throat may be as large as 15t.

[0066] The thickness of the interconnector or cell layer affects the width of the throat due to its mechanical properties. Thicker interconnectors or cell layers provide greater mechanical stability a nd strength, and as such a wider throat can be provided without the interconnect and / or cell layer collapsing into the throat and inhibiting fluid flow. The limit on the upper would be the point at which one of the interconnect or cell layer collapses into the throat under the compressive load (inclusive of a safety margin).

[0067] The width of the throat is ideally as large as possible to increase fluid flow and keep the pressure drop across a cell as low as possible. As such, the width is at least 3.5t, preferably greater than 5t.

[0068] Other dimensions of the fluid guidance insert 52 are defined by corresponding dimensions of the electrochemical cell. The interior diameter (d1 ) corresponds to the diameter of the fluid port. The height (h) of the fluid guidance insert corresponds to the height of the fluid volume. The exterior diameter (d2) corresponds to an exterior diameter of the gasket 50 as this is what transfers the stacking pressure through the stack, which is then transferred through individual cells via the fluid guidance insert 52. It is preferable that d2 is larger than the exterior diameter of the gasket 50 to ensure no significant bending forces are applied to unsupported areas of the interconnect plate 28. In one example d2 is 20-50mm, preferably around 30mm. The material of the insert impacts the potential dimensions, as different materials have varying properties such as thermal expansion and mechanical strength, which can affect the optimal width of the throat. Additionally, the compression load applied during the assembly of the cell unit can alter the deformation characteristics of the insert, thereby impacting the throat width.

[0069] Manufacturing tolerances are another consideration, as variations in the manufacturing process can lead to differences in the actual width of the throat. Also, corrosion resistance may be a factor, oxide scale that accumulates during the lifetime of the stack may act to reduce the effective throat width. This may be accounted for by making the throat larger than necessary at the start of life.

[0070] Finally, specific design specifications, such as the required fluid flow rates and pressure drops, can dictate the necessary width of the throat to ensure optimal performance of the electrochemical cell unit. These properties may vary depending on the position of the electrochemical cell within a stack, for example, the width of the throats may be narrower for electrochemical cells closest to the fluid inlet and wider for electrochemical cells further awayin the stack. This can be achieved by having a set of different inserts which are used when assembling electrochemical cells.

[0071] Figures 4a, 4b, and 4c show two fluid guidance inserts 52 positioned around an inlet port and an outlet port respectively.

[0072] In Figure 4a, the throats of each fluid guidance inserts 52a. 52b are oriented towards each other, i.e. along a line joining the inlet port and the outlet port. This orientation encourages fluid to pass over the active region.

[0073] In Figure 4b, the throat of the fluid guidance insert 52a around the inlet port is oriented directly away from the outlet port. In this orientation, the join between the interconnect and cell layer acts as a fluid guidance feature, spreading the fluid flow.

[0074] In Figure 4c, the throats of each fluid guidance insert 52a, 52b are oriented away from each other. In this orientation, the fluid flow is redirected by the join between the interconnect and cell layer at the inlet and at the outlet, encouraging dispersed flow at both ports.

[0075] Figure 4 may represent three orientations used within a single stack. Figure 4c representing an electrochemical cell nearest the inlet of the stack where pressure drop from inlet to outlet is lowest due to the comparatively short flow path. Figure 4a representing an electrochemical cell furthest from the inlet of the stack where the pressure drop is highest due to the comparatively high flow path. For cells that are further the flow path is longer. Therefore, it is beneficial to increase the pressure drop along the shorter flow paths to compensate for the larger pressure drop of the longer paths and achieve even flow rate for each cell. This can be achieved by varying the orientation of the throats of the fluid guidance inserts in dependence on the position of the cell within the stack.

[0076] Intermediate positions may also be used, as will be discussed in relation to Figure 5.

[0077] Figure 5 shows the throat of a fluid guidance insert 52a oriented at an angle 0 to the line joining the inlet and outlet ports. In one example, 0 is greater than 0 and less than 45°. Such an orientation promotes fluid to flow over the corner of the active area, ameliorating fuel starvation and temperature differences which are harmful to the cell layers.

[0078] In another example, the angle is greater than 45°, preferably between 135° and 180°, preferably 180° (as shown in Figure 4b).

[0079] In all examples, fluid guidance features, such as dimples, may be provided to improve fuel distribution. As mentioned, the join between the interconnect and cell layer acts as a fluid guidance feature for examples where the angle 0 is greater than 90°.

[0080] For cases where 0 is oblique (i.e. not a multiple of 90°), it is advantageous to have a second port with mirror-image angle. Such an arrangement promotes equal fluid distribution across the central region 20. Figure 9 shows one example of such an orientation.

[0081] Figures 4 and 5 show the fluid guidance insert 52a associated with the inlet port in different orientations, however the fluid guidance insert associated with the outlet port may also change. For example, the throat may be oriented ata similar angle; this promotes fluid to flow over the full extent of the active cell area. .

[0082] In some embodiments, the fluid guidance insert 52a associated with the inlet port is positioned at a different angle to the fluid guidance insert associated with the outlet port. This providesenhanced fluid distribution via the alignment of the throat of the fluid guidance insert and the fluid guidance feature whilst maintaining an even distribution of fluid near to the outlet port. Figure 6 shows an example fluid guidance feature 70 in the form of a series of dimples. Such dimples may be formed in the interconnect or cell layer. It is preferable to form these on the interconnect 28 as this already has dimples formed thereon. As with the dimples over the active area on the interconnect, these dimples may be pressed to form a corresponding depression on the other side.

[0083] The dimples form a partial ring around the fluid port from approximately +90° and -90°. For fluid guidance inserts oriented outside this range the join between the cell layer and the interconnect acts as a fluid guidance feature. The dimples are arranged so that one dimple is directly aligned with the throat. This primary dimple acts to split the fluid flow, and the neighbouring dimples redirect the flow back. In such a way the fluid flow is dispersed over a greater area from close to the port.

[0084] In one example, the fluid guidance dimples do not extend the full height of the fluid volume. This allows a portion of the fluid to pass over the top, which improves fluid distribution to areas in the lee of a dimple.

[0085] In other embodiments, a further ring of dimples maybe provided, aligned with the gaps in the first ring of dimples to further spread the flow.

[0086] If only one orientation of the fluid guidance insert intended to be used, only a subset of the ring of dimples would be required, for example, just the dimples nearest the intended orientation of the throat.

[0087] A similar fluid distribution effect can be achieved by a continuous rib which redirects the fluid flow. For example, either side of the rib. As with the dimples described above, the rib, or a portion of the rib, may not extend the full height of the fluid volume to allow a portion of the fluid to pass over the top of the rib.

[0088] As previously mentioned, the angle of orientation of the throat of the fluid guidance insert is important for fluid distribution. As such, it is important that this is accurately positioned during manufacture.

[0089] The circular fluid port can be used as a locating feature for the fluid guidance insert 52. In one implementation, a dowel pin is passed through that port during assembly at which point the insert is affixed to the interconnect (or cell layer, depending on the orientation during manufacture). One method of orienting the fluid guidance insert 52 is to use a picking tool with a feature which engages the throat. The picking tool can then determine the orientation of the throat based on its own orientation and place it accordingly. Similarly, the picking tool could be equipped with a machine with vision system to orient the throat.

[0090] Following placement, the fluid guidance insert 52 is welded to the interconnect 28, and the cell layer 26 is affixed to the interconnector plate 28, for example via a weld around its periphery 22 to the periphery 30 of the interconnector plate 28. Alternatively, the fluid guidance insert 52 is welded to the cell layer 26. In another alternative, the fluid guidance insert 52 is not welded at all, rather held in place and secured once the cell layer 26 and interconnector plate 28 are affixed to one-another, for example via welding.Positive (tabs) or negative (slot, hole, etc) features can also be provided to aid orientation. One such arrangement is shown in Figure 7.

[0091] Figure 7a shows a fluid guidance insert 52 with four holes 80 spaced around at 45° intervals. A projection 82 is provided on the interconnect (or cell layer, depending on the orientation during manufacture) which engages in one of the holes. In such a way, the fluid guidance insert can be accurately oriented in a variety of discrete orientations.

[0092] It should be appreciated that instead of holes 80 they could be depressions, notches in the internal or external circumference, projections from the internal or external circumference and corresponding features in the interconnect (or cell layer) could be provided.

[0093] Figure 8 and Figure 9 show an alternative electrochemical cell design with two inlet ports 42a, 42b and two outlet ports 44a, 44b. Figure 8 shows the cell layer 24 with an electrochemically active area 20. The cell layer 24 has a periphery 26 and a central portion 24 surrounded by the periphery 22, while the interconnector plate 28 also has a periphery 30 and a central portion surrounded by the periphery.

[0094] The cell layer 24 and the interconnector plate 28 are stacked upon one another, with the periphery of the cell layer attached to the periphery of the interconnector plate and the structured area 38 facing the electrochemically active area 20.

[0095] Figure 9 shows the placement of four fluid guidance inserts 52 around the four ports. The fluid guidance inserts 52a associated with the inlet ports are shown to be oriented at an oblique angle (as per Figure 5) and the fluid guidance inserts 52b associated with the outlet ports oriented with their throats facing the inlet ports. However, any combination of orientations discussed with reference to Figures 4 and 5 above would be possible. The design of the fluid guidance insert 52 with a single throat allows for flexibility in orientation, and selecting an orientation depending on the position within the cell (i.e. inlet or outlet) or the position of the cell within a stack.

Claims

CLAIMS1. An electrochemical cell unit comprising:a cell layer having a periphery and a central portion surrounded by the periphery, and an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein:the cell layer and the interconnector plate are stacked upon one another, the periphery of the cell layer is attached to the periphery of the interconnector plate, the central portion of the cell layer and the central portion of the interconnector plate define a fluid volume therebetween, the cell unit having at least one fluid port in fluidic communication with the fluid volume, and a fluid guidance insert disposed in the fluid volume; whereinthe fluid guidance insert partially circumscribes the fluid port thereby forming a throat, the throat providing a passage for fluid between the fluid port and the fluid volume; andthe interconnector and / or the cell layer comprising a fluid guidance feature aligned with said throat to redirect the fluid flow.

2. The cell unit according to any preceding claim, wherein the cell unit comprises at least one fluid inlet port and at least one fluid outlet port.

3. The cell unit according to the preceding claim wherein the throat of the fluid guidance insert is positioned at an angle to a line joining the inlet and outlet ports.

4. The cell unit according to claim 3 wherein the throat of the fluid guidance insert is positioned at an angle of greater than zero but less than 45 degrees to a line joining the inlet and outlet ports.

5. The cell unit according to claim 3 wherein the throat of the fluid guidance insert is positioned greater than 45 degrees to a line joining the inlet and outlet ports.

6. The cell unit according to the preceding claim wherein the throat of the fluid guidance insert is positioned greater than 90 degrees to a line joining the inlet and outlet ports; preferably at least 135 degrees; preferably substantially directly away from the opposing port.

7. The electrochemical cell according to any preceding claim wherein the cell unit comprises at least two fluid guidance inserts, and the at least one fluid inlet port and the at least one fluid outlet port are associated with different ones of the at least two fluid guidance inserts.

8. The cell unit according to the preceding claim wherein the fluid guidance insert associated with the inlet port is positioned at a different angle to the fluid guidance insert associated with the outlet port; preferably wherein the fluid guidance insert associated with the inlet port is positioned away from outlet port and the fluid guidance insert associated with the outlet port is positioned towards the inlet port.

9. The cell unit according to any preceding claim wherein fluid guidance feature comprises the periphery of the cell layer; preferably the attachment of the interconnect plate and the cell layer.

10. The electrochemical cell according to any preceding claim wherein the fluid guidance feature comprises at least one dimple on the central area of the interconnect and / or cell layer adjacent to the fluid guidance insert, the at least one dimple being adapted to distribute the fluid from the fluid port.

11. The electrochemical cell according to any preceding claim wherein the width of the throat (w) is related to the thickness of the interconnector or cell layer (t), whichever smaller, by the formula: w < 15t; preferably w < 11t, preferably w < 8t.

12. The electrochemical cell according to any preceding claim wherein the fluid guidance insert, the cell layer and / or the interconnect comprise a locating feature to locate the fuel guidance insert.

13. The electrochemical cell according to the preceding claim wherein the locating feature comprises a protrusion or depression adapted to interface with a corresponding feature on the fuel guidance insert.

14. The electrochemical cell according to claim 12 wherein the locating feature comprises a tab on the fluid guidance insert adapted to engage with a periphery of the fluid port.

15. The electrochemical cell according to any preceding claim wherein the insert is circular in shape.

16. The electrochemical cell according to any preceding claim wherein the insert is made of metal, preferably steel.

17. The electrochemical cell according to any preceding claim being a solid oxide electrolysis cell (SOEC), solid oxide fuel cell (SOFC), or reversible solid oxide cell (SOC).

18. An electrochemical cell stack comprising a series of electrochemical cells according to any preceding claim arranged in a stack, the cells being electrically connected and the fluid ports being in alignment.

19. The electrochemical cell stack of the preceding claim wherein the orientation of the throat of the fluid guidance insert for each respective cell varies based on the position of the cell within the stack.

20. The electrochemical cell stack of claim 18 or 19 wherein the width of the throat of the fluid guidance insert varies based on the position of the cell within the stack21. The electrochemical cell stack of the preceding claim wherein the width of a throat of the of a fluid guidance insert associated with an electrochemical cell closer to a fluid inlet is narrowerthan the width of a throat of a fluid guidance insert associated with an electrochemical cell further away from the fluid inlet.

22. A method of manufacturing an electrochemical cell, the electrochemical cell comprising a cell layer having a periphery and a central portion surrounded by the periphery, and an interconnector plate having a periphery and a central portion surrounded by the periphery, the method comprising:placing fluid guidance insert around a port of the cell layer;the fluid guidance insert partially circumscribing the fluid port thereby forming a throat, the throat providing a passage for fluid between the fluid port and the fluid volume; andattaching an interconnect to the cell layer, the periphery of the cell layer being attached to the periphery of the interconnector plate, the central portion of the cell layer and the central portion of the interconnector plate defining a fluid volume therebetween.

23. The method according to the preceding claim, wherein the cell unit comprises at least one fluid inlet port and at least one fluid outlet port and the throat of the fluid guidance insert is positioned at an angle to a line joining the inlet and outlet ports.

24. The method according to the preceding claim wherein the throat of the fluid guidance insert is positioned greater than 45 degrees to a line joining the inlet and outlet ports.

25. The method according to the preceding claim wherein the throat of the fluid guidance insert is positioned greater than 90 degrees to a line joining the inlet and outlet ports, preferably wherein the throat of the fluid guidance insert is positioned facing substantially directly away from the opposing port.

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