Electrochemical cell unit

Abstract

The invention relates to an electrochemical cell unit (22), the cell unit comprising a cell housing (44) that defines a fluid volume (46), wherein a housing portion (48) of the cell housing has a structured area (50), wherein a coating (94) is provided on a surface of the structured area that is facing towards the fluid volume, and wherein the structured area comprises one or more first sections in which the coating has a nominal thickness, and one or more second sections that are devoid of the coating or in which the thickness of the coating is lower than the nominal thickness. The invention also relates to an electrochemical cell assembly (10) comprising such a cell unit and to a method for preparing electrochemical cell units.

Description

[0001] Description

[0002] Title

[0003] Electrochemical cell unit

[0004] State of the Art

[0005] The invention relates to the field of electrochemical cell stacks, in particular fuel cell stacks and electrolyser cell stacks. More specifically, the invention relates to electrochemical cell units, to electrochemical cell assemblies comprising such electrochemical cell units, and to methods for preparing such electrochemical cell units.

[0006] 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 fuels (e.g. H2) to electricity. Electrolyser cell units may be considered fuel cell units running in reverse mode, i.e. using electricity to decompose a compound (e.g. H2O) into its constituent parts (e.g. H2 and O2). Reversible cell units are capable of operating in both modes. Such electrochemical cell units typically comprise electrochemically active layers that may be configured to allow for conversion of electrochemical fuel to electricity (fuel cell units) or for decomposing a compound into its constituent parts using electricity (electrolyser cell units).

[0007] Electrochemical cell units typically comprise an internal fluid volume that is defined by a cell housing. During operation of the electrochemical cell unit, fluid, in particular fuel, flows through said fluid volume. Preferably, the fluid volume is in fluid communication with the electrochemically active layers of the cell unit.

[0008] The present invention specifically relates to solid oxide cell units (SOCs). Such solid oxide cell units (SOCs) typically comprise an electrolyte layer formed from a solid oxide, e.g. from Ytrria-stabilised Zirconia (YSZ), Gadolinia-doped Ceria, or Cerium Gadolinium Oxide (CGO). SOCs can be run as solid oxide fuel cell unit (SOFC) or as solid oxide electrolyser cell unit (SOEC).

[0009] Typically, multiple of such electrochemical cell units are stacked upon one another to form a stack of cell units, also referred to as 'cell repeat units'. Said stack of cell units is commonly arranged between two end plates that are located on opposite sides of the stack, thus forming an electrochemical cell assembly. The stack of cell units is usually held in compression between the end plates. That is to say, a compressive force acting along the stacking direction is supplied to the stack of cell units by the end plates. This may secure a direct contact and, thus, an electrical connection between adjacent cell units of the stack.

[0010] It is an object of the present invention to increase the performance of an electrochemical cell unit.

[0011] Description of the Invention

[0012] According to the invention, there is provided an electrochemical cell unit with the features of claim 1. The electrochemical cell unit comprises a cell housing that defines a fluid volume. That is to say, the fluid volume is enclosed by housing portions of the cell housing. During operation of the electrochemical cell unit, fuel such as hydrogen may flow through the fluid volume. The electrochemical cell unit further comprises at least one fluid inlet port for supply of a fluid, e.g. a fuel, from the exterior (i.e. , from the exterior of the cell unit) to the fluid volume and at least one fluid outlet port for removal of a fluid, e.g. a consumed or partly consumed fuel, from the fluid volume to the exterior. The cell housing comprises a housing portion that has a structured area with a plurality of protrusions. The protrusions may define a network of fluidical ly interconnected fluid channels therebetween. Said protrusions or the network of fluid channels may thus serve for distributing a fluid within the fluid volume during operation of the electrochemical cell unit. A coating is provided on a surface of the structured area that faces towards the fluid volume. Accordingly, a fluid that flows through the fluid volume may pass along the coating. According to the invention, the structured area comprises one or more first sections in which the coating has a nominal thickness, and one or more second sections that are devoid of the coating or in which the thickness of the coating is lower than the nominal thickness. There may also be provided one or more second sections that are devoid of the coating and additionally one or more second sections in which the thickness of the coating is lower than the nominal thickness. That is to say, both concepts (second sections that are devoid of a coating and second sections in which the thickness of the coating is lower than the nominal thickness) may be combined.

[0013] The inventors have found that the fluid (e.g., fuel) distribution inside the fluid volume can be optimised by a region-selective application of the coating. The thickness of the coating influences the local height of the fluid volume, i.e. the extent of the fluid volume along a direction that is perpendicular to the housing portion with the structured area, and thus has a significant impact on the local flow resistance in the fluid volume (c.f. the Hagen-Poisseuille equation). By reducing the thickness of the coating or omitting the coating in selected sections of the structured area, the fluid (e.g., fuel) supply to these sections may be enhanced which in turn may result in an improved overall fuel consumption.

[0014] As used herein, a variation of the thickness of the coating, e.g. a thickness that is lower than the nominal thickness, refers to an intended variation of the thickness. It will be understood that due to different influencing factors such as the production method or the material of the coating, every coating will inevitably have a certain roughness, i.e. randomly distributed irregularities. Such irregulatities are not considered a variation of the thickness of the coating within the meaning of the invention. Specifically, a local depression in the coating that corresponds to the roughness of the coating is not considered as a second section within the meaning of the invention.

[0015] The electrochemical cell unit may comprise only one fluid inlet port or several fluid inlet ports. The fluid inlet port or fluid inlet ports may be provided in the electrochemical cell unit as through-holes. The electrochemical cell unit may comprise only one fluid outlet port or several fluid outlet ports. The fluid outlet port or fluid outlet ports may be provided in the electrochemical cell unit as through-holes. In some embodiments, the electrochemical cell unit is a fuel cell unit. In some embodiments, the electrochemical cell unit is an electrolyser cell unit. In some embodiments, the electrochemical cell unit is a solid oxide fuel cell unit (SOFC). In some embodiments, the electrochemical cell unit is a solid oxide electrolyser cell unit (SOEC). Preferably, the electrochemical cell unit is a metal-supported solid oxide cell unit, e.g. metal-supported solid oxide fuel cell unit or metal- supported solid oxide electrolyser cell unit.

[0016] The electrochemical cell unit may be configured flat or planar. Thus, the length extent and the width extent of the electrochemical cell unit are significantly larger than its height extent. Preferably, the housing portion having the structured area is configured flat or planar. This relates to the general configuration of the housing portion without consideration of the structures, e.g. the protrusions, of the structured area.

[0017] The coating may be a single-layered coating. Alternatively, the coating may be a multi-layered coating, i.e. comprising several layers that are provided on top of each other. At a transition from one section of the structured area to another section of the structured area, e.g. from a first section to a second section, the thickness of the coating may vary abruptly or continuously. The thickness of the coating may be reduced in the second sections by reducing the number of layers of the coating and / or by reducing the thickness of at least one layer of the coating.

[0018] Preferably, the thickness of the coating is constant within the same section of the structured area.

[0019] The thickness of the coating in a second section may be equal to or less than 80% and equal to or more than 20% of the nominal thickness, preferably equal to or less than 60% and equal to or more than 20% of the nominal thickness.

[0020] In some preferred embodiments, the second section or at least one of the second sections extends across several protrusions of the plurality of protrusions. That is to say, several protrusions are located within the same second section. By providing one or more second sections with such a dimension, the fuel distribution within the fluid volume can be effectively influenced. In some preferred embodiments, the first section or at least one of the first sections extends across several protrusions of the plurality of protrusions. That is to say, several protrusions are located within the same first section.

[0021] In some preferred embodiments, the structured area comprises one or more third sections in which the thickness of the coating is larger than the nominal thickness. By providing one or more third sections the distribution of the fuel within the fluid volume can be further optimised. Particularly, the third section or third sections may act as flow barriers and thus redirect a fuel stream within the fluid volume. The thickness of the coating may be increased in the third section or third sections by increasing the number of layers of the coating and / or by increasing the thickness of at least one layer of the coating.

[0022] In some preferred embodiments, the third section or at least one of the third sections extends across several protrusions of the plurality of protrusions. That is to say, several protrusions are located within the same third section. By providing one or more third sections with such a dimension, the fuel distribution within the fluid volume can be effectively influenced.

[0023] In some preferred embodiments, the coating comprises a catalyst material. Accordingly, a fluid that flows through the fluid volume may pass the catalyst and may thus be influenced by the catalyst material. Preferably, the catalyst material is a reforming catalyst, for example configured to catalyse the reformation of a hydrocarbon fuel (e.g., methane) to hydrogen.

[0024] The catalyst material may be homogeneously distributed within the coating. That is to say, the concentration of the catalyst material in the coating may be the same throughout the coating. Alternatively, the catalyst material may be inhomogeneuously distributed within the coating. Particularly, the coating may comprise one or more portions that are devoid of the catalyst material.

[0025] In some preferred embodiments, in the third section or at least one of the third sections, the coating has at least one layer that is devoid of the catalyst material. By providing a layer that is devoid of the catalyst material the manufacturing costs may be reduced. Preferably, the at least one layer that is devoid of the catalyst material is a lower layer of the coating, particularly the lowermost layer of the coating. That is to say at least one layer comprising the catalyst material is located on top of the layer that is devoid of the catalyst material.

[0026] In some preferred embodiments, the protrusions protrude into the fluid volume. This may promote a particularly effective distribution in the fluid volume.

[0027] In some preferred embodiments, each protrusion of the plurality of protrusions comprises a peak, wherein said peaks contact a further housing portion of the cell housing that is opposite the housing portion having the structured area. This has the advantage that the distance between the housing portion and the opposite further housing portion is clearly defined, i.e. by the contact of the peaks with the further housing portion. As mentioned above, the electrochemical cell units may be held in compression between the end plates in an assembled electrochemical cell assembly. In this regard, the compressive forces may be securely supported by the contact between the peaks and the further housing portion. Preferably, the further housing portion is configured flat or planar. The further housing portion may carry electrochemically active layers, preferably on a surface that is facing away from the fluid volume. The electrochemically active layers may be carried by a porous area of the further housing portion. Hence, a fuel may reach from the fluid volume to the electrochemically active layers through pores provided in said porous area. The housing portion having the structured area and the opposite housing portion may be provided by different components of the cell housing.

[0028] In some preferred embodiments, at least a majority of the peaks, preferably all peaks, are devoid of the coating. Thus, the majority of the peaks may be part of a second section of the structured area, preferably a respective second section of the structured area. Valleys between adjacent peaks may be occupied by first portions or third portions of the structured area such that the second portions on the peaks are spatially isolated from each other. There may additionally or alternatively be one or more second sections positioned in the valleys between adjacent peaks, or one or more second sections formed by one or more respective peaks may extend to and across said valleys. If the peaks of the protrusions are devoid of the coating, the housing portion is in direct contact with the further housing portion. Since the housing portion having the structured area and the further housing portion may be manufactured with a low production tolerance, a direct contact between those components may be achieved with a high positioning accuracy. Specifically, the positioning accuracy is not influenced by the roughness of a coating on the peaks.

[0029] In some preferred embodiments, at least on a majority of the peaks, preferably on all peaks, the thickmess of the coating is lower than the nominal thickness. Thus, the majority of the peaks may be part of a second section of the structured area, preferably a respective second section of the structured area. Valleys between adjacent peaks may be occupied by first portions or third portions of the structured area such that the second portions on the peaks are spatially isolated from each other. There may additionally or alternatively be one or more second sections positioned in the valleys between adjacent peaks, or one or more second sections formed by one or more respective peaks may extend to and across said valleys. In this embodiment, the peaks are in indirect contact with the further housing portion, namely via the coating provided on the peaks. Nevertheless, the reduction of the thickness of the coating may go along with a reduction of the roughness of the coating. Hence, a reduction of the thickness of the coating will also aid high positioning accuracy.

[0030] In some preferred embodiments, the fluid inlet port is spaced apart from the fluid outlet port in a fluid flow direction, wherein, based on the fluid flow direction, the structured area is located between the fluid inlet port and the fluid outlet port. The fluid flow direction refers to the net flow direction. Thus, fuel that is supplied to the fluid volume through the fluid inlet port will pass the structured area before being removed from the fluid volume through the fluid outlet port.

[0031] In some preferred embodiments, the structured area extends in a first direction that is parallel to the fluid flow direction and in a second direction that is perpendicular to the fluid flow direction and to the first direction.

[0032] Preferably, the structured area has a rectangular shape. In other embodiments, the structured area may be circular in shape or diamond-shaped.

[0033] In some preferred embodiments, the structured area comprises at least one downstream second section that is located at a downstream end portion of the structured area. The downstream end portion is the end portion of the structured area along the fluid flow direction. The inventors have found that the fuel supply at the downstream end portion of the structured area is typically reduced compared to upstream portions of the structured area. This follows from the fuel being partly consumed before reaching to the downstream end portion of the structured area. By providing at least one downstream second section, the fuel may be actively directed into the downstream end portion of the structured area. Preferably, a first section of the structured area is located upstream of the downstream second section. The downstream second section may be devoid of the coating. Alternatively, the thickness of the coating may be lower in the downstream second section than the nominal thickness.

[0034] Preferably, the extent of the downstream second section along the second direction is lower than the extent of the structured area along the second direction and the downstream second section is located centrally with respect to the second direction. That is to say, the downstream second section is surrounded by first sections or third sections along the second direction. Alternatively, the downstream second section may extend along the full extent of the structured area along the second direction.

[0035] In some preferred embodiments, the structured area comprises at least one lateral second section that is located at a lateral end portion of the structured area and extends along the fluid flow direction. The lateral end portions are the end portions of the structured area along the second direction, i.e. the lateral edges of the structured area. The inventors have found that the fuel supply in the lateral end portions of the structured area is typically reduced compared to central portions of the structured area. By providing a second section at a lateral end portion of the structured area the fuel may be directed into this lateral end portion of the structured area. The lateral second section may be devoid of the coating. Alternatively, the thickness of the coating may be lower than the nominal thickness in the lateral second section.

[0036] Preferably, the structured area comprises two opposite lateral end portions, wherein at least one lateral second section is located at each of the lateral end portions. A central first section or central third section may be located between the lateral second sections. In some preferred embodiments, the structured area comprises a central second section that is located centrally with respect to the second direction and extends in the first direction. Said central second section may serve as a fluid channel to distribute fuel along the first direction. The central second section may be devoid of the coating. Alternatively, the thickness of the coating may be lower than the nominal thickness in the central second section.

[0037] In some preferred embodiments, the structured area comprises a central third section that is located centrally with respect to the second direction and downstream of the central second section. The central third section forms a flow barrier downstream of the central second section. Hence, a fluid flowing through the central second section will be spread in the lateral directions, i.e. in the second direction, by the central third downstream of the central second section.

[0038] In some preferred embodiments, the structured area comprises at least one diagonal second section that starts adjacent to the central second section and extends at an angle to the first direction and to the second direction. A fluid that is flowing through the central second section may be spread in the second direction by the diagonal second section. The angle between the first direction and the longitudinal axis of the diagonal second section may be between 20° and 70°, preferably between 35° and 55°. Preferably, the structured area comprises several diagonal second sections that start adjacent to the central second section. The diagonal second sections may be located on the same lateral side of the central second section or on different lateral sides of the central second section. Preferably, several diagonal second sections are located on each lateral side of the central second section. The diagonal second section or diagonal second sections may be devoid of the coating. Alternatively, the thickness of the coating may be lower than the nominal thickness in the diagonal second section or diagonal second sections.

[0039] In some preferred embodiments, the structured area comprises at least one diagonal third section that starts adjacent to the central second section and extends at an angle to the first direction and to the second direction. A fuel may be guided into the second direction by said diagonal third section. The angle between the first direction and the longitudinal axis of the diagonal third section may be between 20° and 70°, preferably between 35° and 55°. Preferably, the structured area comprises several diagonal third sections that start adjacent to the central second section. The diagonal third sections may be located on the same lateral side of the central second section or on different lateral sides of the central second section. Preferably, several diagonal third sections are located on each lateral side of the central second section. Preferably, several diagonal second sections are located on each lateral side of the central second section. At least one diagonal third section may be located between, e.g. sandwiched between, two diagonal second sections, one diagonal second section being located upstream of the diagonal third section, the other diagonal second section being located downstream of the diagonal third section.

[0040] In some embodiments, the cell housing comprises, preferably is built up from, two or more planar, preferably plate-shaped, components that are connected to each other to enclose the fluid volume therebetween. Preferably, a first planar, preferably plate-shaped, component comprises the housing portion having the structured area. Prefearbly, a second planar, preferably plate-shaped, component comprises the further housing portion.

[0041] In some embodiments, the cell housing is formed by an interconnector plate and a support plate, said interconnector plate and said support plate overlying one another and being sealingly attached to each other to enclose the fluid volume therebetween. In such embodiments, the interconnector plate may comprise the housing portion having the structured area. The support plate may carry electrochemically active layers over a porous area.

[0042] In some preferred embodiments, the cell unit comprises an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein the central portion of the interconnector plate comprises, preferably forms, the housing portion having the structured area.

[0043] In some preferred embodiments, the cell unit comprises a support plate having a periphery and a central portion surrounded by the periphery, wherein the central portion of the support plate comprises, preferably forms, the further housing portion. The support plate may carry electrochemically active layers over a porous area. In some preferred embodiments, the periphery of the interconnector plate is sealingly attached to, preferably welded to, the periphery of the support plate, wherein the fluid volume is defined between the central portion of the interconnector plate and the central portion of the support plate. Thus, the cell housing is built up from two plate-shaped components, i.e. the interconnector plate and the support plate. This facilitates the realisation of a flat cell unit that can be easily stacked to obtain a stack of a plurality of cell units.

[0044] The support plate and / or the interconnector plate may be provided with the at least one fluid inlet port and / or the at least one fluid outet port, preferably, both plates are provided with through-holes, which form the ports. Through-holes forming fluid inlet ports may be provided through both plates and aligned in a stacking direction. Similarly, through-holes forming fluid outet ports may be provided through both plates and aligned in the stacking direction.

[0045] The plurality of protrusions provided in the structured area may have one or more of a variety of cross sections (for example a circular, oval, square, rectangular, hexhagonal etc cross section) that do not themselves direct fluid flow in the fluid volume. For example, they may have an aspect ratio (length:width cross section) of less than 10, preferably less than 5, more preferably less than 2. The structured area may also be provided with a plurality of protrusions that protrude away from the fluid volume (and towards a neighboring electrochemical cell unit in a stack of electrochemical cell units). It will be noted that the coating does not typically block fluid flow in the fluid volume, but directs said fluid flow by variation of the height of the fluid volume.

[0046] According to the invention, there is also provided an electrochemical cell assembly with the features of claim 23.

[0047] The cell assembly comprises a first end plate assembly having a first end plate, a second end plate assembly having a second end plate, and a stack of electrochemical cell units, comprising a plurality of electrochemical cell units that are stacked upon one another along a stacking direction. Preferably, the stack of electrochemical cell units is held in compression between the first end plate and the second end plate. At least one electrochemical cell unit of the plurality of electrochemical cell units is configured as described above. Preferably, all electrochemical cell units of the plurality of electrochemical cell units are configured as described above.

[0048] According to the invention, there is also provided a method for preparaing electrochemical cell units with the features of claim 24.

[0049] The method comprises providing a housing portion for a cell housing, said housing portion having a structured area with a plurality of protrusions. The housing portion may be provided by a first planar component, e.g. first plate.

[0050] In preferred embodiments, the housing portion is a central portion of an interconnector plate (see above). Thus, the method may comprise providing an interconnector plate having a structured area with a plurality of protrusions formed therein.

[0051] The method further comprises applying a coating, the coating preferably having a catalyst material, on a surface of the structured area. The coating is applied with a nominal thickness in one or more first sections of the structured area. The coating is omitted or applied with a thickness that is lower than the nominal thickness in one or more second sections of the structured area.

[0052] The method further comprises providing a further housing portion and connecting said further housing portion to the housing portion having the structured area to form a cell housing. The housing portions are connected such that a fluid volume is enclosed between said housing portions, the coating is facing the fluid volume and the protrusions are preferably protruding into the fluid volume.

[0053] The further housing portion may be provided by a second planar component, e.g. second plate. In preferred embodiments, the further housing portion is a central portion of a support plate (see above). Thus, the method may comprise providing a support plate, overlaying the support plate and the interconnector plate, and sealingly attaching the support plate to the interconnector plate. The central portion of the support plate may carry electrochemically active layers. Omitting the coating or providing the coating with a reduced thickness in one or more second sections of the structured area may result in the advantages discussed above. By reducing the thickness of the coating or leaving out the coating in selected sections of the structured area, the fuel supply to these sections may be enhanced which in turn may result in an improved overall fuel consumption.

[0054] The thickness of the coating may be varied, i.e. reduced or increased, by varying the number of layers of the coating and / or by varying the thickness of at least one layer of the coating.

[0055] In some preferred embodiments of the method, the coating is provided on the structured area by means of a print head. A print head is an application device that is configured to deposit the coating as droplets, i.e. dropwise, rather than as a flow jet. By using a print head, the thickness of the coating can be influenced in a targeted manner, e.g. by changing the size of the droplets deposited by the print head. For example, when applying the coating to a second section of the structured area, the size of the droplets may be reduced compared to a first section of the structured area.

[0056] In some other preferred embodiments, the coating is provided on the structured area by vapour deposition. The use of vapour deposition may result in a short production time.

[0057] In some preferred embodiments of the method, the second section or at least one of the second sections is covered at least temporarily during the application of the coating with a mask. This may facilitate the intended variation of the thickness of the coating, particularly in case that a less precise spray head is used as an application device. As mentioned above, the peaks of the protrusions may be devoid of the coating or the thickness of the coating may be lower than the nominal thickness on the peaks of the protrusions. Preferably, the peaks are covered during application of the coating at least temporarily with a mask.

[0058] In some preferred embodiments, the coating is applied with a thickness that is larger than the nominal thickness in one or more third sections of the structured area. By providing one or more third sections the distribution of the fuel within the fluid volume can be further optimised. During operation of the electrochemical cell unit or an electrochemical cell assembly comprising the cell unit the third sections may act as flow barriers.

[0059] Further embodiments are derivable from the following description and the drawings:

[0060] Figure 1 shows a cross-section of an embodiment of an electrochemical cell assembly;

[0061] Figure 2 shows an exploded view of an electrochemical cell unit of the electrochemical cell assembly of Figure 1 ;

[0062] Figure 3 shows a top view of an interconnector plate of the electrochemical cell unit of Figure 2;

[0063] Figure 4 shows a cross-section of a structured area of the interconnector plate;

[0064] Figure 5 shows a top view of the structured area of the interconnector plate of Figure 4;

[0065] Figure 6 shows a second embodiment of the structured area of the interconnector plate;

[0066] Figure 7 shows a third embodiment of the structured area of the interconnector plate;

[0067] Figure 8 shows a first method for preparing electrochemical cell units; and

[0068] Figure 9 shows a second method for preparing electrochemical cell units.

[0069] Referring to Figure 1 , there is shown an exemplary configuration of an electrochemical cell assembly 10 that is configured as a solid oxide cell assembly. The electrochemical cell assembly 10 comprises a first end plate assembly 12 having a first end plate 14 and a second end plate assembly 16 having a second end plate 18.

[0070] The electrochemical cell assembly 10 further comprises a stack 20 having a plurality of electrochemical cell units 22 that are stacked upon one another along a stacking direction 24. The electrochemical cell units 22 extend in a respective cell plane that is perpendicular to the stacking direction 24. The cell units 22 are electrically connected in series. In this example, the cell units 22 are configured flat. An electrical connection between adjacent cell units 22 is established by a direct contact between the cell units 22.

[0071] The stack 20 further comprises gaskets 26 that are interposed between adjacent cell units 22. In this example, the gaskets 26 are configured as annular sealing rings having a central opening 28.

[0072] The stack 20 is arranged between the first end plate 14 and the second end plate 18. That is to say, the first end plate 14 and the second end plate 18 are arranged on opposite sides of the stack 20 and the stack 20 is arranged in a receiving volume defined between the first end plate 14 and the second end plate 18. In this example, the first end plate 14 forms a lower end plate or base plate of the cell assembly 10. The second end plate 18 forms an upper end plate of the cell assembly 10.

[0073] Preferably, the stack 20 is held in compression between the first end plate 14 and the second end plate 18. That is to say, the end plates 14 and 18 are biased towards each other and a compressive force is acting on the stack 20 of cell units 22 along the stacking direction 24. This improves the sealing effect of the gaskets 26 and secures the direct contact between adjacent cell units 22.

[0074] In this example, the cell assembly 10 comprises a first insulating plate 32 that is interposed between the first end plate 14 and the stack 20 of cell units 22. The first insulating plate 32 is in direct contact with the first end plate 14.

[0075] In this example, an electrically conductive first power transmission plate 34 is interposed between the stack 20 of cell units 22 and the first insulating plate 32. The first power transmission plate 34 is in direct contact with the first insulating plate 32 and the stack 20 of cell units 22, i.e. the lowermost cell unit 22.

[0076] In this example, an electrically conductive second power transmission plate 36 is interposed between the stack 20 of cell units 22 and the second end plate 18. The second power transmission plate 36 is in direct contact with the stack 20 of cell units 22, i.e. the uppermost cell unit 22.

[0077] In this example, a second insulating plate 38 is interposed between the second power transmission plate 36 and the second end plate 18. The second insulating plate 38 is in direct contact with the second power transmission plate 36.

[0078] In this example, an electrically conductive third power transmission plate 40 is interposed between the second insulating plate 38 and the second end plate 18. The third power transmission plate 40 is in direct contact with the second insulating plate 38.

[0079] In this example, a third insulating plate 42 is interposed between the third power transmission plate 40 and the second end plate 18. The third insulating plate 42 is in direct contact with the third power transmission plate 40 and the second end plate 18.

[0080] Preferably, the first insulating plate 32, the second insulating plate 38 and the third insulating plate 42 are formed from the same electrically insulating material, e.g. a material comprising at least one mica group mineral.

[0081] Preferably, the third power transmission plate 40 is electrically connected to the first power transmission plate 34 by means of one or more bus bars (not visible) that span the stack 20 of cell units 22 along the stacking direction 24. In consequence, the third power transmission plate 40, the bus bar or bus bars, the first power transmission plate 34, the stack 20 of cell units 22 and the second power transmission plate 36 are electrically connected in series in this order.

[0082] In the following, the configuration of an electrochemical cell unit 22 of the stack 20 will be explained with additional reference to Figures 2, 3, 4 and 5. The electrochemical cell unit 22 comprises a cell housing 44 that defines a fluid volume 46 of the cell unit 22 (see Figure 4). The cell housing 44 comprises a housing portion 48 having a structured area 50 with a plurality of protrusions 52 that protrude into the fluid volume 46. The protrusions 52 define a network of fluidically interconnected fluid channels therebetween. Said network of fluidically interconnected fluid channels may serve for distributing a fuel within the fluid volume 46 during operation of the electrochemical cell assembly 10.

[0083] The cell housing 44 further comprises a further housing portion 56 that is arranged opposite the housing portion 48. The housing portion 48 and the further housing portion 56 extend parallel to each other.

[0084] As shown in Figure 4, the protrusions 52 formed in the housing portion 48 each comprise a peak 53. The peaks 53 are in contact with the further housing portion 56.

[0085] Preferably, the further housing portion 56 carries electrochemically active layers 58 on a surface that is facing away from fluid volume 46. The electrochemically active layers 58 are carried by a porous area 60 of the further housing portion 56 such that a fluid, e.g. a fuel such as hydrogen, can exit the fluid volume 46 through pores formed in the porous area 60 and reach the electrochemically active layers 58. The pores may be formed by a plurality of through-holes formed in the further housing portion 56. For simplicity, the pores of the porous area 60 are not shown in the Figures.

[0086] As can be seen in Figure 4, the structured area 50 further comprises a plurality of second protrusions 62 that protrude away from the fluid volume 46. That is to say, the protrusions 52 and the second protrusions 62 protrude in opposite directions. For the sake of clarity, the second protrusions 62 are only visible in Figure 5. In another example, the structured area 50 may comprise the protrusions 52, but not the protrusions 62.

[0087] In this example, the cell unit 22 comprises an interconnector plate 64 and a support plate 70 (see Figure 2). The housing portion 48 is formed by a central portion 66 of said interconnector plate 64. The central portion 66 is surrounded by a periphery 68 of the interconnector plate 64. The further housing portion 56 is formed by a central portion 72 of the support plate 70. The central portion 72 of the support plate 70 is surrounded by a periphery 74 of the support plate 70.

[0088] In the assembled state of the cell unit 22, the periphery 68 of the interconnector plate 64 is sealingly attached to the periphery 74 of the suport plate 70, preferably by welding. The central portions 66 and 72 of the interconnector plate 64 and the support plate 70 define the fluid volume 46 therebetween.

[0089] The electrochemical cell unit 22 comprises at least one fluit inlet port 76 for providing a fluid, e.g. a fuel, from the exterior of the cell unit to the fluid volume 46 (see Figure 1). In this example, the cell unit 22 comprises two fluid inlet ports 76. The fluid inlet ports 76 are provided by a respective through-hole 78 formed in the interconnector plate 64 and a respective through-hole 80 formed in the support plate 70. The fluid inlet ports 76 are part of a respective fluid inlet manifold 77 that extends through the electrochemical cell assembly 10 along the stacking direction 24.

[0090] The electrochemical cell unit 22 further comprises at least one fluit outlet port 82 for removing a fluid, e.g. a fuel, from the fluid volume 46 to the exterior of the cell unit (see Figure 1). In this example, the cell unit 22 comprises two fluid outlet ports 82. The fluid outlet ports 82 are provided by a respective through-hole 84 formed in the interconnector plate 64 and a respective through-hole 86 formed in the support plate 70. The fluid outlet ports 82 are part of a respective fluid outlet manifold 83 that extends through the electrochemical cell assembly 10 along the stacking direction 24.

[0091] The fluid inlet ports 76 are spaced apart from the fluid outlet ports 82 in a fluid flow direction 88. Based on the fluid flow direction 88, the structured area 50 is located between the fluid inlet ports 76 and the fluid outlet ports 82.

[0092] The structured area 50 extends in a first direction 90 that is parallel to the fluid flow direction 88 and in a second direction 92 that is perpendicular to the first direction 90 and to the fluid flow direction 88. In this example, the structured area 50 is rectangular in shape.

[0093] During operation of the electrochemical cell assembly 10, a fuel can be provided to the fluid volume 46 of the cell units 22 through the fluid inlet manifolds 77 and the fluid inlet ports 76. The fuel may then flow through the fluid volume 46 of the cell units 22, particularly through the network of channels defined between the protrusions 62 of the structured area 50. Consumed or partially consumed fuel can be removed from the cell assembly 10 through the fluid outlet ports 82 and the fluid outlet manifolds 83.

[0094] With reference to Figures 4 and 5, a coating 94 is provided in the structured area 50 on a surface of the housing portion 48 that is facing towards the fluid volume 46. It should be noted that the number of protrusions 52 is reduced in Figure 5 compared with Figures 2 and 3 for the sake of clarity. The coating 94 may comprise a catalyst material. Said catalyst material may be configured to catalyse the reformation of hydrocarbon fuel (e.g., methane) to produce hydrogen. A substantial amount of hydrocarbon may be originally present in the fuel when supplying the fuel from the exterior to the fluid volume 46 during operation.

[0095] In the sections between the protrusions 52, the coating 94 has a constant nominal thickness.

[0096] The peaks 53 of the protrusions 52 however are devoid of the coating 94. Accordingly, the peaks 53 of the protrusions 52 are in direct contact with the further housing portion 56. This has the advantage that the distance between the housing portion 48 and the further housing portion 56, i.e. the height extent of the fluid volume 46, is not influenced by a potential roughness of the coating 94, i.e. randomly distributed irregularities of the coating 94. Alternatively, the thickness of the coating 94 may be lower than the nominal thickness on the peaks 53. A reduction of the thickness of the coating typically goes along with a reduction of the roughness.

[0097] A section of the structured area 50 in which the coating 94 has the nominal thickness will be referred to as a first section of the structured area 50 in the following. A section of the structured area 50 that is devoid of the coating 94 or in which the thickness of the coating 94 is lower than the nominal thickness will be referred to as a second section of the structured area 50 in the following. Due to the lower thickness of the coating 94, the flow resistance is reduced in a second section compared with a first section. As a consequence, the fluid (e.g., fuel) supply to the second sections is enhanced during operation.

[0098] A section of the structured area 50 in which the thickness of the coating 94 is larger than the nominal thickness will be referred to as a third section of the structured area 50 in the following. Due to the larger thickness of the coating 94, the flow resistance is increased in a third section compared to a first section. As a consequence, the third sections act as flow barriers.

[0099] A reduction of the thickness of the coating 94 can be realized by a reduction of the number of layers of the coating 94 and / or by a reduction of the thickness of at least one layer of the coating 94. An increase of the thickness of the coating 94 can be realized by an increase of the number of layers of the coating 94 and / or by an increase of the thickness of at least one layer of the coating 94.

[0100] Figure 6 shows another embodiment of the structured area 50. In the following, only the differences between the structured area 50 of Figure 5 and the structured area 50 of Figure 6 will be described.

[0101] In the example shown in Figure 6, the structured area 50 comprises a downstream second section 96 that is located at a downstream end portion 98 of the structured area 50. The downstream end portion 98 is located downstream with respect to the fluid flow direction 88.

[0102] In this example, the extent of the downstream second section 96 along the second direction 92 is smaller than the extent of the structured area 50 along the second direction 92. The downstream second section 96 is located centrally with respect to the second direction 92. The structured area 50 further comprises a respective lateral second section 100 at its lateral end sections 102. The lateral second sections 100 are configured elongate and extend along the first direction 90.

[0103] A central first section 104, i.e. a section in which the coating 94 has the nominal thickness, is located upstream of the downstream second section 96 and between the lateral second sections 100.

[0104] In the example shown in Figure 6, the coating 94 is present in the second sections 96 and 100, but with reduced thickness. Alternatively, the second sections 96 and 100 are devoid of the coating 94.

[0105] Figure 7 shows another embodiment of the structured area 50. In the following, only the differences between the structured area 50 of Figure 5 and the structured area 50 of Figure 7 will be described.

[0106] In the example shown in Figure 7, the structured area 50 comprises a central second section 106 that is located centrally with respect to the second direction 92 and extends in the first direction 90.

[0107] The structured area 50 further comprises several diagonal second sections 108. The diagonal second sections 108 start adjacent to the central second section 106 and extend at an angle to the first direction 90 and the second direction 92. The diagonal second sections 108 may also directly emanate from the central second section 106. In this example, the angle between the first direction 90 and the longitudinal axis of the diagonal second sections 108 is approximately 45°. Diagonal second sections 108 are located on both lateral sides of the central second section 106.

[0108] The structured area 50 further comprises several diagonal third sections 110.

[0109] The diagonal third sections 110 start adjacent to the central second section 106 and extend at an angle to the first direction 90 and the second direction 92. In this example, the diagonal third sections 110 are parallel to the diagonal second sections 110. A respective diagonal third section 110 is located between adjacent diagonal second sections 108. The structured area 50 further comprises a central third section 112 that is located centrally with respect to the second direction 92 and downstream of the central second section 106.

[0110] In the remaining sections of the structured area 50, the coating 94 has the nominal thickness, i.e. those sections are first sections of the structured area 50.

[0111] In the example shown in Figure 7, the coating 94 is present in the second sections 106 and 108, but with reduced thickness. Alternatively, the second sections 106 and 108 are devoid of the coating 94. In the diagonal third sections 110 and the central third section 112, the thickness of the coating 94 is larger than the nominal thickness.

[0112] Referring to Figure 8, there is shown an exemplary method for the production of electrochemical cell units 22.

[0113] In a first step 200, the housing portion 48 having the structured area 50 is provided as a part of the interconnector plate 64.

[0114] In a second step 202, the coating 94 is provided on the structured area 50 by means of a print head. The use of a print head allows for the intended variation of the thickness of the coating 94, e.g. by varying the size or volume of droplets that are deposited by the print head. By means of a print head, the examples shown in Figures 5, 6 and 7 can be easily realised.

[0115] In a third step 204, the further housing portion 56 is provided as a part of the support plate 70, and the fluid volume 46 is defined by sealingly attaching the periphery 68 of the interconnector plate 64 to the periphery 74 of the support plate 70, such that the coating 94 is facing towards the fluid volume 46 and the protrusions 52 protrude into the fluid volume 46.

[0116] Referring to Figure 9, there is shown a further method for the production of electrochemical cell units 22.

[0117] In a first step 300, the housing portion 48 having the structured area 50 is provided as a part of the interconnector plate 64. In a second step 302, the structured area 50 is partly covered by a mask 114. In this example, the mask 114 is configured such that it may cover the peaks 53 of the protrusions 52 while leaving the sections between the peaks 53 substantially uncovered.

[0118] In a third step 304, the coating 94 is provided on the structured area 50 by means of a spray head while the peaks 53 are covered with the mask 114. Even though a spray head does not provide the precision of a print head, the coating 94 is left out in the peaks 53. Using the mask 114, the example shown in Figure 5 can be easily realized. Other masks may allow the application of different patterns on the structured area 50.

[0119] In a fourth step 306, the further housing portion 56 is provided as a part of the support plate 70, and the fluid volume 46 is defined by sealingly attaching the periphery 68 of the interconnector plate 64 to the periphery 74 of the support plate 70 such that the coating 94 is facing towards the fluid volume 46 and the protrusions 52 are protruding into the fluid volume 46.

Claims

Claims1. An electrochemical cell unit (22), preferably fuel cell unit or electrolyser cell unit, comprising: a cell housing (44) that defines a fluid volume (46), at least one fluid inlet port (76) for supply of a fluid from the exterior to the fluid volume (46), and at least one fluid outlet port (82) for removal of a fluid from the fluid volume (46) to the exterior, wherein: a housing portion (48) of the cell housing (44) has a structured area (50) with a plurality of protrusions (52), a coating (94) is provided on a surface of the structured area (50) that faces towards the fluid volume (46), the structured area (50) comprises one or more first sections in which the coating (94) has a nominal thickness, and one or more second sections that are devoid of the coating (94) or in which the thickness of the coating (94) is lower than the nominal thickness.

2. The cell unit (22) according to claim 1, wherein the second section or at least one of the second sections extends across several protrusions (52) of the plurality of protrusions (52).

3. The cell unit (22) according to any one of the preceding claims, wherein the first section or at least one of the first sections extends across several protrusions (52) of the plurality of protrusions (52).

4. The cell unit (22) according to any one of the preceding claims, wherein the structured area (50) comprises one or more third sections in which the thickness of the coating (94) is larger than the nominal thickness.

5. The cell unit (22) according to the preceding claim, wherein the third section or at least one of the third sections extends across several protrusions (52) of the plurality of protrusions (52).

6. The cell unit (22) according to any one of the preceding claims, wherein the coating (94) comprises a catalyst material.

7. The cell unit (22) according to the preceding claim, wherein, in the third section or at least one of the third sections, the coating (94) has at least one layer that is devoid of the catalyst material.

8. The cell unit (22) according to any one of the preceding claims, wherein the protrusions (52) protrude into the fluid volume (46).

9. The cell unit (22) according to any one of the preceding claims, wherein each protrusion (52) of the plurality of protrusions (52) comprises a peak (53), and wherein said peaks (53) contact a further housing portion (56) of the cell housing (44) that is opposite the housing portion (48) having the structured area (50).

10. The cell unit (22) according to the preceding claim, wherein at least a majority of the peaks (53), preferably all peaks (53), are devoid of the coating (94).

11. The cell unit according to claim 9, wherein at least on a majority of the peaks (53), preferably on all peaks (53), the thickness of the coating (94) is lower than the nominal thickness.

12. The cell unit (22) according to any one of the preceding claims, wherein the fluid inlet port (76) is spaced apart from the fluid outlet port (82) in a fluid flow direction (88), and wherein, based on the fluid flow direction (88), the structured area (50) is located between the fluid inlet port (76) and the fluid outlet port (82).

13. The cell unit (22) according to the preceding claim, wherein the structured area (50) extends in a first direction (90) that is parallel to the fluid flow direction (88) and in a second direction (92) that is perpendicular to the fluid flow direction (88).

14. The cell unit (22) according to any one of claims 12 and 13, wherein the structured area (50) comprises at least one downstream second section (96) that is located at a downstream end portion (98) of the structured area (50).

15. The cell unit (22) according to any one of claims 12 to 14, wherein the structured area (50) comprises at least one lateral second section (100) that is located at a lateral end portion (102) of the structured area (50) and extends along the fluid flow direction (88).

16. The cell unit (22) according to claim 12, wherein the structured area (50) comprises a central second section (106) that is located centrally with respect to the second direction (92) and extends in the first direction (88).

17. The cell unit (22) according to the preceding claim, wherein the structured area (50) comprises a central third section (112) that is located centrally with respect to the second direction (92) and downstream of the central second section (106).

18. The cell unit (22) according to any one of claims 16 and 17, wherein the structured area (50) comprises at least one diagonal second section (108) that starts adjacent to the central second section (106) and extends at an angle to the first direction (90) and to the second direction (92).

19. The cell unit (22) according to any one of claims 16 to 18, wherein the structured area (50) comprises at least one diagonal third section (110) that starts adjacent to the central second section (106) and extends at an angle to the first direcion (90) and to the second direction (92).

20. The cell unit (22) according to any one of the preceding claims, wherein the cell unit (22) comprises an interconnector plate (64) having a periphery (68) and a central portion (66) surrounded by the periphery (68), and wherein the central portion (66) of the interconnector plate (64) comprises the housing portion (48) having the structured area (50).

21. The cell unit (22) according to any one of claims 9 to 20, wherein the cell unit (22) comprises a support plate (70) having a periphery (74) and a central portion (72) surrounded by the periphery (74), and wherein the central portion (72) of the support plate (70) comprises the further housing portion (56).

22. The cell unit (22) according to the preceding claim, wherein the periphery(68) of the interconnector plate (64) is sealingly attached to the periphery(74) of the support plate (70), and wherein the fluid volume (46) is defined between the central portion (66) of the interconnector plate (64) and the central portion (72) of the support plate (70).

23. An electrochemical cell assembly (10), preferably fuel cell assembly or electrolyser cell assembly, comprising a first end plate assembly (12) having a first end plate (14), a second end plate assembly (16) having a second end plate (18), and a stack (20) of electrochemical cell units (22), comprising a plurality of electrochemical cell units (22) that are stacked upon one another along a stacking direction (24), wherein at least one electrochemical cell unit (22) of the plurality of electrochemical cell units (22) is configured according to any one of the preceding claims.

24. A method for preparing an electrochemical cell unit (22), preferably fuel cell unit or electrolyser cell unit, preferably according to any one of claims 1 to 22, comprising: a. providing a housing portion (48), preferably first planar component, said housing portion (48) having a structured area (50) with a plurality of protrusions (52), b. applying a coating (94) on a surface of the structured area (50), comprising: i. applying the coating (94) with a nominal thickness in one or more first sections of the structured area (50), and ii. omitting the coating (94) or applying the coating (94) with a thickness that is lower than the nominal thickness in one or more second sections of the structured area (50), c. providing a further housing portion (56), preferably second planar component, and connecting said further housing portion (56) to the housing portion (48) having the structured area (50) to form a cell housing (44) such that a fluid volume (46) is defined between said housing portions (48, 56), the coating (94) is facing towards said fluid volume (46).

25. The method according to the preceding claim, wherein the coating (94) is provided on the structured area (50) by means of a print head.

26. The method according to claim 24, wherein the coating (94) is provided on the structured area (50) by vapour deposition.

27. The method according to any one of claims 24 to 26, wherein the second section or at least one of the second sections is covered during the application of the coating (94) at least temporarily with a mask (114).

28. The method according to any one of claims 24 to 27, wherein the coating (94) is applied with a thickness that is larger than the nominal thickness in one or more third sections of the structured area (50).

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