Planar fuel cell assembly and method of manufacturing thereof

Abstract

A current collector for a planar fuel cell assembly comprising a plurality of planar fuel cells, the current collector comprising a flexible foil of electrically non-conductive material comprising first and second patterns of electrically conductive material provided on a first and second side thereof, respectively. The first pattern connects the fuel cells in series when the flexible foil is folded over the fuel cells. The second pattern conveys the electrical energy generated in the planar fuel cells to an output terminal.

Description

PLANAR FUEL CELL ASSEMBLY AND METHOD OF MANUFACTURINGTHEREOFTechnical Field

[0001] The present disclosure relates to fuel cell assemblies comprising planar fuel cells. More specifically, it relates to a current collector for a planar fuel cell assembly and a method of manufacturing thereof.Background

[0002] Planar fuel cells are well-known in the art and comprise a plurality of unit planar fuel cells arranged next to each other in one plane. The individual planar fuel cells are electrically connected in series by contacting the anode of one cell with the cathode of an adjacent cell. This is typically achieved in one of two ways. The first, which is often referred to as the banded design, consists of having cathodes arranged on one side and anodes on the opposite side and each cathode being connected to the anode of the next adjacent cell. However, in order to connect the individual cells together, the electric connection must pass through the plane of the cell to the adjacent cell. Examples of this are shown in WO 2006 / 041397 Al, WO 2007 / 117212 A2, WO 2009 / 025613 Al and WO 2011 / 040875 Al, which are incorporated herein by reference. A disadvantage with this configuration is that the individual planar fuel cells require fastidious step-by-step assembly of several components to achieve the cross-plane electrical connection.

[0003] The second way of making a serial connection of planar cells is often referred to as the flip-flop design, and involves construction of two cell-house plates, each having cathodes and anodes alternated along its surface. A cathode of one fuel cell is then electrically connected to an anode of an adjacent fuel cell in the same plane. A disadvantage with this configuration is that the supply of fuel (hydrogen) to the anodes and oxygen to the cathodes along the same surface becomes overly complex.

[0004] US 2012 / 0141840 Al discloses a flexible printed circuit (FPC) board comprising conductive collector portions which may be bent over a fuel cell to connect theindividual fuel cells in series. US 2004 / 0131907 Al discloses a foldable substrate which comprises paired conductor layers and extension electrodes and further includes a circuit pattern on which a device is mountable. However, both these solutions suffer from the considerable separation between the end contacts.

[0005] Hence, there is a need to develop improved solutions for achieving electrical connection in series in planar fuel cell assemblies which facilitate manufacture and / or reduce the number of components.Summary of Invention

[0006] An objective of the present disclosure is therefore to provide improved solutions for planar fuel cell assemblies to solve the problems identified above.

[0007] According to a first aspect of the present disclosure, there is provided a current collector for a planar fuel cell assembly comprising a plurality of planar fuel cells, the current collector comprising a flexible foil of electrically non-conductive material having a first pattern of electrically conductive material provided on a first side thereof. The flexible foil is adapted to be folded with the first side facing the plurality of planar fuel cells in such a way that a first portion of the flexible foil is adjacent to an anode side of the plurality of planar fuel cells and a second portion of the flexible foil is adjacent to a cathode side of the plurality of planar fuel cells. The first pattern of electrically conductive material is arranged to establish electrical connection between an anode of a given planar fuel cell and a cathode of an adjacent planar fuel cell of the plurality of planar fuel cells in the folded configuration of the flexible foil. The flexible foil comprises a second pattern of electrically conductive material provided on a second side thereof, opposite the first side, the second pattern of electrically conductive material being arranged to convey electrical energy generated in the planar fuel cells to an output terminal.

[0008] By means of the novel configuration of the first and second patterns of electrically conductive material in combination with the flexible foil being foldable, the present disclosure provides an improved solution for achieving a serial connection between the planar fuel cells in the fuel cell assembly with low electrical impedance to reducepower loss. Another advantage is that the electrical energy can be conveyed to a single output terminal or electrical contact. The current collector allows for a reduction of number of components and steps required during manufacture of planar fuel cell assemblies. Thus, the time and cost of manufacture is reduced.

[0009] In one embodiment, the second pattern of electrically conductive material comprises electrical leads extending from the output terminal to a first area adjacent to the anode of the last planar fuel cell, and to a second area adjacent to the cathode of the first planar fuel cell, respectively, of the plurality of planar fuel cells, or vice versa. The electrical leads in the second pattern provide the electrical connections between the output terminal and the first and last planar fuel cells to complete the electrical circuit.

[0010] In one embodiment, the electrical leads of the second pattern of electrically conductive material are arranged predominantly on the first portion of the flexible foil. Preferably, the electrical leads of the second pattern of electrically conductive material extend over substantially the whole surface of the first portion of the flexible foil. With this arrangement, the surface area of the return electrical connection can be increased, thus reducing the electrical impedance and power loss even further.

[0011] In one embodiment, the second pattern of electrically conductive material comprises probe leads extending from the output terminal to each of the plurality of planar fuel cells, respectively, for monitoring operation thereof. For example, the cell voltages of individual cells may be monitored. Preferably, the probe leads are arranged predominantly on the second portion of the flexible foil. By separating the electrical leads conveying the electrical energy from the probe leads for monitoring, they do not compete for the same space and can be increased in surface area, which in turn leads to reducing the electrical impedance and power loss. Another advantage is that the thickness of the flexible foil can be made substantially uniform by distributing the electrical leads and probe leads of the second pattern across both the first and second portions of the flexible foil. A uniform thickness reduces the risk of fuel gas leakage which may occur when sealing is applied to variations in thickness.

[0012] In one embodiment, the current collector further comprises a plurality of through-going openings in the flexible foil extending in a longitudinal direction betweenthe first and second portions of the flexible foil. By thus removing foil material, material costs are further reduced whilst facilitating folding of the flexible foil over the planar fuel cells.

[0013] In a second aspect of the present disclosure, there is provided a method for manufacturing a current collector for a planar fuel cell assembly comprising a plurality of planar fuel cells, the method comprising the steps of providing a flexible foil of electrically non-conductive material; depositing a first layer of electrically conductive material on a first side of the flexible foil arranged to face the plurality of planar fuel cells; forming a first pattern of the electrically conductive material; depositing a second layer of electrically conductive material on a second side of the flexible foil, opposite the first side; and forming a second pattern of the second layer of electrically conductive material. The flexible foil comprises a first portion arranged to contact an anode side of the plurality of planar fuel cells and a second portion arranged to contact a cathode side of the plurality of planar fuel cells in a folded configuration of the flexible foil. The first pattern is formed in such a way that the electrically conductive material is arranged to establish electrical connection between an anode of one planar fuel cell and a cathode of an adjacent planar fuel cell of the plurality of planar fuel cells in the folded configuration. The second pattern is formed in such a way that the electrically conductive material is arranged to convey electrical energy generated in the planar fuel cells to an output terminal.

[0014] In one embodiment, the method further comprises forming a plurality of through-going openings in the flexible foil extending in a longitudinal direction between the first and second portions.

[0015] In a third aspect of the present disclosure, there is provided a planar fuel cell assembly comprising a bottom plate; a top plate; a plurality of planar fuel cells interposed between the bottom plate and the top plate; and a current collector according to the first aspect. The current collector is folded with the first side facing the plurality of planar fuel cells in such a way that the first portion of the flexible foil is adjacent to an anode side of the plurality of planar fuel cells and the second portion of the flexible foil is adjacent to a cathode side of the plurality of planar fuel cells. The first pattern of electrically conductive material is arranged to establish electrical connection between an anode of one planar fuel cell and a cathode of an adjacent planar fuel cell of the plurality of planar fuel cells,thereby connecting the plurality of planar fuel cells in series. The second pattern conveys electrical energy generated in the planar fuel cells to an output terminal.

[0016] In one embodiment, the plurality of planar fuel cells is arranged in an in-line configuration extending in a longitudinal direction of the planar fuel cell assembly. As an alternative, the plurality of planar fuel cells may be arranged in two or more parallel rows extending in a longitudinal direction of the planar fuel cell assembly.

[0017] In one embodiment, each planar fuel cell comprises a membrane electrode assembly (MEA) sandwiched between an anode gas diffusion layer (GDL) and a cathode gas diffusion layer (GDL).

[0018] In a fourth aspect of the present disclosure, there is provided a method for manufacturing a planar fuel cell assembly, comprising the steps: providing a bottom plate; placing at least one baseplate on the bottom plate, the at least one baseplate comprising one or more slits defining a gas channel; placing a current collector according to the first aspect on the at least one baseplate; placing a plurality of planar fuel cells on the current collector; folding the current collector with the first side facing the plurality of planar fuel cells in such a way that the first portion of the flexible foil is adjacent to an anode side of the plurality of planar fuel cells and the second portion of the flexible foil is adjacent to a cathode side of the plurality of planar fuel cells; placing a top plate on the folded current collector, the top plate comprising a plurality of through-going openings defining venting holes, or one or more slits defining a gas channel; and attaching the top plate to the bottom plate, thereby clamping together the layers interposed therebetween, wherein the first pattern of electrically conductive material on the current collector is arranged to establish electrical connection between an anode of one planar fuel cell and a cathode of an adjacent planar fuel cell of the plurality of planar fuel cells, thereby connecting the plurality of planar fuel cells in series, and wherein the second pattern of electrically conductive material is arranged to convey electrical energy generated in the planar fuel cells to an output terminalBrief Description of Drawings

[0019] The disclosure is now described, by way of example, with reference to the accompanying drawings, in which:Fig. 1 shows a perspective view of an exemplary planar fuel cell assembly.Fig. 2 shows an exploded view of the planar fuel cell assembly.Fig. 3 shows a cross-sectional view of the planar fuel cell assembly.Fig. 4 shows a perspective view of an exemplary planar fuel cell sandwich used in a planar fuel cell assembly.Fig. 5 shows an exploded view of the planar fuel cell sandwich.Fig. 6 shows a perspective view of an exemplary current collector for use in a fuel cell sandwich.Fig. 7 shows a plan view of a first side of the current collector.Fig. 8 shows a plan view of a second side of the current collector, opposite the first side.Detailed Description

[0020] In the following, a detailed description of a planar fuel cell assembly according to the present disclosure is presented. In the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. It will be appreciated that these figures are for illustration only and do not in any way restrict the scope of the present disclosure. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of ‘including’, ‘comprising’, or ‘having’ and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms ‘mounted’, ‘connected’, ‘supported’, and ‘coupled’ and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, ‘connected’ and ‘coupled’ are not restricted to physical or mechanical connections or couplings.

[0021] In the context of the present disclosure, the term ‘planar fuel cell assembly’ is understood as a plurality of individual fuel cell units arranged side-by-side in the same plane in series and / or parallel connection. Supply of both electrical current and fuel gas can be arranged in series and / or in parallel.

[0022] A ‘fuel cell sandwich’ is a unit consisting of a plurality of individual fuel cell units arranged as an in-plane fuel cell assembly. In particular the fuel cell sandwich comprises all active fuel cell components, i.e. anode and cathode Gas Diffusion Layers (GDL), Membrane Electrode Assembly (MEA), frames defining compartments, and adhesive to fix components to each other, as well as a base foil on which active components are assembled.

[0023] The present disclosure provides a design of a planar multi-cell fuel cell assembly wherein the top plate (cathode side) and the bottom plate (anode side) are clamped together and joined by welding. This design requires that the top and bottom plates are electrically insulated from the active fuel cell components of the fuel cell sandwich being placed between these plates.

[0024] One preferred way of insulating the top plate from the fuel cell sandwich is to use a flexible foil, as defined above, having gold coated Cu foil which also can serve as a current collector for the active fuel cell components. Additional electrical leads on the flexible foil can be used as probes for monitoring e.g. the cell voltages of the individual cells. The flexible foil can have an extension to an electrical contact, thus, making it very simple to electrically attach the fuel cell assembly to the electronic power and control circuit of the fuel cell device.

[0025] Referring now to Figs. 1-3, there is shown a planar fuel cell assembly 1 according to one embodiment of the present disclosure in perspective, exploded as well as cross-sectional views, respectively. The planar fuel cell assembly is a laminated structure comprising a number of layers constituting the components of the fuel cell assembly. From bottom up, the assembly 1 comprises a bottom plate 10, a gas distribution member 20, a fuel cell sandwich 30, a fuel cell mesh 40, and a top plate 50.

[0026] The bottom plate 10 is suitably made of metal since it is to be used for spot welding the fuel cell assembly 1 together. To provide suitable contact points for spot welding and also to provide a spacer function, the bottom plate 10 is provided with protruding welding support members 11, in the shown embodiment in the form of bent tongues similar to WO 2011 / 040875 Al. The tongues may be formed by removing material on three sides of an area of the material in the bottom plate 10, entirely throughthe plate thickness, thereby forming a tongue. The tongue thus formed is bent upwards, and again the tongue is bent such that a portion thereof extends essentially parallel with the surface of the bottom plate 10. These tongues can suitably be provided by a punching operation. In an alternative embodiment, the tongues can be formed on the top clamping plate. In the embodiment shown in Figs. 1-3, the welding support members 11 are formed along the longitudinal edges of the bottom plate 10, thus leaving an uninterrupted central surface area 12 for placement of remaining components of the fuel cell assembly 1. The welding support members 11 may also serve as guiding members for alignment of the remaining components of the fuel cell assembly 1 which may comprise corresponding recesses along their longitudinal edges.

[0027] An advantage with this configuration is that the support is resilient which is useful when the fuel cell assembly 1 is put together. The resilient property of the tongue also helps to maintain the clamping force when, over time, some of the components in the fuel cell sandwich 30 are compressed and deformed (e.g. the GDL).

[0028] The gas distribution member 20 may comprise a gas channel plate 21 sandwiched between two adhesive plates 22 and is arranged on the bottom plate 10. The gas channel plate 21 comprises grooves or slits 23 extending through the material so as to form gas channels when the gas distribution member 20 is clamped between the other components of the fuel cell assembly 1. The adhesive plates 22 also comprise corresponding slits 24 to define the gas channel. The slits 24 may be partially formed, i.e. not forming a continuous gas channel, as shown in Fig. 1.

[0029] The fuel cell sandwich 30 is arranged on top of the gas distribution member 20 such that one side thereof, typically the anode side, faces the gas channel for supply of fuel gas (hydrogen) to the anodes of the fuel cells 340. The fuel cell sandwich 30 will be described in more detail in conjunction with Figs. 4 and 5.

[0030] A fuel cell mesh 40 is arranged on top of the fuel cell sandwich 30 to cover the gas diffusion layers (GDLs) 330, 350 of the fuel cell sandwich 30. Finally, a top plate 50 is arranged on top of the fuel cell mesh 40. The top plate 50 is joined to the bottom plate 10 by spot welding, suitably in one single operation in a welding machine having a first pattern of electrodes matching the welding support members 11 on the bottom plate 10.Other than spot welding with electric current, laser spot welding is also possible. The top plate 50 may comprise a plurality of apertures 51 corresponding to apertures 308 in a current collector of the fuel cell sandwich 30, which will be described in greater detail below. In the assembled state, the top plate 50 and bottom plate 10 clamp the layers of the fuel cell assembly 1 together to ensure gas tightness and good electrical connection.

[0031] Referring now to Figs. 4 and 5, there is shown an exemplary fuel cell sandwich 30. From the bottom up, the fuel cell sandwich 30 comprises a current collector, a first (anode side) gas diffusion layer comprising individual GDLs 330a-f, a plurality of in-line planar fuel cells, also called membrane electrode assemblies (MEA) 340a-f and second (cathode side) GDLs 350a-f. Additionally, frames 360 including adhesive for placement / alignment of the anode side and cathode side GDLs 330a-f, 350a-f are provided.

[0032] The current collector comprises a flexible foil 300, also called a flexible printed circuit (FPC), which is an item similar to a printed circuit board (PCB), except that it is very thin and flexible. The flexible foil 300 is made of an electrically non-conductive material, e.g. plastic. The plastic foil can be made of e.g. polyethylene terephthalate (PET), which is inexpensive, or polyimide (PI), which is more expensive but can withstand soldering operations if needed.

[0033] Referring now to Figs. 6 and 7, the current collector is shown in a perspective view and a plan view, respectively. The flexible foil 300 is provided with a first pattern of electrically conductive material on a first side 310, e.g. copper (Cu) coating, but other materials are also foreseen. In order to improve the electrical contact between e.g. the anode or cathode GDLs 330a-f, 350a-f and the Cu layer, the Cu layer can be coated with for example gold, by e.g. electroplating. Said coating can be done on selected areas by coating (e.g. painting) the Cu-layer with paint on areas which should not be gold coated, and this is done before the gold coating. Typical thickness of the Cu-layer is 20 to 50 pm and of the gold coating about 0.1 to 2.5 pm.

[0034] The flexible foil 300 comprises a first portion 301 and a second portion 302, extending side-by-side in a longitudinal direction of the current collector. The flexible foil 300 is adapted to be folded with the first side 310 facing the MEAs 340a-f sandwichedbetween respective anode side and cathode side GDLs 330a-f, 350a-f during assembly of the fuel cell sandwich 30. In the folded configuration, the first portion 301 of the flexible foil 300 faces the anode side of the MEAs 340a-f and the second portion 302 faces the cathode side of the MEAs 340. Furthermore, the first pattern of electrically conductive material is arranged on the flexible foil 300 in such a manner that an electrical connection is established between the anode of a first MEA 340a and a cathode of second, adjacent MEA 340b in the folded configuration. This arrangement of the first pattern of electrically conductive material is repeated along the longitudinal extension of the flexible foil 300. Thus, the current collector provides a serial connection of all the MEAs 340a-f by folding the flexible foil 300. The advantage is that the electrical connection does not pass through the plane of the MEAs 340a-f, instead spanning the gap between the anode and cathode on the outside of the MEAs 340a-f.

[0035] In one embodiment, the electrically conductive material may be selectively removed in order to form electrical leads 304a-e extending between and covering different areas 305a-f, 306a-f in the flexible foil 300. More particularly, on the first side 310 of the flexible foil 300, the first portion 301 comprises first, anode side areas 305a-f matching the anode of each respective MEA 340a-f and the second portion 302 comprises second, cathode side areas 306a-f matching the cathode of each respective MEA 340a-f. As may be seen in Figs. 4 and 5, each of the anode side areas 305a-e in the first portion 301 is offset from the corresponding electrically connected cathode side area 306b-f in the second portion 302 in the longitudinal direction of the flexible foil 300. Thus, the serial connection between adjacent MEAs 340a-f is achieved. The electrical leads 304a-e may thus be substantially Z-shaped or S-shaped.

[0036] Referring now to Fig. 8, there is shown a plan view of the second side 320 of the flexible foil 300. Analogous to the first side 310, the second side 320 comprises a second pattern of electrically conductive material for conveying electrical energy generated by the MEAs 340a-f to an output terminal 315. To this end, the second pattern of electrically conductive material defines electrical leads 322, 323 extending from the output terminal 315, wherein a first electrical lead 322 extends to an area of the first portion 301 adjacent to the anode of the last planar fuel cell 340f of the plurality of MEAs 340, and asecond electrical lead 323 extends to an area of the first portion 301 adjacent to the cathode of the first planar fuel cell 340a in the plurality of MEAs 340.

[0037] As shown in Figs. 6 and 7, a portion 309 of the anode side area 305f which is aligned with the anode of the last planar fuel cell 340f extends towards the edge of the flexible foil 300. This edge portion 309 provides an area for electrical connection between the area 305f adjacent to the anode of the last planar fuel cell 340f on the first side 310 of the flexible foil and the first electrical lead 322 on the second side 320. The electrical connection may be achieved through a plurality of small perforations in the flexible foil 300 in the edge portion 309, whereby electrically conductive material is allowed to pass through. In a similar fashion, a portion 314 of the cathode side area 306a which is aligned with the first planar fuel cell 340a extends towards (and optionally into) the first portion301. This strip portion 314 likewise provides an area for electrical connection between the area 306a adjacent to the cathode of the first planar fuel cell 340a on the first side 310 of the flexible foil and the second electrical lead 323 on the second side 320.

[0038] The first and second electrical leads 322, 323 may be arranged predominantly on the first portion 301 of the flexible foil 300 and cover substantially the whole surface of the first portion 301. The large surface area of the electrical leads 322, 323 aids in reducing the electrical impedance experienced as the electrical current generated by the MEAs 340a-f is transported to the output terminal 315.

[0039] In one embodiment, the second pattern of electrically conductive material comprises probe leads 324a-f extending from the output terminal 315 to each of the respective MEAs 340a-f. The probe leads 324a-f allow for monitoring the operation of each individual MEA 340a-f, e.g. the individual cell voltage. The probe leads 324a-f may be electrically connected to a respective MEA 340a-f through a small perforation in the flexible foil 300 at corresponding positions adjacent each cathode side area 306a-f, with electrically conductive material allowed to pass through.

[0040] The probe leads 324a-f may be arranged predominantly on the second portion 302 of the flexible foil 300. By distributing the probe leads 324a-f on the second portion302, additional surface space on the first portion 301 is freed up to increase the surface area of the electrical leads 322, 323. The advantage of this configuration is two-fold; theenlarged surface area of the electrical leads 322, 323 further reduces the electrical impedance and thus losses during power transmission, and the distribution of the electrical leads 322, 323 and the probe leads across the first portion 301 and the second portion 302 makes it possible to achieve a substantially uniform thickness of the flexible foil 300. A uniform thickness of the flexible foil 300 reduces the risk of fuel gas leakage, since the sealing does not need to cover variations in thickness.

[0041] The fuel cell assembly 1 may comprise a sensor cell 340s arranged after the last planar fuel cell 340f. Similar to the MEAs 340a-f, the sensor cell 340s is sandwiched between anode side and cathode side GDLs 330s, 350s, and the flexible foil 300 may comprise electrical leads arranged in corresponding first, anode side and second, cathode side areas 305s, 306s, as well as probe leads 324s connected to the output terminal 315 for monitoring operation of the sensor cell 340s.

[0042] In an alternative embodiment, wherein the MEAs 340a-f are not arranged in an in-line configuration, but instead arranged e.g. in two or more parallel rows and the supply of fuel gas (hydrogen) is provided in a serpentine path across the MEAs 340. In this case, the subsequent MEA in the downstream direction of fuel gas flow may be located adjacently in either the longitudinal or transverse direction of the flexible foil 300. To achieve the serial connection of adjacent MEAs 340 a-f, the offset between the corresponding first and cathode side areas 305a-f, 306 a-f may be in the longitudinal direction and / or the transverse direction of the flexible foil 300 in the folded configuration.

[0043] In one embodiment, the flexible foil 300 comprises a plurality of through-going openings 303 positioned along the longitudinal direction of the flexible foil 300 between the first and second portions 301, 302 of the flexible foil 300. The openings 303 may be substantially rectangular in shape with their long sides parallel to the longitudinal direction of the flexible foil 300. This removal of material in the folding area facilitates bending of the flexible foil 300. The remaining portions provide bridges for the electrical leads 304 between the first and second portions 301, 302 for each respective pairing of first and cathode side areas 305a-f, 306a-f.

[0044] For supply of fuel to the anode side of the MEAs 340a-f, the flexible foil 300 comprises a plurality of slits 307 in the first portion 301 forming a gas channel which,when the fuel cell assembly 1 is assembled, are aligned with the slits 23, 24 of the gas distribution member 20. Similarly, the second portion 302 comprises a plurality of apertures 308 which are aligned with the apertures 51 in the top plate to provide venting holes for supply of reducible gas (oxygen in surrounding air) to the cathode side of the MEAs 340a-f. Alternatively, in case oxygen is supplied through a closed gas channel similar to the fuel gas channel, the second portion 302 may comprise slits similar to the slits 307 in the first portion 301.

[0045] The flexible foil 300 may further comprise a tongue portion 312 extending out from the first portion 301 to provide a suitable area for the electrical contact or output terminal 315 for external coupling.

[0046] Embodiments of a current collector for a planar fuel cell assembly and their manufacture according to the present disclosure have been described. However, the person skilled in the art realizes that this can be varied within the scope of the appended claims without departing from the inventive idea.

[0047] All the described alternative embodiments above or parts of an embodiment can be freely combined without departing from the inventive idea as long as the combination is not contradictory.List of Reference Signs1 Planar fuel cell assembly10 Bottom plate11 Welding support member12 Central surface area20 Gas distribution member 21 Gas channel plate 22 Adhesive plate 23 Slit (in gas channel plate) 24 Slit (in adhesive plate) 30 Fuel cell sandwich 300 Flexible foil 301 First portion (of flexible foil) 302 Second portion (of flexible foil) 303 Opening 304a-e Electrical lead (on first side) 305a-f, s First, anode side area (on first portion) 306a-f, s Second, cathode side area (on second portion) 307 Slit (in first portion) 308 Aperture 309 Edge portion 310 First side of flexible foil 312 Tongue portion 314 Strip portion 315 Output terminal 320 Second side of flexible foil 322 First electrical lead (on second side) 323 Second electrical lead (on second side)324a-f, s Probe leads 330a-f, s Anode gas diffusion layer (GDL) 340a-f, s Membrane electrode assembly (MEA) 350a-f, s Cathode gas diffusion layer (GDL)Frame Fuel cell mesh Top plate Aperture

Claims

CLAIMS1. A current collector for a planar fuel cell assembly (1) comprising a plurality of planar fuel cells (340), the current collector comprising a flexible foil (300) of electrically non-conductive material comprising a first pattern of electrically conductive material provided on a first side (310) thereof, wherein the flexible foil is adapted to be folded with the first side facing the plurality of planar fuel cells in such a way that a first portion (301) of the flexible foil is adjacent to an anode side of the plurality of planar fuel cells and a second portion (302) of the flexible foil is adjacent to a cathode side of the plurality of planar fuel cells, wherein the first pattern of electrically conductive material is arranged to establish electrical connection between an anode of a given planar fuel cell (340a-e) of the plurality of planar fuel cells and a cathode of an adjacent planar fuel cell (340b-f) of the plurality of planar fuel cells in the folded configuration of the flexible foil, wherein the flexible foil comprises a second pattern of electrically conductive material provided on a second side (320) thereof, opposite the first side, the second pattern of electrically conductive material being arranged to convey electrical energy generated in the planar fuel cells to an output terminal (315).

2. The current collector according to claim 1, wherein the second pattern of electrically conductive material comprises electrical leads (322, 323) extending from the output terminal to a first area adjacent to the anode of the last planar fuel cell, and to a second area adjacent to the cathode of the first planar fuel cell, respectively, of the plurality of planar fuel cells, or vice versa.

3. The current collector according to claim 2, wherein the electrical leads of the second pattern of electrically conductive material are arranged predominantly on the first portion of the flexible foil.

4. The current collector according to claim 2 or 3, wherein the electrical leads of the second pattern of electrically conductive material extend over substantially the whole surface of the first portion of the flexible foil.

5. The current collector according to any one of the preceding claims, wherein the second pattern of electrically conductive material comprises probe leads (324a-f) extending from the output terminal to each of the plurality of planar fuel cells, respectively, for monitoring operation thereof.

6. The current collector according to claim 5, wherein the probe leads are arranged predominantly on the second portion of the flexible foil.

7. The current collector according to any one of the preceding claims, further comprising a plurality of through-going openings (303) in the flexible foil positioned along a longitudinal direction between the first and second portions of the flexible foil.

8. A method for manufacturing a current collector for a planar fuel cell assembly comprising a plurality of planar fuel cells, the method comprising the steps of: providing a flexible foil of electrically non-conductive material; depositing a first layer of electrically conductive material on a first side of the flexible foil arranged to face the plurality of planar fuel cells; forming a first pattern of the first layer of electrically conductive material; depositing a second layer of electrically conductive material on a second side of the flexible foil, opposite the first side; and forming a second pattern of the second layer of electrically conductive material; wherein the flexible foil comprises a first portion arranged to contact an anode side of the plurality of planar fuel cells and a second portion arranged to contact a cathode side of the plurality of planar fuel cells in a folded configuration of the flexible foil, wherein the first pattern is formed in such a way that the electrically conductive material is arranged to establish electrical connection between an anode of one planar fuelcell and a cathode of an adjacent planar fuel cell of the plurality of planar fuel cells in the folded configuration, and wherein the second pattern is formed in such a way that the electrically conductive material is arranged to convey electrical energy generated in the planar fuel cells to an output terminal.

9. The method according to claim 8, further comprising forming a plurality of through-going openings in the flexible foil extending in a longitudinal direction between the first and second portions.

10. A planar fuel cell assembly comprising: a bottom plate; a top plate; a plurality of planar fuel cells interposed between the bottom plate and the top plate; and a current collector according to any one of claims 1-7, wherein the current collector is folded with the first side facing the plurality of planar fuel cells in such a way that the first portion of the flexible foil is adjacent to an anode side of the plurality of planar fuel cells and the second portion of the flexible foil is adjacent to a cathode side of the plurality of planar fuel cells, wherein the first pattern of electrically conductive material is arranged to establish electrical connection between an anode of one planar fuel cell and a cathode of an adjacent planar fuel cell of the plurality of planar fuel cells, thereby connecting the plurality of planar fuel cells in series, and wherein the second pattern is arranged to convey electrical energy generated in the planar fuel cells to an output terminal.

11. The planar fuel cell assembly according to claim 10, wherein the plurality of planar fuel cells is arranged in an in-line configuration extending in a longitudinal direction of the planar fuel cell assembly.

12. The planar fuel cell assembly according to claim 10, wherein the plurality of planar fuel cells is arranged in two or more parallel rows extending in a longitudinal direction of the planar fuel cell assembly.

13. The planar fuel cell assembly according to any one of claims 10-12, wherein each planar fuel cell comprises a membrane electrode assembly (MEA) sandwiched between an anode gas diffusion layer (GDL) and a cathode gas diffusion layer (GDL).

14. A method for manufacturing a planar fuel cell assembly, comprising the steps: providing a bottom plate; placing at least one baseplate on the bottom plate, the at least one baseplate comprising one or more slits defining a gas channel; placing a current collector according to any one of claims 1-7 on the at least one baseplate; placing a plurality of planar fuel cells on the current collector; folding the current collector with the first side facing the plurality of planar fuel cells in such a way that the first portion of the flexible foil is adjacent to an anode side of the plurality of planar fuel cells and the second portion of the flexible foil is adjacent to a cathode side of the plurality of planar fuel cells; placing a top plate on the folded current collector, the top plate comprising a plurality of through-going apertures defining venting holes, or one or more slits defining a gas channel; and attaching the top plate to the bottom plate, thereby clamping together the layers interposed therebetween, wherein the first pattern of electrically conductive material on the current collector is arranged to establish electrical connection between an anode of oneplanar fuel cell and a cathode of an adjacent planar fuel cell of the plurality of planar fuel cells, thereby connecting the plurality of planar fuel cells in series, and wherein the second pattern of electrically conductive material is arranged to convey electrical energy generated in the planar fuel cells to an output terminal.

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