MANUFACTURING ARRANGEMENT AND METHOD FOR A FUEL CELL STACK

Abstract

A manufacturing arrangement for a fuel cell stack or at least a unit fuel cell of the fuel cell stack includes at least a pre-arrangement site for arranging a membrane electrode assembly and a bipolar plate in a predefined orientation to each other, wherein the bipolar plate has at least one opening and/or at least one specific contour, and wherein the membrane electrode assembly and the bipolar plate are oriented to each other in such a way that the membrane electrode assembly covers at least one opening in the bipolar plate and/or extends over the bipolar plate in at least one area; wherein the manufacturing arrangement further includes at least one cutting site with a cutting device which is adapted to cut the membrane electrode assembly in a predetermined area so that the membrane electrode assembly has a cut opening, which resembles the at least one opening of the bipolar plate, and/or at least one cut contour, which resembles the at least one contour of the bipolar plate, and/or at least one cut alignment structure for aligning the unit fuel cells in a fuel cell stack, as well as a corresponding manufacturing method.

Claims

1-15. (canceled)

16. A manufacturing arrangement for manufacturing a fuel cell stack with a plurality of stacked unit fuel cells or at least a unit fuel cell of the fuel cell stack, wherein the unit fuel cell comprise at least a bipolar plate and a membrane electrode assembly, and the manufacturing arrangement comprising at least: a receiving unit for receiving a membrane electrode assembly and at least a bipolar plate with at least one opening and/or at least one alignment structure, and wherein the receiving unit of the cutting device is further adapted to orient the membrane electrode assembly and the bipolar plate in such a way that the membrane electrode assembly covers the at least one opening in the bipolar plate and/or the at least one alignment structure and/or extends over the bipolar plate in at least one area; and a cutting device for cutting a membrane electrode assembly comprising a cutting element which is adapted to cut the membrane electrode assembly in a predetermined area, so that the membrane electrode assembly has at least one cut opening, which resembles the at least one opening of the bipolar plate, and/or at least one cut alignment structure, which resembles the at least one alignment structure of the bipolar plate, and/or at least one cut alignment structure, which extends over a periphery of the bipolar plate for aligning the unit fuel cells by means of the membrane electrode assembly

17. The manufacturing arrangement according to claim 16, wherein the cutting element is a cutting punch having a shape which resembles the form of one or more opening(s) in a bipolar plate and/or one or more specific contour(s) of the bipolar plate and/or one or more alignment structures and/or the shape of the bipolar plate as such.

18. The manufacturing arrangement according to claim 16, wherein the manufacturing arrangement further comprises a fastening device, which is adapted to fasten the membrane electrode assembly and the bipolar plate, which are received in the holding unit, to each other.

19. The manufacturing arrangement according to claim 16, wherein the receiving unit is further adapted to receive a plurality of bipolar plates and membrane electrode assemblies, and the cutting element is adapted to cut a plurality of membrane electrode assemblies.

20. The manufacturing arrangement according to claim 16, wherein the manufacturing arrangement further comprises a first manipulation unit for handling a bipolar plate, and a second manipulation unit for handling a membrane electrode assembly, wherein the first manipulation unit and the second manipulation unit are adapted to arrange the membrane electrode assembly and the bipolar plate in the receiving unit in a predefined orientation to each other.

21. The manufacturing arrangement according to claim 16, wherein the manufacturing arrangement further comprises an alignment and/or stacking unit (16), which is adapted to receive, align and/or stack a plurality of unit fuel cells, and comprises at least one alignment element which is adapted to align the plurality of unit fuel cells based on a cut area of the membrane electrode assembly.

22. The manufacturing arrangement according to claim 21, wherein the cut area is the at least one cut alignment structure, and the at least one alignment element has a complementary shape to the cut alignment structure.

23. The manufacturing arrangement according to claim 21, wherein the alignment and/or stacking unit further comprises a first alignment element and a second alignment element, and further comprises a handling unit which is adapted to turn at least one of the unit fuel cells by 180° and arrange the turned unit fuel cell at at least one un-turned unit fuel cell, so that the first alignment element is used for aligning the un-turned unit fuel cell and the second alignment element is used for aligning the turned unit fuel cell.

24. A method for manufacturing a fuel cell stack with a plurality of stacked unit fuel cells or at least a unit fuel cell of a fuel cell stack comprising the steps of: orienting a bipolar plate and a membrane electrode assembly to each other in a predefined orientation, wherein the bipolar plate has at least one opening and/or at least one alignment structure, and wherein the membrane electrode assembly and the bipolar plate are oriented to each other in such a way that the membrane electrode assembly covers the at least one opening in the bipolar plate and/or or the at least one alignment structure and/or extends over the bipolar plate in at least one area; fastening the membrane electrode assembly to the bipolar plate; and cutting the membrane electrode assembly in at least one predefined area so that the membrane electrode assembly has a at least one cut opening, which resembles the at least one opening of the bipolar plate, and/or at least one cut alignment structure, which resembles the at least one alignment structure of the bipolar plate, and/or at least one cut alignment structure, which extends over a periphery of the bipolar plate, for aligning the unit fuel cells by means of the membrane electrode assembly in a fuel cell stack.

25. The method according to claim 24, wherein the step of fastening the membrane electrode assembly to the bipolar plate is performed after the cutting step.

26. The method according to claim 24, further comprising the step of aligning the unit fuel cells by using at least one of the cut alignment structures of the membrane electrode assembly.

27. The method according to claim 26, wherein the aligning step further comprises turning of at least one unit fuel cell by 180°.

28. The method according to claim 24, comprising using a manufacturing arrangement according to claim 16.

29. A unit fuel cell for a fuel cell stack, wherein the unit fuel cell is manufactured by the method according to claim 24.

30. A fuel cell stack comprising a plurality of unit fuel cells according to claim 29.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In the following, preferred embodiments of the invention are described in relation to the drawings, wherein the drawings are exemplarily only, and are not intended to limit the scope of protection. The scope of protection is defined by the accompanied claims, only.

[0051] The figures show:

[0052] FIG. 1a-d: schematic illustrations depicting steps of the manufacturing of a unit fuel cell according to a first embodiment;

[0053] FIG. 2: a schematic drawing of a cutting device according to a second embodiment; and

[0054] FIG. 3a-c: a schematic illustration depicting steps of the manufacturing of a unit fuel cell according to a third embodiment.

DETAILED DESCRIPTION

[0055] In the following same or similar functioning elements are indicated with the same reference numerals.

[0056] Further, in the following, the phrases “pre-mounted unit fuel cell” and “ready-to-use unit fuel cell” are used to distinguish unit fuel cells, which are ready to use in a fuel cell stack from unit fuel cells which are not yet finalized. Thus, a pre-mounted unit fuel cell might miss required elements such as openings for reactants or special alignment features for aligning the unit fuel cell into a stack or to unit fuel cells in which the membrane electrode assembly and the bipolar plate are not fastened to each other. The term “ready-to-use unit fuel cell” however, shall describe a unit fuel cell which is ready to use in a fuel cell stack and comprises all elements, structures, openings and contours as in the final fuel cell stack. The simple phrase “unit fuel cell” refers to both “pre-mounted” and “ready-to-use” unit fuel cells. For example, the stacking and aligning of unit fuel cells may be done with ready-to-use unit fuel cells as well as with pre-mounted fuel cells.

[0057] FIG. 1 illustrates schematically the manufacturing steps of a unit fuel cell 1, according to a first embodiments of the invention, which comprises at least a membrane electrode assembly 2 and a bipolar plate 4. Thereby it is to be noted that the membrane electrode assembly 2 comprises at least a membrane, which is sandwiched by two electrodes, (3-layer membrane electrode assembly) and may be surrounded by a subgasket, thereby forming a 5-layer membrane electrode assembly. Additionally, the membrane electrode assembly 2 may also comprise a gas diffusion layer attached to the 5-layer membrane electrode assembly, thereby forming a 7-layer membrane electrode assembly. Of course, other arrangements and more or less layers are also possible. For the sake of simplicity all kind of membrane electrode assemblies are addressed by the phrase membrane electrode assembly 2 in the following.

[0058] FIG. 1a depicts a membrane electrode assembly 2 in a pre-arrangement site of a manufacturing arrangement (not shown), which is arranged on top of a bipolar plate 4. Thereby, the membrane electrode assembly 2 and the bipolar plate 4 are oriented to each other and provide a so-called pre-mounted unit fuel cell. As illustrated in FIG. 1a, in the pre-mounted unit fuel cell, the membrane electrode assembly 2 overlaps over the bipolar plate 4 and does not have any openings and/or contours which resemble the shape of the bipolar plate 4. Preferably, the membrane electrode assembly 2 is attached to the bipolar plate 4 by any suitable fastening procedure, e.g. gluing, welding, particularly ultrasonic welding, soldering, etc.

[0059] Thereby it should be noted that there is a plurality of fastening possibilities of the membrane electrode assembly 2 to the bipolar plate 4. For example, in case a 5-layer membrane electrode assembly 2 is used, the gas diffusion layer is a separate element and may be fastened to the bipolar plate 4 before the membrane electrode assembly is fastened to the bipolar plate 4. Alternatively, it is also possible that the gas diffusion layer is fastened to the 5-layer membrane electrode assembly and then the 7-layer membrane electrode assembly is fastened to the bipolar plate 4. Further it is possible to fasten the 5-layer membrane electrode assembly 2 to the bipolar plate 4 and arrange and fasten the gas diffusion layer afterwards e.g. during stacking.

[0060] It goes without saying, that the step of fasting the membrane electrode assembly 2 to the bipolar plate 4 may also be performed after the membrane electrode assembly 2 has been cut into shape.

[0061] In the next step, as illustrated in FIG. 1b, the membrane electrode assembly 2 and the bipolar plate 4 are inserted into a cutting device 6. The cutting device may be part of a cutting site of the manufacturing arrangement. Of course, it is also possible that the above described orientation step is performed in the cutting device 6 itself, whereby a combined site of pre-arrangement site and cutting site is used. For that the cutting device 6 may comprise e.g. at least one holding unit (not illustrated), which is adapted to receive the membrane electrode assembly 2 and the bipolar plate 4 and orient them to each other. Of course, the holding unit may also be adapted to receive a pre-mounted unit fuel cell as such.

[0062] Further, the cutting device 6 comprises at least one cutting punch 8, which is adapted to cut the membrane electrode assembly 2 in a predefined area. In the illustrated embodiment of FIG. 1b, there are two cutting punch elements 8-1, 8-2, which are adapted to cut the edges 10-1, 10-2 of the membrane electrode assembly 2. Thereby, every pre-mounted unit fuel 1 is provided with the same edges 10-1, 10-2 which may be used for aligning the unit fuel cells 1 in a subsequent, stacking step. Since the cut edges 10-1, 10-2 are identical for each unit-fuel cell 1, it is possible to improve the aligning accuracy and thereby the operation of the fuel cell. A pre-mounted unit fuel cell 1 with only the alignment structures, namely the cut edges 10-1, 10-2 is shown in FIG. 1c. These alignment structures may interact with correspondingly but complementary shaped alignment features during the stacking of the fuel cell stack.

[0063] Besides the cutting of alignment structures, namely the cut edges 10-1, 10-2, it is also possible to cut openings 12 for the reactants and coolants by using a correspondingly shaped cutting punch element 8-3, as illustrated in FIG. 1d. The cutting of the openings 12 may be performed in a subsequent step to the cutting of the alignment structures 10, but it is also possible that all structures, openings 12, alignment structures 10 etc., are cut with a single correspondingly shaped cutting element 8, as is illustrated in FIG. 2.

[0064] Further, it is also possible that the cutting of the openings 12 has already been performed before the membrane electrode assembly 2 and the bipolar plate 4 are oriented to each other, or the membrane electrode assembly 2 already has pre-manufactured openings, as is illustrated in FIGS. 3a-c. In the illustrated embodiment, the cutting of the edges may be used for providing identical alignment structures 10-1, 10-2 at the unit fuel cells, which fit to corresponding alignment features 14 (see FIG. 3c) so that the unit fuel cells can be precisely stacked.

[0065] However, by cutting both, the openings 12 and the alignment structures 10, the risk for short circuit or misalignment of the membrane electrode assembly 2 to bipolar plate 4 may be reduced, as the cutting of the membrane electrode assembly 2 after the orientation of the membrane electrode assembly 2 to the bipolar plate 4 ensures that the membrane electrode assembly 2 covers the bipolar plate 4 in all places and thereby isolates two adjacent bipolar plates 4. An accidental exposure of the bipolar plate 4 by a misaligned membrane electrode assembly 2 can be avoided.

[0066] In a further not illustrated embodiment, a subset of pre-mounted unit fuel cells are first aligned and fastened to each other and only after having aligned the subset of pre-mounted unit fuel cells, the openings in the membrane electrode assembly are cut.

[0067] In the illustrated embodiment of FIG. 3, all structures, e.g. openings, alignment structures contours are performed before the then ready-to-use unit fuel cell is transferred to an alignment site (see FIG. 3c) comprising an alignment unit 16 as schematically illustrated in FIG. 3c. The alignment unit 16 has alignments features 14, which have a corresponding shape to the alignment structures 10-1, 10-2, so that a very precise alignment of the unit fuel cells is possible.

[0068] In summary, by cutting the membrane electrode assembly 2 into shape after having the membrane electrode assembly 2 arranged or preferably attached to the bipolar plate 4, a very precise alignment of the unit fuel cells is possible. Additionally, any risk for short circuits is avoided as it is ensured that the membrane electrode assembly covers the bipolar plate in all places so that the bipolar plate 4 is nowhere exposed and can come into contact with an adjacent bipolar plate 4.

REFERENCE NUMERALS

[0069] 1 unit fuel cell [0070] 2 membrane electrode assembly [0071] 4 bipolar plate [0072] 6 cutting device [0073] 8 cutting punch [0074] 10 cute edges (alignment structure) [0075] 12 openings [0076] 14 alignment features [0077] 16 alignment unit