BIPOLAR PLATE FOR FUEL CELLS, FUEL CELL STACK HAVING SUCH BIPOLAR PLATES, AND VEHICLE HAVING SUCH A FUEL CELL STACK

Abstract

A bipolar plate for a fuel cell, is provided having an anode plate with an anode side and a coolant side, wherein there is formed on the anode side a first structuring in order to form an anode flow field, and a cathode plate with a cathode side and a coolant side, wherein there is formed on the cathode side a second structuring to form a cathode flow field, there being arranged between the anode plate and the cathode plate structural elements to form a coolant flow field, being contacted from the coolant sides of the anode plate and the cathode plate, and having an optimized pressure distribution in a fuel cell stack and an increased stability as compared to the prior art. The structural elements consist of an elastic material. A fuel cell stack and a vehicle including such features are also provided.

Claims

1. A bipolar plate for a fuel cell, comprising: an anode plate with an anode side and a coolant side, wherein there is formed on the anode side a first structuring in order to form an anode flow field; a cathode plate with a cathode side and a coolant side, wherein there is formed on the cathode side a second structuring to form a cathode flow field; and structural elements that consist of an elastic material and are arranged between the anode plate and the cathode plate to form a coolant flow field, being contacted by the coolant sides of the anode plate and the cathode plate.

2. The bipolar plate according to claim 1, wherein the anode plate and the cathode plate consist of metal or a conductive carbon-based material.

3. The bipolar plate according to claim 1, wherein the structural elements consist of an elastic polymer, and at least one structural element is conductive.

4. The bipolar plate according to claim 1, wherein the structural elements are column-shaped.

5. The bipolar plate according to claim 1, wherein the first structuring of the anode plate and the second structuring of the cathode plate are positioned one on top of one another and overlap at least partly with the cross sectional surface of the structural elements in the stacking direction.

6. The bipolar plate according to claim 1, wherein the structural elements are arranged in regular or irregular manner to form flow pathways.

7. The bipolar plate according to claim 1, wherein the structural elements are secured to at least the anode plate or the cathode plate or the structural elements are formed on a carrier plate which is placed against either the anode plate or the cathode plate, and which can be secured to the anode plate or the cathode plate.

8. The bipolar plate according to claim 1, wherein the structurings of the anode plate and/or the cathode plate are column-shaped.

9. A fuel cell stack, comprising: a stack of membrane electrode assemblies and bipolar plates, wherein the membrane electrode assemblies alternate with the bipolar plates, wherein the stack is arranged between two end plates, and wherein each bipolar plate includes: an anode plate with an anode side and a coolant side, wherein there is formed on the anode side a first structuring in order to form an anode flow field; a cathode plate with a cathode side and a coolant side, wherein there is formed on the cathode side a second structuring to form a cathode flow field; and structural elements that consist of an elastic material and are arranged between the anode plate and the cathode plate to form a coolant flow field, being contacted by the coolant sides of the anode plate and the cathode plate.

10. A vehicle comprising a fuel cell stack, the fuel cell stack including: a stack of membrane electrode assemblies and bipolar plates, wherein the membrane electrode assemblies alternate with the bipolar plates, wherein the stack is arranged between two end plates, and wherein each bipolar plate includes: an anode plate with an anode side and a coolant side, wherein there is formed on the anode side a first structuring in order to form an anode flow field; a cathode plate with a cathode side and a coolant side, wherein there is formed on the cathode side a second structuring to form a cathode flow field; and structural elements that consist of an elastic material and are arranged between the anode plate and the cathode plate to form a coolant flow field, being contacted by the coolant sides of the anode plate and the cathode plate.

11. The bipolar plate according to claim 1, wherein the anode plate and the cathode plate consist of graphite or a composite material made of graphite and carbon.

12. The bipolar plate according to claim 1, wherein the structural elements have a rectangular or oval cross section and are arranged at a spacing from each other.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0032] Embodiments of the invention are described with the aid of the corresponding drawings.

[0033] FIG. 1 shows a schematic representation of a fuel cell stack.

[0034] FIG. 2 shows, in perspective top view, a detail of a bipolar plate.

[0035] FIG. 3 shows, in perspective bottom view, detail of the bipolar plate according to FIG. 2.

[0036] FIG. 4 shows, in a cross sectional diagram, detail of the bipolar plate according to FIGS. 2 and 3.

[0037] FIG. 5 shows, in perspective view, a detail of a cathode plate with structural elements.

[0038] FIG. 6 shows, in a cross sectional view, detail of another bipolar plate.

[0039] FIG. 7 shows, in perspective view, a detail of a cathode plate with structural elements arranged on a carrier plate.

[0040] FIG. 8 shows, in perspective view, a detail of another cathode plate with structural elements arranged on a carrier plate.

[0041] FIG. 9 shows, in a front view, structural elements with oval cross section on a carrier plate.

[0042] FIG. 10 shows, in a front view, structural elements with oval cross section on a carrier plate.

DETAILED DESCRIPTION

[0043] FIG. 1 shows in a schematic representation a fuel cell stack, designated overall as 100. The fuel cell stack 100 is part of a vehicle, especially an electric vehicle, comprising an electric traction motor which is supplied with electric energy by the fuel cell stack 100.

[0044] The fuel cell stack 100 comprises a plurality of membrane electrode assemblies 10, arranged alongside each other (stacked), and bipolar plates 12, arranged in alternating manner. Thus, in total, multiple stacked single cells 11 for the fuel cell stack 100, while either one of the single cell 11 or also the fuel cell stack 100 overall can be called a fuel cell. The fuel cell stack 100 has end plates 18 at either side. Between the bipolar plates 12 and the respective membrane electrode assemblies 10 are formed anode and cathode spaces, not represented, which are bounded by encircling seals 20. The fuel cell stack 100 is pressed together (compressed) in the stacking direction S by means of a clamping system in order to produce the sealing function of the seals 20, among other things.

[0045] The clamping system comprises an outer clamping device 22, as well as elastic structural elements, not visible here, which are arranged in the coolant region of the bipolar plates 12. These shall be described in greater detail in the following.

[0046] In order to produce an outer tension, which is transmitted to the structural elements in the fuel cell stack 100, lengthwise tensioning elements 24 of the outer clamping devices 22 pass on tensioning forces between the two end plates 18, so that the end plates 18 are pulled together by means of the tensioning elements 24. For this, the tensioning elements 24 extend in a stacking direction S of the fuel cell stack 100.

[0047] FIGS. 2 to 4 show a bipolar plate 12 in a first embodiment in different views. Each time, one detail of the bipolar plate 12 is represented.

[0048] The bipolar plate 12 here comprises two single plates, an anode plate 30 and a cathode plate 40. The anode plate 30 has an anode side 31 and a coolant side 32, pointing toward the cathode plate 40. The cathode plate 40 has a cathode side 41 and a coolant side 42 pointing toward the anode plate 30. In order to form a coolant flow field 50, elastic structural elements 51 are arranged each time on the coolant side 32, 42 between the anode plate 30 and the cathode plate 40, contacting the anode plate 30 and the cathode plate 40. The structural elements 51 are column-shaped and have a square cross section. These are distributed evenly and thus form flow pathways 52 in the form of a lattice network, through which a coolant can flow in the lengthwise and transverse direction in relation to the principal axis of the bipolar plate 12.

[0049] On the anode side 31 and cathode side 41 facing away from the coolant flow field 50 there are provided a first structuring 33 and a second structuring 43, respectively, both of which are configured analogously to the structural elements 51 of the coolant flow field 50 and form an anode flow field 34 and a cathode flow field 44. That is, they are column-shaped with a square cross section. Furthermore, they form flow pathways 35, 45 for the two reaction media, being congruent with the structural elements 51 in the stacking direction S in FIGS. 2 to 4.

[0050] FIG. 5 likewise shows the embodiment according to FIGS. 2 to 4, but with the difference that the anode plate 30 is not represented. The differing dimensions of the structural elements 51 at the center of the cathode plate 40 as compared to those at the margins is merely due to the cut-out shown and has no technical meaning, it being fundamentally possible, of course, for the structural elements 51 to have different dimensions and to be distributed unevenly. To facilitate the mounting of the bipolar plate 12, the structural elements 51 are secured or bonded at least on the coolant side 42 of the cathode plate 40.

[0051] FIG. 6 in turn shows a detail of a bipolar plate 12 according to a second embodiment, in cross section. In this embodiment, the structural elements 51 are formed as a single piece with a carrier plate 53, which lies with its flat side against the coolant side 42 of the cathode plate 40. The anode plate 30, not shown, is placed with the structural elements 51 on the cathode plate 40, after mounting the carrier plate 53, in order to complete the bipolar plate 12. The use of this carrier plate 53 significantly facilitates the mounting of the bipolar plate 12. In this variant as well, a bonding of the carrier plate 53 and the structural elements 51 can be done.

[0052] The other variant in which the side of the carrier plate 53 carrying the structural elements 51 is placed on the coolant side 42 of the cathode plate 40 is shown in FIG. 8. Otherwise, this variant corresponds to the one shown in FIG. 7.

[0053] FIGS. 9 and 10 each show a carrier plate 53 with structural elements 51 arranged thereon, having an oval cross section with two axes of symmetry (FIG. 9) and an oval cross section with one axis of symmetry (FIG. 10). These embodiments serve for optimizing the flow conditions of a coolant. These cross sections can also be chosen as the first structuring 33 and/or the second structuring 43.

[0054] Unless otherwise explicitly stated, the configurations pertain equally to all the embodiments.

[0055] Again, aspects of the various embodiments described above can be combined to provide further embodiments. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.