BIPOLAR PLATE FOR A FUEL CELL, FUEL CELL HAVING A BIPOLAR PLATE

Abstract

The invention relates to a bipolar plate (1) for a fuel cell, comprising a bipolar plate substrate (2) composed of stainless steel and comprising a coating (3), which is applied to the bipolar plate substrate (2), for increasing the corrosion resistance of the bipolar plate (1). According to the invention, the coating (3) is of single- or multi-layer design and has at least one layer (4) composed of a metal matrix (5) with non-passivating dispersoid particles (6) incorporated therein. The invention further relates to a fuel cell having at least one bipolar plate (1) according to the invention.

Claims

1. A bipolar plate (1) for a fuel cell, the bipolar plate comprising a stainless steel bipolar plate substrate (2) and a coating (3) applied on the bipolar plate substrate (2) to increase the corrosion resistance of the bipolar plate (1), characterized in that the coating (3) has a single-layer or multilayer configuration and comprises at least one layer (4) of a metallic matrix (5) with nonpassivating dispersoid particles (6) incorporated therein.

2. The bipolar plate (1) as claimed in claim 1, characterized in that the metallic matrix (5) consists of silver, nickel or a nickel alloy.

3. The bipolar plate (1) as claimed in claim 1, characterized in that the metallic matrix (5) comprises metal like carbides and/or nitrides and/or graphite as dispersoid particles (6).

4. The bipolar plate (1) as claimed in claim 1, characterized in that the dispersoid particles (6) have a mean particle size of between 0.02 μm and 10 μm.

5. The bipolar plate (1) as claimed in claim 1, characterized in that a volume fraction of the dispersoid particles (6) in the at least one layer (4) is between 5 and 40 vol % based on a total volume of the layer (4).

6. The bipolar plate (1) as claimed in claim 1, characterized in that a layer thickness of the at least one layer (4) is 1 to 10 μm.

7. The bipolar plate (1) as claimed in claim 1, characterized in that the coating (3) has a multilayer configuration and a corrosion-resistant layer (7) is disposed between the bipolar plate substrate (2) and the at least one layer (4).

8. The bipolar plate (1) as claimed in claim 7, characterized in that the corrosion-resistant layer (7) consists of nickel or a nickel alloy.

9. The bipolar plate (1) as claimed in claim 8, characterized in that the at least one layer (4) is configured as outer layer on the corrosion-resistant layer (7) and comprises a metallic matrix (5) of silver and graphite as dispersoid particles (6).

10. The bipolar plate (1) as claimed in claim 2, characterized in that a layer thickness of the corrosion-resistant layer (7) is 1 to 7 μm.

11. A fuel cell having at least one bipolar plate (1) as claimed in claim 1.

12. The bipolar plate (1) as claimed in claim 1, characterized in that the coating (3) has a single-layer configuration.

13. The bipolar plate (1) as claimed in claim 1, characterized in that the metallic matrix (5) consists of silver, nickel or a nickel alloy, the nickel alloy comprising phosphorus and/or tungsten and/or molybdenum.

14. The bipolar plate (1) as claimed in claim 13, characterized in that the metallic matrix (5) comprises metal like carbides and/or nitrides and/or graphite as dispersoid particles (6).

15. The bipolar plate (1) as claimed in claim 14, characterized in that the dispersoid particles (6) have a mean particle size of between 0.05 μm and 0.8 μm.

16. The bipolar plate (1) as claimed in claim 15, characterized in that a volume fraction of the dispersoid particles (6) in the at least one layer (4) is between 10 and 30 vol %, based on a total volume of the layer (4).

17. The bipolar plate (1) as claimed in claim 16, characterized in that a layer thickness of the at least one layer (4) is 1 to 5 μm.

18. The bipolar plate (1) as claimed in claim 16, characterized in that a layer thickness of the at least one layer (4) is 1 to 3 μm.

19. The bipolar plate (1) as claimed in claim 18, characterized in that the coating (3) has a two-layer configuration and a corrosion-resistant layer (7) is disposed between the bipolar plate substrate (2) and the at least one layer (4).

20. The bipolar plate (1) as claimed in claim 19, characterized in that the corrosion-resistant layer (7) consists of nickel or a nickel alloy, the nickel alloy comprising phosphorus and/or tungsten.

21. The bipolar plate (1) as claimed in claim 20, characterized in that the at least one layer (4) is configured as outer layer on the corrosion-resistant layer (7) and comprises a metallic matrix (5) of silver and graphite as dispersoid particles (6).

22. The bipolar plate (1) as claimed in claim 13, characterized in that a layer thickness of the corrosion-resistant layer (7) is 2 to 5 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention is elucidated in more detail below by means of the appended drawings. In these drawings:

[0029] FIG. 1 shows a schematic longitudinal section through a bipolar plate of the invention according to a first preferred embodiment, and

[0030] FIG. 2 shows a schematic longitudinal section through a bipolar plate of the invention according to a second preferred embodiment.

DETAILED DESCRIPTION

[0031] FIG. 1 indicates a first bipolar plate 1 of the invention for a fuel cell. The bipolar plate 1 represented comprises a bipolar plate substrate 2 and a coating 3 applied thereon. The coating 3 has a single-layer configuration, or is configured as one layer 4. The coating 3 or the layer 4 consists of a metallic matrix 5, in which nonpassivating dispersoid particles 6 are incorporated. As a result of the metallic matrix, the corrosion resistance of the bipolar plate 1 is high. The function of the incorporated dispersoid particles 6 is to minimize the contact resistance. The layer 4 therefore fulfils two functions, which are typically taken on by two separate layers.

[0032] The metallic matrix 5 presently consists of a nickel alloy, deposited on the bipolar plate substrate 2 in an electrolytic process. The dispersoid particles 6 are TiN particles. The concentration of the dispersoid particles 6 is selected such that a sufficient quantity of the particles come to lie on the surface of the layer 4 and form an exposed contact face.

[0033] Since the dispersoid particles 6 represent a cost factor, a cost saving can be achieved by reducing the consumption of dispersoid particles 6. This may be accomplished, for example, by lowering the layer thickness of the layer 4 and forming a further layer 7 between the layer 4 and the bipolar plate substrate 2. The function of this further layer is additionally to ensure high corrosion resistance, as the reduced layer thickness of the layer 4 alone is no longer sufficient for this purpose. This exemplary embodiment of a bipolar plate 1 of the invention is represented illustratively in FIG. 2. FIG. 2 shows clearly that the fraction of the dispersoid particles 6 is reduced relative to the exemplary embodiment in FIG. 1. At the same time, the low layer thickness of the layer 4 ensures that the dispersoid particles 6 come to lie at the surface and are partially exposed, thus forming exposed contact faces. In a multilayer coating 3, accordingly, the layer 4 always forms the outer layer.

[0034] Irrespective of whether the coating 3 has a single-layer or multilayer configuration, the layer 4 always has two functions:

[0035] 1. increasing the corrosion resistance, and

[0036] 2. minimizing the contact resistance.

[0037] The first function is realized via the metallic matrix 5, and the second function via the dispersoid particles 6.