METHOD FOR SEALING A FUEL CELL

Abstract

The invention relates to a method for sealing a fuel cell (5) and to a fuel cell (5) which is produced using such a method. The fuel cell (5) has at least one membrane-electrode unit (42) and bipolar plates (18, 22). The method has the steps of attaching a seal material (54) to at least one side of the membrane-electrode unit (42) in a bonded manner, attaching a precursor (62) to seal points (58) of the at least one bipolar plate (18, 22), placing the at least one bipolar plate (18, 22) on the membrane-electrode unit (42) such that the seal points (58) together with the precursor (62) come into contact with the seal material (54), and pressing the at least one bipolar plate (18, 22) and the membrane-electrode unit (42) together under the effect of pressure and/or temperature such that the seal material (54) forms a bonded connection to the at least one bipolar plate (18, 22) and to the membrane electrode unit (42).

Claims

1. A method for sealing a fuel cell (5), wherein the fuel cell (5) has a membrane-electrode unit (42) and a bipolar plate (18, 22), the method comprising the following steps: applying a sealing material (54) to at least one side of the membrane-electrode unit (42) in a bonded manner, applying a precursor (62) to sealing points (58) of the bipolar plate (18, 22), placing the bipolar plate (18, 22) on the membrane-electrode unit (42) so that the sealing points (58) with the precursor (62) come into contact with the sealing material (54), and pressing the bipolar plate (18, 22) together with the membrane-electrode unit (42) under pressure and/or under temperature so that the sealing material (54) forms a bonded connection to the bipolar plate (18, 22) and the membrane electrode unit (42).

2. The method for sealing a fuel cell (5) as claimed in claim 1, characterized in that a primer or a vulcanizing agent is used as the precursor (62).

3. The method for sealing a fuel cell (5) as claimed in claim 1, characterized in that FKM or EPDM is used as the sealing material (54).

4. The method for sealing a fuel cell (5) as claimed in claim 1, characterized in that a bead (14) is formed on the bipolar plate (18, 22) before or after the application of the precursor (62).

5. The method for sealing a fuel cell (5) as claimed in claim 1, characterized in that the sealing material (54) is applied by printing.

6. The method for sealing a fuel cell (5) as claimed in claim 5, characterized in that the sealing material (54) is applied by a screen printing technique.

7. The method for sealing a fuel cell (5) as claimed in claim 1, characterized in that the sealing material (54) is applied by spraying.

8. A fuel cell (5), which is sealed by means of a method for sealing as claimed in claim 1, wherein the fuel cell (5) comprises: at least one membrane-electrode unit (42), to which a sealing material (54) is applied in a bonded manner, and bipolar plates (18, 22), which have sealing points (58) which abut against the sealing material (54) of the membrane-electrode unit (42) and form a sealing connection, wherein a precursor (62) is applied to the sealing points (58) of at least one bipolar plate (18, 22) so that a bonded connection is formed between the sealing material (54) and the at least one bipolar plate (18, 22).

9. The fuel cell (5) as claimed in claim 8, characterized in that the precursor (62) is a primer or a vulcanizing agent.

10. The fuel cell (5) as claimed in claim 8, characterized in that the sealing material (54) is FKM or EPDM.

11. The fuel cell (5) as claimed in claim 8, characterized in that the bipolar plates (18, 22) have a bead (14) at the sealing points (58).

12. A fuel cell stack having at least one fuel cell (5) as claimed in claim 8.

13. A motor vehicle having a fuel cell stack as claimed in claim 12.

14. The method for sealing a fuel cell (5) as claimed in claim 2, characterized in that FKM or EPDM is used as the sealing material (54).

15. The method for sealing a fuel cell (5) as claimed in claim 14, characterized in that a bead (14) is formed on the bipolar plate (18, 22) before or after the application of the precursor (62).

16. The method for sealing a fuel cell (5) as claimed in claim 15, characterized in that the sealing material (54) is applied by printing.

17. The method for sealing a fuel cell (5) as claimed in claim 16, characterized in that the sealing material (54) is applied by a screen printing technique.

18. The method for sealing a fuel cell (5) as claimed in claim 17, characterized in that the sealing material (54) is applied by spraying.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] An exemplary embodiment of the invention is illustrated in the drawing and explained in more detail in the description below.

[0024] FIG. 1 shows a sectional view of an exemplary embodiment of a fuel cell which is sealed according to the inventive method.

DETAILED DESCRIPTION

[0025] FIG. 1 shows a sectional view of an exemplary embodiment of a fuel cell 5 which is sealed according to the inventive method. This method is explained with reference to a detail of an individual cell of the fuel cell 5. The fuel cell 5 is formed from a cathode bipolar plate 18 having a bead 14. An anode bipolar plate 22 is arranged in a mirror-inverted manner with respect to the cathode bipolar plate 18 so that the beads 14 of both bipolar plates 18, 22 are opposite one another. Channels 26 are thus formed between the cathode bipolar plate 18 and the anode bipolar plate 22.

[0026] A layered structure 30 is arranged within the channels 26. This layered structure 30 is shown by way of example in a channel 26. In this case, the layered structure 30 is composed of a first and a second gas diffusion layer 34, 38, which are separated by a membrane-electrode unit 42. The oxygen 46 which is required for the oxidation flows between the first gas diffusion layer 34 and the cathode bipolar plate 18. The hydrogen 50 which is preferably used as fuel flows between the second gas diffusion layer 38 and the anode bipolar plate 22.

[0027] A sealing material 54 is applied to the membrane-electrode unit 42 in a bonded manner at the points at which the beads 14 of the cathode bipolar plate 18 and the anode bipolar plate 22 are opposite one another. Sealing points 58 are formed in regions of the beads 14 which come into contact with the sealing material 54. A precursor 62 has been applied to these sealing points 58 before the placement of the bipolar plates 18, 22.

[0028] As already described above, most defects arise at the sealing points 58. Leaks in such a fuel cell 5 occur at these sealing points 58 as a result of inadequate contact.

[0029] In a next step, the bipolar plates 18, 22 are pressed together under a high temperature and pressure, so that a bonded connection forms between the sealing material 54 and the respective bipolar plate 18, 22 at the sealing points 58 where the precursor 62 is applied.