Method for repairing a fuel cell stack

Abstract

A method for repairing a fuel cell stack having a plurality of individual cells involves the steps of: a) identifying at least one degraded individual cell in the fuel cell stack; and b) deactivating the at least one degraded individual cell.

Claims

1. A method for repairing a fuel cell stack having a plurality of individual cells, the method comprising the steps of: identifying at least one degraded individual cell of the fuel cell stack; and deactivating the at least one degraded individual cell, wherein an electrically conductive connection between two separator plates of the at least one degraded individual cell is generated through an ion-selective separator by applying a high voltage to the individual cell or to two or more directly adjacent individual cells, which generates a passage within the ion-selective separator.

2. The method as claimed in claim 1, wherein the high voltage is applied to the individual cell such that no current between intact individual cells flows by applying the high voltage.

3. The method as claimed in claim 2, wherein the high voltage is applied to the separator plates of the individual cell from the outer edge.

4. The method as claimed in claim 1, wherein the high voltage is applied to the separator plates of the individual cell from the outer edge.

5. The method as claimed in claim 1, wherein an individual cell is operated during deactivation.

6. The method as claimed in claim 1, wherein after generating the passage, after the breakdown of the ion-selective separator at least in sections, and/or after making the ion-selective separator electrically conductive at least in sections, operating the fuel cell stack such that contact surfaces enlarge.

7. The method as claimed in claim 6, wherein the contact surfaces enlarge while the passage is forming or enlarging.

8. The method as claimed in claim 5, wherein the ion-selective separator heats up such that during operation of the individual cell that the ion-selective separator melts at least in sections.

9. The method as claimed in claim 1, wherein the passage is formed such that fuel comes into contact with oxidant through the passage.

10. The method as claimed in claim 1, wherein during the deactivating of the individual cell, oxidant on a cathode side has a lower level of oxygen than ambient air.

11. The method as claimed in claim 1, wherein at least one media supply into the degraded individual cell and/or at least one media discharge out of the degraded individual cell is/are prevented, and a media inlet, a media outlet and/or their distributor structures is/are cast using a sealant.

12. The method as claimed in claim 11, wherein the sealant is introduced into the media inlet, into the media outlet and/or into the distributor structures from an outer edge.

13. The method as claimed in claim 12, wherein the sealant is introduced at a temperature, or during hardening of the sealant assumes such a temperature, which breaks down the ion-selective separator of the individual cell at least in sections.

14. The method as claimed in claim 11, wherein the media supply is prevented by a tool introduced through the media supply channel; the media discharge is prevented by a tool introduced through the media discharge channel; and/or a substance and/or a solvent is introduced by a tool introduced through the media discharge channel.

15. The method as claimed in claim 14, wherein an electrical potential is applied to the degraded individual cell, and the tool identifies the degraded individual cell based on the electrical potential.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates a fuel cell stack 100.

(2) FIG. 2 schematically illustrates a degraded individual cell 10.sub.2.

(3) FIG. 3 schematically illustrates a degraded individual cell 10.sub.2 with passage D.

(4) FIG. 4 schematically is a top view of a separator plate 14.

(5) FIG. 5 schematically is a top view of a separator plate 14 with a cast fuel inlet 131 and a fuel outlet 151.

DETAILED DESCRIPTION OF THE DRAWINGS

(6) FIG. 1 schematically shows a fuel cell stack 100 with a variety of individual cells, of which the individual cells 10.sub.1, 10.sub.2, 10.sub.3, 10.sub.4 are shown as an example. The individual cells are held by two end plates 30 and pre-tensioned. Current collectors 20 are provided adjacent to the end plates. The separator plates are designed as bipolar plates 14, 14, 14, 14 here. Together with a MEA 12, 12, 12, 12, arranged between them, each half of two adjacent bipolar plates 14, 14, 14,14 form an individual cell 10.sub.1, 10.sub.2, 10.sub.3, 10.sub.4. The bipolar plates shown are connected to a cell monitoring system 40 that is designed to monitor the state of the cells. The degraded individual cell 10.sub.2 is highlighted. In order to form a passage D, a high voltage of several kV can be applied to the separator plates 14 , 14. Then a passage D is formed (cf. FIG. 3). If the adjacent individual cells 10.sub.2 and 10.sub.3 were degraded, the outer separator plates 14,14 of the two degraded individual cells 10.sub.2, 10.sub.3, together with the separator plate 14 in between them could also be used to apply a high voltage so that this results in the breakthrough of the membranes 12 and 12 of the degraded individual cells.

(7) FIG. 2 schematically shows a magnified detail of an individual cell 10.sub.2. It should be noted that the proportions of the individual layers are not true to scale. In the bipolar plates 14, 14, flow fields 142, 144 are provided, by means of which the fuel and the oxidant are distributed onto the reactive surface. The media then penetrate through the gas-diffusion layers 128, 129 to the catalyst layers 124, 125. The catalyst layers 124 , 125 both directly abut the membrane 122.

(8) FIG. 3 schematically shows a magnified detail of the individual cell 10.sub.2 according to the design of the passage D. Through the passage D, the catalyst layers 124, 125 provided on both sides of the membrane come into contact. If the fuel cell stack 100 or the degraded individual cell 10.sub.2 operate, the membrane heats up in the area of the passage D. The areas of the membrane, which are arranged directly adjacent to the passage D, gradually melt and the contact surface of the catalyst layers 124, 125 enlarge. In addition, due to a chemical reaction of the media, which come into contact with each other within the area of the passage, the membrane can heat up and ultimately melt. If the contact surface of the catalyst layers 124, 125 enlarge, the electric conductivity is improved by means of the individual cell to be deactivated.

(9) FIG. 4 shows a top view of an anode side of the separator plate 14. The fuel supply channel 130, the fuel discharge channel 150, the oxidant supply channel 160, the oxidant discharge channel 180, the coolant supply channel 170 and the coolant discharge channel 190 run perpendicular to the drawing plane. These channels could also be arranged differently in the separator plate. In the following, the flow is explained based on the fuel path. However, the same principle can, so to speak, be applied to the oxidant path and/or the coolant path. The fuel passes through the fuel inlet 131 into the (pre-)distribution structure 132 on the inlet side. From there, it is distributed onto the flow field 142. The distributor structure 152 on the outlet side (it can also be referred to as a collection structure) leads the fuel to the fuel outlet 151, which flows into the fuel discharge channel 150.

(10) FIG. 5 shows a top view of an anode side of the separator plate 14 with a sealant M in the fuel inlet 131 and in the fuel outlet 151. The sealants M prevent fuel from penetrating through the fuel inlet 131 or through the fuel outlet 151 into the flow field 142. Thereby, it is prevented that fuel passes through the passage D into the oxidant path. In addition or as an alternative, a sealant M can likewise be arranged in the oxidant inlet or in the oxidant outlet. In order to seal the inlets or the outlets, for example, the sealant M could be supplied via an endoscopic tool. Furthermore, an injection device could be led from the outer edge R through the channels Z in order to apply the sealant M. For this purpose, it can be advantageous, if the distributor structures, 132, 152 are arranged and designed as disclosed in the German patent application with patent application number DE 102015215258.8 (there: manifold channel 130, 140) by the applicant. The contents of this patent application with regard to the distributor channels is made into an integral part of this patent application by reference.

REFERENCE LIST

(11) fuel cell stack 100

(12) degraded individual cell 102;

(13) individual cell 101, 102, 103, 104

(14) bipolar plate 14, 14, 14, 14

(15) MEA 12, 12, 12, 12

(16) ion-selective separator, membrane 122

(17) catalyst layer 124, 125

(18) gas-diffusion layer 128, 129

(19) fuel supply channel 130

(20) fuel inlet 131

(21) distributor structure inlet 132

(22) media channels 142, 144

(23) fuel discharge channel 150

(24) fuel outlet 151

(25) distributor structure outlet 152

(26) passage D

(27) sealant M

(28) edge R

(29) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.