WO2011026543A1

WO2011026543A1 - Fuel cell unit, fuel cell stack having fuel cell units

Info

Publication number: WO2011026543A1
Application number: PCT/EP2010/004610
Authority: WO
Inventors: Christian Martin Erdmann; Martin Keuerleber; Uwe Pfister; Harald Tober
Original assignee: Daimler Ag
Priority date: 2009-09-03
Filing date: 2010-07-28
Publication date: 2011-03-10
Also published as: DE102009039901A1

Abstract

The invention relates to a fuel cell unit and a fuel cell stack having such fuel cell units, the fuel cell unit being economical to produce and at the same time providing high functional reliability. The fuel cell unit (1) has an MEA plate (2), bipolar plates (3) adjacent thereto, the bipolar plates being arranged in such a way that one electrode chamber (7a, b) is formed on both sides of the MEA plate (2), a seal (8), wherein the seal (8) seals at least one of the electrode chambers (7a, b), a hinterland stopper area (9), which is designed to space the bipolar plates (3) and/or the MEA plate (2), wherein the seal (8) is applied to the MEA plate (2) by means of a spraying method.

Description

Fuel cell unit, fuel cell stack with

The fuel cell units

The invention relates to a fuel cell unit with an MEA plate, with bipolar plates adjacent thereto, which are arranged such that an electrode space is formed on both sides of the MEA plate, with a seal, wherein the seal seals at least one of the electrode spaces and with a Hinterlandstopperbereich , which is designed for spacing the bipolar plates and / or the MEA plate. The invention also relates to a

Fuel cell stack with a variety of these

Fuel cell units.

Fuel cell systems are considered mobile

Power supply units used in vehicles and provide the necessary power for a drive motor. The fuel cell systems include one or more fuel cell stacks in which a plurality of individual fuel cells are arranged. It is common to place more than 50 or 100 such fuel cells per stack to achieve sufficient voltage.

However, the stack construction is also occupied with problems in terms of sealing and mechanical stress of the individual fuel cell or stacked body. Looking at z. B. a fuel cell stack with 100 fuel cells, so there are 200 electrode spaces, so cathode or

Anode rooms, as well as a corresponding number of supply or discharge lines for the working gases.

The document US 2006/70147785 AI, probably the

closest prior art shows a

Fuel cell stack with bipolar plates and MEA units as stacked bodies, which are arranged alternately, wherein fuel cells are formed. One of the bipolar plates per fuel cell has a stopper in an edge region, which is provided, for example, by a thickening of the

Bipolar plate is formed so that the gap between the bipolar plates within a reasonable amount

is controlled and in particular no too narrow or too wide gap between the bipolar plates can arise.

The invention is based on the object

To propose fuel cell unit or a fuel cell stack with such fuel cell units, which is economical to manufacture and at the same time a high

Provides functional security.

This object is achieved by a fuel cell unit with the features of claim 1 and by a

Fuel cell stack solved with the features of claim 14. Preferred or advantageous embodiments of the invention will become apparent from the dependent claims, the

following description and the accompanying figures.

In the context of the invention, a fuel cell unit is proposed, which is preferably suitable and / or designed for integration in a fuel cell stack for a vehicle. The fuel cell unit comprises a MEA plate (membrane-electrode assembly), which at least one membrane, in particular a proton-conducting membrane (PEM), and preferably catalyst layers and / or

Has gas diffusion layers.

Adjacent to bipolar plates are arranged, the

form on both sides of the MEA plate in each case an electrode space, namely an anode space and a cathode space. MEA plate and bipolar plates are used as stacked bodies in a fuel cell stack and / or in the

Fuel cell unit arranged. In the electrode spaces, which are separated by the membrane, takes place during operation of the electrochemical process through which

chemical energy from a fuel, usually hydrogen, and an oxidant, usually oxygen, is converted into electrical energy.

There is a seal provided, with the seal

at least one, preferably both electrode spaces,

especially circumferentially seals.

In addition, the fuel cell unit has a

Hinterlandstopperbereich, which is designed for spacing the bipolar plates and / or the MEA plate in the stacking direction. The Hinterlandstopperbereich is outside the electrode spaces, so separated from the electrode spaces by the seal arranged.

In the context of the invention it is proposed that the seal is applied to the MEA plate via a spraying process.

Advantages of the new concept can be seen in the fact that the seal before the installation of the MEA plate in the

Fuel cell stack or in the fuel cell unit the MEA plate can be applied. This will be the

Mounting much easier, as a faulty assembly of the

Seal can not be done as a separate part.

Another advantage is that the function

"Positioning" of the stacking body in the stacking direction in the stack to each other is decoupled from the function of sealing the gases in the stack.Thus, the seal can be relieved and optionally softer designed.

This new design freedom allows an optimal design for both the positioning function and for the

Sealing function in terms of material and

Manufacturing technology can be achieved. Overall, this results in an easy to install and therefore cost-effective and very reliable fuel cell unit.

In a preferred embodiment of the invention, the seal is made in a LIM (Liquid Injection Molding) process. Here, the MEA plate is placed in a tool and the seal, for example, as a liquid

Two-component plastic molded.

Preferred materials for gaskets are elastomers, e.g. Silicones, silicone rubbers (eg VMQ, FVMQ), silicone-based elastomers (eg fluorosilicone, FVMQ), thermoplastic elastomers (TPE), butyl rubbers (HR), polybutyl rubbers (PIB), ethylene-propylene rubbers (EPDM), fluororubbers (FKM, FFKM ), as well as polyamide elastomers and

Polyurethane rubbers and the like. In principle, combinations and mixtures of the above

mentioned materials in question. At the present

Invention, however, one of the aforementioned silicone material is preferred as the sealing material. It is particularly preferred if the seal after the

Spray process with the MEA plate is permanently connected. In this embodiment, during assembly of the MEA plate in the stack or fuel cell unit, the seal is forcibly mounted at the same time. The connection between MEA plate and seal, for example, via a

Material bond, a bond and / or a positive connection with the MEA plate done. In a positive connection, e.g. corresponding recesses or through holes may be provided in the MEA plate.

It is particularly preferred if the seal is formed completely circumferentially around the MEA plate. With a circumferential seal, the electrode spaces can be sealed very easily. Particularly preferably, the seal in a one-piece design seals both the

Anode space and the cathode compartment.

In a preferred embodiment of the invention

provided that the seal surrounds the gas diffusion layer or layers in the stacking direction of the MEA plate and / or laterally seals. Preferably, the lateral and / or encompassing seal is completely circumferential around the MEA plate. When embracing the seal shows in

Contact area to the MEA plate in a longitudinal section parallel to the stacking direction, for example, a U-shaped

Shape, wherein the free legs of the U rest on the top or bottom of the MEA plate. If only the

Side surfaces are to be sealed perpendicular to the stacking direction, no sealing areas are positioned on the top or bottom of the MEA plate. However, it is particularly preferred if the seal in

Stacking direction at least in sections between the MEA plate, in particular the gas diffusion layer, and the

adjacent bipolar plate is arranged sealingly, so that there is a frictional connection between the bipolar plate, gasket and gas diffusion layer in the stacking direction. The seal is thus not or not only between the

Bipolar plates, but between the MEA plate and the

Bipolar plate. In the event that the bipolar plate

is formed metallic, this may have a parallel to the seal extending bead to the

To increase functional reliability of the seal.

In a preferred structural design

provided that the hinterland stopper areas

adjacent bipolar plates support each other. Of the

Power flow then takes place between the bipolar plates, excluding the MEA plate. It is optionally possible that an electrical insulation and / or an elastic region is arranged between the hinterland stopper regions of adjacent bipolar plates.

In general, it is preferred that the

Main force closure of the fuel cell stack over the

Hinterlandstopperbereiche carried out and only a small Nebenkraftschluss is removed through the seals in order to interpret these independently of mechanical stress can. However, it makes sense between the

Outback stopper areas electrical insulations

to avoid a short circuit. Alternatively, the Hinterlandstopperbereiche can also be made of an electrically insulating material. In a preferred embodiment of the invention, the electrical insulation between the

Hinterlandstopperbereichen elastically formed to compensate for any manufacturing tolerances elastic.

In one possible embodiment of the invention, the seal extends to between the Hinterlandstopperbereiche the adjacent bipolar plates. Thus, in addition to the sealing function, the seal also forms an elastic and / or electrically insulating intermediate element between the two

Outback stopper areas. This embodiment has the advantage that components can be saved, as can be dispensed with an additional electrically insulating / elastic intermediate layer between the Hinterlandstopperbereichen.

The bipolar plates may e.g. consist of a metallic or a graphitic material. The

Hinterlandstopperbereiche can circulating and / or

interrupted and / or be installed only in areas.

Isolated solutions are also possible.

Particularly preferably, the Hinterlandstopperbereiche are integrally formed with the bipolar plates. In the case of a metallic material, for example, when the

Bipolar plates are made of stainless steel sheets, the Hinterlandstopperbereiche can be introduced by forming. In the case of graphitic materials, the inland stopper regions are preferably created by ablating other regions. Other manufacturing methods such as e.g. Urformen, joining etc. for the production of

Hinterlandstopperbereiche are also conceivable. Prinzipiel it is also possible that the Hinterlandstopperbereiche are used as separate components. The Hinterlandstopperbereiche can in some

Embodiments rigid or substantially rigid

be educated. In other embodiments, the Hinterlandstopperbereiche can also be implemented yielding and / or elastic, wherein the elastic property is achieved either by a formula elasticity and / or a material elasticity. In the interpretation, however, it is preferred - as already explained - when the main force closure over the Hinterlandstopperbereiche and only a side force across the seal or the active areas of

Fuel cell unit, ie via the gas diffusion layer and the membrane are derived. Thus, by the

Supporting the bipolar plates over the

Hinterlandstopperbereiche the main sealing area from the

Main force closure taken.

Another object of the invention relates to a

Fuel cell stack, which is suitable and / or designed for a vehicle, in particular, to provide drive energy for a drive motor. Of the

Fuel cell stack has a variety of

Fuel cell units, as described above or according to one of the preceding claims. By the use of the invention

Fuel cell units is achieved that the end plates of the fuel cell stack over the

Support hinterland stopper areas and the active areas, with the main force closure on the

Hinterlandstopperbereiche done.

Further features, advantages and effects of the invention will become apparent from the following description of preferred embodiments of the invention. Showing: Figure 1 is a schematic longitudinal section along the

Stacking direction by a fuel cell unit as a first embodiment of the invention;

Figure 2 in the same representation as the figure 1, a second

Embodiment of the invention.

FIG. 1 shows in a schematic

Longitudinal sectional view of a fuel cell unit 1 as a first embodiment of the invention. The

Fuel cell unit 1 is designed in particular for mobile use, for example in a vehicle, for generating the drive energy. For this purpose, a plurality, for example, more than 50 or 100 such

Fuel cell units arranged in a fuel cell stack.

In the area shown, three stacked bodies are arranged in a stacking direction S, wherein an MEA plate 2 lies in the middle, which is adjacent to bipolar plates 3 in the stacking direction S on both sides. The MEA plate 2 comprises a membrane 4, on both sides of each of which a catalyst layer 5 and a

Gas diffusion layer 6 adjacent. Membrane 4, catalyst layer 5 and gas diffusion layer 6 extend flat in a plane perpendicular to the plane of the drawing. Through the membrane 4, which is designed in particular as a proton exchange membrane (PEM), an anode space and a cathode space 7a, b are separated from each other. By the adjacent

Bipolar plates 3, the anode or cathode space 7 a, b is completed in or against the stacking direction S. The

Bipolar plates 3 may be made of a graphitic material or - as shown here - of a metallic material, for example made of stainless steel sheets. The seal between the bipolar plates 3 and the MEA plate 2 is effected by a seal 8, which is formed circumferentially around the anode or cathode space 7a, b. The

In the example shown, seal 8 is designed as a LIM seal, that is to say a liquid injection molding seal, and is injection-molded laterally against the MEA plate 2 prior to installation of the MEA plate 2. As can be seen from FIG. 1, the seal 8 surrounds the MEA plate 2 such that the gas diffusion layers 6 are also encompassed in a U-shape. By this design, the sealing of the Kathodenbzw. Anode spaces 7a, b not only in the lateral direction next to the MEA plate 2, but in the stacking direction S also

congruent with the MEA plate 2.

Viewed constructively, the bipolar plates 3 show, at their edge regions facing away from the anode or cathode space 7a, an inland stop 9, that is to say a region whose

Extension or thickness in the stacking direction S is greater than the other bipolar plate 3. Optionally, these are yielding and / or elastic. The elasticity is achieved in the embodiment in Figure 1 by a formula elasticity. By Hinterlandstopper 9, a spacing of the bipolar plates 3 is ensured to each other outside the sealed area. This also leads to forces in the stacking direction S being removed via the hinterland stops 9 and not or less via the seals 8 or the gas diffusion layers 6. The hinterland stops 9 are supported in the stacking direction S on both sides on the bipolar plates 3. In the embodiment shown, the

Hinterlandstopper 9 integrally formed with the bipolar plates 3. For each other, the hinterland stopper 9 are electrically insulated by an insulation 10. Optionally, the insulation 10 may be formed as an elastic intermediate layer be and thus represents another component, the interpretation of the relationship between the main power flow on the hinterland stopper 10 and the seal 8 is to influence.

FIG. 2 shows an alternative embodiment of the fuel cell unit 1 as a second embodiment of the invention. Compared to the embodiment in FIG. 1, the insulation 10 is an integral part of the gasket 8. In a first alternative, the insulation 10 may be injected as a separate component into the gasket 8 and thus connected thereto. In another implementation alternative, the insulation 10 is injected together with the seal 8, ie urgeformt in the tool. The Hinterlandstopper 9 are based on this

Embodiment directly on the seal 8 and the insulation 10 from.

LIST OF REFERENCE NUMBERS

1 fuel cell unit

2 MEA plate

3 bipolar plate

4 membrane

5 catalyst layer

6 gas diffusion layer

7a, anode and cathode compartment

8 seal

9 hinterland stopper

10 insulation

Claims

Patent claims

Fuel cell unit (1) with an EA plate (2), with adjacent bipolar plates (3), which are as follows

are arranged so that an electrode space (7a, b) is formed on both sides of the MEA plate (2), with a seal (8), the seal (8) sealing at least one of the electrode spaces (7a, b), a hinterland stopper area (9), which for

Spacing of the bipolar plates (3) and/or the MEA plate (2) is formed, characterized in that the seal (8) is attached to the MEA plate via a spraying process

(2) is applied.

Fuel cell unit (1) according to claim 1, characterized in that the seal (8) in a LIM process (Liquid Injection Molding) process

is manufactured.

3. Fuel cell unit (1) according to claim 1 or 2, characterized in that the seal (8) consists of and / or comprises silicone.

4. Fuel cell unit (1) according to one of the preceding claims, characterized in that the seal is permanently connected to the MEA plate (2).

5. Fuel cell unit (1) according to claim 4, characterized

characterized in that the seal (8) is connected to the MEA plate (2) in a cohesive, adhesive and/or form-fitting manner.

6. Fuel cell unit (1) according to one of the preceding claims, characterized in that the seal (8) is formed completely around the MEA plate (2).

7. Fuel cell unit (1) according to one of the preceding claims, characterized in that the MEA plate (2) has a membrane (4), catalyst layers (5) and

Gas diffusion layers (6), wherein the seal (8) the gas diffusion layers (6) in the stacking direction (S)

completely surrounds and/or seals laterally.

8. Fuel cell unit (1) according to one of the preceding claims, characterized in that the seal (8) in the stacking direction (S) at least in sections between the MEA plate (2), in particular the gas diffusion layer (6), and the adjacent bipolar plate (3 ) is arranged sealingly.

9. Fuel cell unit (1) according to one of the preceding claims, characterized in that

Support the hinterland stopper areas (9) of adjacent bipolar plates (3) against each other.

10. Fuel cell unit (1) according to one of the preceding claims, characterized in that between the hinterland stopper areas (9) adjacent

Bipolar plates (3) an electrical insulation (10) is arranged.

11. Fuel cell unit (1) according to claim 10, characterized

characterized in that the electrical insulation (10) is elastic.

12. Fuel cell unit (1) according to one of the preceding claims, characterized in that the seal (8) extends between the hinterland stopper areas (9) of the adjacent bipolar plates (3).

13. Fuel cell unit (1) according to one of the preceding claims, characterized in that

Hinterland stopper areas (9) are designed to be elastic.

14. Fuel cell stack for a vehicle, characterized by a plurality of fuel cell units (1) according to one of the preceding claims.