DE102009039901A1 - Fuel cell unit, fuel cell stack with fuel cell units - Google Patents

Abstract

The invention relates to a fuel cell unit with an MEA plate, with adjacent bipolar plates, which are arranged such that an electrode space is formed on both sides of the MEA plate, with a seal, the seal sealing at least one of the electrode spaces and with a hinterland stop area , which is designed to space the bipolar plates and / or the MEA plate. The invention also relates to a fuel cell stack with a plurality of these fuel cell units. Fuel cell systems are used as mobile energy supply units in vehicles and provide the electricity required for the drive motor. The fuel cell systems comprise one or more fuel cell stacks in which a multiplicity of individual fuel cells are arranged. It is customary to arrange more than 50 or 100 such fuel cells per stack in order to achieve sufficient voltage or power. However, the stacked construction is also problematic with regard to the sealing and the mechanical load on the individual ...

Description

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 having a plurality of these fuel cell units.

Fuel cell systems are used as mobile power supply units in vehicles and provide the power necessary 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, the result is 200 electrode spaces, ie cathode or anode compartments, and a corresponding number of supply or discharge lines for the working gases.

The publication US 2006/70147785 A1 , which is 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 formed, for example, by a thickening of the bipolar plate, so that the gap between the bipolar plates is controlled to a reasonable degree and, in particular, no too narrow or too wide gap can arise between the bipolar plates ,

The invention has for its object to propose a fuel cell unit or a fuel cell stack with such fuel cell units, which is economical to manufacture and at the same time provides a high level of reliability.

This object is achieved by a fuel cell unit having the features of claim 1 and by a fuel cell stack having 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 drawings.

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 an MEA plate (membrane-electrode assembly) which has at least one membrane, in particular a proton-conducting membrane (PEM), and preferably catalyst layers and / or gas diffusion layers.

Bipolar plates are arranged adjacent thereto and 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 arranged as stacked bodies in a fuel cell stack and / or in the fuel cell unit. In the electrode spaces, which are separated by the membrane, takes place during operation of the electrochemical process, is converted by the chemical energy from a fuel, usually hydrogen, and an oxidant, usually oxygen, into electrical energy.

There is provided a seal, wherein the seal at least one, preferably both electrode spaces, in particular 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 are that the gasket can be applied to the MEA plate before the MEA plate is installed in the fuel cell stack or in the fuel cell unit. As a result, the assembly is much easier because incorrect assembly of the seal can not be done as a separate part.

Another advantage is that the function "positioning" of the stacked body in the stacking direction in the stack is mutually 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 can provide optimal design for both Positioning function as well as 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 mold and the seal molded on, for example, as a liquid two-component plastic. In one possible embodiment, the sealing material is a silicone material.

It is particularly preferred if the seal is permanently connected to the MEA plate after the injection molding process. 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 can be made, for example, via a material bond, a bond and / or a positive connection with the MEA plate. In a positive connection z. B. 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 compartment and the cathode compartment.

In a preferred embodiment of the invention, it is provided that the gasket surrounds the gas diffusion layer or layers in the stacking direction of the MEA plate and / or seals laterally. Preferably, the lateral and / or encompassing seal is completely circumferential around the MEA plate. In a gripping around the seal in the contact area to the MEA plate in a longitudinal section parallel to the stacking direction, for example, a U-shaped configuration, wherein the free legs of the U abut on the top and 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 board.

However, it is particularly preferred if the seal in the stacking direction, at least in sections between the MEA plate, in particular the gas diffusion layer, and the adjacent bipolar plate is sealingly arranged, 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 increase the reliability of the seal.

In a preferred structural design is provided that the Hinterlandstopperbereiche adjacent bipolar plates support each other. 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 takes place via the hinterland stopper regions and only a smaller secondary force closure is removed via the seals in order to be able to design these independently of mechanical loads. However, it is useful to arrange electrical insulation between the hinterland stopper areas in order 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 is elastically designed 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 hinterland 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 can z. B. consist of a metallic or a graphitic material. The Hinterlandstopperbereiche may be circumferential and / or interrupted and / or mounted 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 Hinterlandstopperbereiche preferably generated by ablation of other areas. Other manufacturing processes such. As archetypes, joining etc for the production of Hinterlandstopperbereiche are also conceivable. In principle, it is also possible that the Hinterlandstopperbereiche are used as separate components.

The Hinterlandstopperbereiche may be rigid or substantially rigid in some embodiments. 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 design, however, it is preferred, as already explained, for the main force closure to be conducted via the hinterland stopper regions and only a secondary force closure via the seal or the active regions of the fuel cell unit, ie via the gas diffusion layer and the membrane. Thus, by supporting the bipolar plates over the inland stopper regions, the main seal region is removed from the main force fit.

Another object of the invention relates to a fuel cell stack, which is suitable and / or designed for a vehicle, in particular in order to provide drive energy for a drive motor. The fuel cell stack has a multiplicity of fuel cell units as described above or according to one of the preceding claims. Through the use of the fuel cell units according to the invention it is achieved that the end plates of the fuel cell stack are supported by the hinterland stopper areas and the active area, with the main force closing occurring via the hinterland stopper areas.

Further features, advantages and effects of the invention will become apparent from the following description of preferred embodiments of the invention. Showing:

1 a schematic longitudinal section along the stacking direction by a fuel cell unit as a first embodiment of the invention;

2 in the same representation as the 1 A second embodiment of the invention.

The 1 shows 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, to generate the drive energy. For this purpose, a multiplicity, for example more than 50 or 100, of such fuel cell units are arranged in a fuel cell stack.

In the area shown, three stacked bodies are arranged in a stacking direction S, with an MEA plate in the center 2 lies in the stacking direction S on both sides of bipolar plates 3 borders. The MEA plate 2 includes a membrane 4. , on each of which on both sides a catalyst layer 5 and a gas diffusion layer 6 adjoin. 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 formed in particular as a proton exchange membrane (PEM), becomes an anode space and a cathode space 7a , b separated from each other. Through the adjacent bipolar plates 3 becomes the anode or cathode space 7a , b in or against the stacking direction S completed. The bipolar plates 3 can be made of a graphitic material or - as shown here - of a metallic material, eg. B. made of stainless steel sheets, be made.

The seal between the bipolar plates 3 and the MEA plate 2 done by a seal 8th which circumscribes around the anode or cathode space 7a , b is formed. The seal 8th is formed in the example shown as a LIM seal, so a liquid injection molding gasket and is prior to installation of the MEA plate 2 laterally surrounding the MEA plate 2 molded. As is clear from the 1 results, embraces the seal 8th the MEA plate 2 so that also the gas diffusion layers 6 U-shaped with embraces. By this design, the sealing of the cathode or anode chambers takes place 7a , b not only in the lateral direction next to the MEA plate 2 but also in the stacking direction S congruent to the MEA plate 2 ,

Structurally, the bipolar plates show 3 at their the anode or cathode compartment 7a , B remote edge areas an inland stopper 9 , So a region whose extent or thickness in the stacking direction S larger than the other bipolar plate 3 is. Optionally, these are yielding and / or elastic. The elasticity is in the embodiment in the 1 achieved by a formulaic elasticity. Through the hinterland stopper 9 is outside the sealed area a spacing of the bipolar plates 3 secured each other. This also leads to forces in the stacking direction S over the hinterland stoppers 9 be removed and not or less about the seals 8th or the gas diffusion layers 6 , The hinterland stoppers 9 supported in the stacking direction S on both sides of the bipolar plates 3 from. In the embodiment shown, the Hinterlandstopper 9 integral with the bipolar plates 3 educated. To each other are the Hinterlandstopper 9 through insulation 10 electrically isolated. Optionally, the insulation 10 when be formed an elastic intermediate layer and thus represents another component, on their interpretation, the ratio between the main power flow over the hinterland stopper 10 and the seal 8th is to be influenced.

The 2 shows an alternative embodiment of the fuel cell unit 1 as a second embodiment of the invention. Compared to the embodiment in the 1 is the insulation 10 an integral part of the seal 8th , In a first alternative, the insulation 10 as a separate component in the seal 8th be injected and connected with it. Another implementation alternative is isolation 10 together with the seal 8th injected, so urformed in the tool. The hinterland stoppers 9 are based directly on the seal in this embodiment 8th or the insulation 10 from.

LIST OF REFERENCE NUMBERS

1

fuel cell unit

2

MEA-plate

3

bipolar

4

membrane

5

catalyst layer

6

Gas diffusion layer

7a, b

Anode and cathode compartment

8th

poetry

9

Hinterland stopper

10

insulation

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2006/70147785 A1 [0004]

Claims (14)

Fuel cell unit ( 1 ) with an MEA plate ( 2 ), with adjacent bipolar plates ( 3 ), which are arranged so that on both sides to the MEA plate ( 2 ) each an electrode space ( 7a , b) forms, with a seal ( 8th ), the seal ( 8th ) at least one of the electrode spaces ( 7a , b) seals, a hinterland stopper area ( 9 ), which is used for spacing the bipolar plates ( 3 ) and / or the MEA plate ( 2 ), characterized in that the seal ( 8th ) via a spray process to the MEA plate ( 2 ) is applied. Fuel cell unit ( 1 ) according to claim 1, characterized in that the seal ( 8th ) is produced in a LIM (Liquid Injection Molding) process. Fuel cell unit ( 1 ) according to claim 1 or 2, characterized in that the seal ( 8th ) consists of silicone and / or comprises. Fuel cell unit ( 1 ) according to one of the preceding claims, characterized in that the seal with the MEA plate ( 2 ) is permanently connected. Fuel cell unit ( 1 ) according to claim 4, characterized in that the seal ( 8th ) material-locking, adhesive-locking and / or form-fitting with the MEA plate ( 2 ) connected is. Fuel cell unit ( 1 ) according to one of the preceding claims, characterized in that the seal ( 8th ) completely around the MEA board ( 2 ) is trained. Fuel cell unit ( 1 ) according to one of the preceding claims, characterized in that the MEA plate ( 2 ) a membrane ( 4. ), Catalyst layers ( 5 ) and gas diffusion layers ( 6 ), wherein the seal ( 8th ) the gas diffusion layers ( 6 ) completely embraces in the stacking direction (S) and / or laterally seals. Fuel cell unit ( 1 ) according to one of the preceding claims, characterized in that the seal ( 8th ) 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. Fuel cell unit ( 1 ) according to one of the preceding claims, characterized in that the hinterland stopper areas ( 9 ) of adjacent bipolar plates ( 3 ) support each other. Fuel cell unit ( 1 ) according to one of the preceding claims, characterized in that between the hinterland stopper areas ( 9 ) of adjacent bipolar plates ( 3 ) an electrical insulation ( 10 ) is arranged. Fuel cell unit ( 1 ) according to claim 10, characterized in that the electrical insulation ( 10 ) is elastic. Fuel cell unit ( 1 ) according to one of the preceding claims, characterized in that the seal ( 8th ) between the hinterland stopper areas ( 9 ) of the adjacent bipolar plates ( 3 ). Fuel cell unit ( 1 ) according to one of the preceding claims, characterized in that the hinterland stopper areas ( 9 ) are elastically formed. Fuel cell stack for a vehicle, characterized by a multiplicity of fuel cell units ( 1 ) according to any one of the preceding claims.

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