DE102018003774A1 - Membrane electrode arrangement for a fuel cell - Google Patents

Abstract

The invention relates to a membrane electrode assembly (1) for a fuel cell with a membrane (2) comprising on a first membrane flat side (2.1) a first catalyst (K1) and on a second membrane flat side (2.2) opposite one of the first membrane flat side (2.1) second catalyst (K2), with a first gas diffusion layer (3) facing the first membrane flat side (2.1) and arranged parallel thereto and with a second gas diffusion layer (4), which the second membrane flat side (2.2) facing and arranged parallel thereto is. According to the invention, the membrane electrode assembly (1) comprises a frame (5) having an upper side (5.1), a lower side (5.2), inner end faces (5.3) and outer end faces (5.4), the membrane (2) being completely within one of the inner end faces (5.3) surrounded frame interior (RR) is arranged, the first gas diffusion layer (3) and the second gas diffusion layer (4) respectively over the membrane flat sides (2.1, 2.2) protrude, in the protruding areas parallel to the top (5.1) and bottom (5.2) of the frame (5) and cover the frame interior (RR) completely surrounding portion of top (5.1) and bottom (5.2) and between the gas diffusion layers (3, 4) and the frame (5), the gas diffusion layers (3 , 4) and a peripheral edge region of the membrane (2) and between the membrane (2) and the frame (5) an adhesive (6) is arranged.

Description

The invention relates to a membrane electrode assembly for a fuel cell according to the preamble of claim 1.

The invention further relates to a fuel cell.

From the WO 2005 029 620 A1 For example, a membrane electrode assembly for a fuel cell is known. The membrane electrode assembly includes an ion conducting membrane having a front side and a back side, a first catalyst layer on the front side, a second catalyst layer on the back side, a first gas diffusion layer on the front side, a second gas diffusion layer on the back side, and a sealing material. The sealing material is in edge areas circumferentially in a width of at least 1 mm in contact with inner sides of the gas diffusion layers. A compound of the sealing material with the gas diffusion layers takes place under pressure and heat in a lamination process.

The invention is based on the object to provide a comparison with the prior art improved membrane electrode assembly for a fuel cell and an improved fuel cell.

With regard to the membrane electrode assembly, the object is achieved by the features specified in claim 1 and in terms of the fuel cell by the features specified in claim 5.

Advantageous embodiments of the invention are the subject of the dependent claims.

The membrane electrode assembly for a fuel cell comprises a membrane comprising a first catalyst on a first membrane side and a second catalyst on a second membrane flat side opposite the first membrane flat side, a first gas diffusion layer facing the first membrane flat side and parallel thereto, and a second one Gas diffusion layer which faces the second membrane flat side and is arranged parallel thereto.

According to the invention, the membrane electrode assembly comprises a frame having an upper side, a lower side, inner end faces and outer end faces, wherein the membrane is arranged completely within a frame interior surrounded by the inner end faces. The first gas diffusion layer and the second gas diffusion layer each protrude beyond the membrane flat sides, extend in the protruding areas parallel to the top and bottom of the frame, and cover a portion of top and bottom completely surrounding the frame interior. Between the gas diffusion layers and the frame, the gas diffusion layers and a peripheral edge region of the membrane and between the membrane and the frame, an adhesive is arranged.

Due to the arrangement of the membrane within the frame interior, the membrane electrode assembly is characterized by a reduced height compared to the prior art, since only three layers formed from the membrane and the gas diffusion layers, and two adhesive layers are superimposed, whereas in the state of Technique known solutions in which portions of the frame between one of the gas diffusion layers and the membrane are arranged, four layers formed of the membrane, the gas diffusion layers and the frame, and three adhesive layers are superimposed. As a result, further, a significant reduction in height of a fuel cell stack comprising a plurality of membrane electrode assemblies can be achieved.

Furthermore, in comparison with known solutions in which sections of the frame are arranged between one of the gas diffusion layers and the frame, air pockets in the region of the frame interior can be avoided, so that a reaction of process gases at any point of the membrane electrode assembly can take place without restriction and control. As a result, an extension of a service life of the fuel cell can be achieved and a degradation of the fuel cell is avoided.

Furthermore, a material utilization can be increased by a smaller membrane can be used with the same size of a controlled active area, since an overlapping area with the frame is eliminated. It is also possible to use small gas diffusion layers with a smaller area.

In addition, bonding to pressure and heat lamination results in a significant reduction in cycle time in the manufacture of the membrane electrode assembly, and scrap rates can be minimized.

Embodiments of the invention are explained in more detail below with reference to drawings.

• 1 schematisch eine Seitenansicht eines Ausschnitts einer Membranelektroden-Anordnung für eine Brennstoffzelle nach dem Stand der Technik,
• 2 schematisch eine Explosionsdarstellung einer Membranelektroden-Anordnung für eine Brennstoffzelle,
• 3 schematisch eine Seitenansicht eines Ausschnitts der Membranelektroden-Anordnung gemäß 2 und
• 4 schematisch eine Seitenansicht eines Ausschnitts eines Brennstoffzellenstapels mit einer Membranelektroden-Anordnung gemäß 2.

Showing:

• 1 1 is a schematic side view of a section of a membrane electrode assembly for a fuel cell according to the prior art;
• 2 1 is an exploded view of a membrane electrode assembly for a fuel cell;
• 3 schematically a side view of a section of the membrane electrode assembly according to 2 and
• 4 schematically a side view of a section of a fuel cell stack with a membrane electrode assembly according to 2 ,

Corresponding parts are provided in all figures with the same reference numerals.

In 1 is a side view of a section of a membrane electrode assembly 1' for a fuel cell, not shown, according to the prior art.

The membrane electrode assembly 1' comprises in a known manner a semipermeable membrane 2 ' , which on a first membrane flat side 2.1 ' a first catalyst K1 and on one of the first membrane flat side 2.1 ' opposite second membrane flat side 2.2 ' a second catalyst K2 includes.

Furthermore, the membrane electrode assembly comprises 1' a first gas diffusion layer 3 ' , which is the first membrane flat side 2.1 ' facing and partially arranged in parallel to this. Furthermore, the membrane electrode assembly comprises 1' a second gas diffusion layer 4 ' , which is the second membrane flat side 2.2 ' facing and arranged parallel to this.

Furthermore, a frame 5 ' provided, which is a top 5.1 ' , a bottom 5.2 ' , inner faces 5.3 ' and outer faces 5.4 ' includes.

The gas diffusion layers 3 ' . 4 ' and the membrane 2 ' each protrude above a frame interior RR ' out.

Here is the membrane electrode assembly 1' formed such that between the gas diffusion layers 3 ' . 4 ' and the membrane 2 ' a reaction space R ' which forms on an upper side and a lower side respectively through one of the gas diffusion layers 3 ' . 4 ' is limited. A lateral boundary of the reaction space R ' is by a media-tight connection of the gas diffusion layers 3 ' . 4 ' with the frame 5 ' and the membrane 2 ' formed, wherein in the region of the connection, the first gas diffusion layer 3 ' , the frame 5 ' , the membrane 2 ' and the second gas diffusion layer 4 ' are arranged one above the other.

Due to the arrangement of the frame shown 5 ' results in a curved course of the first gas diffusion layer 3 ' from the region of the compound starting from the reaction space R ' , wherein in the region of a bend the risk of air pockets, so that in this area a reaction of process gases, especially air and hydrogen, take place only limited and uncontrolled. An unrestricted and controlled reaction, starting from the connection, is only after a displayed limit G' possible, after which the first gas diffusion layer 3 ' parallel to the membrane 2 ' runs.

In the illustrated solution, in which sections of the frame 5 ' between the gas diffusion layer 3 ' and the membrane 2 ' are arranged, the height of the membrane electrode assembly results 1' from a sum of heights of four layers, formed from the membrane 2 ' , the gas diffusion layers 3 . 4 ' and the frame 5 ' , as well as three layers of adhesive.

2 shows an exploded view of a possible embodiment of a membrane electrode assembly according to the invention 1 for a fuel cell, not shown. In 3 is a side view of a section of the membrane electrode assembly 1 according to 2 shown.

The membrane electrode assembly 1 comprises a semipermeable membrane 2 , which on a first membrane flat side 2.1 a first catalyst K1 and on one of the first membrane flat side 2.1 opposite second membrane flat side 2.2 a second catalyst K2 includes.

Furthermore, the membrane electrode assembly comprises 1 a first gas diffusion layer 3 , which is the first membrane flat side 2.1 facing and arranged parallel to this. Furthermore, the membrane electrode assembly comprises 1 a second gas diffusion layer 4 , which is the second membrane flat side 2.2 facing and arranged parallel to this.

Furthermore, a frame 5 provided, which is a top 5.1 , a bottom 5.2 , inner faces 5.3 and outer faces 5.4 includes.

Unlike the in 1 illustrated membrane electrode assembly 1' according to the prior art, the membrane is 2 completely within one of the inner faces 5.3 surrounded frame interior RR arranged.

Furthermore, the first gas diffusion layer protrude 3 and the second gas diffusion layer 4 each over the membrane flat sides 2.1 . 2.2 towards, extend in the protruding areas parallel to the top 5.1 and bottom 5.2 of the frame 5 and cover the frame interior RR completely surrounding section from top 5.1 and bottom 5.2 ,

Between the gas diffusion layers 3 . 4 and the frame 5 in the area of overlap, between the gas diffusion layers 3 . 4 and a peripheral edge region of the membrane 2 as well as between the membrane 2 and the frame 5 , in particular between the membrane 2 and the inner faces 5.3 of the frame 5 is an adhesive 6 brought in. Thus, an adhesive and sealing effect between the gas diffusion layers 3 . 4 , the membrane 2 and the frame 5 reached.

Here is the frame 5 For example, formed from polyethylene naphthalate and thus formed electrically insulating.

The adhesive 6 is in particular electrically insulating, ionically non-conductive and gas-tight with respect to the process gases, such as air and hydrogen, formed. For example, the glue 6 an epoxy resin.

Unlike the in 1 illustrated embodiment of the membrane electrode assembly 1' According to the prior art results in a height of the membrane electrode assembly 1 due to the arrangement of the membrane 2 inside the frame interior RR from heights of three layers, formed from the membrane 2 and the gas diffusion layers 3 . 4 , as well as two adhesive layers.

Thus, compared to the in 1 illustrated embodiment of the membrane electrode assembly 1' According to the prior art, a height of the membrane electrode assembly 1 by a material thickness of the membrane 2 and the height of an adhesive layer can be reduced. For example, indicates the membrane 2 a material thickness of 25 microns and an adhesive layer has a height of 10 microns after pressing all the components of the membrane electrode assembly 1 on, so can per membrane electrode assembly 1 a reduction in height of 35 microns can be achieved. This can happen with a fuel cell stack 7 with for example 500 cells and thus 500 membrane electrode assemblies 1 to a reduction in a height of the fuel cell stack 7 lead by 17.5 mm.

Furthermore, due to the arrangement of the frame shown 5 a curved course of the first gas diffusion layer 3 from the area of the bonding starting to a reaction space R and the consequent danger of trapped air are avoided, so that the limit G immediately adjacent to the region of the bond and the reaction of process gases, in particular air and hydrogen, in the entire reaction space R unrestricted and controlled.

In the membrane electrode assembly ( 1 ) it can further be provided that the membrane ( 2 ), in its peripheral edge region or where the adhesive ( 6 ) is arranged at least on a membrane flat side ( 2.1 . 2.2 ) at least in sections no catalyst ( K1 . K1 ) (so-called "Edge Free Catalyst"). The gas diffusion layers ( 3 . 4 ) and the ion-conducting membrane of the membrane ( 2 ) directly at the corresponding catalyst-free sites, ie without intervening catalyst ( K1 . K2 ). As a result, the gas tightness and the adhesive effect at the covering areas between gas diffusion layers ( 3 . 4 ) and peripheral edge region of the membrane ( 2 ) be improved.

It is also possible that the catalyst is recessed on at least one side to improve the gas-tightness and adhesion to the overlap surfaces to the adhesive, so that a connection is made directly to the membrane. (Edge Free Catalyst)

4 shows a side view of a section of a fuel cell stack 7 with a membrane electrode assembly 1 according to 2 ,

The fuel cell stack 7 includes, for example, multiple membrane electrode assemblies 1 , wherein in the illustrated section only a membrane electrode assembly 1 is shown.

Furthermore, the fuel cell stack comprises 7 several bipolar plates 8th . 9 , wherein in the illustrated section only two bipolar plates 8th . 9 are shown. Here is a first bipolar plate 8th on an upper first flat side of the membrane electrode assembly 1 arranged and a second bipolar plate 9 on a lower flat side opposite the first flat side of the membrane electrode assembly 1 arranged.

To a seal of the fuel cell stack 7 is the first bipolar plate 8th with one above the first gas diffusion layer 3 outgoing area of the bottom 5.2 of the frame 5 Media-tight either glued or pressed. Further, the second bipolar plate 9 with one over the second gas diffusion layer 4 outgoing area of the top 5.1 of the frame 5 Media-tight either glued or pressed.

The bonding takes place by means of an adhesive 10 media-tight, with the adhesive 10 in a possible embodiment of the adhesive 6 equivalent.

LIST OF REFERENCE NUMBERS

1

Membrane electrode assembly

1'

Membrane electrode assembly

2

membrane

2 '

membrane

2.1

first membrane flat side

2.1 '

first membrane flat side

2.2

second membrane flat side

2.2 '

second membrane flat side

3

Gas diffusion layer

3 '

Gas diffusion layer

4

Gas diffusion layer

4 '

Gas diffusion layer

5

frame

5 '

frame

5.1

top

5.1 '

top

5.2

bottom

5.2 '

bottom

5.3

inner face

5.3 '

inner face

5.4

outer face

5.4 '

outer face

6

adhesive

7

fuel cell stack

8th

bipolar

9

bipolar

10

adhesive

G

border

G'

border

K1

catalyst

K2

catalyst

R

reaction chamber

R '

reaction chamber

RR

Frame interior

RR '

Frame interior

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

• WO 2005029620 A1 [0003]

Claims (7)

Membrane electrode arrangement (1) for a fuel cell with - a membrane (2) comprising on a first membrane flat side (2.1) a first catalyst (K1) and on a first membrane flat side (2.1) opposite the second membrane flat side (2.2) a second catalyst ( K2), - a first gas diffusion layer (3) which faces the first membrane flat side (2.1) and is arranged parallel thereto and - a second gas diffusion layer (4) which faces the second membrane flat side (2.2) and is arranged parallel thereto by - a frame (5) having an upper side (5.1), a lower side (5.2), inner end faces (5.3) and outer end faces (5.4), wherein - the membrane (2) is completely surrounded within one of the inner end faces (5.3) Frame interior (RR) is arranged, - the first gas diffusion layer (3) and the second gas diffusion layer (4) each protrude beyond the membrane flat sides (2.1, 2.2), in de n extending portions parallel to the top (5.1) and bottom (5.2) of the frame (5) and a frame interior (RR) completely surrounding portion of the top (5.1) and underside (5.2) and cover - between the gas diffusion layers (3, 4) and the frame (5), the gas diffusion layers (3, 4) and a peripheral edge region of the membrane (2) and between the membrane (2) and the frame (5) an adhesive (6) is arranged. Membrane electrode arrangement (1) according to Claim 1 , characterized in that the adhesive (6) - is formed electrically insulating and / or - ionic non-conductive and / or - gas-tight. Membrane electrode arrangement (1) according to Claim 1 or 2 , characterized in that the adhesive (6) comprises epoxy resin. Membrane electrode arrangement (1) according to one of the preceding claims, characterized in that the frame (5) is designed to be electrically insulating. Membrane electrode arrangement (1) according to one of the preceding claims, characterized in that the membrane (2), in the peripheral edge region of the membrane (2), in which the adhesive (6) is arranged, at least on a membrane flat side (2.1, 2.2) at least in sections, no catalyst (K1, K1) has. Fuel cell with a fuel cell stack (7), comprising at least one membrane electrode assembly (1) according to one of the preceding claims, - At least a first bipolar plate (8), which is arranged on a first flat side of the membrane electrode assembly (1) and - At least a second bipolar plate (9), which is arranged on one of the first flat side opposite the second flat side of the membrane electrode assembly (1). Fuel cell after Claim 6 , characterized in that - the first bipolar plate (8) with a beyond the first gas diffusion layer (3) outgoing region of the underside (5.2) of the frame (5) is glued or compressed media-tight and - the second bipolar plate (9) with a on the second gas diffusion layer (4) outgoing area of the top (5.1) of the frame (5) is glued media-tight or compressed.

Images