EP2002499A1

EP2002499A1 - Method for producing a membrane electrode unit for a fuel cell

Info

Publication number: EP2002499A1
Application number: EP07727310A
Authority: EP
Inventors: Dennis LÖSCH; Sven Thate
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2006-03-27
Filing date: 2007-03-23
Publication date: 2008-12-17
Also published as: US20090165933A1; CN101454933A; TW200810218A; KR20080110643A; JP2009531818A; WO2007110397A1

Abstract

The invention relates to a method for producing a membrane electrode unit for a fuel cell having the following method steps: A) the production of at least one multilayer zone on a carrier, wherein, the at least one multilayer zone comprises at least one electrode layer and at least one membrane layer, wherein the at least one multilayer zone is applied to the carrier in such a way that the at least one multilayer zone is surrounded by channels on the carrier which are delimited at least on one side by edges of the at least one multilayer zone, and B) introduction of a free-flowing, durable sealing material into the channels which is distributed there in order to produce a seal surrounding the edges of the at least one multilayer zone.

Description

Method for producing a membrane electrode assembly for a fuel cell

description

The invention relates to a manufacturing method for membrane electrode assemblies (MEA's), are produced in the seals for reliable sealing of the membrane electrode assemblies.

Fuel cells are energy converters that convert chemical energy into electrical energy. In a fuel cell, the principle of electrolysis is reversed. In this case, a fuel (for example hydrogen) and an oxidant (for example oxygen) are locally separated from one another and converted into electric current, water and heat at two electrodes. Today, various types of fuel cells are known, which generally differ in operating temperature from each other. The structure of the cells is basically the same for all types. They generally consist of two electrodes, an anode and a cathode, where the reactions take place, and an electrolyte between the two electrodes. In the case of a polymer electrolyte membrane fuel cell (PEM fuel cell), the electrolyte used is a polymer membrane which conducts ions (in particular H ⁺ ions). The electrolyte has three functions. It establishes the ionic contact, prevents electrical contact and also ensures the separation of the gases supplied to the electrodes. The electrodes are usually supplied with gases, which are reacted in the context of a redox reaction. The electrodes have the task of supplying the gases (for example hydrogen or methanol and oxygen or air), removing reaction products such as water or CO ₂ , catalytically reacting the starting materials and removing or supplying electrons. The conversion of chemical to electrical energy occurs at the three phase boundary of catalytically active sites (eg, platinum), ionic conductors (eg, ion exchange polymers), electron conductors (eg, graphite), and gases (eg, H ₂ and O ₂ ). For the catalysts, the largest possible active area is crucial.

The heart of a PEM fuel cell is the so-called membrane electrode assembly (MEA - Membrane Electrode Assambly), a composite of a centrally located membrane, which is covered on both sides by optionally containing catalysts, which in turn of gas diffusion layers (GDL - Gas Diffusion Layer ) are occupied - ie a 5-layer composite. In the fuel cell, the MEA is mounted between two bipolar plates. After installation in a fuel cell, the membrane Electrode unit on the anode side with the fuel gas and on the cathode side with the oxidizing agent in contact. The polymer electrolyte membrane separates the areas where fuel gas and oxidant are located from each other. In order to prevent fuel gas and oxidants from coming into direct contact with each other, which could cause explosive reactions, a reliable seal of the gas spaces must be ensured. Therefore, a sealing concept is required that prevents gas exchange along the edges of the membrane.

Various sealing concepts are known in the prior art, for example from WO 02/093669 A2 or US Pat. No. 5,523,175 A. WO 98/33225 A1, for example, describes a method by which a sealing edge is formed around the circumference of the membrane-electrode assembly, which connects the membrane and the electrodes or the electrodes gas-tight with each other and which can also be connected in a gastight manner with a bipolar plate. The sealing edge is produced by a sealing agent, for example a plastic or a mixture of plastics, penetrating into edge regions of the electrodes on the circumference of the membrane-electrode assembly, so that the pores of the electrodes are substantially filled and no gas is allowed to pass through. The plastic, preferably a thermoplastic or a thermosetting, low viscosity liquid plastic may penetrate the electrodes by capillary action and then be cured, or a plastic in liquid form, i. melted, uncured or dissolved in a solvent, are pressed with the electrodes, optionally by applying the required pressure (preferably up to about 200 bar) and / or elevated temperature in a suitable device, and the pores of the electrode are filled in this way.

EP 1 018 177 B1 relates to a method of manufacturing a membrane-electrode assembly (MEA) with elastic integral seals, in which the MEA is placed inside a mold, the mold having open channels. Then a fluently processable electrically insulating sealing material is introduced into the mold. The sealing material is passed through the channels to the desired sealing regions of the MEA. The channels also serve as molding surfaces for forming one or more raised ridges or beads and for impregnating at least a portion of the electrode layers of the MEA with the sealing material in the sealing areas. Furthermore, the channels serve to guide the sealing material to extend laterally beyond the membrane-electrode assembly, thereby enclosing an edge region of the membrane-electrode assembly. The sealant material is cured to form the resilient integral seal, wherein the resilient integral seal further includes the at least one or more raised ridges or beads. Subsequently, the MEA can be removed from the mold. Another method for producing a seal for an MEA is the subject of WO 2005/008818 A2. In this case, the electrode surfaces are coated in a region of their concern on the circumference of the membrane with a surface surfactant penetrating them and the edge surfaces of the MEA circumferentially covered by a curable sealant. Starting from the edge surfaces, the sealant penetrates the areas of the electrodes coated with the surface surfactant. The surface surfactant significantly increases the wettability for the areas treated with it and, as a result, facilitates the application of the sealant and improves its adhesion.

However, the methods known in the prior art often have the disadvantage that they are not suitable for simple and efficient mass production. The proposed processes are usually clocked with long waiting times and / or are very complicated and multi-step processes.

The object of the present invention is therefore to avoid the disadvantages of the prior art and, in particular in the production of a membrane-electrode unit, to ensure reliable sealing with simple and efficient production. The continuity of the production of a plurality of membrane-electrode units is to be improved.

This object is achieved by a method for producing a membrane electrode assembly for a fuel cell with the method steps

A) producing at least one multilayered field on a carrier, wherein the at least one multilayered field comprises at least one electrode layer and at least one membrane layer, wherein the at least one multilayered field is applied to the carrier such that the at least one multilayered field passes through channels on the carrier is surrounded, which are bounded at least on one side by edges of the at least one multilayer field and

B) introducing a flowable, curable sealant material into the channels which spreads there to create a seal surrounding the edges of the at least one multilayered field.

The multilayer field comprises at least two superimposed

Layers, particularly preferably consists of an electrode layer and a membrane layer. The multilayer field can be used in the method according to the invention. but also comprise a majority of the layers or all layers of the membrane-electrode assembly to be sealed, for example an anode layer, a membrane layer and a cathode layer or a first gas diffusion layer, an anode layer, a membrane layer, a cathode layer and a second gas diffusion layer.

The electrode layer in the present invention contains at least one or more electrocatalysts. It preferably contains a carrier material such as carbon black or graphite and one or more electrocatalysts. It optionally contains other ingredients, for example an ionomer. The menbran layer contains polymer electrolyte materials. Usually, a tetrafluoroethylene fluorovinyl ether copolymer having acid functions, especially sulfonic acid groups, is used. Such a material is, for example, you pont sold under the trade name Nafion ^® from EI. Examples of membrane materials that may be used in the present invention include the following polymeric materials and mixtures thereof:

Nafion ^® (DuPont, USA) perfluorinated and / or partially fluorinated polymers such as "Dow Experimental Membrane" (Dow Chemicals, USA), - Aciplex-S ^® (Asahi Chemicals, Japan),

Raipore R-1010 (PaII Rai Manufacturing Co., USA),

Flemion (Asahi Glass, Japan),

Raymion ^® (Chlorine Engineering Corp., Japan).

However, it is also possible to use other, in particular substantially fluorine-free membrane materials, for example sulfonated phenol-formaldehyde resins (linear or linked); sulfonated polystyrene (linear or linked); sulfonated poly-2,6-diphenyl-1,4-phenylene oxides, sulfonated polyaryl ether sulfones, sulfonated polyarylene ether sulfones, sulfonated polyaryl ether ketones, phosphonated poly-2,6-dimethyl-1,4-phenylene oxides, sulfonated polyether ketones, sulfonated polyether ether ketones, aryl ketones or polybenzimidazoles ,

In addition, such polymer materials are used which contain the following constituents (or mixtures thereof): polybenzimidazole-phosphoric acid, sulfonated polyphenylenes, sulfonated polyphenylene sulfide and polymeric sulfonic acids of the type polymer SO ₃ X (X = NH ₄ ⁺ , NH ₃ R ⁺ , NH ₂ R ₂ ^+, NHR ₃ ^+, NR ₄ ^+).

In the method according to the invention, a multilayer field is preferably produced by applying a membrane layer field to a carrier layer and subsequently applying an electrode layer field to the membrane layer field produced. The carrier layer used is preferably a carrier film, in particular a film of polyester, polyethylene, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polypropylene (PP), polyvinyl chloride (PVC), polycarbonate, polyamide, polyimide, polyurethane or comparable film materials. The carrier layer preferably has a thickness between 10 and 250 μm, more preferably between 90 and 110 μm.

The application of the membrane layer field on the carrier is carried out by methods known in the art, for example by doctor blade, spray, casting, printing or Extrusi- onsverfahren. Subsequently, the membrane layer field is dried. The application of the electrode layer field on the membrane layer field can also be carried out by methods known in the art. For example, the membrane layer field can be coated with a catalyst-containing ink. In this case, the ink is a solution containing an electrocatalyst which is largely liquid or optionally paste-like. It is applied for example by printing, spraying, knife coating or rolling on the membrane layer field fully or partially. Subsequently, the electrode layer field is dried.

Suitable drying methods for the individual layers of the multilayered film are, for example, hot-air drying, infrared drying, microwave drying, plasma processes or combinations of these processes.

The multilayer field produced by the process according to the invention may also contain further layers, for example a gas diffusion layer.

The support is preferably planar in the present invention so that the multilayer field is applied to a flat surface.

According to the invention, the multilayer field is surrounded on the support along its circumference by channels which, at least on one side, pass through the edges of a multilayered surface

Field are limited. A channel is a given in this context

Flow path for the introduced sealing material along the multilayer

Field runs and the depth of which corresponds at least to the thickness of the multilayer field. For example, a channel may be on one side of the edge (s) of a first multilayered field and on the other side of it

Edge (the edge surfaces) of a second multi-layered field are limited, while its underside is formed by the carrier and it is open at the top.

However, a channel can also be bounded on one side only by a multilayer field and otherwise by at least one other limiting element on the carrier. According to the invention, a flowable, hardenable sealing material is introduced into the channels. The flowable sealing material is distributed in the channels (self-organization), wherein it preferably fills the channels evenly. The sealing material preferably combines with the edges of the multi-layered fields adjacent to the channels, so that a seal surrounding the edges of the at least one multi-layered field is produced. For example, the sealing material may be poured into the channels or introduced into the channels by any other method known to those skilled in the art. The elastic seal present at the end of the method according to the invention surrounds, in particular, the electrode layer and the membrane layer gap-free, without the need for precise and therefore expensive positioning of the sealing material, in that self-assembly is utilized. Preferably, the sealing material adheres to the membrane material.

As sealing materials for the process according to the invention preferably polymer materials are used, in particular polyethylenes, polypropylenes, polyamides, epoxy resins, silicones, Teflon (dispersion), polyvinylidene difluoride (PVDF), polysulfones, polyetheretherketones (PEEK), UV and thermally curable acrylates or polyester resins.

Preferably, the sealing material is a material which adheres well to the materials of the membrane-electrode assembly, in particular to the material of the membrane layer. For example, as a sealing material, a hot melt adhesive can be used, as disclosed in DE 199 26 027 A1, which contains ionic or strongly polar groups for generating a surface interaction with the ionic groups of the polymer electrolyte membrane and thus a high adhesive effect.

After introducing the sealing material into the channels, it is solidified, for example, by drying, crosslinking (e.g., by UV radiation) or cooling.

According to a preferred embodiment of the present invention, the at least one multilayer field is produced such that the at least one electrode layer and the at least one membrane layer are flush with one another or that the membrane layer is larger than the electrode layer. Particularly preferably, the membrane layer is larger than the electrode layer. This has the advantage that no very exact positioning of the electrode layer field is required when the electrode layer field is applied to the membrane layer field. However, the membrane layer field should survive over the associated electrode layer field. This results, inter alia, in the advantage of a secured electrical insulation of the electrode layer through the membrane layer compared to another, on the other side the membrane layer to be arranged electrode layer. Furthermore, the sealing material can connect to the protruding region at the edge of the membrane layer.

In the area of the edges of the multi-layered panel, in the present invention, prior to the introduction of the sealing material, a wetting enhancer may be applied to effect wetting of the edges by the sealing material. Such a wetting improver is, for example, a solvent for the sealing material used, with which the edge regions of the multi-layered field are wetted. Another possible wetting improver is, for example, a surface surfactant, as described in WO 2005/008818 A2, in particular a fluorosurfactant. The areas treated by the surface surfactant have significantly increased wettability. This facilitates the application of the sealant and improves its adhesion.

According to a preferred embodiment of the method according to the invention, the sealing material is distributed in the channels and is additionally introduced in the region of the channels in pores of a gas diffusion layer. The gas diffusion layer is gas-permeable and porous and, in a PEM fuel cell, serves to guide the reaction gases close to the polymer electrolyte membrane.

In the present invention, for example, the gas diffusion layer together with a carrier film can form a carrier on which at least one multilayer field is arranged, for example a field with an electrode layer and a membrane layer. Channels that run along the gas diffusion layer along the field adjoin the field. However, the gas diffusion layer may also be present as a gas diffusion layer field as part of the multilayer field, wherein the edges of the gas diffusion layer field (together with the edges of the other layers of the multilayer field) bound channels on one side, which are filled with sealing material according to the invention. By allowing the sealing material to penetrate into the pores of the gas diffusion layer (due to capillary action) and therefore impregnating it with sealing material in this area, a seal is formed over the edge of the multi-layered field which also encloses and at least substantially envelopes the gas diffusion layer penetrates.

According to a preferred embodiment of the present invention, the method according to the invention comprises the steps:

i) producing at least two half-membrane-electrode units (half-MEAs) in each case by producing a multilayered field with a membrane layer and an electrode layer on a carrier of a gas diffusion layer and a carrier layer and introducing the sealing material into the channels surrounding the multilayer field and

ii) joining two half-membrane electrode assemblies (half-MEA's) by joining the membrane layers of the two half-membrane-electrode assemblies (half-MEAs) to obtain a membrane-electrode assembly.

According to this method, a membrane electrode assembly (comprising at least the 5 layers of gas diffusion layer, electrode, membrane, electrode, gas diffusion layer of two half membrane electrode units (comprising at least the three layers gas diffusion layer, electrode, In this case, the seals produced in each case on the half-MEAs by the method according to the invention together form a seal of the membrane-electrode unit.

The joining of the membrane layers of the two half-MEA's can be carried out by methods familiar to the person skilled in the art, for example by hot pressing, laminating, laminating with additional solvent application or ultrasonic welding. Bonding is preferably by compression using heat and / or pressure, for example using laminating rollers. The temperature is preferably between 60 ° C and 250 ° C and the pressure preferably between 0.1 and 100 bar. When connecting the two half-MEAs is from the two membrane layers, a total membrane layer having on the one hand the anode layer and a gas diffusion layer and on the other side, the cathode layer and a gas diffusion layer. When connecting the half-MEA's also the seals of the two half-MEAs can connect to an overall seal or they are in the resulting membrane-electrode assembly at least gas-tight to each other.

In one embodiment of the present invention, a plurality of multi-layered fields separated from each other by channels is formed

a) each having a membrane layer and an electrode layer on a common carrier of a carrier layer and a gas diffusion layer or

b) each having a membrane layer, an electrode layer and a gas diffusion layer on a common carrier of a carrier layer

produced. In case a), the gas diffusion layer is part of the carrier, in case b) part of the multilayer field. In this embodiment of the method according to the invention In addition, adjacent multi-layered fields bound the channels laterally and in case a) forms part of the gas diffusion layer and in case b) a part of the carrier layer forms the lower side of the channels.

According to one embodiment of the present invention, at least one additional limiting element is applied to the carrier, which limits at least one of the channels on one side. The boundary elements may be, for example, boundary strips that are parallel and spaced from the edges of the multilayered fields. The delimiting elements can be produced, for example, from the same material and in the same working step as the membrane layer. Their thickness should be at least equal to the thickness of the multilayered field.

The multilayered fields in the present invention are preferably quadrangular, more preferably square or rectangular.

The method according to the invention for producing a membrane-electrode assembly has, inter alia, the advantage that it can be carried out as a low-cost, cost-effective, continuous roll-to-roll process. For this purpose, for example, the carrier layer and optionally the gas diffusion layer are present as bands on a respective roll. The half-MEAs produced therewith can also be wound up on rolls. All steps of the process according to the invention are compatible with continuous roll-to-roll processes. In particular, distributing the sealing material by self-assembly in the channels between the multi-layered fields eliminates the need for a timed method, as is often unavoidable in the art for attaching or applying seals or for inserting and removing from molds.

According to a preferred embodiment, the sealing material is poured into the channels by means of casting devices, wherein the casting devices continuously deliver the sealing material or periodically release certain quantities of sealing material. This embodiment also allows for a continuous roll-to-roll process in which, for example, a carrier tape having multi-layered panels and enclosing channels move uniformly beneath the pouring devices. Channels in the longitudinal direction of the belt (transport direction) can be filled with the sealing material by a casting device that continuously delivers sealing material in a fixed direction. Channels extending transversely to the transport direction of the belt may be filled with transversely pivoted narrow casting devices or with fixed, periodically sealing material dispensing wide casting devices with sealing material. According to a preferred embodiment of the present invention, in a continuous process for producing a plurality of spaced-apart multilayered fields on a carrier, a multiplicity of membrane layer fields are applied in quadrangular form to a band-shaped first carrier layer, in each case one electrode layer field is applied to the membrane layer fields , a band-shaped gas diffusion layer is connected as a closed layer to the electrode layer fields, a band-shaped second carrier layer is applied to the gas diffusion layer and the band-shaped first carrier layer is removed from the multilayer fields. After turning the thus prepared layer arrangement, so that the band-shaped second support layer on the bottom and the membrane layer fields are on the top, the sealing material is introduced from above according to the invention in the channels in which it then (preferably evenly) distributed.

Preferably, therefore, a multiplicity of membrane electrode units which are connected to one another at least via the seal are produced, which can be separated by a cut through the seal. For example, if the gasket is sandwiched between two membrane-electrode assemblies, it may be cut centrally so that each half of the gasket belongs to a membrane-electrode assembly.

The invention will be explained in more detail with reference to the drawing below.

Show it:

1A and 1B show a first carrier layer with a plurality of membrane layer fields and boundary strips in the production of a membrane electrode assembly according to the method of the invention,

FIGS. 2A and 2B show a first carrier layer with a plurality of multilayer fields of membrane layer and electrode layer in the production of a membrane-electrode unit according to the method according to the invention,

FIGS. 3A and 3B show a gas diffusion layer which is arranged as a layer on the multilayer fields in the production of a membrane-electrode unit according to the method according to the invention, FIGS. 4A and 4B show a second carrier layer on the gas diffusion layer in the production of a membrane-electrode assembly according to the method of the invention;

FIGS. 5A and 5B multilayer fields of electrode layer and membrane layer on a support of gas diffusion layer and second support layer in the production of a membrane electrode assembly according to the method of the invention,

FIGS. 6A and 6B show the sealing material distributed in the channels during the production of a membrane electrode assembly according to the method of the invention;

FIGS. 7A and 7B show a third carrier layer on a multiplicity of interconnected half-MEAs in the production of a membrane-electrode unit according to the method according to the invention;

8A and 8B, the plurality of interconnected half-MEA's without the third carrier layer in the manufacture of a membrane-electrode assembly according to the inventive method,

FIGS. 9A and 9B show a multiplicity of interconnected membrane-electrode assemblies after bonding the membrane layers of the semiconductor membranes in the production according to the method of the invention;

FIGS. 10A and 10B are the sectional lines for separating the membrane-electrode assemblies during production according to the method of the invention;

FIG. 11 schematically shows a roll-to-roll process by which the intermediates of the membrane electrode assemblies according to the invention are produced according to FIGS. 1A to 4B, FIG. 12 schematically shows a roll-to-roll process by which the half-MEAs according to FIGS. 5A to 7B are produced.

FIG. 13 schematically shows a roll-to-roll process by means of which the membrane-electrode assemblies according to FIGS. 8A to 9B are produced and

Figure 14 shows an embodiment of a fuel cell assembly with a membrane electrode assembly produced by the method according to the invention.

Figure 1A shows a first intermediate in the manufacture of membrane-electrode assemblies according to the present invention.

Membrane layer fields 1 and strip-shaped limiting elements 2 are applied to a first carrier layer 3 for the production of this intermediate product. For example, the membrane layer material (for example a sPEEK casting solution - sulfonated polyether ether ketone) is cast in rectangular form as a membrane layer field 1 onto the carrier film (for example made of PET).

The casting of the membrane layer fields 1 can be done by periodically casting and stopping three parallel and spaced apart, wide casting devices (not shown).

Furthermore, strip-shaped limiting elements (for example likewise made from sPEEK), which run in the longitudinal direction of the first carrier layer and are thicker than the membrane layer fields 1, are also applied to the first carrier layer 3. The membrane layer fields 1 and the delimiting elements 2 must be dried after being applied to the first carrier layer 3.

In Figure 1 B, the intermediate product of Figure 1 A can be seen in section.

Figure 2A shows a second intermediate in the preparation of membrane-electrode assemblies according to the present invention.

To produce this intermediate product, electrode layer fields 4 are applied to the membrane layer fields 1, which are arranged on the first carrier layer 3, for example by batch doctoring or by screen printing. The electrode layer fields 4 according to FIG. 2A are rectangular and smaller than the membrane layer fields 1, see FIG the membrane layer fields 1 project beyond the electrode layer fields 4. The electrode layer fields 4 are dried after application to the membrane layer fields 1.

FIG. 2B shows the intermediate product from FIG. 2A in section.

Figure 3A shows a third intermediate in the manufacture of membrane-electrode assemblies according to the present invention.

To produce this intermediate product, a gas diffusion layer 5 is laminated onto the electrode layer fields 4 as a full layer. The gas diffusion layer 5 covers all the electrode layer fields 4 and the strip-shaped limiting elements 2.

In Figure 3B, the intermediate product of Figure 3A is shown in section.

Figure 4A shows a fourth intermediate in the preparation of membrane-electrode assemblies according to the present invention.

To produce this intermediate product, a second carrier layer 6 (for example made of PET) is placed loosely on the gas diffusion layer 5. The second carrier layer 6 covers the entire gas diffusion layer 5.

In Figure 4B, the intermediate product of Figure 4A is seen in section.

Figure 5A shows a fifth intermediate in the preparation of membrane-electrode assemblies according to the present invention.

For the preparation of this intermediate, the fourth intermediate product according to FIGS. 4A and 4B is turned over and the first carrier layer 3 is removed. There then remain a support 7 made of second carrier film 6 and gas diffusion layer 5, on which the delimiting elements 2 and the multi-layered fields 8 of electrode layer 4 and membrane layer 1 are arranged. The inwardly facing edges of the delimiting elements 2 and the edges 9 of the multilayered fields define a plurality of longitudinally extending channels 10, 12 extending in the transverse direction 11 and extending on the gas diffusion layer 5. The somewhat larger membrane layer fields 1 are now arranged over the slightly smaller electrode layer fields 4.

FIG. 5B shows the intermediate product from FIG. 5A in section. Figure 6A shows a sixth intermediate (Hal-MEA) in the preparation of membrane-electrode assemblies according to the present invention.

In order to produce this intermediate product, according to the invention a flowable, hardenable sealing material 13 is introduced into the channels 12, where it is evenly distributed. The introduction of the low-viscosity sealing material 13 can be carried out in a longitudinal direction 10 moving carrier 7 in the channels 12 in the longitudinal direction 10 by individual pouring devices or other feeding techniques. For the introduction of sealing material 13 in the running in the transverse direction 1 1 channels, for example, intermittently (periodically) working casting devices or reciprocating feeds can be used. An exact alignment of the sealing material 13 is not necessary, since the self-organization is utilized.

The sealing material 13 flows into the channels and also wets the edge regions of the undersides of the membrane layer fields 1 projecting beyond the electrode layer fields 4. Furthermore, the sealing liquid 13 impregnates the gas diffusion layer 5 in the region of the channels 12 by being introduced into the pores of the gas diffusion layer 5. The impregnated region of the gas diffusion layer 5 is identified by reference numeral 14 in FIG. 6B. The sealing material 13 is then solidified (for example, by drying, crosslinking or cooling). Then there is an elastic seal that surrounds the electrode layer field 4 and the membrane layer field 1 of the respective HaIb MEA gap-free without an exact and thus laborious positioning.

In Figure 6B, the intermediate product of Figure 6A is shown in section.

FIG. 7A shows the intermediate product from FIG. 6A, covered with a third carrier layer.

If the intermediate product of Figure 6A is to be rolled up or stacked (for example, for temporary storage), it is covered for protection with a third carrier layer 15, which is removed for further processing (see Figures 8A and 8B - corresponds to the intermediate product of Figures 6A and 6B) ).

In Figure 7B, the intermediate product of Figure 7A is shown in section.

Figure 9A shows a seventh intermediate in the manufacture of membrane-electrode assemblies according to the present invention. For the preparation of this intermediate product, two half-MEAs are connected to membrane-electrode units by connecting their membrane layer fields 16, 17 together. The membrane layer fields 16, 17 combine to form an overall membrane 18. The resulting intermediate product is a layer of, inter alia, 5-layer membrane electrode assemblies 25 (first gas diffusion layer 19, first electrode layer 20, membrane 18, second electrode layer 21 and second gas diffusion layer 22), which is arranged between two carrier layers 23, 24.

In Figure 9B, the intermediate product of Figure 9A is shown in section.

For separating the membrane-electrode units 25, cuts may be made along the cut lines 26 drawn in FIGS. 10A and 10B which extend (preferably centrally) through the sealing material 13. As a result, a multiplicity of individual membrane-electrode units are obtained, in which the membrane and the electrodes are completely surrounded by the sealing material 13 toward the outside. In addition, if the gas diffusion layers were penetrated by the sealing material 13, all 5 layers of the membrane electrode assembly are sealed to the edge. When installing between two bipolar plates, both gas chambers of the fuel cell are consequently separated from each other gas-tight.

FIG. 11 schematically shows a continuous roll-to-roll process by means of which the intermediates according to FIGS. 1A to 4B can be prepared.

In this roll-to-roll process, which takes place in the transport direction 36, a first roll 27 delivers a first carrier layer 3 as a roll product. A first pouring device 28 pours membrane layer fields of membrane material 29 (for example sPEEK) onto the first carrier layer 3 moved in the transporting direction 36 in order to obtain the intermediate product according to FIGS. 1A and 1B. A second casting apparatus 30 pours electrode layer fields of electrode material 31 onto the membrane layer fields which are moved further in the transport direction 36 in order to obtain the intermediate product according to FIGS. 2A and 2B. From a second roller 32, a gas diffusion layer 5 is unwound as a roll and laminated on the further moving in the transport direction 36 Elektrodenschichtfel- to obtain the intermediate product according to Figures 3A and 3B. From a third roller 33, a second carrier layer 6 is unwound as a roll and placed on the further moving in the transport direction 36 gas diffusion layer 5 to obtain the intermediate product according to Figures 4A and 4B. The band-shaped first MEA intermediate product 34 thus obtained can, as shown in FIG. 11, be wound onto a fourth roll 35 or processed further directly. Figure 12 shows schematically a continuous roll-to-roll process with which the intermediates of Figures 5A-7B can be made.

In this roll-to-roll process, the first MEA intermediate product 34 obtained in a process according to FIG. 11 is unwound in the transport direction 36 from the fourth roll 35, which was turned over, so that now the first carrier layer 3 on the Top is located. The first carrier layer 3 is removed from the first MEA intermediate 34 by being wound onto a fifth roller 37 to obtain the intermediate product according to Figs. 5A and 5B. By means of a third casting device 38 sealing material 13 is introduced into the channels between the multi-layered fields of electrode material 31 and membrane material 29, which are arranged on the moving in the transport direction 36 band-shaped carrier 7 of second carrier layer 6 and gas diffusion layer 5. Thereby, the intermediate product (band-shaped contiguous half-MEA's 40) according to Figures 6A and 6B is obtained. From a sixth roller 39, a third carrier layer 15 is unwound as a roll and placed on the in the transport direction 36 further moving half-MEA's 40 to obtain the intermediate product according to Figures 7A and 7B. As shown in FIG. 12, the tape-like contiguous half-MEAs 40 thus obtained are wound onto a seventh roll 41 or further processed directly.

Figure 13 shows schematically a continuous roll-to-roll process by which the membrane-electrode assemblies of Figures 8A-9B are made.

Of two opposing rollers 42, 43 containing half-MEAs 40 as the seventh roller 41 in Figure 12, the third support layer 15 is removed and wound on two other rollers 44, 45 respectively. The remaining half-MEAs 40 according to FIGS. 8A and 8B are unwound in the transport direction 36 from the two opposing rollers 42, 43 in such a way that the membrane layer fields of membrane material 29 are opposite each other. Each two half-MEAs 40 are then connected to one another in order to obtain band-shaped interconnected membrane-electrode units 46 according to FIGS. 9A and 9B. The membrane-electrode units 46 have the layer sequence first gas diffusion layer 19, first electrode layer 20, overall membrane 18, second electrode layer 21 and second gas diffusion layer 22. The band-shaped interconnected membrane-electrode units 46 can be wound with carrier layers 48, 49 on a bearing roller 47 or isolated by a (not shown) cutting device.

FIG. 14 shows a schematic sectional view of an embodiment of a fuel cell assembly with a membrane-electrode unit produced according to the method according to the invention. The membrane-electrode assembly 50 comprises five layers, a first gas diffusion layer 19, a first electrode layer 20, a membrane 18, a second electrode layer 21 and a second gas diffusion layer 22. The membrane 18 is larger than the electrode layers 20, 21 and protrudes thereover out. The membrane-electrode assembly 50 further includes a seal 51 surrounding the periphery of the membrane-electrode assembly. The gasket 51 was made by introducing flowable gasket material into channels wherein the channels were bounded on one side by the edges 52 of the electrode layers 20, 21 and the membrane layers contained in the membrane 18 and the gasket material distributed therein by self-assembly. Therefore, the seal lies gap-free at the edges 52. Furthermore, the sealing material was introduced into the pores of the gas diffusion layers 19, 22, so that the areas 53 impregnated with sealing material were formed. The gasket 51 thereby extends the full thickness of the membrane-electrode assembly 50. The membrane-electrode assembly 50 is disposed between two bipolar plates 54, 55 to complete the fuel cell assembly. In a fuel cell stack (not shown), a plurality of cells are stacked in electrical order with each other separated by an impermeable, electrically-conductive, bipolar plate, referred to as a bipolar plate 54, 55. The bipolar plate 54, 55 connects two cells mechanically and electrically. Since the voltage of a single cell is in the range of 1V, it is necessary for practical applications to switch numerous cells in series. Often, up to 400 cells are stacked separately by bipolar plates 54, 55. The cells are stacked on top of each other in such a way that the oxygen side of one cell is connected to the hydrogen side of the next cell via the bipolar plate 54, 55. The bipolar plate 54, 55 fulfills several functions. It is used to electrically interconnect the cells, to supply and distribute reactants (reaction gases) and coolants, and to separate the gas spaces. By the seal 51 of the two bipolar plates 54, 55 installed membrane electrode assembly 50, the two gas chambers of a fuel cell are separated from each other gas-tight.

LIST OF REFERENCES

1 membrane layer fields 38 third casting device

2 delimiting elements 39 sixth role

3 first carrier layer 40 half MEAs

4 electrode layer fields 41 seventh roller

5 gas diffusion layer 42 eighth roll

6 second carrier layer 43 ninth roll

7 bearer 44 tenth roll

8 multilayer fields 45 eleventh role

9 edges 46 membrane electrode assemblies

10 longitudinal direction 47 bearing roller

1 1 transverse direction 48 carrier layer

12 channels 49 carrier layer

13 Seal Material 50 Membrane Electrode Assembly

14 impregnated area 51 seal

15 third carrier layer 52 edges

16 first membrane layer field 53 impregnated areas

17 second membrane layer field 54 first bipolar plate

18 total membrane 55 second bipolar plate

19 first gas diffusion layer

20 first electrode layer

21 second electrode layer

22 second gas diffusion layer

23 upper carrier layer

24 lower carrier layer

25 membrane electrode units

26 cutting lines

27 first role

28 first pouring device

29 membrane material

30 second casting device

31 electrode material

32 second roll

33 third role

34 first MEA intermediate

35 fourth roll

36 transport direction

37 fifth role

Claims

claims

1. A method for producing a membrane electrode assembly for a fuel cell, characterized by the method steps

A) producing at least one multilayered field on a support, the at least one multilayered field comprising at least one electrode layer and at least one membrane layer, wherein the at least one multilayered field is applied to the support such that the at least one multilayered field is through channels is surrounded on the support, which are bounded at least on one side by edges of the at least one multilayer field and

B) introducing a flowable, curable sealing material into the channels, which is distributed there, to produce a seal surrounding the edges of the at least one multi-layered field.

2. The method according to claim 1, characterized in that the at least one multilayer field is produced so that the at least one electrode denschicht and the at least one membrane layer flush with each other or that the membrane layer is larger than the electrode layer.

3. The method according to any one of claims 1 or 2, characterized in that in the region of the edges of the multilayer field before the introduction of the sealing material, a wetting agent is applied, which causes an improvement in the wetting of the edges by the sealing material.

4. The method according to any one of claims 1 to 3, characterized in that the sealing material, which is distributed in the channels, is additionally introduced in the region of the channels in pores of a gas diffusion layer.

5. The method according to any one of claims 1 to 4, characterized by

i) producing at least two half-membrane-electrode units by respectively producing a multilayered field having a membrane layer and an electrode layer on a carrier of a gas diffusion layer and a carrier layer and introducing the sealing material into the channels surrounding the multilayered field and ii) joining two half membrane electrode assemblies by bonding the membrane layers of the two half membrane electrode assemblies to obtain a membrane electrode assembly.

6. The method according to any one of claims 1 to 5, characterized in that a plurality of mutually separated by channels multilayer fields

will be produced.

7. The method according to any one of claims 1 to 6, characterized in that on the carrier at least one additional limiting element is applied, which limits at least one of the channels on one side.

8. The method according to any one of claims 1 to 7, characterized in that the sealing material is poured into the channels by means of pouring devices, wherein the casting devices continuously deliver the sealing material or periodically deliver certain amounts of sealing material.

9. The method according to any one of claims 1 to 8, characterized in that in a continuous process for producing a plurality of spaced apart multilayer fields on a support, a plurality of membrane layer fields is applied in quadrangular form on a band-shaped first carrier layer, depending on an electrode layer field on the Membrane layer fields is applied, a band-shaped gas diffusion layer is connected as a closed layer with the electrode layer fields, a band-shaped second carrier layer is applied to the gas diffusion layer and the band-shaped first carrier layer is removed from the multilayer fields.

10. The method according to any one of claims 1 to 9, characterized in that a plurality of at least over the seal band-shaped interconnected membrane-electrode assemblies are produced, which are separated by a section through the seal.