METHOD FOR PRODUCTION OF AN AT LEAST TWO-LAYERED LAMINATE OF A MEMBRANE ELECTRODE ASSEMBLY

Abstract

A method for production of an at least two-layered laminate of a membrane electrode assembly for a fuel cell comprises: preparing a membrane material from a proton-conducting electrolyte, preparing an electrode material comprising at least one catalyst, applying a liquid adhesive on a surface of the membrane material and/or on a surface of the electrode material, and contacting the surfaces of the membrane material and the electrode material to form a material connection by means of the liquid adhesive, wherein additionally a production aid is introduced into or applied onto an assemblage formed from the electrode material, the membrane material and the still unhardened liquid adhesive, the production aid being designed to stabilize the unhardened assemblage.

Claims

1. A method for producing an at least two-ply laminate of a membrane electrode assembly for a fuel cell, comprising: providing a membrane material made of a proton-conductive electrolyte, providing an electrode material comprising at least one catalyst, applying a liquid adhesive to a surface of the membrane material and/or on a surface of the electrode material, and contacting the surfaces of the membrane material and the electrode material to form a firmly bonded connection of using the liquid adhesive, wherein, a production aid is introduced into or applied onto a composite formed from the electrode material, the membrane material and the still uncured liquid adhesive, wherein the production aid is designed to stabilize the uncured composite, wherein the production aid is formed as a joining agent for the firmly bonded connection to the membrane material and/or to the electrode material, which has a shorter curing time compared to the liquid adhesive.

2. The method according to claim 1, wherein the production aid for stabilizing the uncured composite is applied in an edge area remote from an active area of the membrane electrode assembly.

3. The method according to claim 1, wherein the production aid for stabilizing the uncured composite is applied at points and/or flat and/or linearly.

4. The method according to claim 1, wherein the joining agent is an adhesive which can be cured by UV light, and the joining agent is cured with UV radiation before the liquid adhesive has cured.

5. The method according to claim 1, wherein the joining agent is an adhesive in the form of an adhesive tape, which is applied to one or both surfaces away from the liquid adhesive.

6. The method according to claim 1, wherein the joining agent is a hot-melt adhesive which liquefies under the action of heat and cures before the liquid adhesive has cured.

7. The method according to claim 1, wherein the joining agent forms a laminating joint which cures before the liquid adhesive.

8. The method according to claim 1, wherein the production aid comprises a frame which is placed on or integrated into the uncured composite, and that the frame is melted and cured at points and/or flat and/or linearly even before the liquid adhesive cures.

9. The method according to claim 1, wherein the production aid remains in the composite after the liquid adhesive has cured.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0026] Further benefits, features and details will emerge from the claims, the following description of embodiments, and the drawings.

[0027] FIG. 1 shows a schematic representation of a layout of a fuel cell having a three-part laminate of a membrane electrode assembly (MEA).

DETAILED DESCRIPTION

[0028] FIG. 1 shows a fuel cell 1. A semipermeable electrolyte membrane 2 here is covered with and materially joined to a first electrode 4 on a first side 3, in the present case the anode, and on a second side 5 with a second electrode 6, in the present case the cathode. The electrodes 4, 6 and the membrane 2 form a composition of a so-called membrane electrode assembly (MEA). The first electrode 4 and the second electrode 6 comprise substrate particles 14, on which catalyst particles of precious metals or mixtures containing precious metals such as platinum, palladium, ruthenium or the like are arranged or substrated. These catalyst particles serve as reaction accelerants in the electrochemical reaction of the fuel cell 1. The substrate particles may contain carbon. Yet substrate particles may also be considered which are formed from a metal oxide or carbon with an appropriate coating. The electrodes 4, 6 may be formed with a multitude of catalyst particles, which can be formed as nanoparticles, such as “core-shell nanoparticles.” These have the advantage of a large surface, while the precious metal or the precious metal alloy is arranged only on the surface, and a less valuable metal, such as nickel or copper, forms the core of the nanoparticle. In such a polymer electrolyte membrane fuel cell (PEM fuel cell), fuel or fuel molecules, especially hydrogen, are split up into protons and electrons at the first electrode 5 (anode). The electrolyte membrane 2 lets through the protons (e.g., H.sup.+), but is impenetrable to the electrons (e). The electrolyte membrane 2 in this embodiment is formed from an ionomer, such as a sulfonated tetrafluorethylene polymer (PTFE) or a polymer of perfluorinated sulfonic acid (PFSA). At the anode, the following reaction occurs: 2H.sub.2.fwdarw.4H.sup.++4e.sup.− (oxidation/electron surrender). While the protons pass through the electrolyte membrane 2 to the second electrode 6 (cathode), the electrons are taken by an external circuit to the cathode or to an energy accumulator. At the cathode, a cathode gas is provided, especially oxygen or oxygen-containing air, so that the following reaction occurs here: O.sub.2+4H.sup.++4e.sup.−.fwdarw.2H.sub.2O (reduction/electron uptake). In the present case, the electrodes 4, 6 are each associated with a gas diffusion layer 7, 8, one gas diffusion layer 7 being associated with the anode and the other gas diffusion layer 8 with the cathode. Moreover, the anode-side gas diffusion layer 7 is associated with a flow field plate, shaped as a bipolar plate 9, for supply of the fuel gas, having a fuel flow field 11. By means of the fuel flow field 11, the fuel is supplied through the gas diffusion layer 7 to the electrode 4. At the cathode side, the gas diffusion layer 8 is associated with a flow field plate having a cathode gas flow field 12, likewise shaped as a bipolar plate 10, for supply of the cathode gas to the electrode 6.

[0029] The membrane electrode assembly (MEA) as described herein need not be produced in discrete steps, nor is it necessary to wait for the individual components to be bonded firmly together during the material joining with a liquid adhesive before the membrane electrode assembly is further processed. Thus, the embodiments described herein deal with the fact that the liquid adhesive requires a certain time during the production process until it has achieved the required firmness, so that the handling with the liquid adhesive alone, especially during a continuous production process, has proven to be difficult.

[0030] It is therefore advantageous to unroll a weblike proton-conducting membrane material, provided on a roll, and to transport this in a suitable device to a first applicator tool, with which the liquid adhesive is deposited on one surface of the membrane material. In addition or alternatively, however, the liquid adhesive can also be deposited on a surface of an electrode material, which can also be provided for example on a roll or also as a single piece. After the depositing of the liquid adhesive, the surfaces of the membrane material and the electrode material are placed on top of each other and make a through contact to form a material connection by means of the liquid adhesive. In addition, a production aid is introduced into or applied onto an assemblage formed from the electrode material, the membrane material, and the still unhardened liquid adhesive, the production aid being designed to stabilize the still unhardened assemblage.

[0031] In this regard, the production aid for stabilizing the unhardened assemblage is applied in a marginal area situated away from the active region of the membrane electrode assembly. In this way, the production aid is applied away from the active region, i.e., the region in which the fuel cell reaction takes place. In other words, no production aid, so that this does not adversely affect the flow of process gases. Instead, the production aid for stabilizing the unhardened assemblage occurs in the active region. The production aid can be applied in a spot and/or on a surface and/or in a line and it may be an additional joint compound for a material binding of the membrane material and/or the electrode material, yet possessing a shorter hardening time than the liquid adhesive.

[0032] The joint compound can be for example a UV-hardening adhesive, the joint compound becoming hardened under UV-light even before the liquid adhesive has hardened. Alternatively or additionally, the joint compound can be a pressure sensitive adhesive in the form of an adhesive tape, being applied away from the liquid adhesive on one or both surfaces of the membrane material or the electrode material. The joint compound can also be a hot melt glue, which is liquefied under the action of heat and hardens once more even before the liquid adhesive has hardened. The joint compound may form a laminate bonding which hardens as such even before the liquid adhesive.

[0033] Alternatively or additionally, however, the production aid may also comprise a frame, which is placed on or integrated in the unhardened assemblage, the frame being melted in a spot and/or on a surface and/or in a line, especially by using a laser, and hardening once more even before the liquid adhesive hardens.

[0034] The possibility exists for the production aid to remain after the hardening of the liquid adhesive in the now dried assemblage, i.e., in the finished membrane electrode assembly. Yet it is not necessary for the production aid to meet the product requirements demanded of a fuel cell, it only needs to provide the required strength for the handling and thus to ensure the required stabilization of the membrane electrode assembly in the production process. If desired, the production aid can be removed after the production of the membrane electrode assembly, in particular after the hardening of the liquid adhesive and especially after the bonding of the membrane material to a first electrode material on its one side and to a second electrode material on its second side, but it can also remain in the assemblage as long as it does not impair the product properties of the finished (proper) membrane electrode assembly.

[0035] On the whole, the embodiments described herein provide the benefit that the production aid is applied immediately before, during, or after the application of the liquid adhesive for the production of the membrane electrode assembly and in the shortest of time it takes over the role of strengthening the membrane electrode assembly until the actual liquid adhesive itself has hardened and thus all the individual components of the membrane electrode assembly have been joined.

[0036] Aspects of the various embodiments described above can be combined to provide further embodiments. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.