Method for connecting at least two components of a membrane electrode assembly of a fuel cell

Abstract

Method for connecting at least two components (B1, B2) of a membrane electrode assembly of a fuel cell (2), characterized in that an adhesive (1) for connecting the components (B1, B2) is applied in predetermined partial areas with different layer thicknesses to a surface of at least one of the components (B1, B2) and the components (B1, B2) are glued to one another.

Description

[0001] The invention relates to a method for connecting at least two components of a membrane electrode assembly of a fuel cell according to the features of the preamble of claim 1.

[0002] A method for bonding a membrane electrode assembly to a gas diffusion layer of a fuel cell stack is known from the prior art, as described in US 2010 / 0000679 A1. In the method, a catalyst layer is applied to a surface of a polymer electrolyte membrane, a seal is applied to an edge region of the polymer electrolyte membrane, and then a gas diffusion layer is applied to a surface of the catalyst layer by bonding a surface or part of the surface of the seal to an edge region of the gas diffusion layer.

[0003] DE 11 2005 002 974 B4 discloses a method for increasing the bond strength between elements of a fuel cell membrane electrode assembly that are to be bonded together using an adhesive. US 2007 / 0087259 A1 describes a method for producing a catalyst-coated membrane. DE 198 29 142 A1 discloses a composite of a bipolar plate and an MEA with a gas-tight bond.

[0004] The invention is based on the object of providing an improved method for connecting at least two components of a membrane electrode assembly of a fuel cell.

[0005] The object is achieved according to the invention by a method for connecting at least two components of a membrane electrode assembly of a fuel cell having the features of claim 1.

[0006] Advantageous embodiments of the invention are the subject of the subclaims.

[0007] In a method for bonding at least two components of a membrane electrode assembly of a fuel cell, according to the invention, an adhesive for bonding the components is applied to a surface of at least one of the components in predetermined partial areas with different layer thicknesses, and the components are bonded together. Advantageously, the adhesive is applied to the surface of at least one of the components in a predetermined minimum possible partial area or in several predetermined minimum possible partial areas and in a predetermined minimum possible layer thickness.

[0008] This optimized adhesive technology enables the production of thinner fuel cells, thus maximizing the number of fuel cells in a fuel cell stack within a given, limited installation space. The process allows the adhesive to be applied selectively and in variable thickness using a suitable application technique. This results in thinner adhesive bonds and thus thinner fuel cells, allowing a larger number of fuel cells to be arranged in the fuel cell stack within the given, limited installation space.

[0009] Embodiments of the invention are explained in more detail below with reference to drawings.

[0010] Showing: Fig. 1 schematically shows an adhesive application according to the state of the art, Fig. 2 schematically shows a section of a fuel cell according to the prior art, Fig. 3 schematically shows an adhesive application according to the method according to the invention and Fig. 4 schematically shows a section of a fuel cell produced using the method according to the invention.

[0011] Corresponding parts are provided with the same reference numerals in all figures.

[0012] Fig. Figure 1 schematically shows an adhesive application according to the prior art for joining two components B1, B2 of a membrane electrode assembly. According to the prior art, the adhesive 1 is applied over the entire surface to an edge region of the first component B1, and the first component B1 is bonded to a Fig. 2 shown second component B2.

[0013] Fig. Figure 2 shows an edge region of a fuel cell 2 according to the prior art. The fuel cell 2 comprises the membrane electrode assembly and two bipolar plates 3, with seals 5 arranged between the bipolar plates 3 and a frame 4 of the membrane electrode assembly formed by the two components B1, B2 of the membrane electrode assembly. By compressing the fuel cell 2 to effectively seal an interior region of the fuel cell 2 enclosed by the seals 5, the seals 5 are pressed against the bonded frame 4 of the membrane electrode assembly.

[0014] Due to the adhesive 1 between the components B1, B2 of the membrane electrode assembly, which in this embodiment of the fuel cell 2 according to the prior art is arranged in the sealing area of ​​the fuel cell 2, the fuel cell 2 has a relatively large thickness. As a result, only a certain number of fuel cells 2 can be arranged to form a fuel cell stack within a given, limited installation space, and due to the relatively large thickness, only a relatively small number, which limits the performance of the fuel cell stack.

[0015] In addition, the compression of the fuel cell 2 and the resulting pressing of the seals 5 onto the frame 4 of the membrane electrode assembly bonded by means of the adhesive 1 displaces the adhesive 1, particularly during operation of the fuel cell 2 and the resulting temperature fluctuations, during which the adhesive 1 is not always fully cured. This is also referred to as creep of the adhesive 1 and can lead to a diminished adhesive effect and leaks in the fuel cell 2. Furthermore, this can lead to a reduction in the performance of the fuel cell 2 if the adhesive 1 is displaced into unintended areas within the fuel cell 2 and, for example, clogs the membrane electrode assembly.

[0016] Fig. 3 shows a method for bonding at least two components B1, B2 of the membrane electrode assembly of the fuel cell 2, by means of which the described disadvantages of the prior art are avoided. In this method, the adhesive 1 for bonding the components B1, B2 is applied selectively and in a variable layer thickness to a surface of at least one of the components B1, B2 of the membrane electrode assembly, i.e., in predetermined partial areas with different layer thicknesses, advantageously to one or more predetermined minimum possible partial areas and in a predetermined minimum possible layer thickness. The components B1, B2 are then bonded to one another.

[0017] Using the method, the Fig. 4 shown fuel cell 2 can be produced, which has a compared to the one shown in Fig. 2, has a reduced thickness according to the prior art. In the example shown here, the components B1, B2 of the membrane electrode assembly to be connected to one another are two polymer films, preferably made of polypropylene, which form the frame 4 of the membrane electrode assembly.

[0018] In the example shown here, the adhesive 1 is applied in two predetermined, spaced-apart parallel stripes to a circumferential edge region of the surface of the first component B1 of the membrane-electrode assembly, which is designed as a polymer film. In addition, a further strip of the adhesive 1 is applied to the surface of the polymer film on a side of openings 6 in the polymer film facing away from the edge region. These openings 6 serve, for example, to pass reaction gases and a coolant through the fuel cell 2. After the application of the adhesive 1, this first component B1, designed as a polymer film, is bonded to the second component B2 of the membrane-electrode assembly, which is also designed as a polymer film.

[0019] The adhesive 1 can be applied, for example, using a screen printing process, an offset printing process, and / or a blasting process analogous to an inkjet process, also known as an inkjet process. In this case, instead of ink, the adhesive 1 is sprayed, or in the aforementioned printing processes, the adhesive 1 is applied to the first component B1 of the membrane-electrode assembly instead of ink.

[0020] These adhesive application methods enable targeted and highly precise adhesive application, allowing the adhesive 1 to be applied in an optimal amount and distribution. This allows targeted strengths and stiffnesses of the membrane electrode assembly to be achieved, which are advantageous both for further processing of the membrane electrode assembly during the manufacture of the fuel cell 2 and during operation of the fuel cell 2.

[0021] To increase and improve the adhesion of the adhesive 1 to the polymer film of the first and / or second component B1, B2, it is possible to activate the surface of the polymer film that comes into contact with the adhesive 1. Such activation of the polymer film is carried out, for example, with an atmospheric plasma before the adhesive 1 is applied.

[0022] In addition, as in Fig. 4, a reduced thickness of the fuel cell 2 is achieved, whereby more fuel cells 2 can be arranged within a given installation space. This is achieved by applying the adhesive 1 in the two predetermined spaced-apart parallel strips in the edge region of the surface of the first component B1. This creates a free space without adhesive 1 between the strips, in which the two components B1, B2 of the membrane-electrode assembly, i.e., the two polymer films that form the frame 4 of the membrane-electrode assembly, rest directly on one another.

[0023] In this way, the frame 4 of the membrane electrode assembly is thinner in this area than the frame in Fig. 2 shows the frame 4 according to the prior art. During further production of the fuel cell 2, the seals 5 are placed on this thin area of ​​the frame 4 without adhesive 1. These seals are pressed against the frame 4 by means of the bipolar plates 3 to effectively seal the interior of the fuel cell 2.

[0024] Since no adhesive 1 is arranged in the sealing area of ​​the fuel cell 2, the fuel cell 2 is thinner than the one in Fig. 2 shows a fuel cell 2 according to the prior art. As already mentioned, this allows more fuel cells 2 to be arranged in the fuel cell stack within the given installation space, thereby forming a fuel cell stack with a higher power output, i.e., the power density of the fuel cell stack within a given installation space is increased.

[0025] Furthermore, sources of error such as adhesive settling or adhesive creep and resulting leaks are avoided or at least reduced, since in the sealing area, ie in the area of ​​the frame 4 of the membrane electrode assembly onto which the seals 5 are pressed, no adhesive 1 is present due to the predetermined distance between the two adhesive strips, as in Fig.4. Due to this missing adhesive 1 beneath the seals 5, the sealing effect of the seals 5 is also improved due to an improved or no longer existing settling behavior of the fuel cell 2, since the sealing effect is no longer impaired by displaced adhesive 1 and the resulting cavities in the area of ​​the seals 5. Furthermore, better tolerance compensation is possible, since the additional tolerances of the adhesive layer between the seals 5 no longer need to be taken into account. In addition, the targeted and minimized adhesive application results in a material saving of the adhesive 1 and thus a cost saving. List of reference symbols 1 adhesive 2 fuel cells 3 bipolar plate 4 frames 5 Seal 6 Opening B1 first component B2 second component

Claims

[1] Method for connecting at least two components (B1, B2) of a membrane electrode assembly of a fuel cell (2), characterized by that an adhesive (1) for connecting the components (B1, B2) in predetermined partial areas with different layer thicknesses is applied to a surface of at least one of the components (B1, B2) and the components (B1, B2) are glued together. [2] Method according to claim 1, characterized by that the adhesive (1) is applied in at least two predetermined spaced-apart parallel strips. [3] Method according to claim 1 or 2, characterized by that the adhesive (1) is applied by means of a screen printing process, by means of an offset printing process and / or by means of a blasting process. [4] Method according to one of claims 1 to 3, characterized bythat the adhesive (1) is applied to a peripheral edge region of the surface of a first polymer film and the first polymer film is bonded to a second polymer film.

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