Separator for fuel cell

Abstract

The invention relates to a separator plate (1) for guiding a medium in a fuel cell, having at least one recess (2, 3, 4, 5, 6, 7) for the input of the medium and at least one recess (2, 3, 4, 5, 6, 7) for the output of the medium, having a channel structure (12) for the uniform guiding of the medium, and having a distribution area (9) connecting the recesses (2, 3, 4, 5, 6, 7) with the channel structure (12). The invention is characterized in that at least one distribution area (9) surrounds the at least one recess (2, 3, 4, 5, 6, 7) associated with the at least one distribution area over the entire periphery of the at least one recess.

Description

Technical Field

[0001] The invention relates to a separator for conducting a medium in a fuel cell of the type defined in detail in the preamble of claim 1 . Background Art

[0002] The construction of a fuel cell stack consisting of multiple individual cells is generally known from the prior art. In PEM fuel cells, for example, a membrane electrode assembly (MEA) is arranged between two separators that supply the anode and cathode media. This membrane electrode assembly consists of a gas diffusion layer, a catalyst, the actual membrane that forms the electrolyte of the individual cells, and optionally an electrically insulating membrane or layer. The separators are then often combined into so-called bipolar plates, where one surface of the separator forms the anode side of one cell and the other surface forms the cathode side of an adjacent cell. Channels for a cooling medium are also typically provided between the surfaces of the separators, or between the two subplates of the bipolar plate, to remove waste heat from the fuel cell. All of this is known to those skilled in the art from the prior art.

[0003] The separators are typically designed to have various openings that, when the individual cells are stacked with their separators, form continuous channels within the so-called fuel cell stack. These openings are then used for the input and output of media. Depending on the separator surface and its function, such as distributing hydrogen to the anode side, the channel structure arranged in the separator is configured to evenly distribute the media (here, hydrogen, for example) to the anode side of the MEA. These channel structures are connected to the corresponding openings for hydrogen input via distribution areas and connecting channels, also known as passages. This applies similarly to the other side of the separator in the flow direction. Distribution areas are also provided here, each with openings for discharging excess hydrogen and generated product water. Other openings are used, for example, for the input and output of air on opposite sides of the plates and / or for the input and output of cooling media, for example, between two bipolar plates, each with a surface facing the anode and cathode. This is also known in the art to those skilled in the art. A problem with this design is that, depending on the installation position, the fuel cell stack tends to become blocked to varying degrees by frozen water in the area of ​​the distribution plate, so that in practice, very precise attention must be paid to the correct installation position. Furthermore, the separators have a relatively high pressure loss, thus creating a high resistance to the medium flowing through the medium-conducting structures of the separators.

[0004] With regard to further prior art, reference may be made, merely by way of example, to the documents DE 10 2009 003946 A1 and US 2011 / 0177423 A1 with regard to such structures. Summary of the Invention

[0005] The object of the present application is to provide an improved separator having the structure according to the preamble of claim 1, which is improved with respect to the prior art and, in particular, avoids or minimizes the above-mentioned disadvantages in the installation position and pressure loss.

[0006] According to the application, this object is achieved by a separator having the features of claim 1 and, in particular, in the characterizing part of claim 1. Advantageous embodiments and improvements of the separator are given in the dependent claims relating thereto.

[0007] According to the solution of the application, the distribution region is designed such that it is connected directly to the recess / through-opening corresponding thereto and surrounds the recess over the entire circumference of the recess. Thus, the recess is located inside the distribution region and is no longer connected to the distribution region by an inlet channel or passage, as in the prior art. The inventors have recognized that, as a result, the pressure loss can be significantly reduced, since a correspondingly larger flow cross-section is now provided in order to optimize the entry of gas from the region of the recess into the distribution region and, ultimately, into the channel structure, for the purpose of distributing the medium, for example, in order to achieve cooling purposes or for the purpose of transferring the medium to the entire surface of the individual cells.

[0008] A further very important advantage also lies in the fact that the distribution region is arranged to surround the recess associated therewith over the entire circumference of the recess, which arrangement offers the advantage that gas from the region of the recess or gas flowing into the recess from all directions can enter the recess. If, for reasons of the installation position, one side is wetted by moisture and blocked by ice when the temperature falls below the freezing point, the other sections around the circumference of the recess are still available, thus ensuring that the corresponding medium flows into the channel structure via the distribution region extending around the entire circumference of the recess / around the entire circumference of the recess. Thus, it is no longer necessary to have a prescribed installation position in order to reliably start the fuel cell stack even in freezing conditions. Moreover, the fuel cell stack can be constructed in the most advantageous manner and method in terms of packaging, which is a very important advantage, in particular, in vehicle applications of the fuel cell stack and, in particular, when the problem of freezing starts frequently occurs in vehicle applications. As a result, the available installation space can be ideally utilized, and thus a small, compact and relatively easily mountable fuel cell system into the intended vehicle body is provided.

[0009] According to an advantageous embodiment of this concept, the distribution area has a supporting structure in the form of fins and / or projections. On the one hand, the supporting structure contributes to this design by preventing the distribution area from being compressed even under the strong pressure used to clamp the fuel cell stack. On the other hand, especially when the supporting structure is designed in the form of projections and is therefore designed as an open structure in the distribution area, the supporting structure has the advantage that it can guide the flow through the distribution area relatively evenly, or the flow can "find" a preferred flow path. If individual areas are blocked by water or ice, the flow can simply be bypassed, thus achieving very good overall flow distribution even in difficult operating conditions. This is a particularly important advantage of projections or fins compared to individual channels that are inherently closed.

[0010] Here, the distribution region also has these supporting structures, in particular protrusions, in the portion of the distribution region surrounding the notch. According to a highly advantageous development of the separator according to the present invention, provision can now be made for at least the portion of the distribution region surrounding the notch to be covered by an intermediate layer. This partial region surrounding the notch provides coverage of this portion of the distribution region and has the advantage of having a flat structure on the side facing away from the distribution region. This flat structure provides ideal contact conditions for the sealing material disposed around the notch and extending along the outer edge of the separator. For example, only the area surrounding the notch can be covered with an annular intermediate layer, the outer contour of which corresponds to the corresponding contour of the distribution region surrounding the notch. The intermediate layer, with a corresponding inner contour, frees up the notch so that the medium can still flow through the notch to the next adjacent plate. Alternatively, provision can be made for the entire distribution region to be covered with the corresponding intermediate layer. This is advantageous in terms of structural design and component tolerances, and allows for a correspondingly large surface area in the distribution region, which generally does not correspond to the electrochemically active area of ​​the MEA, for simple and reliable sealing of a stack formed from individual fuel cells having such a separator.

[0011] In this case, the support structure in the distribution area can be arranged so that it is formed on the partition plate itself, for example, by a pressed protrusion or by a pressed protrusion and a corresponding recess, with the recess then forming a protrusion on the opposite side, for example, for the distribution area of ​​the coolant. Alternatively, a highly advantageous development of this concept can also provide that the support structure is formed in the intermediate layer. The support structure is then implemented in the intermediate layer, so that the actual distribution plate, for example, only has the channel structure and has a smooth surface in the area of ​​the distribution area. This is advantageous if other components are arranged on the opposite side or if corresponding structures are required there. By transferring the support structure to the intermediate layer, the material thickness and stability of the distribution area can be optimized.

[0012] According to a very advantageous development of this concept, the separator can be made of metal. Such a separator made of metal, for example as a subplate of a so-called metal bipolar plate, has the advantage that the bipolar plate can be very thin yet very stable. However, alternative configurations, such as those made of graphite, carbon, or conductive plastic, are also conceivable.

[0013] In particular, in designs in which the partition is made of metal, it can be provided according to an advantageous development of the partition that the intermediate layer is obtained by forming the material previously arranged in the recess. In the case of metal partitions, the recess can be produced in particular by punching or cutting, for example using a laser. In this embodiment variant, it can now be considered that the material only needs to be cut in the desired manner in the area of ​​the subsequent recess and then formed, for example stretched, bent, etc., so that the intermediate layer is thus formed in one piece from the material of the partition and is designed accordingly. This construction is particularly suitable for producing an intermediate layer that only covers the part around the recess. For this purpose, the material can be cut accordingly and bent or stretched upwards so that the material is then curled in the area around the recess, whereby corresponding openings or holes must of course be provided in order to achieve a connection of the distribution area to the recess around the entire circumference.

[0014] In the sense of the invention, the expression “around the entire circumference” also includes designs in which the connection between the distribution area and the opening is established in this area by a grid, a perforated plate structure or the like, provided that this structure surrounds the entire circumference of the opening with as uniform a structure as possible.

[0015] An alternative embodiment is to manufacture the intermediate layer from plastic, but in this embodiment the last-described manufacturing step cannot be performed. This intermediate layer made of plastic can be implemented both with metal separators and with separators made of other conductive materials, such as graphite or the like. This design is relatively simple and effective and can, for example, be integrated into the structure of the separator.

[0016] According to a particularly advantageous development of this concept, the intermediate layer is designed to be connected to the MEA. Thus, the intermediate layer can be connected, for example, bonded or welded, to the MEA, i.e., the uppermost layer of the MEA facing the respective separator, such as a film located in the region of the recess and the distribution area, or a frame surrounding the MEA. This allows the intermediate layer to be precisely positioned in its intended position during positioning of the MEA, thereby eliminating a manufacturing step during assembly.

[0017] As already mentioned, the openings in the separators can be used to supply and discharge various media, particularly oxygen or air, hydrogen or hydrogen-containing gases, and / or coolants. According to a highly advantageous refinement of this concept, the openings, which are surrounded by the distribution area around their entire circumference, are designed for supplying and discharging separated / educted / reactants and products. Thus, while this structure is implemented on the anode and cathode sides in the manner described, it is not implemented in the area of ​​the coolant in this embodiment. However, this still allows for the aforementioned advantages, which primarily occur in the cathode and anode areas, because the aforementioned problems do not arise, or at least not to the same extent, on the side that conducts the coolant.

[0018] The separators can be designed as any desired separators. According to a particularly advantageous refinement of the invention, as already mentioned several times by way of example, the separators can be formed as part of a bipolar plate, so that two such separators, placed with their backs facing each other, form a bipolar plate that is connected on one side to the anode of one cell and on the other side to the cathode of another adjacent cell, and that has a structure for a coolant, in particular, between the two separators used as part of the bipolar plate. The coolant does not necessarily need to be fed in and out through the openings. It is sufficient if the coolant-carrying channels between the two separators that form part of the bipolar plate are laterally open and connected to the inlet and outlet of the coolant (here, liquid or gaseous). For example, a housing through which the coolant flows is arranged around the fuel cell stack.

[0019] Further advantageous embodiments of the partition wall also result from the exemplary embodiments described in detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings show:

[0021] FIG1 shows a top view of a partition according to a configuration scheme of the prior art;

[0022] Figure 2 A partial view showing an embodiment of a separator according to the present invention;

[0023] Figure 3 Shows something like Figure 2 A partial view of a first variant of the invention having an intermediate layer;

[0024] Figure 4 Shows something like Figure 2 A partial view of a second variant of the invention having an intermediate layer;

[0025] Figure 5 Show the basis Figure 3 A sectional view of the section line VV in FIG.

[0026] Figure 6 Show the basis Figure 4 A sectional view of the section line VI-VI in FIG;

[0027] Figure 7 Showing that the structure is Figure 6 an exploded view of an alternative embodiment similar to the cross-sectional view in FIG; and

[0028] Figure 8 Shown with Figure 5 Another embodiment that is basically similar to the embodiment in . DETAILED DESCRIPTION

[0029] FIG1 shows a top view of a separator, designated by reference numeral 1, such as the anode side of a bipolar plate. The structure here essentially corresponds to the prior art, but is not shown to scale. Separator 1 has multiple indentations 2 to 7 on both sides for supplying and discharging a medium. In the embodiment shown here, a top view of the surface of separator 1 facing the anode side of an adjacent cell of a fuel cell stack (not shown) is shown. For example, the separator has an indentation designated by 2 in its upper right corner, which, together with corresponding indentations in adjacent separators, forms a hydrogen supply channel. Hydrogen then flows through these indentations 2, forming part of the supply channel, to each of the separators 1 and, through connecting channels, so-called vias, designated by reference numeral 8, into a distribution area 9 of the flow field / flow zone, designated overall by reference numeral 10. Distribution area 9 has an open structure, for example, with protrusions 11 (shown schematically here), to facilitate lateral distribution of hydrogen. Further along in the flow direction of flow field 10, a channel structure 12 is provided. Through this channel structure 12, the gas is distributed on the anode side of the individual cells using parallel, closed channels to the active surfaces of the individual cells, in particular to the gas diffusion layers of the so-called membrane electrode assembly (MEA) 13. The distribution region 9 helps ensure that all channels of the channel structure 12 are flowed through as evenly as possible. After flowing through the channels of the channel structure 12, the remaining gas mixes with the product water produced in the fuel cell and reaches a further distribution region 9, which serves as a collection area. There, the gas / liquid mixture is collected accordingly. This gas / liquid mixture then flows via further connecting channels 10 on the outflow side into the opening denoted by 5, which, together with other corresponding openings in the adjacent separator 1, forms the outlet channel.

[0030] A bipolar plate typically consists of two separate plates in the form of separators 1, which are connected to each other at their rear faces, for example, by welding in the case of metallic bipolar plates. This creates additional channels between the rear faces of the separate plates, through which the coolant can flow via the notches 3 and 6. All of this is known to those skilled in the art and therefore requires no further explanation.

[0031] Now, in Figure 2 The view of FIG shows a portion of the separator 1 that is important for the separator 1 according to the present invention. Here, the present invention is illustrated using the example of the indentation 2, through which hydrogen is to flow. The present invention can be equally well applied to any other indentation among indentations 3 to 7 for the supply and discharge of separated materials, products, or cooling medium. Therefore, the content described below with respect to indentation 2 can also be transferred similarly to all other indentations 3 to 7.

[0032] The core concept here is that the distribution region 9 extends around the entire circumference of the cutout 2. Thus, unlike the prior art, the cutout 2 is not only connected to the distribution region 9 via a connecting channel or passage 8, but is also directly connected to the distribution region or located within the surface / area of ​​the distribution region 9. The distribution region has a protrusion 11 over its entire area, and therefore also around the cutout 2, to achieve sufficient stability against pressure when stacking the cells, while at the same time providing an open structure around the entire circumference of the cutout 2. This ensures that even if portions of the distribution region 9 are blocked by ice, gas can still penetrate to the channel structure 12, thereby enabling a fuel cell or fuel cell stack having such a separator 1 to be installed in a largely arbitrary position. This allows for freeze starts / cold starts even under adverse conditions, as the transition from the cutout 2 into the distribution region 9 and, ultimately, the distribution of gas to the channel structure 12 on the active surface of the cells can be guaranteed to be unobstructed.

[0033] In previous designs, an intermediate layer, sometimes also referred to as a shim, covers the connecting channel 8 in order to ensure a neat fit of the MEA 13 or of a plastic frame 15 designed around the active surface of the MEA, which is typically made of polyethylene naphthalate (PEN). This intermediate layer (here indicated by reference numeral 14) is used in Figure 3 is shown purely by way of example in the diagram. Figure 5 The basis Figure 3This structure can be seen again in the corresponding sectional view along the section line VV in FIG. Here, the projection 11 is designed to be slightly lower in height in the area around the notch 2, so that the intermediate layer 14 rests on it and then forms a flat support surface for the MEA 13 (illustrated here) and for the MEA's PEN frame 15 in the distribution area 9. The PEN frame can thus be neatly and securely positioned around the notch 2 and can form a sealing mating surface between the individual components of the fuel cell stack. Similarly to the notch 2, the PEN frame 15 and the intermediate layer 14 also have corresponding notches to ensure further gas conduction to adjacent cells.

[0034] exist Figure 4 In the diagram and here also with Figure 4 The diagram is similar to Figure 6 It can be seen again in the cross-sectional view of that the intermediate layer 14 is designed to be slightly larger here. It covers not only the part of the distribution area 9 that is adjacent to the recess 2, but also the entire distribution area 9, or in an alternative embodiment that is not shown here, only a part of the distribution area. In addition, the construction corresponds to the Figure 3 and Figure 5 The construction described in , wherein the projections 11 are always designed to be of the same height.

[0035] In the previous embodiments, the projections 11 are always designed as part of the partition 1 itself, for example in such a way that they are Figure 5 and Figure 6 Of course, pressing from above is also conceivable, so that in this case, for example, further protrusions are produced on the lower surface, which is drawn flat here, which can, for example, constitute distribution areas for the cooling medium.

[0036] Here Figure 7 An alternative embodiment is shown in the exploded view in the figure of FIG. Here, the figure essentially corresponds to Figure 5 and Figure 6 However, the projections 11 are not formed on the actual separator 1, but on the intermediate layer 14, so that the separator 1 can be formed flat, which is particularly useful when sealingly connected to the intermediate layer 14. Figure 7 The intermediate layer 14 can be formed, for example, from a metal material or also from a plastic, for example by stamping, injection molding, sintering or 3D printing. In the case of an embodiment made of plastic, the intermediate layer 14 can then be connected to the MEA 13 or its PEN frame 15 accordingly, for example by gluing, which is particularly advantageous in the case of an embodiment made of plastic. Figure 7This is shown only as an example. This allows the MEA 13 with its PEN frame 15 to be easily placed on the separator 1 and, combined with the precise positioning of the MEA 13 or its active surface on the channel structure 12, also allows the intermediate layer 14 to be positioned securely. This not only makes it possible to Figure 7 As shown, this can be achieved by arranging the protrusions 11 on the intermediate layer 14, and can also be achieved by Figure 5 and Figure 6 This is achieved when the projections 11 are arranged in reverse as shown in FIG.

[0037] As mentioned above, an alternative is that the intermediate layer 14 consists of metal, for example. In this case, the intermediate layer can be welded, for example, to the projections 11 located on the separator 1 in order to secure it in place. It is of course also conceivable to integrate the projections 11 into the intermediate layer 14. This can then also be welded to the separator 1 accordingly, without changing the described operating principle.

[0038] exist Figure 8 In the view of , another embodiment of the intermediate layer 14 can be seen, in which the partition 1 consists of metal. In this embodiment variant, the material arranged in the area of ​​the recess 2 is cut laterally, for example by laser cutting, and individual openings or holes 16 are provided around the entire circumference of the subsequent recess 2. The material thus cut, which is initially located in the area of ​​the recess 2, is then deformed, for example bent and / or curled or stretched. The intermediate layer 14 can thus be implemented as one piece with the partition 1 by bending the corresponding material and then resting it on the projection 11 at the desired position, as in Figure 8 , as shown accordingly in . Once the material is positioned at the desired location, it can also be welded to the protrusion 11, as in the previously described intermediate layer. The advantage of this design is that only a single material is used, and the material removed from the notch, which would normally be wasted, can be directly used for the intermediate layer. To ensure a uniform outflow of the medium from the notch into the distribution area 9, a large number of openings 16 are provided in the material, arranged above the circumference of the notch 2. These openings can, for example, be distributed around the circumference of the notch 2 in the form of perforations, thereby also making the material more easily deformable in this area and ensuring the required flat surface of the PEN frame 15 for supporting the MEA 13.

Claims

1. A separator (1) for conducting a medium in a PEM fuel cell, the separator having at least one opening (2, 3, 4, 5, 6, 7) for supplying the medium and at least one opening (2, 3, 4, 5, 6, 7) for discharging the medium, the separator having a channel structure (12) for uniformly conducting the medium and a distribution region (9) connecting the opening (2, 3, 4, 5, 6, 7) to the channel structure (12). in, At least one of the distribution areas (9) surrounds at least one notch (2, 3, 4, 5, 6, 7) associated with the at least one distribution area around its entire circumference, at least the portion of the distribution area (9) surrounding the notch (2, 3, 4, 5, 6, 7) being covered by an intermediate layer (14), The distribution area (9) has a supporting structure in the form of fins and / or protrusions (11), The supporting structure is formed in an intermediate layer (14), which has a flat structure on its side facing away from the distribution area (9).

2. The separator (1) according to claim 1, It is characterized by: The partition is made of metal.

3. The separator (1) according to claim 2, It is characterized by: The intermediate layer (14) is produced by shaping a material previously arranged in the recesses (2, 3, 4, 5, 6, 7).

4. The separator (1) according to any one of claims 1 to 2, It is characterized by: The intermediate layer (14) is made of plastic.

5. The separator (1) according to claim 1, It is characterized by: The intermediate layer (14) is implemented to be connected to the membrane electrode assembly (13) or to a frame (15) supporting the membrane electrode assembly.

6. The separator (1) according to any one of claims 1 to 3, It is characterized by: The openings (2, 4, 5, 7) are configured for input and output of the separation material and the product.

7. The separator (1) according to any one of claims 1 to 3, It is characterized by: The separator is formed as part of the bipolar plate.

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