Fuel cells with stacked structure

Abstract

The present invention relates to a fuel cell (10) having a stacked structure (12) consisting of a plurality of stacked individual elements (14) tensioned together by a first end plate (20) and a second end plate (22). The end plates (20, 22) are constructed as composite components (24) with different stiffness regions (36, 38).

Description

Technical Field

[0001] The present invention relates to a fuel cell having a stacked structure consisting of a plurality of stacked individual elements tensioned together by a first end plate and a second end plate, and to the use of a fuel cell as an energy source for an electrically driven vehicle. Background Technology

[0002] For fuel cells, especially PEN fuel cells, it is important that the individual cells or elements connected in series are uniformly pressed together. Because a typical fuel cell stack can include up to 1200 individual elements, such as anode elements, cathode elements, and / or flow plates, manufacturing tolerances have a significant impact on the quality of tensioning. Therefore, elastic intermediate layers for leveling are typically installed at both ends of the stack. A planar elastic plate is known from WO 2008 / 081962 A1, which is disposed between the individual cells and end plates of the stacked structure and is capable of shear elastic deformation orthogonal to the tension force.

[0003] A fuel cell stack with tension bands is known from US 5,789,091. Tension bands are provided to maintain a stacked structure of individual elements between a pair of end plates, the tension bands surrounding the end plate assembly and the stacked individual elements located therebetween. At least one of the end plates includes a flexible element that interacts with each tension band such that a first end plate is pressed into a second end plate, thereby applying compressive force to the stacked structure to ensure sealing and electrical contact between the individual layers forming the stacked structure of the fuel cell.

[0004] Furthermore, it is known that the rigidity of stacked individual elements differs in the region of the active membrane sheet or, in the case of a gas diffusion layer composed of carbon fiber pads, in the edge region with a mounted seal. Additionally, it is known to implement end plates in geometrically, for example, as continuously cast profiles, to facilitate high rigidity, i.e., to achieve low weight.

[0005] Silicone pads used to date as shear elastic elements have manufacturing-determined tolerances, meaning that improvements in flatness or tolerance are not characteristic of these pads. Therefore, a 2mm thick silicone sheet with a tolerance of approximately 0.2mm can result in a 10% pressure variation. In the case of elastomeric seals, hardness also typically fluctuates by about 10%.

[0006] Furthermore, this depends on whether the individual components within the stacked structure are implemented as, for example, bipolar plates milled from graphite or stamped metal plates. The number of components to be installed should be as small as possible for cost-effective mass production; however, this can be hampered by the addition of compensating components. Summary of the Invention

[0007] According to the present invention, a fuel cell with a stacked structure is proposed, which consists of a plurality of individual elements arranged in a stacked manner, these individual elements being tensioned together by a first end plate and a second end plate. According to the present invention, the end plates are implemented as composite components with different stiffness regions.

[0008] By varying the stiffness of localized areas, such as through different elastic moduli or lateral elongation coefficients of the materials used, a composite component can be achieved as an end plate with stiffness regions, thereby significantly simplifying the assembly of fuel cell stacks. The solution according to the invention allows for the satisfaction of rigidity requirements for stacked individual components in both the active membrane region and the edge region of the seal.

[0009] In an improved embodiment of the solution proposed according to the present invention, the end plate can have inserts in at least a first region, which is a first stiffness region; furthermore, a shear elastic element can be placed on the end plate, and another elastic element is located therein. Alternatively, a planar frame element can be provided, with a soft or hard core embedded in the center of the frame element.

[0010] In the fuel cell proposed according to the present invention, the end plate or the region thereof located outside at least one first region is a second stiffness region.

[0011] In the fuel cell according to the present invention, the rigidity of the material in at least one first region exceeds the rigidity of a second stiffness region, the first region forming a first stiffness region. The second stiffness region is particularly located in the edge region of the end plate.

[0012] In the fuel cell proposed according to the invention, the force introduction point for introducing preload into the stack structure is located on the end plate, particularly in at least one first region. Because this region is the first stiffness region, it ensures that uniform surface pressure can be achieved within the stack structure through the introduction point located there.

[0013] In the fuel cell proposed according to the invention, the area of ​​at least one first region corresponds to the area of ​​the active membrane region of a single element. This at least one first region enables uniform surface pressure, particularly hermetically tight contact, between the active membrane regions within the stacked structure and between the individual elements of the stack. The geometry of the at least one first region, particularly its area corresponding to the active membrane region of a single element, enables uniform surface pressure, especially in the region of the seal on the active membrane region, thereby achieving a hermetically tight stacked structure.

[0014] In the fuel cell according to the present invention, the end plate mounted on the fuel cell can be made of a thermoplastic or thermosetting polymer. An insert can be inserted into the end plate, particularly into a basin-shaped receiving portion, wherein the insert can be made of a thermoplastic or thermosetting polymer, and optionally, an increased glass fiber content is present in the region of the force introduction point.

[0015] In another advantageous implementation, the composite can be made, for example, as an injection-molded component in which the two polymers are combined with each other. Alternatively, the injection-molded polymer, or the harder regions of the polymer thereof, can be selectively reinforced with fibers; the reinforcing fibers in these regions can be selectively oriented such that individual regions are harder due to the orientation of the fibers in the injection molding of the fiber-reinforced polymer, while other regions are configured to be more flexible. The end plates are made of, for example, thermoplastic or thermosetting polymers, wherein the glass fiber fraction is oriented during injection molding for reinforcement such that the stiffness is particularly high, for example, at the point of force introduction.

[0016] In the solution proposed according to the invention, fiber reinforcement can be applied to the more rigid regions. Thus, for example, short fibers are incorporated into the molten polymer, while the softer regions are manufactured using other polymers or without fibers or with a blend of fibers, although the fibers are oriented differently compared to their orientation in the membrane regions. Alternatively, elastic rubber microspheres can be incorporated into the softer regions to make those regions selectively softer in terms of their rigidity. Furthermore, it is possible for the polymer to foam in one region while not foaming in another.

[0017] Furthermore, the present invention relates to the use of a fuel cell as an energy source for an electrically driven vehicle.

[0018] According to the solution proposed in this invention, the end plate can be manufactured as a composite component, resulting in a composite component with locally very different stiffness. Furthermore, additional geometric structures can be present. By employing locally different stiffnesses, with at least one first stiffness region and a second stiffness region, the composite component can be manufactured as a single component, which significantly simplifies assembly. Different stiffness regions can be achieved and influenced, for example, by corresponding material selection in terms of elastic modulus or lateral elongation. Furthermore, in the end plate, the edge region can be a second stiffness region. In the solution proposed in this invention, the end plate can advantageously be made of a thermoplastic polymer or a thermosetting polymer. Inserts can be incorporated, particularly arranged in, for example, basin-shaped receptacles within the end plate, which has a high glass fiber content, especially in the region for introducing preload into the stacked structure.

[0019] By constructing the endplate as a composite component with different stiffness regions according to the present invention, the assembly of the fuel cell stack can be simplified. On the other hand, the solution proposed according to the present invention allows for cost-effective mass production, by keeping the number of components to be installed small or limiting it to an invariable minimum.

[0020] The advantages in terms of structural height of the stacked structure can be achieved through the solution proposed according to the present invention. Alternatively, it is possible to change the material thickness of the individual components. However, in this case, similar to spring stiffness, the thickness varies by a factor of 2 from the edge region to the diaphragm region; according to the present invention, the stiffness varies by a factor of 2, which is simply achieved by changing the polymer or by changing the filler density. Attached Figure Description

[0021] The present invention will now be described in detail with reference to the accompanying drawings.

[0022] The attached diagram shows:

[0023] Figure 1 A fuel cell has a stacked structure consisting of individual components, which are fixed together by end plates fabricated as composite components.

[0024] Figure 2 A top view of a single element with a perforation and an active membrane region.

[0025] Figure 3 A top view of an insert with an opening and an end plate arranged in the receiving section, and

[0026] Figure 4 A schematic diagram of the sensor array.

[0027] In the following description of embodiments of the invention, the same or similar elements are designated by the same reference numerals, and in some cases these elements are not described repeatedly. The drawings are for illustrative purposes only, showing the subject matter of the invention. Detailed Implementation

[0028] According to Figure 1 The illustration shows a fuel cell 10 as a stacked structure 12 composed of individual elements 14. The stacked structure 12 is composed of individual elements 14, which are arranged stacked and occupy a stack height 16. The individual elements 14 constituting the stacked structure 12 are tensioned to each other via a first end plate 20 and a second end plate 22. Possible tensioning elements for pre-tensioning the stacked structure 12 include, for example, threaded connections or tension bands, or similar types. Figure 1 As shown in the diagram, the stacked structure 12 of the fuel cell 10 is penetrated by channels 18. Each channel 18 is formed by a through-hole 26 (see diagram). Figure 2and Figure 3 (as illustrated in the diagram) The perforations are implemented on individual elements 14 that form the stacked structure 12.

[0029] also, Figure 1 As shown, the first end plate 20 and the second end plate 22 are respectively implemented as composite members 24. For example, the composite member 24 is configured such that it has at least one first region 32, which is a first stiffness region 36.

[0030] The composite component 24 may include a basin-shaped receiving portion 34 into which an insert can be placed, the insert forming different stiffness regions 36, 38.

[0031] Figure 2 A top view of a single element 14 is shown, the single element being... Figure 1 The components of the stacked structure 12 shown in the figure. According to Figure 2 The single element 14 in the top view is a planar component and has an active membrane region 28 implemented in a roughly square manner. According to... Figure 2 In the top view, a perforation 26 exists in the edge region 30 of a single element 14, which forms a corresponding channel 18 when the single elements 14 are stacked inside the stacked structure 12, as it is in Figure 1 As shown in the diagram, channel 18 extends continuously from the first end plate 20 to the second end plate 22 through the stacked structure 12.

[0032] Figure 3 The second end plate 22 is shown in top view. The second end plate 22 also has a through-hole 26, which is part of the channel 18. At least one first region constitutes a first stiffness region 36, within which there exists a higher stiffness than that present within a second stiffness region 38 in the edge region 30 of the second end plate 22. The first end plate 20 and the second end plate 22 are preferably made of a thermoplastic or thermosetting polymer material.

[0033] In addition, from Figure 3 As can be seen, there is high rigidity within at least one first region 32, and within this first region there is a first stiffness region 36, with the force introduction point 40 located within the first stiffness region. (Comparison) Figure 2 and Figure 3 It is evident that the area of ​​at least one first region 32 substantially corresponds to that according to Figure 2 The area of ​​the active membrane region 28 of a single element 14. Figure 2 In the middle, the force input point 40 is drawn with a dashed line.

[0034] If a certain number of individual elements 14 are now stacked in the stacked structure 12, their active membrane regions 28 are also stacked. If a preload is introduced into the stacked structure 12 constructed from such stacked individual elements 14, the force introduction point 40 is located within at least one first region 32, and a first stiffness region 36 is located within the first region. This means that when a tension force is applied, a uniform surface pressure can be achieved within the area of ​​at least one first region 32 and therefore within the active membrane regions 28 of the stacked individual elements 14.

[0035] Tension force can be introduced at the force introduction point 40, for example, through a preload element, such as a tension bolt or tension band, or the like. If the force introduction point 40 is located within the at least one first region, i.e., the first stiffness region 36, then according to Figure 1 When the stacked structure 12 is tensioned, it enables the individual active membrane regions 28 to be hermetically sealed against the individual element 14. If the stacked structure 12 is tensioned, there is hermetically sealed contact between the individual element 14, especially inside the active membrane regions 28.

[0036] Of particular significance is that, for example in the region of the force introduction point 40, an increased share of glass fiber may be present in at least one first region 32, through which a first stiffness region 36 is formed there, i.e. particularly in the region of the force introduction point 40.

[0037] Compared to the first stiffness region 36, the edge region 30 of the second end plate 22 forms a second stiffness region 38, in which the material stiffness is smaller than that of the material inside at least one first region 32, which is the first stiffness region 36.

[0038] By constructing different stiffness regions 36, 38 in the end plates 20 or 22, the number of components to be installed within the stacked structure 12 can be kept limited, thereby enabling cost-effective mass production. Additional compensating components, as have been used previously, can be omitted. When manufacturing the end plates 20 or 22, which are constructed as composite components 24, thermoplastic or thermosetting polymers are preferably used. For reinforcement, a glass fiber fraction is added during injection molding, and the glass fiber fraction is oriented such that stiffness, particularly the first stiffness region 36, is formed at least at the force introduction point 40 within the area of ​​the first region 32.

[0039] Besides thermoplastic or thermosetting polymers, polyimides, and PVDF or PPS or PEEK, other materials can be used as materials for manufacturing composite components 24 with different stiffnesses. In terms of creating different stiffness regions 36, 38 by mixing components into the polymer, in addition to glass fibers, high-hardness carbon fibers with a size of 10 μm or glass-ceramic powder (glass carbon) can be added to the aforementioned materials in different orientations. Glass-ceramic powder can also be processed, for example, into PVDF, which is itself a relatively soft material. Besides glass-ceramic powder, ceramic powders can also be simply mixed to specifically modify the stiffness of the polymer material.

[0040] Composite component 24 can be manufactured, for example, as an injection-molded component in which two polymeric materials are combined with each other. The harder regions of the polymer can be specifically reinforced with fibers, such as the aforementioned ceramic powder, glass fiber ceramic powder, or the like. Within the regions of composite component 24 to be reinforced or strengthened, the reinforcing fibers can be specifically oriented such that individual regions acquire higher stiffness compared to other regions with lower stiffness and therefore greater flexibility through the orientation of the reinforcing fibers during the injection molding process. Fiber reinforcement for harder regions can be achieved, for example, by mixing short fibers with molten polymer. The softer, i.e., more flexible regions of composite component 24 can be manufactured with another polymer, or with or without reinforcing fibers, but with a different orientation compared to the orientation of the reinforcing fibers in the active membrane region 28. Furthermore, elastic microspheres, such as rubber microspheres, can be processed into regions that should have lower stiffness, i.e., should be configured to be more flexible, so that these regions are specifically made more flexible in terms of stiffness. Furthermore, there is the possibility that, in the case of injection molding, one polymer can be foamed while the other is not, thus creating regions with different stiffnesses in the composite component 24 in this way.

[0041] Elastic elements with different stiffnesses can be placed in this area. Alternatively, it is also possible to use a planar frame element, in which a core with greater or less stiffness, made of a material or a mixture of materials, can be placed in the center.

[0042] Figure 4 A schematic diagram of the sensor array is shown. The sensor array is housed as a single element 14 within the fuel cell 10. Here, the single element 14 containing the sensor array can be arranged at any location inside the fuel cell 10, or located in the region of the first end plate 20 or the region of the second end plate 22. Multiple sensor arrays can also be used as single elements 14 within the fuel cell 10. The local surface pressure within the fuel cell 10 can be determined using the sensor array.

[0043] This invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, various modifications that are within the scope of a person skilled in the art can be implemented within the scope defined by the claims.

Claims

1. A fuel cell (10) having a stacked structure (12) comprising a plurality of stacked individual elements (14), said individual elements being tensioned together by a first end plate (20) and a second end plate (22), characterized in that, The end plate is constructed as a composite component (24) with different stiffness regions, wherein the end plate has at least one first region (32), the first region being a first stiffness region (36), and the end plate has a second stiffness region (38) outside the at least one first region (32), wherein the stiffness of the material in the first stiffness region (36) exceeds the stiffness of the material in the second stiffness region (38), wherein the area of ​​the at least one first region (32) corresponds to the area of ​​the active membrane region (28) of the individual element (14), wherein the composite component (24) is planar and includes frame elements, the frame elements having a basin-shaped receiving portion (34) into which an insert is placed, wherein the insert forms the first stiffness region (36) and the frame elements form the second stiffness region (38).

2. The fuel cell (10) according to claim 1, characterized in that, The force introduction point (40) on the end plate for introducing preload into the stacked structure (12) is located in the at least one first region (32), which is the first stiffness region (36).

3. The fuel cell (10) according to claim 1 or 2, characterized in that, Uniform surface pressure between the individual elements (14) is achieved through the first stiffness region (36).

4. The fuel cell (10) according to claim 1 or 2, characterized in that, The end plates are made of thermoplastic or thermosetting polymers.

5. The fuel cell (10) according to claim 2, characterized in that, The at least one first region (32) is made of a thermoplastic or thermosetting polymer and has an increased share of reinforcing fibers in the region of the force introduction point (40).

6. The fuel cell (10) according to claim 5, characterized in that, The reinforcing fibers are mixed with carbon fibers, glass-ceramic powder, or ceramic powder.

7. The fuel cell (10) according to claim 1 or 2, characterized in that, The stacked structure (12) consisting of a single element (14) includes at least one single element (14) having a sensor array or having at least one single sensor for determining local surface pressure in the stacked structure (12).

8. The fuel cell (10) according to claim 5, characterized in that, The reinforcing fibers are oriented above the polymer such that a single stiffness region is given by the orientation of the reinforcing fibers in the injection molding process.

9. The fuel cell (10) according to claim 3, characterized in that, The first stiffness region (36) enables airtight contact between the active membrane regions (28) of the individual element (14).

10. The fuel cell (10) according to claim 4, characterized in that, The end plates are made of polyimide, PVDF, PPS or PEEK.

11. Use of a fuel cell (10) according to any one of claims 1 to 10 as an energy source for an electrically driven vehicle.

Images