Bipolar plates and fuel cell stacks

Abstract

The invention relates to a bipolar plate (10) for a fuel cell stack (100), having a main extension plane (HE) and a main flow direction (HR) in the main extension plane (HE), a first bipolar plate half (12) and a second bipolar plate half (14), an active field (40), a distribution area (50) and a port area (60), wherein the port area (60) has at least one port for introducing at least one fluid (F) into the main extension plane (HE), wherein the active field (40) has at least one cooling fluid channel structure (42) for cooling by means of a cooling fluid (KF) and at least one fuel channel structure (44) for supplying at least one fluid (F) to at least one adjacent membrane electrode assembly (110) of the fuel cell stack (100), wherein the first bipolar plate half (12) and the second bipolar plate half (14) form at least one distribution channel structure (52) in the distribution area (50), wherein the distribution channel structure (52) is configured at an angle to the main flow direction (HR) in the main extension plane (HE) in order to be flowed through by a cooling fluid (KF), wherein the bipolar plate (10) has a greater thickness (D1) in the distribution area (50) than a maximum thickness (D2) of the bipolar plate (10) in the active field (40). Furthermore, the invention discloses a fuel cell stack (100) having at least one bipolar plate (10) and at least one membrane electrode assembly (110).

Description

Background Technology

[0001] As an energy storage device for mobile applications, hydrogen is an excellent alternative to batteries because it eliminates the need for environmentally harmful raw materials (such as lithium) in the manufacture of storage devices, and pressure vessels filled with hydrogen weigh only a fraction of those of batteries for the same energy content. To generate electricity in fuel cells, hydrogen is oxidized to H2O, for example, along with oxygen in the air, in mobile applications. Most of the released energy is generated as electricity and can be used by the power-consuming devices in mobile applications.

[0002] In known fuel cells, bipolar plates are primarily used for guiding the flow of fuel fluid and / or cooling fluid. The purpose of the bipolar plate is to uniformly distribute the gas and cooling medium on the active surface of the cell. Each cell is connected to other cells in the stack via inlet and outlet channels, also known as ports, for each medium. Gas must be guided from the ports to the active surface. This is achieved through distribution channels in the distribution field. In pressed metal bipolar plates, the channel structure of the cooling medium is generated as a mold shape for the channel structure of air or hydrogen. To reduce pressure loss of reactants, multiple channels in the active field are typically connected to a single distribution channel. This situation results in not all cooling medium tabs being connected in the active surface without adjusting the channel structure; only those cooling medium tabs with a tab in the distribution field are connected in the active surface. For example, in the case of three supplied active channels with one distribution channel, two tabs in the triplet assembly are not supplied with cooling medium by that half-plate. Due to the different boundary conditions in the inlet and outlet regions, especially in the connection from at least one port to the active surface, a non-uniform mass flow distribution is formed in the active field, particularly for the cooling fluid. Summary of the Invention

[0003] This invention discloses a bipolar plate for fuel cell stacking and a fuel cell stack having at least one bipolar plate and at least one membrane electrode assembly. Further features and details of the invention are derived from the specification and drawings.

[0004] According to a first aspect, the present invention discloses a bipolar plate for a fuel cell stack. The bipolar plate has a main extending plane and a main flow direction in the main extending plane, a first bipolar plate half and a second bipolar plate half, an active field, a distribution region, and a port region. The port region has at least one port for directing at least one fluid into the main extending plane. The active field has at least one cooling fluid channel structure for cooling by means of a cooling fluid, and at least one fuel channel structure for supplying at least one fluid to at least one adjacent membrane electrode assembly of the fuel cell stack. The first and second bipolar plate halves form at least one distribution channel structure in the distribution region, wherein the distribution channel structure is configured at an angle to the main flow direction in the main extending plane for passage of cooling fluid, and wherein the bipolar plate has a thickness in the distribution region greater than the maximum thickness of the bipolar plate in the active field.

[0005] The thickness described herein should be understood within the scope of this invention as an extension dimension orthogonal to the main extension plane of the bipolar plate. The main extension plane is defined by the dimensions of the bipolar plate and extends along the length and width of the bipolar plate. The main flow direction is defined by the channel structure of the active field of the bipolar plate, which allows the flow of at least one fluid, particularly fuel and / or reactants, parallel or substantially parallel to the bipolar plates and / or membrane electrode assemblies of the fuel cell stack. In the fuel cell stack according to the invention, the bipolar plates are preferably stacked alternately with the membrane electrode assemblies along the stacking direction. Here, the main extension planes of the bipolar plates and / or membrane electrode assemblies are arranged relatively parallel or substantially parallel to each other. The expression "X or substantially X" should be understood within the scope of this invention as possible small deviations, for example due to manufacturing tolerances and / or material properties, without altering the intended function on which the feature is based.

[0006] Preferably, the distribution field and the active field are arranged adjacent to each other in the main extension plane, particularly wherein the distribution field surrounds the active field and / or is adjacent to the active field on both sides, particularly on two opposite sides. The distribution field is preferably arranged in the main extension plane of the bipolar plate between the port region and the active field.

[0007] The cooling fluid channel structure and fuel channel structure of the bipolar plate are configured along the main flow direction so that cooling fluid or fuel can flow through them. In order to supply fuel to the membrane electrode assembly adjacent to the bipolar plate in the fuel cell stack according to the invention, the fuel channel structure can preferably additionally enable the fuel to flow orthogonally or substantially orthogonally to the main extension plane of the bipolar plate, especially to the membrane electrode assembly and / or the gas diffusion layer.

[0008] The distribution channel structure is angled relative to the main flow direction in the main extension plane, particularly vertically or substantially vertically, so that the cooling fluid can flow through it. Therefore, more precisely, the distribution channel structure preferably extends laterally in the main extension plane of the bipolar plate, along with the active field, cooling fluid channel structure, and / or fuel channel structure. Hydrogen and oxygen are preferably understood as the reactants used in the bipolar plates of the fuel cell stack according to the invention.

[0009] The bipolar plate according to the invention is particularly advantageous because it has a greater thickness in the distribution region than its maximum thickness in the active field. The thickness of the bipolar plate in the active field is configured in a varying manner across the cross-section by the channel structure of the bipolar plate. The first and second bipolar plate halves typically have highly compressed and deeply compressed regions that form channel structures within the bipolar plate configuration. The maximum thickness of the bipolar plate in the active field is derived, for example, in the cross-section by the depth of the cooling fluid channel structure within the active field. When the bipolar plates according to the invention are stacked into a fuel cell stack, membrane electrode assemblies are arranged between the bipolar plates. Therefore, the thickness of the membrane electrode assemblies must be considered when designing the configuration of the bipolar plates in the active field. However, this means that for distribution regions where the thickness of the membrane electrode assemblies is absent and / or need not be considered, there is a potential structural space in the bipolar plate thickness within the distribution region. This structural space is utilized by the bipolar plate according to the invention, particularly advantageous for the distribution channel structure, which allows the cooling fluid to flow through at an angle to the main flow direction in the main extension plane. In other words, the bipolar plate design according to the invention advantageously utilizes the thickness difference between the active field and the distribution region by taking into account the thickness of the diaphragm electrode assembly, and the distribution channel structure is designed to be flowed by cooling fluid at an angle to the main flow direction in the main extension plane.

[0010] Therefore, the bipolar plate according to the invention is particularly advantageous because the distribution channel structure is configured in a particularly spatially optimized manner, and thus, a uniform mass flow distribution of the cooling fluid in the active field can be achieved and / or improved.

[0011] The features described in the bipolar plate according to the invention are of course applicable to the end bipolar plates (sometimes also called "monopolar plates") of known fuel cells within the scope of the invention, and are also included in the disclosure of the invention.

[0012] According to a preferred embodiment of the bipolar plate of the invention, at least one distribution channel structure is fluidly connected to each of at least one cooling fluid channel structure for distributing cooling fluid. Connecting all at least one cooling fluid channel structure of the active field of the bipolar plate to the distribution channel structure enables the cooling fluid to be advantageously distributed to the cooling fluid channel structures and thus to the active field. This configuration of the bipolar plate advantageously achieves pressure compensation transverse to the main flow direction and / or in the active field. Therefore, non-uniform mass flow distribution of the cooling fluid in the bipolar plate is reduced and / or even prevented. More specifically, the distribution channel structure of this configuration of the bipolar plate briefly shorts the cooling fluid channel structures, especially all the cooling fluid channel structures, through the active field and thus enables a particularly advantageous exchange of cooling fluid.

[0013] In a preferred embodiment of the bipolar plate according to the invention, the fuel channel structure of the active field has multiple channels, wherein at least two channels are fluidly connected to at least one port via a common fuel supply channel for supplying fluid. It is advantageous for the bipolar plate according to the invention to have multiple fuel channels. Furthermore, it is advantageous that the multiple fuel channels are respectively clustered into at least two or more fuel supply channels, such that uniform fuel flow is preferably achieved through these clustered fuel channels. For example, two fuel channels of the active field are clustered into a single fuel supply channel in the distribution region and / or port region; within the scope of the invention, this should be understood as the fluid flow being clustered through, for example, a common channel structure, without physical separation between the fluid flows.

[0014] In a preferred embodiment of the bipolar plate according to the invention, at least one common fuel supply channel is arranged at least sectionally above and / or extends above the distribution channel structure in the distribution region. This configuration of the bipolar plate advantageously utilizes the available structural space in the distribution region as described above, particularly the available thickness in the distribution region. The arrangement of at least one fuel supply channel above the distribution channel structure should be understood within the scope of the invention as at least one fuel supply channel being arranged at least sectionally above the distribution channel structure. "Above" and "below" should be understood as directions through the orthogonal axis of the main extension plane, wherein the bipolar plate can, of course, be configured mirror-image along the main extension plane, and therefore, at least one fuel supply channel may also be arranged, or only below, the distribution channel structure. This configuration of the bipolar plate is particularly advantageous because it enables the distribution of cooling fluid transverse to the active field through the distribution channel structure, and the arrangement of the fuel supply channel above the distribution channel structure enables advantageous fuel supply to the active field, thereby improving the utilization of the bipolar plate's structural space.

[0015] In a preferred embodiment of the bipolar plate according to the invention, the first bipolar plate half and / or the second bipolar plate half are configured at least twice along the main flow direction in the extended dimension to configure the distribution channel structure, particularly wherein the first bipolar plate half and / or the second bipolar plate half are configured at least once along the main flow direction in the extended dimension to be angled relative to each other. For particularly advantageous utilization of the structural space of the bipolar plate, the bipolar plate according to the invention has a thickness difference between the active field and the distribution region. To take this thickness difference into account in the design configuration of the bipolar plate, according to an extension of the invention, the bipolar plate is preferably constructed at least twice along the main flow direction to be angled. The two bends thus formed are preferably opposite each other, such that the bipolar plate is preferably configured parallel before and after the two bends and / or the bends create an inclination of the bipolar plate between two parallel planes. The first bipolar plate half and the second bipolar plate half are preferably configured as mirror images of each other and / or configured at least once along the main flow direction in the extended dimension to be angled relative to each other. Such a bipolar plate configuration is particularly advantageous because the distribution channel structure can be configured cost-effectively with particularly simple design means, wherein the bipolar plate is configured in a particularly optimized manner in terms of structural space.

[0016] According to a preferred embodiment of the bipolar plate of the present invention, the bipolar plate has at least one cooling fluid supply channel structure, wherein the at least one cooling fluid supply channel structure has a fluid communication connection from at least one port region to a distribution channel structure. The cooling fluid supply channel structure enables fluid communication between the cooling fluid port and the distribution channel structure, and thus provides a cooling medium for the active field of the bipolar plate. The cooling fluid supply channel structure is preferably arranged on the main extension plane of the bipolar plate. The cooling fluid supply channel structure can be configured as a single channel structure or a clustered channel structure.

[0017] According to a preferred embodiment of the bipolar plate of the invention, the cooling fluid supply channel structure is configured as a hollow tab, particularly wherein at least one hollow tab configuration of the cooling fluid supply channel structure defines or substantially defines the thickness of the bipolar plate in the distribution region. The hollow tab configuration of the cooling fluid supply channel structure should be understood as the cooling fluid supply channel structure being configured with tabs and / or tab-like structures. These tabs and / or tab-like structures are elongated, elongated portions relative to the surrounding structure. The tab-like configuration of the cooling fluid supply channel structure is particularly advantageous because it has small structural space requirements and provides favorable flow guidance not only for the internal cooling fluid supply channel structure but also for external flow. In particular, the hollow tab configuration of the cooling fluid supply channel structure stands out from the rest of the bipolar plate design, such that the thickness of the bipolar plate in the distribution region is defined and / or determined by the hollow tab configuration of the cooling fluid supply channel structure. In other words, the hollow tab configuration of the cooling fluid supply channel structure preferably constitutes the maximum thickness of the bipolar plate in the distribution region.

[0018] In a preferred embodiment of the bipolar plate according to the invention, at least one cooling fluid supply channel structure separates at least two fuel supply channels from each other in fluid communication at least sectionally. Particularly preferably, the at least two fuel supply channels are separated from each other in fluid communication by a hollow tab-like configuration of the cooling fluid supply channel structure. This configuration of the bipolar plate is particularly advantageous because the hollow tab-like configuration of the cooling fluid supply channel structure thus fulfills a flow guiding function not only through its internal structure but also through its external structure. On the one hand, the cooling medium is guided within the hollow tab-like configuration of the cooling fluid supply channel structure; on the other hand, the at least two fuel supply channels are separated from each other in fluid communication along the external structure of the hollow tab-like configuration of the cooling fluid supply channel structure.

[0019] In a preferred embodiment of the bipolar plate according to the invention, at least one cooling fluid supply channel structure is arranged at least partially above the distribution channel structure, particularly wherein the cooling fluid supply channel structure is fluidly connected downwards to the distribution channel structure. This configuration of the bipolar plate is particularly advantageous because at least one cooling fluid supply channel structure is advantageously arranged at least partially above the distribution channel structure in a space-efficient manner. Furthermore, in this configuration, the downward fluid communication connection of the cooling fluid supply channel structure toward the distribution channel structure is achieved, i.e., at least partially orthogonal to the main extension plane. This configuration of the bipolar plate is particularly advantageous because a separate channel structure is not required for the fluid communication connection between the cooling fluid supply channel structure and the distribution channel structure, and therefore, structural space is advantageously optimized and saved.

[0020] According to a second aspect, the present invention discloses a fuel cell stack. The fuel cell stack has at least one bipolar plate and at least one membrane electrode assembly, wherein the at least one bipolar plate is configured according to the first aspect, and in particular, the at least one membrane electrode assembly has a thickness corresponding to or substantially corresponding to the difference between the thickness of the bipolar plate in the distribution region and the maximum thickness of the bipolar plate in the active field. At least one sub-gasket and / or other sealing material may be arranged, in particular, between adjacent bipolar plates. Preferably, when considering the thickness difference between the bipolar plates according to the invention in the active region and the distribution region, at least one sub-gasket and / or other sealing material may be disregarded, because the sub-gasket and / or other sealing material is preferably arranged not only in the active field but also in the distribution region and / or parallel to or substantially parallel to these regions. Therefore, the gas diffusion layer of at least one membrane electrode assembly preferably has a thickness, and the thickness of the gas diffusion layer corresponds to or substantially corresponds to the difference between the thickness of the bipolar plate in the distribution region and the maximum thickness of the bipolar plate in the active field.

[0021] Furthermore, in the fuel cell stack according to the invention, the first bipolar plate half, the second bipolar plate half, and the diaphragm electrode assembly can be configured in a plate-like manner, wherein the diaphragm electrode assembly has a bottom surface smaller than that of the first bipolar plate half and / or the second bipolar plate half. Furthermore, in the fuel cell stack according to the invention, the fuel cell stack, particularly at least one bipolar plate, can be configured to have an active field for cooling and / or supplying at least one fluid to at least one diaphragm electrode assembly and a distribution field for distributing at least one fluid. Furthermore, in the fuel cell stack according to the invention, at least one diaphragm electrode assembly can be arranged in this region, particularly only in the region of the active field. The fuel cell stack also possesses the aforementioned advantages, as described above with respect to the bipolar plate according to the invention. Therefore, the fuel cell stack according to the invention is particularly advantageous because the distribution channel structure is configured with particular spatial optimization, and thus, a uniform mass flow distribution of the cooling fluid in the active field can be achieved and / or improved. Attached Figure Description

[0022] The bipolar plate according to the invention and the fuel cell stack according to the invention are described in more detail below with reference to the accompanying drawings. The drawings schematically illustrate: Figure 1 Side view of a fuel cell stack with three bipolar plates. Figure 2 : A three-dimensional view of the bipolar plate, and Figure 3 Another three-dimensional view of the other bipolar plate.

[0023] Components with the same function and mode of operation Figures 1 to 3 The same reference numerals are used for each of the attached figures. Detailed Implementation

[0024] exist Figure 1 The figure shows a side view of a fuel cell stack 100 having three bipolar plates 10. Each bipolar plate 10 has a main flow direction HR, a first bipolar plate half 12 and a second bipolar plate half 14, an active field 40, a distribution region 50, and a port region 60. The active field 40 has at least one cooling fluid channel structure 42 (not shown) for cooling by means of a cooling fluid KF, and at least one fuel channel structure 44 (not shown) for supplying at least one fluid F (not shown) to at least one adjacent membrane electrode assembly 110 of the fuel cell stack 100. The first bipolar plate half 12 and the second bipolar plate half 14 each form a distribution channel structure 52 in the distribution region 50, wherein the distribution channel structure 52 is configured at an angle to the main flow direction HR, for example, in the plane of the figure, so that the cooling fluid KF can flow through it, and wherein the bipolar plate 10 in the distribution region 50 has a thickness D1 greater than the maximum thickness D2 of the bipolar plate 10 in the active field 40. The diaphragm electrode assembly 110 has a thickness D3, which corresponds to the difference between the thickness D1 of the bipolar plate in the distribution region 50 and the maximum thickness D2 of the bipolar plate 10 in the active field 40. The first bipolar plate half 12 and the second bipolar plate half 14 are configured at an angle twice along the main flow direction HR in the extended dimension to configure the distribution channel structure 52, wherein the first bipolar plate half 12 and the second bipolar plate half 14 are configured at an angle to each other at least once along the main flow direction HR in the extended dimension.

[0025] exist Figure 2 A perspective view of the bipolar plate 10 is shown. This perspective view illustrates how the active field 40 has a cooling fluid channel structure 42 for cooling by means of cooling fluid KF, and a fuel channel structure 44 for supplying at least one fluid F to at least one adjacent membrane electrode assembly 110 (not shown) of the fuel cell stack 100. Furthermore, Figure 2 As shown, the fuel channel structure 44 of the active field 40 has multiple channels 45, wherein each group of three channels 45 is fluidly connected to at least one port via a common fuel supply channel 64 for supplying fluid F, wherein the common fuel supply channel 64 is arranged above the distribution channel structure 52 in the distribution area 50. Furthermore, Figure 2As shown, the bipolar plate 10 has a plurality of cooling fluid supply channel structures 43, wherein the cooling fluid supply channel structures 43 have fluid communication connections from at least one port region 60 to a distribution channel structure 52. The cooling fluid supply channel structures 43 are configured in a hollow tabular shape, wherein the hollow tabular configuration of the cooling fluid supply channel structures 43 defines a thickness D1 (not shown) of the bipolar plate 10 in the distribution region 50. Furthermore, the cooling fluid supply channel structures 43 fluidly separate the fuel supply channels 64 from each other. The cooling fluid supply channel structures 43 are at least partially arranged above the distribution channel structure 52, wherein the cooling fluid supply channel structures 43 are fluidly connected downward to the distribution channel structure 52.

[0026] Figure 3 Another bipolar plate 10 is shown in another perspective view. The main extension plane HE of the bipolar plate 10 is drawn in dashed lines. Figure 3 Viewed in perspective from the active field 40, opposite to the main flow direction HE, towards the distribution region 50 with the laterally arranged distribution channel structures 52 and towards the port region 60. The cooling fluid channel structures 42 are partially directly connected to the distribution channel structures 52 and, in part, every third channel, are guided through the distribution channel structures 52. The design configuration above the distribution channel structures 52 advantageously separates the fuel supply channels 64 from each other in fluid communication, and on the other hand, enables a defined thickness D1 in the distribution region 50 for advantageous stacking (not shown) of the bipolar plates 10 in the fuel cell stack 100. Cooling fluid KF is guided to the distribution channel structures 52 via the cooling fluid supply channel structure 43, and is preferably distributed from there to all the cooling fluid channel structures 42.

Claims

1. A bipolar plate (10) for a fuel cell stack (100), the bipolar plate (10) having a main extension plane (HE) and a main flow direction (HR) in the main extension plane (HE), a first bipolar plate half (12) and a second bipolar plate half (14), an active field (40), a distribution region (50) and a port region (60). Its features are, The port region (60) has at least one port for introducing at least one fluid (F) into the main extension plane (HE), wherein the active field (40) has at least one cooling fluid channel structure (42) for cooling by means of cooling fluid (KF), and at least one fuel channel structure (44) for supplying at least one fluid (F) to at least one adjacent membrane electrode assembly (110) of the fuel cell stack (100). The cooling fluid (KF) flows through the at least one cooling fluid channel structure (42) along the main flow direction (HR). The at least one fluid (F) flows through the at least one fuel passage structure (44) along the main flow direction (HR). The first bipolar plate half (12) and the second bipolar plate half (14) form at least one distribution channel structure (52) in the distribution region (50), wherein the distribution channel structure (52) is configured perpendicular to the main flow direction (HR) in the main extension plane (HE) so that the cooling fluid (KF) can flow through it, and wherein the bipolar plate (10) in the distribution region (50) has a thickness (D1) greater than the maximum thickness (D2) of the bipolar plate (10) in the active field (40).

2. The bipolar plate (10) according to claim 1. Its features are, The at least one distribution channel structure (52) has a fluid communication connection with each of the at least one cooling fluid channel structure (42) for distributing cooling fluid (KF).

3. The bipolar plate (10) according to claim 1 or 2. Its features are, The fuel channel structure (44) of the active field (40) has a plurality of channels (45), wherein at least two channels (45) are respectively fluidly connected to the at least one port via a common fuel supply channel (64) for supplying fluid (F).

4. The bipolar plate (10) according to claim 3. Its features are, At least one common fuel supply channel (64) is arranged at least sectionally above the distribution channel structure (52) in the distribution area (50).

5. The bipolar plate (10) according to claim 1 or 2. Its features are, The first bipolar plate half (12) and / or the second bipolar plate half (14) are configured at least twice at an angle along the main flow direction (HR) on the extended scale in order to configure the distribution channel structure (52).

6. The bipolar plate (10) according to claim 1 or 2. Its features are, The bipolar plate (10) has at least one cooling fluid supply channel structure (43), wherein the at least one cooling fluid supply channel structure (43) has a fluid communication connection from the at least one port region (60) to the distribution channel structure (52).

7. The bipolar plate (10) according to claim 6. Its features are, The cooling fluid supply channel structure (43) has a hollow, plate-like configuration.

8. The bipolar plate (10) according to claim 6. Its features are, The at least one cooling fluid supply channel structure (43) separates at least two fuel supply channels (64) from each other in fluid communication at least in sections.

9. The bipolar plate (10) according to claim 6. Its features are, The at least one cooling fluid supply channel structure (43) is arranged at least partially above the distribution channel structure (52).

10. The bipolar plate (10) according to claim 1 or 2. Its features are, The first bipolar plate half (12) and / or the second bipolar plate half (14) are configured at an angle to each other at least once along the main flow direction (HR) on the extended scale.

11. The bipolar plate (10) according to claim 7. Its features are, The hollow tab-like configuration of the at least one cooling fluid supply channel structure (43) defines or substantially defines the thickness (D1) of the bipolar plate (10) in the distribution area (50).

12. The bipolar plate (10) according to claim 9. Its features are, The cooling fluid supply channel structure (43) is connected downward in fluid communication with the distribution channel structure (52).

13. A fuel cell stack (100) having at least one bipolar plate (10) and at least one membrane electrode assembly (110). Its features are, The at least one bipolar plate (10) is configured according to any one of claims 1 to 12.

14. The fuel cell stack (100) according to claim 13. Its features are, The at least one diaphragm electrode assembly (110) has a thickness (D3), and the thickness (D3) of the diaphragm electrode assembly (110) corresponds to the difference between the thickness (D1) of the bipolar plate in the distribution region (50) and the maximum thickness (D2) of the bipolar plate (10) in the active field (40).

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