Bipolar plate and method for manufacturing the bipolar plate

Abstract

A bipolar plate (1) intended for use in the stacking of electrochemical cells and assembled from two half - plates (2, 3) positioned one above the other, having three ports (5, 6, 7) arranged in proximity to each other, an active field (9), and a distributor field (8) connecting the ports (5, 6, 7) to the active field (9) and configured to direct three different fluids between the ports (5, 6, 7) and the active field (9). A flow space for one of the fluids is formed between the half - plates (2, 3), and flow spaces for the other two fluids are formed outside the half - plates (2, 3). The distributor field (8) comprises four flow fields (10, 12, 14, 16) in a flat configuration. In particular, each of them is: One coolant flow field (10) opening with respect to the central port (6); Two two - fluid flow fields (12, 14), each adjacent to the coolant flow field (10) at one end and opening at the other end into one of the two outer ports (5, 7), and each configured such that the coolant flows and the working media as further fluids form layers parallel to each other; One three - fluid flow field (16) adjacent to the two two - fluid flow fields (10), opening with respect to the active field (9) and configured such that the coolant flows and the working media as further fluids form three layers parallel to each other. Here, the half - plates (2, 3) are embossed structures (4) structured in the form of points, i.e., in the form of islands, such that in each of the four flow fields (10, 12, 14, 16), the half - plates (2, 3) are supported relative to each other and relative to flat components arranged outside the half - plates (2, 3).

Description

Technical Field

[0001] The present invention relates to a bipolar plate intended for use in the stacking of an electrochemical cell as described in the preamble of claim 1. The present invention further relates to a method for manufacturing such a bipolar plate.

Background Art

[0002] A general bipolar plate and a fuel cell unit assembled using the same are known, for example, from German Patent Application Publication No. 102005057045. This known bipolar plate is assembled from a cathode-side partial plate and an anode-side partial plate, that is, from two half plates. A flowable internal space is formed between the half plates. Other fluids, that is, the working media of the fuel cell unit, flow around the outer side portions of the bipolar plate. In the distributor region of the bipolar plate, the two half plates are supported against each other by raised negative-type support points.

[0003] Similar to the bipolar plate according to German Patent Application Publication No. 102005057045, in many other possible configurations of the bipolar plate, three ports, that is, one port for the coolant and two ports for the working media, are arranged in proximity. In this regard, as examples, reference is made to the documents of US Patent No. 10381675 and German Patent Application Publication No. 102014206333. In either case, there is an overlap between the inlet or outlet, that is, the port, and the different channels formed between the active field of the fuel cell. Other possible configurations of the bipolar plate including flow channels are described, for example, in the documents of German Patent Application Publication No. 102013210542, US Patent No. 9685664, and US Patent No. 9337498.

[0004] The configurations of the bipolar plate and the entire fuel cell disclosed in the documents of European Patent No. 3577708 and European Patent No. 3167505 are intended to achieve an improvement in flow distribution and reaction fluid flow. Both documents deal with fuel cells having a gas diffusion layer and a catalyst material. A further fuel cell having a flow distributor is described, for example, in European Patent No. 2926399.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The object of the present invention is to further develop a bipolar plate suitable for use in a fuel cell stack in terms of aspects related to flow and aspects related to manufacturing, as compared with the above-mentioned prior art.

Means for Solving the Problems

[0006] According to the present invention, this problem is solved by a bipolar plate having the features of claim 1. The bipolar plate can be manufactured by the method described in claim 10.

[0007] The bipolar plate is suitable for use in an electrochemical cell, particularly in a stack of fuel cells, and in the known basic concept, it is assembled from two overlapping and interconnected half-plates. The bipolar plate has three ports arranged in proximity to each other for supplying or discharging fluid. For example, the first such arrangement of the three ports is provided for supplying fluid, and the second such arrangement of the three ports is provided for discharging fluid. It is also possible for the fluid to flow in a countercurrent manner, thereby providing a single port for guiding the fluid flowing through or around the bipolar plate in a direction opposite to the fluid passing through the other two ports of the same port row out of the three ports arranged in proximity to each other. The ports are also referred to as manifold openings or simply manifolds.

[0008] The extending portions approximately at the center of the bipolar plates are assigned to the active zones of the respective electrochemical cells, i.e., the regions where the desired electrochemical reactions occur, and the term "active zone" is also used for the corresponding parts of the bipolar plates. In many configurations, the active zones of the bipolar plates have a rectangular basic shape. Further, there is a distributor zone in the bipolar plates, and the distributor zone is configured to connect the ports to the active zones, i.e., to conduct three different fluids between the ports and the active zones. A flow space for one of the three fluids is formed between the half plates. This is generally a flow space for a coolant, in particular, cooling water. At the same time, flow spaces for the other two fluids, i.e., typically the working media of the electrochemical cells, are formed on the outer sides of the half plates.

[0009] According to the claims, the distributor zone comprises four flat flow zones in the plan view of the half plates, each having a triangular basic shape, i.e., - one coolant flow zone opening to the central port among the three ports, - two two-fluid flow zones, each adjacent to the coolant flow zone at one end and opening to one of the two outer ports at the other end, and each configured such that the coolant flows and the working media as further fluids form layers parallel to each other, - one three-fluid flow zone adjacent to the two two-fluid flow zones, opening to the active zone, and configured such that the coolant flows and the working media as further fluids form three overlapping layers parallel to each other, having.

[0010] Here, the half plate is an embossed, particularly circular, structural part, which is configured as points, i.e., in the form of islands, such that in each of the four flow fields, the half plates are supported relative to each other and relative to flat components arranged outside the half plates. It is structured by an embossed, specifically circular, structural part. In addition to the triangular basic shape of the flow field, flow fields having other shapes, such as quadrilateral or pentagonal, may also be possible. This applies in particular to the coolant flow field and to two lateral flow fields, i.e., the two-media flow field. All four flow fields function as flow fields with controlled pressure loss during the operation of an electrochemical cell stack in a typical manner. With regard to the use of parallel layers through which a medium flows in each layer, it should be understood that this means that the layers are essentially arranged parallel to each other, i.e., the layers are positioned one above the other, and flow components perpendicular to the plane given by the individual layers may also be visible.

[0011] In a plan view of the bipolar plate, there may be a single point where all four flow fields intersect. This particularly applies to configurations having a triangular flow field. The first flow field connected to the central port, as well as the fourth flow field through which all three media flow and which is arranged closest to the active field, may draw an isosceles triangle. The two two-media flow fields, which typically do not draw an isosceles triangle, may have a similar configuration.

[0012] In each of the four flow fields that are part of the distributor field, the fluid in this flow field spreads or two or three different fluids flowing in separate overlapping layers spread on the surface. The stacking of the layers is always stable. This means, for example, that the medium, i.e., the fluid, in the top layer is only conducted in this layer. The absence of a diversion of the medium from one layer to another, for example from the top side to the bottom side of the bipolar plate, is particularly advantageous with regard to the flow resistance that occurs during the operation of a cell stack, particularly a fuel cell stack.

[0013] According to one possible embodiment, the half-plates in the region of the coolant flow field are provided to abut flatly against similarly flat components around the battery stack. The proportion of the region of the coolant flow field in which round, in particular circular, supports are formed to keep the half-plates at a distance from each other is relatively small compared to the regions adjacent to these components. The height of these supports corresponds to half of the maximum distance between the two half-plates, provided that the embossing depth of both half-plates is the same. The supports represent pin-shaped barriers that, within the flow space through which the coolant flows, on the one hand do not significantly narrow the free flow cross-section and, on the other hand, ensure a uniform distribution of the coolant. This also applies to variants in which the coolant is supplied or discharged through a plurality of ports.

[0014] As far as two-media flow fields are concerned, the half-plates within the regions of these flow fields are, according to one possible embodiment, provided on exactly one outer side to abut flatly against similarly flat surrounding components, while the half-plates forming the opposite outer side are provided to be arranged at a large distance from the similarly flat surrounding components. This results in three planes that can be distinguished from each other, namely, a central plane in which both half-plates are in contact with each other, a plane in which one of the two half-plates is in flat contact with the surrounding component, and a further plane delineated by the other half-plate and raised so as to be defined from the flat surrounding component to provide a free flat flow cross-section for the working medium. The distance between the latter planes is at most half of the maximum distance between the two half-plates. At the same time, the same half-plate that defines the flow cross-section forms supports that protrude beyond the plane parallel to the central plane and are intended to support the bipolar plate against the flat component that protrudes significantly from the half-plate.

[0015] The central plane is generally referred to as the plane where two half plates abut flat against each other. This also applies to configurations where different half plates have different throttling depths. In such cases, the two half plates project at different distances from the central plane.

[0016] In the three-media flow field, each of the two half plates can have a contour that basically corresponds to the depicted contour of the half plate in the two-media flow field that bulges flatly from the central plane and significantly flatly from the surrounding components with respect to the presence of a region that bulges flatly from the central plane and a support facing outward. In the three-media flow field, the distance of the region of the half plate that bulges flatly from the central plane and from the surrounding components is in any case smaller than the distance in the two-media flow field between the central plane and a plane defined by one of the half plates and spaced parallel from the surrounding components. Also in the three-media flow field, in a typical configuration, the total area of all the supports is less than half of the total area of the corresponding flow field in the plan view of the bipolar plate.

[0017] In the two-media flow field and the three-media flow field, there are different possibilities for constructing and arranging the supports. For example, the layout of the bipolar plate can be configured such that the supports facing inward and outward of the half plate are offset from each other. Alternatively, a concentric arrangement of the supports facing inward and outward of the half plate is possible.

[0018] According to a possible further development, the channel guiding region of the distributor field is connected between the bipolar plate and thus the three-media flow field and the active field of the entire electrochemical cell, and the width of the distributor field can correspond to the width of the active field and the width of the three-media flow field. In this configuration, the flows of the various media on the cathode side and the anode side, as well as the coolant flow, can be distributed such that they are uniform in a good approximation over the entire width of the active region. In particular, the channel guiding region can be configured using channels of non-uniform width such that a uniform flow distribution is achieved over the entire width.

[0019] The metal bipolar plate according to the present invention can generally be manufactured by the forming process according to claim 10, in particular, by three-dimensionally structuring two half plates made of a steel sheet, alternatively, for example, a titanium alloy, and then joining them together. The connection can be made, for example, by soldering, welding, or adhesion. A continuous and / or discontinuous process can be used to cut out the contour of the half plate.

[0020] Two exemplary embodiments of the present invention will be described in more detail below with reference to the drawings.

[0021] The figures show the following, partly schematically and simplified.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

DETAILED DESCRIPTION OF THE INVENTION

[0023] Unless otherwise specified, the following description relates to both exemplary embodiments. In all the figures, corresponding parts or parts having basically the same effect are identified by the same reference numerals.

[0024] The bipolar plate labeled with reference numeral 1 is further part of a PEM fuel cell stack not shown further. Regarding the basic structure and function of such a fuel cell system, reference may be made to the prior art cited at the beginning. The bipolar plate 1 may be particularly intended for stationary or mobile use in an automobile. When terms such as "top side" or "bottom side" are used below, this does not imply any description regarding the actual mounting position of the bipolar plate 1 in an adjacent structure. In particular, the bipolar plate 1 can be positioned vertically, unlike what is shown in the figures.

[0025] The bipolar plate 1 consists of two half-plates 2, 3 with two cut-out contours. The embossed structures of the half-plates 2, 3 are generally designated by 4. In this case, the bipolar plate 1 does not have a square shape but rather an overall rectangular basic shape, and in FIGS. 1 and 7, only one of the short sides and a part of the long side are visible. Other configurations of the bipolar plate 1, such as square or bone-shaped, are also possible.

[0026] On the short side of the illustrated bipolar plate 1, there are a plurality of ports 5, 6, 7. These are port 5 for the cathode cavity of the fuel cell, port 6 for the coolant, and port 7 for the anode cavity. Ports 5, 6, 7 are arranged in a row adjacent to each other, and the port 6 for the coolant is located between the ports 5, 7 for the working medium. In an embodiment, ports 5, 7 are square, i.e., trapezoidal in shape, while port 6 depicts an elongated rectangular shape extending along the short side of the half plates 2, 3 in a plan view.

[0027] The arrangement of the three ports 5, 6, 7 is adjacent to a distributor field, generally labeled 8, which is fluidly connected between the ports 5, 6, 7 and the active field 9 of the bipolar plate 1. The widths of the individual ports 5, 6, 7 are each measured at the transition to the distributor field 8 and are labeled b5, b6, b7. The distributor field 8 includes a channel guide region, labeled 18, that abuts the active field 9. Further, the distributor field 8 is configured without any channel guidance, as will be explained in more detail below.

[0028] Adjacent to port 6, there is a coolant flow field 10, which represents one of four distinguishable flow fields 10, 12, 14, 16 in which the distributor field 8 is assembled, separate from the channel guide region 18. Each of the flow fields 10, 12, 14, 16 has a basic triangular shape.

[0029] Possible cross-sectional configurations of the coolant flow field 10 are shown in FIGS. 4 and 9. The two half plates 2, 3 bulge significantly from the central plane ME where the half plates 2, 3 contact each other, thereby providing the largest possible flow cross-section for the coolant. The distance from the central plane ME of the plane in which the half plates 2, 3 are mostly located is h amax (anode side) or h kmax (cathode side). Further, more planar components of the fuel cell stack (not shown) are at a distance h from the central plane ME amax or h kmaxIt is in contact with the continuously flat regions of the half plates 2 and 3 which are only separated. The pin-shaped support 11 which is circular in plan view is formed directly through the half plates 2 and 3, keeping the half plates 2 and 3 at a distance from each other.

[0030] In addition to the coolant, one of the two working media of the fuel cell flows in the flow field 12. Thereby, the flow field 12 represents a two-media flow field. The same applies to the flow field 14. Compared with the coolant flow field 10, the free flow cross-section of the coolant in the two-media flow fields 12 and 14 is significantly smaller. In the case schematically shown in the figure, the two two-media flow fields 12 and 14 are assembled identically and arranged point-symmetrically to each other. In contrast, for example, the anode port can be smaller than the cathode port, and thereby there is no symmetry.

[0031] One of the two half plates 2 and 3 is structured in the two-media flow fields 12 and 14 in the same way as the coolant flow field 10. In the case of FIG. 5, this applies to the upper half plate 2, and in the case of FIG. 10, it applies to the lower half plate 3. The aforementioned point symmetry that does not necessarily exist and can be seen in FIGS. 1 and 7 refers to the point where all the flow fields 10, 12, 14, 16 intersect.

[0032] The second half plate 3, 2 is almost located in a plane offset by an amount h k1 , h a1 from the central plane ME, and h k1 or h a1 is, h kmax or h amax is smaller than. In the configuration according to FIG. 5, in this case the amount h k1On the half plate 3 which is only largely offset, a support 13 is formed which supports the half plate 3 inwards, i.e. towards the other half plate 2, and outwards, i.e. towards the flat surrounding components. The cathode gas passes through the flow field 12. The support 13 appears ring-shaped in plan view. The same applies to the support 15 which is located in the flow field 14 through which the anode gas passes.

[0033] In contrast to the configuration according to FIG. 1, in the configuration according to FIG. 7, there are different partial supports 19, 20, 21, 22 in the two-fluid flow fields 12, 14 and the three-fluid flow field 16 provided for guiding the cathode gas or the anode gas, which support the half plates 2, 3 in different directions and are arranged close to each other in plan view.

[0034] Similar to the flow fields 10, 12, 14, the three-fluid flow field 16 which is also configured as an open flow field in the configuration according to FIG. 1 is adjacent to both the two-fluid flow fields 12, 14 and the channel guiding region 18 of the distributor field 8. In an exemplary embodiment, the width of the three-fluid flow field 16 shown as b16 corresponds to the width b9 of the active field 9 and also to the width of the region 18. In the case of FIG. 1, a number of supports 17 are formed in the three-fluid flow field 16, and these supports are ring-shaped in plan view, similar to the supports 13, 15.

[0035] In the three-fluid flow field 16, the flows of the working medium and the cooling medium are projected in three layers vertically, and the coolant flow represents the central layer. The flow cross-section available for the coolant is defined by the half plates 2, 3 and is limited at the top and bottom by a plane which is cut off by an amount h a2 or h k2 Here, h a2 is smaller than h a1 and h k2 is smaller than h k1 In an exemplary embodiment, h a1 is the same as h k1 and h a2 is the same as h k2 ​

Description of Symbols

[0036] 1 Bipolar plate 2 Half plate 3 Half plate 4 Embossed structure part 5 Cathode cavity port 6 Coolant port 7 Anode cavity port 8 Distributor field 9 Active field 10 Coolant flow field 11 Support of coolant flow field 12 Coolant flow field and cathode side flow field 13 Support of flow field 12 14 Coolant flow field and anode side flow field 15 Support of flow field 14 16 Flow field for three fluids 17 Support of flow field 16 18 Channel induction area of distributor field 19 Partial support of flow field 12 20 Partial support of flow field 12 21 Partial support of flow field 16 22 Partial support of flow field 16 b5 Width of port 5 b6 Width of port 6 b7 Width of port 7 b9 Width of active field b16 Width of flow field 16 h amax Maximum embossing depth, anode side h a1 、h a2 Embossing depth, anode side h k1 、h k2 Embossing depth, cathode side h kmax Maximum embossing depth, cathode side ME Center plane

Claims

1. A bipolar plate (1) assembled from two vertically positioned half plates (2, 3) for an electrochemical cell, comprising three ports (5, 6, 7) arranged close to each other, an active field (9), a distributor field (8) connecting the ports (5, 6, 7) to the active field (9) and configured to direct three different fluids between the ports (5, 6, 7) and the active field (9), wherein a flow space for one of the fluids is formed between the half plates (2, 3), and flow spaces for the other two fluids are formed outside the half plates (2, 3). In the bipolar plate (1), the distributor field (8) comprises four flow fields (10, 12, 14, 16) of a flat configuration, namely: - One coolant flow field (10) opening to the central port (6); - Two two-fluid flow fields (12, 14), each adjacent to the coolant flow field (10) at one end and opening to one of the two outer ports (5, 7) at the other end, each configured such that the coolant flows and the working media as further fluids form parallel layers with each other; - One three-fluid flow field (16) adjacent to the two two-fluid flow fields (10), opening to the active field (9) and configured such that the coolant flows and the working media as further fluids form three parallel layers with each other. The bipolar plate (1) is characterized in that the half plates (2, 3) are embossed structures (4) structured by the embossed structures (4) configured as points, i.e., in the form of islands, such that in each of the four flow fields (10, 12, 14, 16), the half plates (2, 3) are supported relative to each other and relative to flat components arranged outside the half plates (2, 3).

2. Each of the four flow fields (10, 12, 14, 16) of the distributor field (8) has a basic triangular shape in the plan view of the half plates (2, 3), and all of the four flow fields (10, 12, 14, 16) intersect at a single point. The bipolar plate (1) according to Claim 1 is characterized thereby.

3. ​ The bipolar plate (1) according to claim 1 or 2, characterized in that the two two-fluid flow fields (12, 14) have a similar configuration.

4. The half plates (2, 3) are provided in the region of the coolant flow field (10) so as to abut flatly against similarly flat surrounding components, and a rounded, in particular circular support (11) is formed in a relatively small proportion of the region of the coolant flow field (10), the support (11) keeping the half plates (2, 3) at a distance from each other, the height (h ａｍａｘ , h ｋｍａｘ ) corresponding to half of the maximum distance between the half plates (2, 3), characterized in that the bipolar plate (1) according to any one of claims 1 to 3.

5. The half-plates (2, 3) within the region of the two media flow fields (12, 14) are provided precisely on one outer side in order to abut flatly against similarly flat surrounding components, while the half-plates (3, 2) forming the outer side on the respective opposite sides are provided for being arranged at a large distance from similarly flat surrounding components, and, measured from a central plane (ME) where both half-plates (2, 3) are in contact with each other, most of the half-plates (3, 2) that are greatly raised from the surrounding components are within a plane offset by an amount (h ｋ１ , h ａ１ ) that is at most half the magnitude of the maximum distance between the two half-plates from the central plane (ME), and the same half-plates (3, 2) simultaneously project beyond the plane parallel to the central plane (ME), and form supports (13, 15) provided for supporting against the flat components that are greatly raised from the half-plates (3, 2), the bipolar plate (1) according to any one of claims 1 to 4.

6. In the three-media flow field (16), each of the two half-plates (2, 3) has a contour (4) that significantly and flatly protrudes from the surrounding components with respect to the presence of a region that flatly protrudes from the central plane (ME) and a support (17, 22) facing outward, corresponding to the contour (4) of the half-plate (3, 2) of the two-media flow fields (12, 14) that flatly protrudes significantly from the surrounding components. In the three-media flow field (16), the distance (h ｋ２ , h ａ２ ) in each case is defined by the central plane (ME) and a plane that is parallelly spaced from the surrounding components and is defined by one of the half-plates (3, 2), and is smaller than the distance (h ｋ１ , h ａ１ ) in the two-media flow fields (12, 14). The bipolar plate (1) according to claim 5 is characterized in that.

7. The bipolar plate (1) according to claim 5 or 6, characterized in that the supports (19, 20, 21, 22) facing the inside and outside of the half plates (2, 3) are arranged offset from each other.

8. The bipolar plate (1) according to claim 5 or 6, characterized in that the supports (11, 13, 15, 17) facing the inside and outside of the half plates (2, 3) are arranged concentrically with each other.

9. The bipolar plate (1) according to any one of claims 1 to 8, characterized in that the channel guiding region (18) of the distributor field (8) is connected between the three-fluid flow field (16) and the active field (9), and the width of the channel guiding region corresponds to the width (b9) of the active field (9) and the width (b16) of the three-fluid flow field (16).

10. A method for manufacturing a bipolar plate (1) for an electrochemical cell, wherein two half plates (2, 3) are three-dimensionally structured by the forming method according to claim 1 and then permanently connected to each other.

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