Bipolar plate for fuel cell system

Abstract

The invention relates to a bipolar plate (100) for a fuel cell system (1), comprising a cathode-side plate (10) having a first channel structure (K1) for an oxygen-containing reactant (O2) on a first side (11) and a second channel structure (K2) for a coolant (KM) on a second side (12), and an anode-side plate (20) having a first channel structure (A1) for a fuel-containing reactant (H2) on a first side (21) and a second channel structure (A2) for a coolant (KM) on a second side (22), wherein the cathode-side plate (10) and the anode-side plate (20) abut against each other with the second sides (12, 22) for the coolant (KM). To this end, according to the invention, the first channel structure (K1) of the cathode-side plate (10) is geometrically different from the second channel structure (K2) of the cathode-side plate (10).

Description

Technical Field

[0001] This invention relates to a bipolar plate for a fuel cell system. Furthermore, this invention also relates to a corresponding fuel cell system according to the independent system claims. Background Technology

[0002] Bipolar plates for fuel cells are generally known. For example, distribution channels for reactants and coolants on bipolar plates are formed by pressing flat plates. Several optimization issues must typically be considered when designing these distribution channels. On one hand, the hydraulic diameter for the reactants must be optimized so that the pressure drop observed along the reactant flow direction is not too large. On the other hand, the height of the bipolar plates must be reduced to increase the system's power density. Furthermore, the width of the support surface on the membrane electrode assembly, especially on the cathode side of the system, must be reduced so that losses in reactant mass transport are not excessive at peak power. Additionally, the width of the channels themselves must be reduced so that the pressure distribution in the middle of the channels is not too low. Summary of the Invention

[0003] According to a first aspect, the present invention provides: a bipolar plate for a fuel cell system having the features of the independent device claim, particularly the features from the feature portions of the independent device claim. According to a second aspect, the present invention provides: a corresponding fuel cell system according to the independent system claim. Herein, the features and details described in conjunction with each aspect of the invention are of course also applicable to conjunction with other aspects of the invention, and vice versa, so that the disclosures regarding the various aspects of the invention are always mutually referential or can be mutually referenced.

[0004] According to a first aspect, the present invention provides a bipolar plate for a fuel cell system, comprising: a cathode side plate having a first channel structure on a first side for an oxygen-containing reactant or oxidant, and a second channel structure on a second side for a coolant; and an anode side plate having a first channel structure on a first side for a fuel-containing reactant, and a second channel structure on a second side for a coolant, wherein the cathode side plate and the anode side plate are abutted against each other on the second side for the coolant. Therefore, according to the present invention, the first channel structure of the cathode side plate has a different geometry than the second channel structure of the (specifically, the same) cathode side plate.

[0005] The fuel cell system according to the invention can have multiple fuel cells, each separated from the other by bipolar plates, and arranged in a stack. From the end side, the stack can be limited by single-end plates.

[0006] In the context of this invention, the channel structure can be introduced into a planar plate, for example, by modification or molding, such as stamping, extrusion, deep drawing, and bending, which then serves as a cathode side plate or an anode side plate. Furthermore, the finished plate can be manufactured by casting in a mold.

[0007] When a conventional groove structure is introduced, for example, pressed into a flat plate, this groove structure appears as a recess on one side of the plate, and the recess forms a corresponding bulge on the other side. Here, the present invention relates to a channel structure that is geometrically identical on both sides of a modified plate.

[0008] This invention intentionally provides configurations with different geometries for a first channel structure on a first side of the cathode sideplate and a second channel structure on a second side of the cathode sideplate. In the context of this invention, the different geometries mean that the first channel structure on the cathode sideplate is not necessarily a precise negative mapping of the second channel structure. That is, for example, a depression observed on one side of the cathode sideplate does not necessarily correspond simultaneously to a bulge (especially only one) observed on the other side of the cathode sideplate, or vice versa.

[0009] Within the scope of this invention, on the cathode side plate, two reactant channels may follow each coolant channel. In other words, on the cathode side plate, two channels for oxygen-containing reactants may be alternately arranged after each channel for coolant. Therefore, according to the invention, two oxidant channels can be provided for each coolant channel. The invention particularly allows for the channels for oxygen-containing reactants to be configured in two parts or in a dual manner. Within the scope of this invention, the channels for oxygen-containing reactants may be separated from each other by a partition, which may serve as additional landing when supported on the cathode side of the membrane electrode unit.

[0010] Within the scope of this invention, channel structures can be formed on the anode side plate not only with the same geometry but also with different geometry.

[0011] With the aid of this invention, the second channel structure on the cathode side plate can provide a large hydraulic diameter for the coolant channel. Simultaneously, this invention ensures that a small support portion can be provided on the first side of the cathode side plate for support on the cathode side of the membrane electrode unit. Furthermore, this invention enables the use of larger draft angles to form the cooling medium channel on the cathode side plate.

[0012] Furthermore, in this invention, the bipolar plate can be configured such that, viewed transversely to the respective channels of the first and second channel structures, the cathode side plate alternately has one channel for the coolant and two channels for oxygen-containing reactants. In other words, the invention can be configured in the bipolar plate such that the first channel structure of the cathode side plate has dual and / or two-part channels for oxygen-containing reactants, and / or the second channel structure of the cathode side plate has a single channel for the coolant. Therefore, relatively wide channels for the coolant can be provided to reduce pressure loss along the coolant flow direction. Simultaneously, smaller supports can be provided for the cathode side of the membrane electrode unit to prevent product water accumulation below the supports and to achieve better pressure distribution along the cathode side plate when the fuel cell is stacked.

[0013] Furthermore, the present invention allows for a configuration in the bipolar plate where the dual channels of the first channel structure are separated from each other by a separator. Advantageously, the separator between the oxidant channels can form a central support column to enable better pressure distribution along the cathode side plate during fuel cell stacking. The central support portion below the separator can, for example, be rounded.

[0014] Furthermore, the present invention allows for the arrangement of a bipolar plate where the dual channels of the first channel structure are formed by two independently pressed grooves. Therefore, the cathode side plate can be provided continuously with substantially the same material thickness. In this way, the cathode side plate can be manufactured simply and cost-effectively, for example, through molding.

[0015] Furthermore, in this invention, the first channel structure of the anode side plate and the second channel structure of the anode side plate can be configured with different geometries in the bipolar plate. Here, it is conceivable that the anode side plate can be formed similarly to the cathode side plate. Similarly, it is possible that, viewed transversely to the respective channels of the first and second channel structures, the anode side plate can alternately have one channel for the coolant and two channels for the fuel-containing reactants. Advantageously, the two plates of the bipolar plate can be placed such that the partitions in the dual reactant channels are stacked on top of each other. In this way, a wider support surface can be created on the contact surface between the two plates of the bipolar plate. Therefore, it is possible to prevent the plates from sliding into each other and interlocking. Thus, it is also possible to reduce electrical contact losses between the plates. Furthermore, due to the wider support surface in the middle of the reactant channel, the height of the channel can be reduced.

[0016] However, in principle, it is also possible to consider that the first channel structure and the second channel structure of the anode side plate can be constructed with identical geometric shapes. Because there is no problem of product water accumulation on the anode side of the fuel cell and fuel reactants are provided at a higher concentration than oxygen-containing reactants, a conventional cost-effective pressed plate can be used on the anode side, which has a recess when viewed from one side and forms a corresponding bulge when viewed from the other side of the plate.

[0017] Furthermore, the present invention allows for the following configuration in the bipolar plate: a first channel structure on the anode side plate has a support portion below the coolant channel, configured to support the anode of the fuel cell in a fuel cell system; and a first channel structure on the cathode side plate also has a support portion below the coolant channel, configured to support the cathode of the fuel cell in a fuel cell system. The support portion on the anode side plate has a wider width than the support portion on the cathode side plate. In this way, the coolant channel can be substantially moved to the anode side of the bipolar plate. This also enables the realization of a wider channel for oxygen-containing reactants on the cathode side plate.

[0018] Furthermore, the present invention allows for a configuration in the bipolar plate where the release angle of the coolant channel on the anode side plate is smaller than that of the coolant channel on the cathode side plate. In this way, the support portion on the cathode side plate can be reduced in size, since product water may accumulate there below the support portion.

[0019] Furthermore, in this invention, the height of the coolant channel on the anode side plate can be less than the height of the coolant channel on the cathode side plate. Therefore, the coolant channel can also be substantially moved to the anode side of the bipolar plate.

[0020] According to a second aspect, the present invention provides a fuel cell system having at least one bipolar plate constructed as described above. By means of the fuel cell system according to the invention, the same advantages as described above in conjunction with the bipolar plate according to the invention can be achieved. These advantages are fully referenced herein. Attached Figure Description

[0021] The present invention and its improvements, as well as their advantages, are described in detail below with reference to the accompanying drawings. The drawings are schematically illustrated as follows:

[0022] Figure 1 The bipolar plate according to the present invention. Detailed Implementation

[0023] Figure 1A bipolar plate 100 is shown in the context of the present invention, implemented for use in a fuel cell system 1. A fuel cell system 1 having at least one corresponding bipolar plate 100 is also an aspect of the present invention. The fuel cell system 1 according to the present invention can have multiple fuel cells provided in the form of a stack. In the context of the present invention, bipolar plates 100 are arranged between two fuel cells respectively. Monopolar plates are mostly provided on the end sides of the stack for defining the stack.

[0024] In the context of this invention, the bipolar plate 100 has the following elements: a cathode side plate 10 having a first channel structure K1 on a first side 11 for an oxygen-containing reactant O2 or an oxidant, and a second channel structure K2 on a second side 12 for a coolant KM; and an anode side plate 20 having a first channel structure A1 on a first side 21 for a fuel-containing reactant H2, and a second channel structure A2 on a second side 22 for a coolant KM, wherein the cathode side plate 10 and the anode side plate 20 are in contact with each other on the second sides 12 and 22 for the coolant KM.

[0025] In this invention, the first channel structure K1 of the cathode side plate 10 and the second channel structure K2 of the cathode side plate 10 have different geometries.

[0026] The present invention intentionally provides channel structures K1 and K2 with different geometries on the first side 11 and the second side 12 of the cathode side plate 10. That is, in the sense of the present invention, the first channel structure K1 on the first side 11 of the cathode side plate 10 does not necessarily have to be an exact negative mapping of the second channel structure K2 on the second side 12 of the cathode side plate 10. In other words, this means that a depression observed on one side of the cathode side plate 10 does not necessarily map to (especially only) a bulge observed on the other side of the cathode side plate 10, or vice versa.

[0027] Within the scope of this invention, two channels k1 and k2 for the oxygen-containing reactant O2 are arranged adjacent to each coolant channel km on the cathode side plate 10. Therefore, two oxidant channels k1 and k2 can be provided for each coolant channel km.

[0028] like Figure 1 As shown, the channels k1 and k2 for the oxygen-containing reactant O2 can be constructed in two parts or in a dual manner. It is conceivable that the channels k1 and k2 for the oxygen-containing reactant O2 can be separated from each other by a separator Sk, which can serve as an additional support Lk when supported on the cathode side of the membrane electrode unit or simply on the cathode K of the fuel cell. However, it is also conceivable that the separator Sk can be provided through a fold between two closely abutting slots in the cathode side plate 10, such as... Figure 1 As shown by the dashed line in the image.

[0029] On the anode side plate 20, channel structures A1 and A2 can be formed not only with the same geometry (not shown for brevity) but also with different geometries (e.g. Figure 1 (as shown in the image).

[0030] The bipolar plate 100 according to the invention can provide a large hydraulic diameter for the coolant passage KM to reduce pressure loss along the flow direction of the coolant KM. Simultaneously, the bipolar plate 100 according to the invention enables the provision of a relatively small support Lk on the first side 11 of the cathode side plate 10 for supporting the cathode K of the corresponding fuel cell, thereby preventing the accumulation of product water below the support Lk and enabling better pressure distribution along the cathode side plate 10 when the fuel cells are stacked.

[0031] As stated above, and as Figure 1 As shown, the first channel structure A1 and the second channel structure A2 of the anode side plate 20 can also have different geometries. Here, it can be considered that the anode side plate 20 can be constructed similarly to the cathode side plate 10. Here, viewed in the direction R transverse to the respective channels a1, a2, and km of the first channel structure A1 and the second channel structure A2, the anode side plate 20 can alternately have one channel am for the coolant KM and two channels a1 and a2 for the fuel reactant H2.

[0032] like Figure 1 As shown, the channel am on the anode side plate 20 for coolant KM can be fluidly transitioned into the channel km on the cathode side plate 10 for coolant KM, or in other words, form a common coolant channel.

[0033] like Figure 1 As shown, the two plates 10 and 20 of the bipolar plate 100 can be positioned such that the separators Sa and Sk in the dual reactant channels k1, k2 and a1, a2 are stacked on top of each other. In this way, a wider support surface can be provided on the contact surface between the two plates 10 and 20 of the bipolar plate 100 to prevent the plates 10 and 20 from sliding into each other and interlocking. Therefore, electrical contact losses between the plates 10 and 20 can also be reduced. Due to the wider support surface at the middle of the dual reactant channels k1, k2 and a1, a2, the height of the channels can be further reduced.

[0034] However, it is also possible to consider that the first channel structure A1 and the second channel structure A2 of the anode side plate 20 can be constructed with identical geometric shapes (in...). Figure 1(Not shown for brevity only). This is possible because there is no problem of product water accumulation on the anode side A of the fuel cell, and the fuel-containing reactant H2 is provided at a higher concentration than the oxygen-containing reactant O2, so a conventional plate can be used on the anode side A. When viewed from one side of the anode side plate 20, the plate conventionally has recesses, and when viewed from the other side of the anode side plate 20, these recesses form corresponding bulges.

[0035] like Figure 1 As shown, the first channel structure A1 on the anode side plate 20 may have a support portion La below the channel am for coolant KM, which is configured to support the anode A of the corresponding fuel cell in the fuel cell system 1. The first channel structure K1 on the cathode side plate 10 may also have a support portion Lk below the channel km for coolant KM, which is configured to support the cathode K of the adjacent fuel cell in the fuel cell system 1. Here, the width ba of the support portion La on the anode side plate 20 may be greater than the width bk of the support portion Lk on the cathode side plate 10. In this way, the coolant channel can be substantially moved to the anode side A of the bipolar plate 100. This also enables the realization of wider channels k1 and k2 on the cathode side plate 10 for the oxygen-containing reactant O2.

[0036] like Figure 1 As further shown, the demolding angle αa of the channel am for coolant KM on the anode side plate 20 can be smaller than the demolding angle αk of the channel km for coolant KM on the cathode side plate 10. In this way, the support portion Lk on the cathode side plate 10 can be reduced, because product water may accumulate there below the support portion Lk. In this way, especially at high current densities, the mass transport loss of oxygen-containing reactant O2 can be reduced.

[0037] also, Figure 1 As shown, the height ha of the channel am for coolant KM on the anode side plate 20 can be less than the height hk of the channel km for coolant KM on the cathode side plate 10. Therefore, the coolant channel can also be substantially moved to the anode side A of the bipolar plate 100.

[0038] exist Figure 1 The figures shown are merely illustrative. Figure 1 The foregoing description illustrates the invention only within the scope of examples. Of course, the various features of the embodiments can be freely combined with each other without departing from the scope of the invention, as long as it is technically meaningful.

Claims

1. A bipolar plate (100) for a fuel cell system (1), comprising: Cathode side plate (10). The cathode side plate has a first channel structure (K1) for oxygen-containing reactants (O2) on the first side (11), and The cathode side plate has a second channel structure (K2) for coolant (KM) on the second side (12); and Anode side plate (20). The anode side plate has a first channel structure (A1) on the first side (21) for fuel-containing reactants (H2), and The anode side plate has a second channel structure (A2) for coolant (KM) on the second side (22). The cathode side plate (10) and the anode side plate (20) are abutted against each other on their second sides (12, 22) for the coolant (KM). Its features are, The first channel structure (K1) of the cathode side plate (10) has a different geometry than the second channel structure (K2) of the cathode side plate (10). in, Looking in the direction (R) of each channel (k1, k2, km) transverse to the first channel structure (K1) and the second channel structure (K2), The cathode side plate (10) alternately has one channel (km) for coolant (KM) and two channels (k1, k2) for oxygen-containing reactants (O2), that is, two channels for oxygen-containing reactants are alternately arranged after each channel for coolant.

2. The bipolar plate (100) according to claim 1. Its features are, The first channel structure (K1) of the cathode side plate (10) has dual channels (k1, k2) for oxygen-containing reactants (O2), and / or The second channel structure (K2) of the cathode side plate (10) has a single channel (km) for the coolant (KM).

3. The bipolar plate (100) according to claim 2. Its features are, The dual channels (k1, k2) of the first channel structure (K1) are separated from each other by a partition (Sk), and / or The first channel structure (K1) has dual channels (k1, k2) formed by two independently pressed slots.

4. The bipolar plate (100) according to any one of claims 1 to 3. Its features are, The first channel structure (A1) of the anode side plate (20) has a different geometry than the second channel structure (A2) of the anode side plate (20).

5. The bipolar plate (100) according to claim 4. Its features are, Looking in the direction (R) transverse to each channel (a1, a2, am) of the first channel structure (A1) and the second channel structure (A2), The anode side plate (20) alternately has one channel (am) for coolant (KM) and two channels (a1, a2) for fuel-containing reactants (H2).

6. The bipolar plate (100) according to any one of claims 1 to 3. Its features are, The first channel structure (A1) and the second channel structure (A2) of the anode side plate (20) are constructed with the same geometry.

7. The bipolar plate (100) according to any one of claims 1 to 3. Its features are, The first channel structure (A1) on the anode side plate (20) has a support (La) below the channel (am) for coolant (KM), which is configured to support the anode (A) of the fuel cell in the fuel cell system (1), and The first channel structure (K1) on the cathode side plate (10) has a support (Lk) below the channel (km) for coolant (KM), which is configured to support the cathode (K) of the fuel cell in the fuel cell system (1). The support portion (La) on the anode side plate (20) has a width (ba) greater than the width (Lk) of the support portion on the cathode side plate (10).

8. The bipolar plate (100) according to any one of claims 1 to 3. Its features are, The demolding angle (αa) of the channel (am) for coolant (KM) on the anode side plate (20) is smaller than the demolding angle (αk) of the channel (km) for coolant (KM) on the cathode side plate (10).

9. The bipolar plate (100) according to any one of claims 1 to 3. Its features are, The height (ha) of the channel (am) for coolant (KM) on the anode side plate (20) is less than the height (hk) of the channel (km) for coolant (KM) on the cathode side plate (10).

10. A fuel cell system (1) having at least one bipolar plate (100) according to any one of claims 1 to 9.

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