Bipolar Plates for Fuel Cell Systems

Abstract

The present invention relates to a bipolar plate (100) for a fuel cell system (1), comprising a cathode-side plate (10) having a first passage structure (K1) for an oxygen-containing reactant (O2) on a first side (11) and a second passage structure (K2) for a coolant (KM) on a second side (12), and an anode-side plate (20) having a first passage structure (A1) for a fuel-containing reactant (H2) on a first side (21) and a second passage 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 at the second side (12, 22) for the coolant (KM). In addition, according to the present invention, it is contemplated that the first passage structure (K1) of the cathode side plate (10) is geometrically different from the second passage structure (K2) of the cathode side plate (10).

Description

[Technical field]

[0001] The invention relates to a bipolar plate for a fuel cell system according to the independent device claim.Furthermore, the invention relates to a corresponding fuel cell system according to the independent system claim. [Background technology]

[0002] Bipolar plates for fuel cells are basically known. The dividing channels for the reactants and the coolant in the bipolar plates are formed, for example, by embossing a flat plate. When designing the dividing channels, several optimization issues must usually be taken into account. On the one hand, the hydraulic diameters for the reactants must be optimized in order to avoid too high a pressure drop in the flow direction of the reactants. On the other hand, the height of the bipolar plates must be kept low in order to increase the power density of the system. Furthermore, the width of the resting surface for the membrane-electrode unit, especially on the cathode side of the system, must be kept low in order to avoid too high losses in the mass transport of the reactants at maximum power. Furthermore, the width of the channels themselves must be kept low in order to avoid too low a pressure distribution in the center of the channels. Summary of the Invention

[0003] According to a first aspect, the present invention provides a bipolar plate for a fuel cell system with the features of the independent apparatus claim, in particular with the features consisting of the characterizing parts of the independent apparatus claim. According to a second aspect, the present invention provides a corresponding fuel cell system according to the independent system claim. It is to be noted that the features and details explained in relation to the individual aspects of the present invention naturally also apply in relation to the other aspects of the present invention and vice versa, so that the disclosures for the individual aspects of the present invention are always mutually associated or can be associated with each other.

[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 passage structure for an oxygen-containing reactant or oxidant on a first side and a second passage structure for a coolant on a second side; and an anode side plate having a first passage structure for a fuel-containing reactant on a first side and a second passage structure for a coolant on a second side, the cathode side plate and the anode side plate abutting each other with the second side for the coolant. In addition, the present invention provides that the first passage structure of the cathode side plate is (and this is what is meant) geometrically different from the second passage structure of the cathode side plate.

[0005] A fuel cell system within the meaning of the invention may have several fuel cells, each separated from one another by a bipolar plate and arranged one on top of the other in the form of a stack, which may be delimited from the end sides by monopolar end plates.

[0006] The channel structure in the sense of the present invention can be incorporated into the flat plates which are subsequently used as cathode or anode side plates by deformation or plastic forming, for example, impact extrusion, extrusion, deep drawing, bending, etc. Furthermore, the finished molded plates can be produced by casting in a mold.

[0007] When a conventional groove structure is incorporated into a flat plate, e.g., engraved, such a groove structure will have a number of recesses visible on one side of the plate which have corresponding protrusions when viewed from the other side of the plate, whereas the present invention is directed to channel structures which are geometrically identical on both sides of the deformed plate.

[0008] The present invention consciously takes into account a geometrically different configuration of the first passage structure on the first side of the cathode plate and the second passage structure on the second side of the cathode plate. By geometrically different configuration is meant in the sense of the present invention that the first passage structure on the cathode plate does not have to be an exact negative image of the second passage structure, i.e. for example, a recess on one side of the cathode plate does not have to simultaneously correspond to a protrusion, in particular only one protrusion, on the other side of the cathode plate and vice versa.

[0009] Within the scope of the present invention, two reactant channels may be provided adjacent to each coolant channel in the cathode-side plate. In other words, two channels for oxygen-containing reactants may be provided alternately after each channel for the coolant in the cathode-side plate. Thus, according to the present invention, two oxidant channels can be provided for each coolant channel. In particular, the present invention may take into account that the channels for oxygen-containing reactants are formed in two parts or double. Within the scope of the present invention, the channels for oxygen-containing reactants may be separated from one another by a strip that can be used as an additional landing point when mounting the membrane-electrode unit on the cathode side.

[0010] In the anode plate, the passage structures may be geometrically identical or geometrically different within the scope of the invention.

[0011] According to the invention, the second passage structure in the cathode plate can provide a large hydraulic diameter for the coolant passages. At the same time, the invention ensures that the first side of the cathode plate can be provided with a small landing for mounting on the cathode side of the membrane electrode unit. Furthermore, the invention makes it possible to utilize a relatively large release angle, the so-called draft angle, for forming the coolant passages in the cathode plate.

[0012] Furthermore, the invention may take into account that in the bipolar plate, the cathode side plate has, viewed transversely to the individual channels of the first and second channel structures, one channel for the coolant and two channels for the oxygen-containing reactants, alternating therewith. In other words, the invention may take into account that in the bipolar plate, the first channel structure of the cathode side plate has double and / or bipartite channels for the oxygen-containing reactants and / or the second channel structure of the cathode side plate has a single channel for the coolant. Thus, a relatively wide channel can be provided for the coolant, reducing the pressure loss in the coolant flow direction. Thus, at the same time, a relatively small landing for the cathode side of the membrane-electrode unit can be provided, avoiding accumulation of product water below the landing and allowing a good pressure distribution along the cathode side plate when pressing the fuel cells to form a stack.

[0013] The invention may also take into account that in the bipolar plate the double channels of the first channel structure are separated from each other by a strip. Advantageously, the strip may form a central support pillar between the oxidant channels in order to achieve a good pressure distribution along the cathode plate when pressing the fuel cells into a stack. A central landing below the strip may be formed, for example, with a chamfer.

[0014] Furthermore, the invention may take into account that in the bipolar plate, the double passages of the first passage structure are formed by two grooves that are cut independently of each other, thus providing a cathode side plate with a substantially uniform material thickness throughout, which allows the cathode side plate to be produced simply and cost-effectively, for example by plastic forming.

[0015] In addition, the invention may take into account that in the bipolar plate, the first passage structure of the anode side plate is geometrically different from the second passage structure of the anode side plate. It is conceivable that the anode side plate may be shaped similarly to the cathode side plate. It may also be taken into account that the anode side plate may have, viewed transversely to the individual passages of the first and second passage structures, one passage for the coolant and two passages for the fuel-containing reactant alternating. In an advantageous embodiment, the two plates of the bipolar plate may be placed one above the other such that the strips are located overlapping in the double reactant passage. In this way, a relatively wide support surface can be formed at the contact surface between the two plates of the bipolar plate, which prevents the two plates from slipping and overlapping each other. This also reduces the electrical contact losses between the two plates. Furthermore, the relatively wide support surface in the center of the reactant passages allows the height of the passages to be reduced.

[0016] However, it is also conceivable that the first passage structure of the anode side plate and the second passage structure of the anode side plate may be geometrically identical.Since the anode side of a fuel cell does not suffer from product water accumulation problems and the fuel-containing reactants are provided in higher concentrations than the oxygen-containing reactants, the anode side may use a conventional, cost-effective embossed plate having a number of recesses visible on one side of the plate with corresponding protrusions on the other side of the plate.

[0017] Furthermore, the invention may take into account that in the bipolar plate, the first passage structure in the anode-side plate has a number of landings under the passages for the coolant, which are designed for placement on the anodes of the fuel cells of the fuel cell system, and the first passage structure in the cathode-side plate has a number of landings under the passages for the coolant, which are designed for placement on the cathodes of the fuel cells of the fuel cell system, the landings in the anode-side plate having a width greater than the width of the landings in the cathode-side plate. In this way, the coolant passages can be substantially shifted towards the anode side of the bipolar plate. This also allows for relatively wide passages for the oxygen-containing reactants in the cathode-side plate.

[0018] Furthermore, the invention may take into account that in the bipolar plates the break-off angle of the passages for the coolant in the anode side plate is smaller than the break-off angle of the passages for the coolant in the cathode side plate, in this way the landing area in the cathode side plate can be made smaller, since it is exactly there that the product water can accumulate under the landing area.

[0019] Furthermore, the invention may take into account that in the bipolar plates the height of the coolant passages in the anode side plate is lower than the height of the coolant passages in the cathode side plate, which also allows the coolant passages to be substantially shifted towards the anode side of the bipolar plate.

[0020] According to a second aspect, the invention contemplates a fuel cell system comprising at least one bipolar plate, which may be formed as described above. The fuel cell system according to the invention makes it possible to achieve the same advantages as those explained above in connection with the bipolar plate according to the invention, which advantages are hereby incorporated by reference in their entirety.

[0021] The invention and further configurations as well as its advantages are explained in more detail below with the aid of the drawings, which are shown diagrammatically here. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 shows a bipolar plate in the sense of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 1 shows a bipolar plate 100 in the sense of the invention implemented for a fuel cell system 1. The fuel cell system 1 with at least one corresponding bipolar plate 100 likewise shows one aspect of the invention. The fuel cell system 1 in the sense of the invention may comprise several fuel cells arranged in a stack. Between every two fuel cells a bipolar plate 100 in the sense of the invention is arranged. At the end faces of the stack, monopolar plates are usually provided to define the stack.

[0024] A bipolar plate 100 in the sense of the present invention comprises the following elements: a cathode-side plate 10, which has on its first side 11 a first passage structure K1 for an oxygen-containing reactant O2 or oxidant and on its second side 12 a second passage structure K2 for a coolant KM, and an anode-side plate 20, which has on its first side 21 a first passage structure A1 for a fuel-containing reactant H2 and on its second side 22 a second passage structure A2 for the coolant KM, the cathode-side plate 10 and the anode-side plate 20 abutting against each other with the second sides 12, 22 for the coolant KM.

[0025] The present invention takes into account that the first passage structure K1 of the cathode side plate 10 is (what is meant to be) geometrically different from the second passage structure K2 of the cathode side plate 10.

[0026] The present invention deliberately provides geometrically different passage structures K1, K2 on the first side 11 of the cathode side plate 10 and on the second side 12 of the cathode side plate 10. That is, in the sense of the present invention, the first passage structure K1 on the first side 11 of the cathode side plate 10 does not have to be an exact negative image of the second passage structure K2 on the second side 12 of the cathode side plate 10. In other words, a recess found on one side of the cathode side plate 10 does not have to simultaneously copy a protrusion, in particular only one protrusion, found on the other side of the cathode side plate 10, or vice versa.

[0027] Within the scope of the present invention, two passages k1, k2 for the oxygen-containing reactant O2 may be arranged adjacent to each coolant passage km in the cathode side plate 10, thereby providing two oxidant passages k1, k2 for each coolant passage km.

[0028] As shown in Fig. 1, the passages k1, k2 for the oxygen-containing reactant O2 may be divided into two or may be formed double. It is conceivable that the passages k1, k2 for the oxygen-containing reactant O2 may be separated from one another by a strip Sk, which can be used as an additional landing Lk when mounting on the cathode side of the membrane-electrode unit or, simply, on the cathode K of the fuel cell. At the same time, however, it is also conceivable that the strip Sk can be provided by a fold between two closely adjoining strips in the cathode-side plate 10, as suggested by the dashed line in Fig. 1.

[0029] In the anode side plate 20, the passage structures A1, A2 may be shaped to be geometrically the same (not shown for simplicity) or may be shaped to be geometrically different (this is shown in FIG. 1).

[0030] The bipolar plate 100 according to the invention allows for a large hydraulic diameter of the coolant passages KM in order to reduce the pressure loss in the flow direction of the coolant KM. At the same time, the bipolar plate 100 according to the invention allows for a relatively small landing Lk to be provided on the first side 11 of the cathode-side plate 10 for resting on the cathode K of the corresponding fuel cell, thus avoiding accumulation of product water under the landing Lk and allowing a good pressure distribution along the cathode-side plate 10 when pressing several fuel cells into a stack.

[0031] 1, the first passage structure A1 of the anode side plate 20 may likewise be geometrically different from the second passage structure A2 of the anode side plate 20. It is conceivable that the anode side plate 20 may be configured similarly to the cathode side plate 10. In this case, the anode side plate 20 may have, viewed in the transverse direction R to the individual passages a1, a2, km of the first and second passage structures A1 and A2, one passage am for the coolant KM alternating with two passages a1, a2 for the fuel-comprising reactant H2.

[0032] In this case, as shown in FIG. 1, the passages am for the coolant KM in the anode side plate 20 may flow into the passages km for the coolant KM in the cathode side plate 10 or may form one common coolant passage.

[0033] As shown in Fig. 1, both plates 10, 20 of the bipolar plate 100 may be placed one on top of the other such that the strips Sa, Sk are located one above the other in the double reactant passages k1, k2 and a1, a2. In this way, a relatively wide support surface can be provided at the contact surface between both plates 10, 20 of the bipolar plate 100, preventing the plates 10, 20 from slipping and overlapping each other. Thus, the electrical contact loss between the plates 10, 20 can also be reduced. Moreover, the relatively wide support surface in the center of the double reactant passages k1, k2 and a1, a2 allows the height of the passages to be reduced.

[0034] However, at the same time, it is also conceivable that the first passage structure A1 of the anode side plate 20 and the second passage structure A2 of the anode side plate 20 may be geometrically identical, which is not shown in Fig. 1 for the sake of simplicity. This is possible because the anode side A of the fuel cell does not have the problem of product water accumulation and the fuel-containing reactant H2 is provided in higher concentration than the oxygen-containing reactant O2, and the anode side A can use a conventional plate having a recess on one side of the anode side plate 20 replicating a corresponding protrusion on the other side of the anode side plate 20.

[0035] As FIG. 1 suggests, the first passage structure A1 on the anode-side plate 20 may have a landing La below the passages am for the coolant KM, which is designed for placement on the anode A of a corresponding fuel cell of the fuel cell system 1. The first passage structure K1 on the cathode-side plate 10 may likewise have a landing Lk below the passages km for the coolant KM, which is designed for placement on the cathode K of an adjacent fuel cell of the fuel cell system 1. The landing La on the anode-side plate 20 may then have a width ba that is greater than the width bk of the landing Lk on the cathode-side plate 10. In this way, the position of the coolant passages can be substantially shifted towards the anode side A of the bipolar plate 100. This likewise allows for relatively wide passages k1, k2 for the oxygen-containing reactant O2 on the cathode-side plate 10.

[0036] 1 further suggests, the take-off angle αa of the channels am for the coolant KM in the anode-side plate 20 can be smaller than the take-off angle αk of the channels km for the coolant KM in the cathode-side plate 10. In this way, the landing Lk in the cathode-side plate 10 can be made smaller, since it is precisely there that the product water can accumulate below the landing Lk. In this way, losses in the mass transport of the oxygen-containing reactant O2 can be reduced, especially at high flow densities.

[0037] 1 further shows that the height ha of the passages am for the coolant KM in the anode side plate 20 may be lower than the height hk of the passages km for the coolant KM in the cathode side plate 10. This also allows the position of the coolant passages to be substantially shifted to the anode side A of the bipolar plate 100.

[0038] The figures shown in Fig. 1 are merely examples. The above description of Fig. 1 merely describes the present invention within the scope of some examples. Of course, if there is a technical meaning, the individual components of the multiple embodiments may be freely combined with each other without departing from the scope of the present invention. [Explanation of symbols]

[0039] 1. Fuel cell system 10 Cathode side plate 11 First side of cathode side plate 12 Second side of cathode plate 20 Anode side plate 21 First side surface of the anode side plate 22 Second side of the anode plate 100 Bipolar Plates A1: A first passage structure for fuel-containing reactants on the anode side plate A2: Second passage structure for oxidant on the anode side plate a1, a2 Passages for fuel-containing reactants in the anode plate am Passage for coolant in the anode plate H2 fuel-containing reactant K1: First passage structure for oxygen-containing reactants on the cathode side plate K2: Second passage structure for the oxidant of the cathode plate KM Coolant k1, k2 Passages for oxygen-containing reactants on the cathode side plate km Coolant passages in the cathode plate La,4 Landing section O2 Oxygenated reactant R Horizontal Sk strips

Claims

1. A cathode side plate (10), the cathode side plate has a first passage structure (K1) for an oxygen-containing reactant (O2) on a first side (11); and On the second side (12) there is a second passage structure (K2) for the coolant (KM), An anode side plate (20), the anode side plate has a first passage structure (A1) for a fuel-containing reactant (H2) on a first side (21); and On the second side (22) there is a second passage structure (A2) for the coolant (KM), the cathode side plate (10) and the anode side plate (20) abut against each other with the second side (12, 22) for the coolant (KM); A bipolar plate (100) for a fuel cell system (1), the first passage structure (K1) of the cathode side plate (10) is geometrically different from the second passage structure (K2) of the cathode side plate (10); the cathode side plate (10) has, in a transverse direction (R) relative to the individual passages (k1, k2, km) of the first passage structure (K1) and the second passage structure (K2), one passage (km) for the coolant (KM) and two passages (k1, k2) for the oxygen-containing reactant (O2) alternating therewith; A bipolar plate (100) comprising:

2. the first passage structure (K1) of the cathode side plate (10) having double and / or bifurcated passages (k1, k2) for the oxygen-containing reactant (O2); and / or the second passage structure (K2) of the cathode side plate (10) has a single passage (km) for the coolant (KM), The bipolar plate (100) of claim 1, characterized in that

3. The double passages (k1, k2) of the first passage structure portion (K1) are separated from each other by a strip portion (Sk); and / or the double passage (k1, k2) of the first passage structure (K1) is formed by two narrow grooves engraved independently of each other; The bipolar plate (100) according to claim 2, characterized in that

4. The bipolar plate (100) according to any one of claims 1 to 3, characterized in that the first passage structure (A1) of the anode side plate (20) is geometrically different from the second passage structure (A2) of the anode side plate (20).

5. 5. The bipolar plate (100) according to claim 4, characterized in that the anode side plate (20) has, viewed in a transverse direction (R) relative to the individual passages (a1, a2, am) of the first passage structure (A1) and the second passage structure (A2), one passage (am) for the coolant (KM) alternating with two passages (a1, a2) for the fuel-containing reactant (H2).

6. The bipolar plate (100) according to any one of claims 1 to 3, characterized in that the first passage structure portion (A1) of the anode side plate (20) and the second passage structure portion (A2) of the anode side plate (20) are formed geometrically identically.

7. the first passage structure (A1) provided in the anode side plate (20) has a plurality of landing portions (La) below the passages (am) for the coolant (KM); the landing portion is formed for placement on an anode (A) of a fuel cell of the fuel cell system (1); and the first passage structure (K1) in the cathode side plate (10) has a plurality of landings (Lk) below the passages (km) for the coolant (KM), the landing portion is formed for placement on a cathode (K) of a fuel cell of the fuel cell system (1); The landing portion (La) provided on the anode side plate (20) has a width (ba) larger than a width (bk) of the landing portion (Lk) provided on the cathode side plate (10); A bipolar plate (100) according to any one of claims 1 to 6, characterized in that

8. The bipolar plate (100) according to any one of claims 1 to 7, characterized in that the release angle (αa) of the passages (am) for the coolant (KM) provided in the anode side plate (20) is smaller than the release angle (αk) of the passages (km) for the coolant (KM) provided in the cathode side plate (10).

9. The bipolar plate (100) according to any one of claims 1 to 8, characterized in that the height (ha) of the passages (am) for the coolant (KM) provided in the anode side plate (20) is lower than the height (hk) of the passages (km) for the coolant (KM) provided in the cathode side plate (10).

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

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