Method for sealing a coolant chamber of a bipolar plate of a fuel cell and fuel cell

Abstract

Fuel cell (20) with at least one bipolar plate (1) and at least one membrane electrode assembly (21), wherein the bipolar plate (1) has a first (2) and a second bipolar plate half (3), at least one of the bipolar plate halves (2, 3) has a coolant distributor structure (4) and a coolant chamber (5) formed at least by the coolant distributor structure (4) is formed between the bipolar plate halves (2, 3), and wherein the at least one bipolar plate (1) is arranged planarly on the membrane electrode assembly (21) to form a gas chamber (24) of an anode (22) or a cathode (23) of the fuel cell (20) between the bipolar plate (1) and the membrane electrode assembly (21), wherein the fuel cell (20) has a seal (10) for sealing the gas space (24) and the coolant space (5) can also be sealed by contacting both bipolar plate halves (2, 3) through the seal (10), characterized by that at least one of the bipolar plate halves (2, 3) has a bend (7) in the area of ​​contact by the seal (10), wherein the bipolar plate (1) has at least one through-opening (8) opposite the bend (7), wherein when arranging, in particular injection molding, the seal (10) passes through the at least one through-opening (8) and can be arranged on both sides of the bipolar plate (1).

Description

[0001] The present invention relates to a method for sealing a coolant chamber of a bipolar plate of a fuel cell, wherein the fuel cell has at least one membrane electrode unit and the bipolar plate has a first and a second bipolar plate half, at least one of the bipolar plate halves has a coolant distributor structure and the coolant chamber formed at least by the coolant distributor structure is formed between the bipolar plate halves.Furthermore, the invention relates to a fuel cell with at least one bipolar plate and at least one membrane electrode assembly, wherein the bipolar plate has a first and a second bipolar plate half, at least one of the bipolar plate halves has a coolant distributor structure and a coolant space formed at least by the coolant distributor structure is formed between the bipolar plate halves, and wherein the at least one bipolar plate is arranged flatly on the membrane electrode assembly to form a gas space of an anode or a cathode of the fuel cell between the bipolar plate and the membrane electrode assembly. STATE OF THE ART

[0002] Fuel cells can have multiple bipolar plates and membrane electrode assemblies. In the manufacture of bipolar plates, it is also known that these bipolar plates can each have two bipolar plate halves. In particular, it is also possible for one bipolar plate half to have a gas distribution structure on one side of the plate, for example, for hydrogen in the case of an anode of the fuel cell or for air in the case of a cathode, and the other side of the plate to have a coolant distribution structure for distributing a coolant. It is known to permanently join the two bipolar plate halves by gluing, welding, soldering, or similar joining processes in a spot, line, and / or partial-surface manner. It is also known to arrange a seal on the outer surface of such a bipolar plate.Both possibilities are based on the need to prevent coolant from escaping the coolant chamber formed between the two bipolar plate halves.

[0003] Furthermore, it is known to also arrange seals between a bipolar plate and a membrane electrode assembly of a fuel cell. Such seals or sealing arrangements are known, for example, from DE 10 2006 056 468 A1 or DE 199 08 555 A1. These seals are used to prevent the gases used in the fuel cell, in particular hydrogen and air, from unintentionally escaping from the fuel cell.

[0004] However, a disadvantage of this approach is that, in addition to sealing the gas spaces, either a separate seal for the coolant space or a coolant-tight, permanent connection between the bipolar plate halves is required. Both options are costly and result in increased material and time expenditure during the manufacturing and / or assembly of such a fuel cell.

[0005] Furthermore, fuel cells with a bipolar plate and various seals, which seal the respective coolant chamber as well as the gas chambers of the anode and cathode, are known from DE 103 01 052 A1, US 2012 / 0251918 A1, US 2012 / 0107718 A1 and US 2009 / 0004539 A1. However, these seals have a complex design or require complex manufacturing. REVELATION OF THE INVENTION

[0006] It is therefore an object of the present invention to at least partially overcome the disadvantages described above of known methods for sealing a coolant chamber of a bipolar plate and of known fuel cells. In particular, it is an object of the present invention to provide a fuel cell which enables the simple and cost-effective manufacture of a fuel cell or a sealed coolant chamber, thereby reducing the time and material costs of production.

[0007] The foregoing problem is solved by a fuel cell having the features of independent claim 1.

[0008] Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the fuel cell according to the invention, and vice versa, so that the disclosure regarding the individual aspects of the invention always refers, or can refer, to each other.

[0009] In a first aspect of the invention, the problem is solved by a method for sealing a coolant chamber of a bipolar plate of a fuel cell, wherein the fuel cell has at least one membrane electrode assembly and the bipolar plate has a first and a second bipolar plate half, at least one of the bipolar plate halves has a coolant distributor structure, and the coolant chamber, formed at least by the coolant distributor structure, is formed between the bipolar plate halves. In particular, a method according to the invention is characterized by the following steps: a) Planar arrangement of the bipolar plate on the at least one membrane electrode unit b) Forming a gas space of an anode or a cathode of the fuel cell between the bipolar plate and the membrane electrode assembly, c) Arranging a seal to seal the gas space such that the coolant space is also sealed by the seal, with both bipolar plate halves of the bipolar plate being contacted by the seal.

[0010] During operation of the fuel cell, a cooling fluid flows through the coolant chamber to cool the fuel cell. The coolant distribution structure, which comprises at least one, preferably both, bipolar plate halves, ensures optimal distribution of the cooling fluid within the coolant chamber, thereby achieving reliable and efficient cooling of the fuel cell. The coolant distribution structure can also be made of a particularly porous material and / or be formed from it, and is arranged between the bipolar plate halves. Furthermore, the coolant distribution structure can be configured to act as a spacer, defining the distance between the two bipolar plates."Planar" within the meaning of the invention means, in particular, that the extent of the bipolar plate and the membrane electrode assembly is significantly larger in two spatial dimensions than in the third dimension, wherein "planar arrangement" means arranging the two components in such a way as to achieve the largest possible contact area between the bipolar plate and the membrane electrode assembly. In addition to the coolant distribution structure, a bipolar plate can also have a gas distribution structure through which a gas flow in the gas space, in particular a flow of hydrogen or air, can be optimally distributed and directed. In particular, a bipolar plate can also be designed such that the at least one coolant distribution structure on the other side of the bipolar plate half forms at least a part of the gas distribution structure.

[0011] Crucial for the safe operation of a fuel cell is that both the coolant chamber and the gas chamber are sealed. The two chambers must be sealed separately, both individually and from each other. The coolant chamber in a bipolar plate is located between the two bipolar plate halves. According to the invention, a seal for sealing the gas chamber is arranged such that, firstly, the gas chamber is sealed. Secondly, both bipolar plate halves of the bipolar plate are additionally contacted by the seal. The seal thus contacts both the membrane electrode assembly and both bipolar plate halves of the bipolar plate. By contacting both bipolar plate halves, the coolant chamber formed between them is also sealed. This makes it possible to simultaneously, i.e.,The same seal is used to seal both the gas chamber and the coolant chamber separately and from each other. Using only a single seal results in a particularly simple sealing of both the gas chamber and the coolant chamber. This saves costs, material, and time during manufacturing. Furthermore, the mandatory requirement for a bipolar plate that the two halves must be permanently and tightly bonded before the fuel cell is assembled is eliminated. This also saves manufacturing time during fuel cell production.

[0012] Furthermore, in a method according to the invention for sealing a coolant chamber, the seal can be arranged on the membrane electrode assembly. The seal can be arranged on the membrane electrode assembly either before the fuel cell is assembled or after the bipolar plate has been attached to the membrane electrode assembly. In particular, the bipolar plate can be pressed into the seal arranged on the membrane electrode assembly during assembly. A particularly secure hold of the seal on the membrane electrode assembly can also be ensured by directly attaching the seal to the membrane electrode assembly.

[0013] Alternatively, in a method according to the invention for sealing a coolant chamber, the seal can be arranged on the bipolar plate. This also makes it possible to connect the two bipolar plate halves. This can also be done prior to the assembly of the fuel cell. The bipolar plate is thus connected by the seal as a single unit consisting of the two bipolar plate halves. A particularly good seal of the coolant chamber can be achieved in this way.

[0014] Furthermore, in a method according to the invention for sealing a coolant chamber, the seal can be injection-molded and bonded in place. Injection molding the seal onto the membrane electrode assembly, onto the two bipolar plate halves, or onto both components, represents a particularly flexible method for arranging the seal. In this way, the seal can penetrate even very small gaps between the bipolar plate and the membrane electrode assembly, ensuring a seal of the coolant chamber and / or the gas space even there.Adhering the seal, which can be either adhering to the membrane electrode unit or adhering to the two bipolar plate halves of the bipolar plate or adhering to both components, particularly enables the production of a fuel cell in which the individual components of the fuel cell have a particularly firm hold with each other.

[0015] In a second aspect of the invention, the problem is solved by a fuel cell with at least one bipolar plate and at least one membrane electrode assembly, wherein the bipolar plate has a first and a second bipolar plate half, at least one of the bipolar plate halves has a coolant distributor structure, and a coolant chamber, at least partially formed by the coolant distributor structure, is formed between the bipolar plate halves, and wherein the at least one bipolar plate is arranged flat against the membrane electrode assembly to form a gas chamber for an anode or a cathode of the fuel cell between the bipolar plate and the membrane electrode assembly. In particular, the fuel cell according to the invention is characterized in that the fuel cell has a seal for sealing the gas chamber, and the coolant chamber can also be sealed by contacting both bipolar plate halves through the seal.

[0016] A fuel cell according to the invention can, in particular, also comprise several membrane electrode assemblies and several bipolar plates, which are preferably arranged in an alternating stack relative to one another. During operation of the fuel cell, a cooling fluid flows through the coolant chamber of the bipolar plate to cool the fuel cell. The coolant distributor structure, which comprises at least one half of the bipolar plate, enables optimized distribution of the cooling fluid in the coolant chamber and thus particularly efficient cooling of the fuel cell. The bipolar plate and the membrane electrode assembly, in particular, have a planar shape, and when the two components of the fuel cell are arranged together, the bipolar plate and the membrane electrode assembly can be arranged such that they preferably have the largest possible common contact area.It can also be provided that the bipolar plate has a gas distribution structure, which is arranged particularly in the gas space formed between the bipolar plate and the membrane electrode assembly. It is particularly preferred that the coolant distribution structure of one bipolar plate half forms at least part of this gas distribution structure on the other side of the bipolar plate half, which then forms the outer surface of the bipolar plate. Thus, the gas space is formed between the membrane electrode assembly and the bipolar plate, and the coolant space between the two bipolar plate halves. For safe operation of the fuel cell, it is necessary that both the gas space and the coolant space are sealed separately from each other. According to the invention, a seal is provided which is intended to seal the gas space and simultaneously seal the coolant space.This is ensured in particular by the fact that the seal contacts both halves of the bipolar plate. This makes it possible to reliably seal the coolant space formed between the two bipolar plate halves. Furthermore, the seal is also designed to seal the gas space. This dual function of the seal—sealing both the gas space and the coolant space—enables a particularly simple design for the fuel cell. Specifically, a single seal is sufficient to seal both the gas space and the coolant space. Consequently, the present invention eliminates the need for additional seals for sealing the gas space and / or the coolant space.Furthermore, this method allows for a particularly reliable seal. This results in savings of material and time in the manufacturing of the fuel cell, and consequently, a reduction in manufacturing costs. Separate sealing of the coolant chamber between the two bipolar plate halves, and especially permanent joining of the two bipolar plate halves by welding, bonding, or similar manufacturing steps, are therefore no longer strictly necessary.

[0017] Furthermore, in a fuel cell according to the invention, the seal for contacting the bipolar plate halves can be formed in an edge region of the bipolar plate. The edge region of the bipolar plate preferably also forms the edge region of the two bipolar plate halves. These bipolar plate halves thus lie abutted or butt-to-abut in the edge region. This makes contacting both bipolar plate halves particularly easy when arranging the seal. In particular, the seal can also penetrate into the space between the bipolar plates. This allows for a particularly good seal of the coolant chamber between the two bipolar plate halves. It is also conceivable that the seal can be arranged on both flat outer surfaces of the bipolar plate.This is particularly advantageous for a fuel cell designed as a stack of membrane electrode units and bipolar plates, as it allows a single seal to close a coolant chamber and two gas chambers on either side of the bipolar plate.

[0018] Furthermore, it is particularly advantageous in a fuel cell according to the invention that the seal with respect to the membrane electrode assembly and / or the bipolar plate is a substantially circumferential seal. A substantially circumferential seal allows for the formation of a particularly large coolant space between the bipolar plate halves and a particularly large gas space between the bipolar plate and the membrane electrode assembly. The coolant space and the gas space are, in particular, essentially limited only by the surface area of ​​the bipolar plate and the membrane electrode assembly. This enables particularly efficient use of space in a fuel cell.

[0019] A fuel cell according to the invention can also be designed such that at least one of the bipolar plate halves has an upward bend in the area of ​​contact with the seal. This causes at least one bipolar plate half to project at least slightly into the seal. A particularly good connection between the bipolar plate half and the seal can thus be achieved. This further improves the sealing of the coolant chamber. It is particularly preferred that both bipolar plate halves have an upward bend in the area of ​​contact with the seal. In this way, the sealing effect of the seal with respect to the coolant chamber can be further improved.

[0020] Furthermore, in a fuel cell according to the invention, the bipolar plate can be provided with at least one through-hole, wherein, during the arrangement, in particular injection molding, of the seal, the seal passes through the at least one through-hole and can be arranged on both sides of the bipolar plate. In this way, it is possible to arrange a seal on both sides of the bipolar plate in a single manufacturing step. This represents a significant time saving in the production of a fuel cell according to the invention. In addition, a connection between the two bipolar plate halves can be achieved by a seal that passes through the through-hole and can be arranged simultaneously, i.e., in a single process step, on both sides of the bipolar plate. This also results in a particularly high level of stability for a fuel cell according to the invention.

[0021] Particularly preferred in a fuel cell according to the invention is the provision that the coolant compartment of the at least one bipolar plate of the fuel cell is sealed by a method according to the first aspect of the invention. All the advantages described for a method according to the first aspect of the invention naturally also apply to a fuel cell according to the invention whose coolant compartment is sealed by such a method. PREFERRED EXAMPLES

[0022] The inventive method and its further developments and their advantages, as well as the inventive fuel cell and its further developments and their advantages, are explained in more detail below with reference to the drawings. They show schematically: Fig. 1 a bipolar plate according to the state of the art, Fig. 2 a possible design form of a fuel cell, Fig. 3a) - d) possible embodiments of a fuel cell, Fig. 4a) - d) possible design forms of the edge region of a bipolar plate and Fig. 5 a possible embodiment of a bipolar plate according to the invention.

[0023] Elements with the same function and mode of operation are in the Fig. 1, Fig. 2, Fig. 3a) to d), 4a) to d) and 5 are each provided with the same reference numerals.

[0024] Fig. Figure 1 shows a bipolar plate 1 whose coolant chamber 5 is sealed according to the prior art. For this purpose, the first bipolar plate half 2 and the second bipolar plate half 3 are connected to each other in the edge region 6 of the bipolar plate 1 by a continuous connection 9. Such a continuous connection 9 can, for example, be a laser weld, an adhesive bond, or a solder joint. The coolant chamber 5, which is formed in particular by a coolant distribution structure 4 of the first 2 and second bipolar plate half 3, is thereby sealed. A disadvantage of this method is that this sealing constitutes a separate manufacturing step, which entails both greater material consumption and, in particular, greater time expenditure.

[0025] In Fig. Figure 2 shows a fuel cell 20 comprising two bipolar plates 1 and a membrane electrode assembly 21. Each of the two bipolar plates 1 has a first bipolar plate half 2 and a second bipolar plate half 3. A coolant chamber 5 is formed between the respective bipolar plate halves 2 and 3 in each of the two bipolar plates 1. In particular, each bipolar plate half 2 and 3 of the two bipolar plates 1 also has a coolant distribution structure 4, which structures the coolant chamber 5 of the two bipolar plates 1. Such a coolant distribution structure 4 ensures optimal distribution of the coolant in the coolant chamber 5 and thus particularly efficient cooling of the fuel cell 20. A gas chamber 24 is formed between each of the two bipolar plates 1 and the membrane electrode assembly 21.On different sides of the membrane electrode assembly 21, this represents, firstly, the gas space 24 of an anode 22 or a cathode 23. In the illustrated embodiment of the fuel cell 20 according to the invention, the bipolar plate half 2 or 3 facing the membrane electrode assembly 21 is each equipped with a coolant distributor structure 4 such that this coolant distributor structure 4 also forms a gas distributor structure for the respective gas space 24. In the fuel cell 20 according to the invention, a seal 10 is also arranged in a peripheral region 6 of each of the two bipolar plates 1. In this embodiment of a fuel cell 20 according to the invention, the seal 10 is arranged directly on the membrane electrode assembly 21. It is located between the membrane electrode assembly 21 and the bipolar plate 1, which is arranged flat against it.A key aspect of the invention is that the respective seal 10 also contacts both bipolar plate halves 2, 3 of the bipolar plate 1 in the edge region 6 of the bipolar plate 1. This ensures that the coolant chamber 5, which is bounded and formed by the two bipolar plate halves 2, 3, is also reliably sealed by the seal 10. This makes it possible to seal both the gas chamber 24 and the coolant chamber 5 with just one seal 10. This represents a significant simplification, as only a single seal 10 is required. A separate seal for the coolant chamber 5, whether by a continuous connection 9 or by a separate seal for the coolant chamber 5, is unnecessary. This allows for savings in material, manufacturing time, and therefore also manufacturing costs in the production of a fuel cell 20 according to the invention.

[0026] The Fig. Figures 3a) to d) show possible arrangement variants of a seal 10 of a fuel cell 20 according to the invention. Only one bipolar plate 1 and a membrane electrode unit 21, on which the seal is arranged in a planar fashion, are shown in each case. The gas space 24 of an anode 22 is formed between the bipolar plate 1 and the membrane electrode unit 21. A coolant space 5 is formed between the bipolar plate halves 2, 3. The respective bipolar plate halves 2, 3 also each have a coolant distributor structure 4, which structures the coolant space 5 and thus enables particularly good cooling of the fuel cell 20 during operation. Fig. In 3a) and c), the seal 10 is arranged directly on the membrane electrode unit 21. The difference between the two figures is that in Fig. 3a) The edge region 6 of the bipolar plate 1 is designed such that a guide groove for the seal 10 is formed. This guide groove facilitates the secure placement of the seal 10. However, such a guide groove is not strictly necessary, as is the case, for example, in Fig. 3c) is visible. However, it is clearly visible in both figures that the seal 10 contacts both bipolar plate halves 2, 3 of the bipolar plate 1. In the Fig. In contrast to 3b) and d), in this case, the seal 10 is directly injection-molded onto the bipolar plate 1. This allows for particularly effective penetration of the sealant of the seal 10 between the two bipolar plate halves 2, 3. This, in addition to sealing the coolant chamber 5, also ensures that the two bipolar plate halves 2, 3 are held together. Again, the design in Fig. 3b) with a guide groove in the bipolar plate 1 for the seal 10 and in the Fig. 3d) shown without such a guide groove in the bipolar plate 1.

[0027] The Fig. Figures 4a) to d) each show a bipolar plate 1, consisting of two bipolar plate halves 2, 3, the ends of which have varying degrees of upward bending 7 in the edge region 6 of the bipolar plate. Depending on the degree of upward bending 7, the sealing compound of the seal 10 can flow behind or penetrate between the two bipolar plate halves 2, 3 particularly well. Especially in the Fig. 4c) and d), in which a particularly distinct upward bending 7 is visible, this penetration and backfilling of the space between the two bipolar plate halves 2, 3 by the sealing compound of the seal 10 is particularly evident. Also, in Fig. 4c) a bending 7 is shown on both bipolar plate halves 2, 3, so that a particularly secure hold of the two bipolar plate halves 2, 3 to each other can be ensured.

[0028] In Fig.Figure 5 shows a further embodiment of a bipolar plate 1 for a fuel cell 20 according to the invention. A coolant chamber 5 formed by a coolant distributor structure 4 is again visible between the bipolar plate halves 2, 3. In particular, both bipolar plate halves 2, 3 also have upturns 7 in the edge region 6 of the bipolar plate 1. A special feature of this embodiment of the bipolar plate 1 is the passage openings 8, which are also arranged in the edge region 6 of the bipolar plate 1. This allows the sealant material of the seal 10 to pass through the passage openings 8 when a seal 10 (not shown) is applied, in particular by injection molding, in the edge region 6 of the bipolar plate 1 and thus be applied to both sides of the bipolar plate 1 in a single manufacturing step. This eliminates a manufacturing step in the production of a fuel cell 20 according to the invention.Secondly, a particularly secure connection between the two bipolar plate halves 2, 3 to form bipolar plate 1 can be achieved.

Claims

[1] Fuel cell (20) with at least one bipolar plate (1) and at least one membrane electrode assembly (21), wherein the bipolar plate (1) has a first (2) and a second bipolar plate half (3), at least one of the bipolar plate halves (2, 3) has a coolant distributor structure (4) and a coolant chamber (5) formed at least by the coolant distributor structure (4) is formed between the bipolar plate halves (2, 3), and wherein the at least one bipolar plate (1) is arranged flat against the membrane electrode assembly (21) to form a gas chamber (24) of an anode (22) or a cathode (23) of the fuel cell (20) between the bipolar plate (1) and the membrane electrode assembly (21), wherein the fuel cell (20) has a seal (10) for sealing the gas space (24) and the coolant space (5) can also be sealed by contacting both bipolar plate halves (2, 3) through the seal (10), characterized by , that at least one of the bipolar plate halves (2, 3) has a bend (7) in the area of ​​contact by the seal (10), wherein the bipolar plate (1) has at least one through-opening (8) opposite the bend (7), wherein when arranging, in particular injection molding, the seal (10) passes through the at least one through-opening (8) and can be arranged on both sides of the bipolar plate (1). [2] Fuel cell (20) according to claim 1, characterized by , that the seal (10) is formed for contacting the bipolar plate halves (2, 3) in an edge region (6) of the bipolar plate (1). [3] Fuel cell (20) according to one of claims 1 or 2, characterized by , that the seal (10) is a substantially circumferential seal (10) with respect to the membrane electrode assembly (21) and / or to the bipolar plate (1).

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