Fuel cell, fuel cell stack, and fuel cell vehicle

Abstract

The invention relates to a fuel cell with a membrane electrode assembly, comprising a bipolar plate arranged on each side of the membrane electrode assembly and a sealing assembly with a sealing pad adjacent to the membrane electrode assembly. On the side of the sealing pad facing away from the membrane electrode assembly, first sealing lips are formed on each side of a sealing carrier of the sealing assembly, the free ends of which are provided with a thickening opposite a first lip base on the sealing carrier and have a thickness corresponding to the distance between the bipolar plates. On the side of the first sealing lips facing the sealing carrier, at least one channel is formed in the first sealing lips and / or the sealing carrier, at least in the region of the thickening. The invention further relates to a fuel cell stack and a fuel cell vehicle.

Description

[0001] The invention relates to a fuel cell with a membrane electrode assembly, comprising a bipolar plate arranged on each side of the membrane electrode assembly and a sealing assembly with a sealing pad adjacent to the membrane electrode assembly. On the side of the sealing pad facing away from the membrane electrode assembly, first sealing lips are formed on each side of a sealing carrier of the sealing assembly, the free ends of which are provided with a thickening opposite a first lip base on the sealing carrier and have a thickness corresponding to the distance between the bipolar plates. On the side of the first sealing lips facing the sealing carrier, at least one channel is formed in the first sealing lips and / or the sealing carrier, at least in the region of the thickening. The invention further relates to a fuel cell stack and a fuel cell vehicle.

[0002] Fuel cells utilize the chemical reaction of a fuel with oxygen to produce water, thereby generating electrical energy. As a core component, fuel cells contain the membrane electrode assembly (MEA), which consists of an ion-conducting (usually proton-conducting) membrane and two catalytic electrodes (anode and cathode) positioned on either side of the membrane. These electrodes typically comprise carbon-supported precious metals, particularly platinum. Additionally, gas diffusion layers (GDLs) can be arranged on either side of the MEA, on the electrodes facing away from the membrane. A fuel cell is generally comprised of multiple MEAs stacked together, the electrical outputs of which are additive.Bipolar plates (also called flow field or separator plates) are typically arranged between the individual membrane electrode assemblies. These plates ensure the supply of the operating media, i.e., the reactants, to the individual cells and usually also serve for cooling. Furthermore, the bipolar plates provide an electrically conductive contact with the membrane electrode assemblies.

[0003] During operation of the fuel cell, the fuel (anode operating medium), in particular hydrogen H2 or a hydrogen-containing gas mixture, is fed to the anode via an anode-side open flow field of the bipolar plate, where an electrochemical oxidation of H2 to protons H + with the release of electrons (H2→ 2H + + 2 e -). A membrane (electrolyte), which separates the reaction chambers from each other in a gas-tight manner and electrically insulates them, transports the protons (water-bound or water-free) from the anode chamber to the cathode chamber. The electrons provided at the anode are conducted to the cathode via an electrical line. Oxygen or an oxygen-containing gas mixture (e.g., air) is supplied to the cathode as the operating medium via a cathode-side open flow field of the bipolar plate, so that a reduction of 02 to 0 2- taking place with the uptake of electrons (½ O2 + 2 e - → 0 2- ). Simultaneously, in the cathode compartment, the oxygen anions react with the protons transported across the membrane to form water (0 2- +2H + → H2O).

[0004] Seals must be present between the bipolar plates and the membrane electrode assemblies of fuel cells to ensure a fluid-tight seal between the anode and cathode compartments and thus prevent the reactant media (anode or cathode operating medium) from escaping. For this purpose, seals are provided that surround the active areas on the one hand and the supply openings of the bipolar plates or membrane electrode assemblies on the other. These are stacked in the fuel cell stack in alignment with the main supply channels. Various sealing concepts are known. DE 10 2017 214 983 A1 shows a sealing arrangement in which the seal is partially embedded in the edge region of the membrane electrode assembly and partially located outside, completely covering the edge region.The membrane electrode assembly is surrounded by a sealing frame that encircles the edge area with the seal to interrupt any leakage path at the edge. A detachable sealing element for a bipolar plate with a U-shaped cross-section is known from DE 10 2018 117 345 A1. DE 10 2020 103 624 A1 discloses a sealing element for bipolar plates of a fuel cell that has an asymmetrical geometry with inclined surfaces.

[0005] The contact between the seals and the relatively rigid bipolar plates often results in a flat contact that is relatively sensitive to sliding, which can lead to seal failure.

[0006] It is therefore the object of the present invention to provide a fuel cell with improved sealing properties. A further object is to provide an improved fuel cell stack and an improved fuel cell vehicle.

[0007] This object is achieved by a fuel cell having the features of claim 1, by a fuel cell stack having the features of claim 9, and by a fuel cell vehicle having the features of claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0008] The fuel cell of the type mentioned above is characterized by the fact that a basic level of tightness is maintained even when the fuel cell is not in operation and the reaction chambers are not pressurized. However, as soon as the pressure is increased, the tightness also increases, since the channel creates a pressure connection to the reaction chambers, thus pressing the first sealing lips against the bipolar plates with increased force. This can also be understood as "inflating" the area within the first sealing lips like a balloon, thereby improving the tightness. The risk of the seal slipping against the bipolar plate, with the corresponding loss of seal, is significantly reduced or even virtually eliminated. A good sealing effect is achieved even without high sealing forces.Furthermore, due to the larger contact and bearing surface of the first sealing lips on the bipolar plates, smaller forces or surface pressures act on the bipolar plates, which protects them and prevents plate failure.

[0009] It is advantageous if the channel is present multiple times, as this allows the flow cross-section to be easily increased and improves the response of the first sealing lips.

[0010] It is advantageous if the channel is formed in the first sealing lips, as this ensures that the sealing carrier remains unweakened as the backbone of the sealing arrangement, while improving the elasticity of the first sealing lips, which promotes contact with the bipolar plates.

[0011] To ensure that the channels can be flowed through unimpeded, the free ends of the first sealing lips are spaced away from the sealing cushion.

[0012] According to a further embodiment, the seal carrier can thicken between the first sealing lips, from their first lip base toward the sealing cushion. The load-bearing capacity of the seal carrier is thus increased, which also facilitates the possibility of forming the channels in the seal carrier. The seal carrier can thicken to the thickness of the sealing cushion, thus providing a smooth transition with increased load-bearing capacity.

[0013] It is further preferred if, on the side of the first sealing lips facing away from the membrane electrode assembly, second sealing lips are formed at a distance therefrom on each side of the seal carrier of the seal assembly, the free ends of which point away from the first sealing lips and are thickened with a thickening relative to a second lip base on the seal carrier and have a thickness corresponding to the spacing of the bipolar plates, and that, on the side of the second sealing lips facing the seal carrier, at least one channel is formed in the second sealing lips and / or the seal carrier, at least in the region of the thickening. The advantages associated with the first sealing lips can thus also be used for sealing the ports for the reaction media.

[0014] A gap can be provided between the first sealing lips and the second sealing lips, whereby support elements can be formed on the two bipolar plates that project into this gap and thereby improve the stability and interaction of the sealing arrangement with the bipolar plates.

[0015] The aforementioned advantages and effects also apply to a fuel cell stack with a plurality of fuel cells of the aforementioned type or to a fuel cell vehicle with a fuel cell device comprising such a fuel cell stack.

[0016] The features and feature combinations mentioned above in the description, as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figure, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also considered to be encompassed and disclosed by the invention that are not explicitly shown or explained in the figure, but which emerge and can be produced through separate feature combinations from the explained embodiments.

[0017] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the drawings. Herein: Fig. 1 a schematic exploded view of a fuel cell in a longitudinal section, Fig. 2 an isolated representation of the sealing arrangement from Fig. 1, Fig. 3 an enlarged view without the sealing cushion of the sealing arrangement from Fig. 2, Fig. 4 a schematic representation of a fuel cell in a longitudinal section showing the deformation of the seal at 40 percent compression and ambient pressure as internal pressure, Fig. 5 one of the Fig. 4 corresponding representation at 40 percent compression and increased internal pressure, Fig. 6 a schematic representation of a fuel cell in a longitudinal section showing the sealing pressure of the seal at 40 percent compression and ambient pressure as the internal pressure, Fig. 7 one of the Fig. 6 corresponding representation at 40 percent compression and increased internal pressure, Fig. 8 one of the Fig. 1 corresponding representation of an alternative embodiment, Fig. 9 an isolated, perspective view of the sealing arrangement made of Fig. 8, Fig. 10 another illustration of the sealing arrangement Fig. 8, Fig. 11 a schematic representation of a fuel cell in a longitudinal section with a representation of the deformation of the sealing arrangement according to Fig. 8 at 40 percent compression and ambient pressure as internal pressure, Fig. 12 one of the Fig. 11 corresponding representation at 40 percent compression and increased internal pressure, Fig. 13 a schematic representation of a fuel cell in a longitudinal section with a representation of the sealing pressure of the sealing arrangement made of Fig. 8 at 40 percent compression and ambient pressure as internal pressure, Fig. 14 one of the Fig. 13 corresponding representation at 40 percent compression and increased internal pressure, and Fig. 15 one of the Fig. 1. Corresponding representation of another alternative embodiment.

[0018] A fuel cell system comprises, as its core component, a fuel cell stack comprising a plurality of bipolar plates 1 with sealing assemblies 2 and membrane electrode assemblies 3 stacked alternately in the stacking direction. Each membrane electrode assembly 3 and two adjacent half-sides of a bipolar plate 1 form a fuel cell 4 (single cell). Typically, several hundred fuel cells 4 are combined to form a fuel cell stack and electrically connected in series.

[0019] To supply the fuel cell stack with the operating media, a fuel cell device has, on the one hand, an anode supply and, on the other hand, a cathode supply. The anode supply comprises an anode supply path, which serves to supply an anode operating medium (the fuel), for example, hydrogen, to the anode compartments of the fuel cell stack. For this purpose, the anode supply path connects a fuel reservoir to an anode inlet of the fuel cell stack. The anode supply further comprises an anode exhaust gas path, which removes the anode exhaust gas from the anode compartments via an anode outlet of the fuel cell stack. The cathode supply comprises a cathode supply path, which supplies the cathode compartments of the fuel cell stack with an oxygen-containing cathode operating medium, in particular air drawn in from the environment.The cathode supply system also includes a cathode exhaust path, which removes the cathode exhaust gas (especially the exhaust air) from the cathode compartments of the fuel cell stack and, if necessary, feeds it into an exhaust system. A compressor is arranged in the cathode supply path to pump and compress the cathode operating fluid. Such a fuel cell device can be used, for example, to power a traction motor in a fuel cell vehicle.

[0020] Fig. Figure 1 shows a fuel cell 4 with a membrane electrode assembly 3, which is enclosed on both sides by a bipolar plate 1. Each bipolar plate 1 has two main sides, each with a flow field consisting of a plurality of flow channels. The flow fields serve to supply and distribute a reactant medium to the catalytic electrodes (anode and cathode, respectively) of the adjacent membrane electrode assembly 3. An anode operating medium is supplied to the anode of the membrane electrode assembly 3 via a flow field located on the anode side of the bipolar plate 1, and a cathode operating medium is supplied to the cathode of the membrane electrode assembly 3 via a flow field located on the anode side of the bipolar plate 1. The bipolar plate 1 also has two non-active supply areas adjacent to the flow field on both sides, in which various supply openings are arranged as ports.Typically, at least one supply port and one supply port for each reactant medium are provided. Furthermore, a coolant field is often formed inside the bipolar plate 1, through which a coolant can be routed to dissipate the heat of the fuel cell reaction. In this case, the bipolar plate 1 also has one supply port and one outlet for the coolant.

[0021] If the conventional bipolar plates 1 and membrane electrode assemblies 3 are stacked on top of each other, the supply openings and recesses form supply channels that penetrate the fuel cell stack in its stacking direction.

[0022] The Fig. Figure 1 indicates that the fuel cell 4 comprises a membrane electrode assembly 3 with a bipolar plate 1 arranged on each side of the membrane electrode assembly 3 and a sealing assembly 2 having a sealing pad 5 adjacent to the membrane electrode assembly 3, wherein first sealing lips 7 are formed on each side of a sealing carrier 6 of the sealing assembly 2 at a distance from the sealing pad 5 on the side facing away from the membrane electrode assembly 3. The free ends 8 of the first sealing lips 7 are provided with a thickening 10 opposite a first lip base 9 on the sealing carrier 6. The free ends 8 have a thickness corresponding to the distance between the bipolar plates 1, so that, as shown in Figure 1, the sealing pad 5 is formed on each side of a sealing carrier 6 of the sealing assembly 2. Fig. As can be seen in Figure 4, the sealing arrangement 2 in this area rests flat against the bipolar plates 1. On the side of the first sealing lips 7 facing the sealing carrier 6, at least one channel 11 is formed in the first sealing lips 7 and / or the sealing carrier 6, at least in the area of ​​the thickening 10, wherein in the Fig. In the embodiment shown in 1 to 3, the channel 11 is present multiple times and is assigned to the first sealing lips 7.

[0023] The free ends 8 of the first sealing lips 7 are spaced away from the sealing cushion 5 to ensure free access to the channels 11.

[0024] The Fig. Figure 4 shows the deformation of the sealing arrangement 2 when ambient pressure is present in the reaction chambers. Fig. Figure 5 shows the change in deformation at an increased pressure in the reaction chambers, which also acts on the first sealing lips 7, so that pressure equalization can take place through the channels 11, which leads to an improved sealing effect, since the first sealing lips 7 are "inflated" and rest against the bipolar plates 1 with increased pressure. The effective sealing pressure in megapascals is shown in the Fig. 6 and Fig. 7 shown.

[0025] The Fig. Figure 8 indicates that the seal carrier 6 can be thickened between the first sealing lips 7 from their first lip base 9 toward the sealing cushion 5, whereby the channels 11 can then also be formed in the seal carrier 6. The seal carrier 6 thickens to the thickness of the sealing cushion 5.

[0026] The Fig. Figure 15 shows an embodiment in which, on the side of the first sealing lips 7 facing away from the membrane electrode assembly 3, second sealing lips 12 are formed at a distance from the first sealing lips 7 on each side of the sealing carrier 6 of the sealing assembly 2. The free ends 8 of these second sealing lips 12 point away from the first sealing lips 7 and are thickened with a thickening 10 opposite a second lip base 13 on the sealing carrier 6. The thickness of the free ends 8 corresponds to the distance between the bipolar plates 1. On the side of the second sealing lips 12 facing the sealing carrier 6, at least one channel 11 is formed in the second sealing lips 12 and / or the sealing carrier 6, at least in the region of the thickening. This design of the sealing assembly 2 also improves the sealing effect with respect to the ports.

[0027] There is a gap 15 between the first sealing lips 7 and the second sealing lips 12, with support elements 14 being formed on the two bipolar plates 1, which project into this gap 15 ( Fig. 15). REFERENCE MARK LIST: 1 Bipolar plate 2 Sealing arrangement 3 Membrane electrode arrangement 4 Fuel cell 5 sealing cushions 6 sealing carriers 7 first sealing lip 8 free end 9 first lip base 10 Thickening Channel 11 12 second sealing lip 13 second lip base 14 Support element 15 Distance between sealing lips

Claims

[1] Fuel cell (4) with a membrane electrode assembly (3), with a bipolar plate (1) arranged on each side of the membrane electrode assembly (3) and with a sealing assembly (2) which has a sealing cushion (5) adjacent to the membrane electrode assembly (3), characterized by that on the side of the sealing pad (5) facing away from the membrane electrode arrangement (3), first sealing lips (7) are formed at a distance therefrom on each side of a seal carrier (6) of the sealing arrangement (2), the free ends (8) of which are provided with a thickened portion (10) opposite a first lip base (9) on the seal carrier (6) and have a thickness which corresponds to the distance between the bipolar plates (1), and that on the side of the first sealing lips (7) facing the seal carrier (6), at least one channel (11) is formed in the first sealing lips (7) and / or the seal carrier (6), at least in the region of the thickened portion (10). [2] Fuel cell (4) according to claim 1, characterized by that the channel (11) is present multiple times. [3] Fuel cell (4) according to claim 1 or 2, characterized by that the channel (11) is formed in the first sealing lips (7). [4] Fuel cell (4) according to one of claims 1 to 3, characterized by that the free ends (8) of the first sealing lips (7) are at a distance from the sealing cushion (5). [5] Fuel cell (4) according to one of claims 1 to 4, characterized by that the seal carrier (6) between the first seal lips (7) thickens from their first lip base (9) in the direction of the seal cushion (5). [6] Fuel cell (4) according to claim 5, characterized by that the seal carrier (6) thickens to the thickness of the seal cushion (5). [7] Fuel cell (4) according to one of claims 1 to 6, characterized bythat on the side of the first sealing lips (7) facing away from the membrane electrode arrangement (3), second sealing lips (12) are formed at a distance therefrom on each side of the seal carrier (6) of the seal arrangement (2), the free ends (8) of which second sealing lips point away from the first sealing lips (7) and are thickened with a thickening (10) opposite a second lip base (13) on the seal carrier (6) and have a thickness which corresponds to the distance between the bipolar plates (1), and that on the side of the second sealing lips (12) facing the seal carrier (6), at least one channel (11) is formed in the second sealing lips (12) and / or the seal carrier (6), at least in the region of the thickening (10). [8] Fuel cell (4) according to claim 7, characterized bythat a distance (15) is provided between the first sealing lips (7) and the second sealing lips (12), and that support elements (14) are formed on the two bipolar plates (1) and project into this distance (15). [9] Fuel cell stack comprising a plurality of fuel cells (4) according to one of claims 1 to 8. [10] A fuel cell vehicle comprising a fuel cell device having a fuel cell stack according to claim 9.

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