Fuel cell stack

Abstract

The invention relates to a fuel cell stack (100) having at least one fuel cell (101) with a membrane (CCM) for separating an anode side (A) of the fuel cell (101) from a cathode side (K) of the fuel cell (101), an anode side gas diffusion layer (GDLA), a cathode side gas diffusion layer (GDLK) and a bipolar plate (BPP) for separating the fuel cell (101) from an adjacent fuel cell (101) or housing. To this end, according to the invention, the membrane (CCM) protrudes in an edge region (R) outside an active face (AF) of the membrane (CCM) beyond the anode side gas diffusion layer (GDLA) and the cathode side gas diffusion layer (GDLK) and the membrane (CCM) has a centring dam (10) in the edge region (R) from the anode side (A) or the cathode side (K).

Description

Technical Field

[0001] The invention relates to a fuel cell stack and a corresponding method for producing a fuel cell stack. Background Art

[0002] Fuel cell stacks are generally known. In today's fuel cell stacks, it is often difficult to center the membrane so that the active surface of the membrane is fully oriented relative to the bipolar plate. Problems arise if the membrane is not aligned with the edge area of ​​the bipolar plate in the edge area of ​​the membrane and in the port area of ​​the fuel cell stack. The drop of the membrane and / or the sealing layer of the membrane in these edge areas can potentially lead to short circuits between the different potentials of successive bipolar plates. Due to the less rigid structure of the fuel cell stack, mechanical damage exacerbates this problem. However, if the membrane or the sealing layer of the membrane protrudes sufficiently beyond the edge area of ​​the bipolar plate, this problem can usually be avoided. However, due to the throttling of the medium flow, such a protrusion is not always desirable in the port area of ​​the fuel cell or in the area of ​​the fuel cell stack that is used to orient the membrane and bipolar plate when assembling the fuel cell stack. Summary of the Invention

[0003] According to a first aspect, the present invention provides a fuel cell stack. Furthermore, according to a second aspect, the present invention provides a method for manufacturing a fuel cell stack. Further advantages, features, and details of the present invention are apparent from the description and the accompanying drawings. Features and details described in conjunction with the fuel cell stack according to the present invention naturally also apply to features and details described in conjunction with the method according to the present invention, and vice versa, so that cross-references are always made to the disclosures of the various inventive aspects.

[0004] According to a first aspect, the present invention provides a fuel cell stack comprising at least one fuel cell, the fuel cell comprising a membrane for separating an anode side of the fuel cell from a cathode side of the fuel cell, an anode-side gas diffusion layer, a cathode-side gas diffusion layer, and a bipolar plate for separating the fuel cell from an adjacent fuel cell or a housing. To this end, the present invention provides that an edge region of the membrane, located outside the active surface of the membrane, protrudes beyond the anode-side gas diffusion layer and the cathode-side gas diffusion layer (at least in a direction perpendicular to the channels of the bipolar plate), and that the membrane has a centering dam in the edge region on the anode side or the cathode side.

[0005] In the sense of the present invention, a fuel cell stack can have one or more fuel cells, which can be stacked on top of one another in layers and clamped between two end plates.

[0006] The present invention is based on the concept of providing an optimized edge region of the membrane through a centering dam. This edge region enables improved alignment of the membrane and bipolar plates within the fuel cell stack, provides improved protection against electrical leakage, and ensures improved sealing of the fuel cell. The centering dam integrates a relatively rigid region into the edge region of the membrane. The centering dam advantageously serves to align the bipolar plates and the centering aids for the membrane relative to the bipolar plates. The protruding region of the membrane beyond the anode-side gas diffusion layer and / or cathode-side gas diffusion layer prevents electrical short circuits between successive bipolar plates of adjacent fuel cells and mechanical damage to the successive bipolar plates. Furthermore, the edge region of the membrane stabilizes the fuel cell against mechanical stresses in this region. This offers significant advantages when stacking the fuel cells into a fuel cell stack. The edge region of the membrane can be designed to align with the edge regions of the bipolar plates or protrude beyond them, as desired. This reduces electrical leakage. Improper membrane orientation is immediately visible at the edge region due to the protruding centering dam. In this way, errors in the centering of the membrane are reliably avoided. Furthermore, the structural rigidity of the membrane is increased by the centering dam during assembly of the fuel cell stack.

[0007] Furthermore, the present invention can be provided in a fuel cell stack in which the centering dam is secured to the membrane in a material-locking manner. This facilitates handling of the membrane with the centering dam secured thereto during assembly of the fuel cell stack. Furthermore, the material-locking connection provides a sealed connection between the membrane and the centering dam.

[0008] Furthermore, in fuel cell stacks, the centering dam can be sprayed, vulcanized, or embossed onto the diaphragm. This allows for flexible fixing of the centering dam to the diaphragm. Almost all plastics can be processed by injection molding. Vulcanization can convert thermoplastics, such as natural or synthetic rubber, into elastomeric plastics (rubbers). Embossing methods allow for the production of flexible geometries.

[0009] Furthermore, the invention can be provided in a fuel cell stack in which the membrane is provided with an elastic sealing layer (so-called subgasket) in the edge region, wherein the centering dam is fixed to the sealing layer in a material-locking manner. The centering dam can thus serve as a reinforcing seal.

[0010] Furthermore, the present invention can be implemented in a fuel cell stack by spraying, vulcanizing, or stamping the center dam onto the sealing layer. The advantages of these methods have been described above and are incorporated herein.

[0011] It is furthermore conceivable that the centring dam is produced by folding a sealing layer. The sealing layer can be provided as a thin, flat, elastic layer, for example an elastic layer made of a thermoplastic material. By folding such a layer, a rigid element with sealing properties can be provided. Such a centring dam can also be advantageous in that no additional material and / or tools are required for producing the centring dam.

[0012] Furthermore, the application can be provided in a fuel cell stack, the centring dam having a height which is less than the height of the coolant channel of the bipolar plate (or the height of the bipolar plate). In this way, manufacturing tolerances in the provision of the membrane, the gas diffusion layer and / or the bipolar plate can be compensated for, which can be a significant advantage when stacking the membranes and the bipolar plates.

[0013] Furthermore, the application can be provided in a fuel cell stack, the centring dam having a height which is 0.5 to 0.99, in particular 0.7 to 0.9, times the height of the coolant channel of the bipolar plate. In this way, manufacturing tolerances in the provision of the membrane, the gas diffusion layer and / or the bipolar plate can be compensated for in an improved manner.

[0014] Furthermore, the application can be provided in a fuel cell stack, the bipolar plate having a closed coolant channel in the edge region of the membrane. Advantageously, the closed coolant channel can be used to abut against the centring dam in order to centre the membrane in the fuel cell stack and in order to seal the at least one fuel cell.

[0015] Advantageously, the closed coolant channel can be produced by bending two plates of the bipolar plate in the same direction. Thus, a bent edge can be provided on the bipolar plate, which can be sealingly supported on the centring dam.

[0016] According to a further advantage, the closed coolant channel can be oriented at an angle of between 0° and 90°, in particular between 30° and 60°, preferably 45°, with respect to the membrane. In this way, a sealing support on the centring dam can be achieved in a simple manner.

[0017] Furthermore, the application can be provided in a fuel cell stack, the centring dam in the edge region of the membrane matching the geometry of the bipolar plate in order to centre the membrane in the fuel cell stack and in order to seal the at least one fuel cell. Thus, it can be achieved that the membrane is centred in the edge region by the abutment of the centring dam on the bevel (or the closed coolant channel) of the bipolar plate. Furthermore, it can be ensured that a closed and sealed region can be produced between the membrane and the bipolar plate on the edge region of the membrane.

[0018] Furthermore, the application can be provided in a fuel cell stack, the centring dam being configured in the shape of a trapezium.

[0019] Here, the base of the trapezoid advantageously rests on the diaphragm or the sealing layer of the diaphragm, thereby enabling a stable support of the dam on the diaphragm and also an improved support of the dam on the inclined surface of the bipolar plate (or on a closed coolant channel).

[0020] Furthermore, the present invention can be provided in a fuel cell stack in which the trapezoidal shape has side edges that are oriented parallel to and sealingly abut the closed coolant channels of the bipolar plates. This allows for improved sealing of the fuel cell and centering of the membrane relative to the bipolar plates.

[0021] Furthermore, according to a second aspect, the present invention can provide a method for manufacturing a fuel cell stack, wherein at least one fuel cell is provided, the fuel cell comprising a membrane for separating the anode side of the fuel cell from the cathode side of the fuel cell, an anode-side gas diffusion layer, a cathode-side gas diffusion layer, and a bipolar plate for separating the fuel cell from an adjacent fuel cell or a housing. To this end, according to the present invention, the membrane is positioned such that an edge region of the membrane, located outside the active surface of the membrane (at least in a direction perpendicular to the channels of the bipolar plate), protrudes beyond the anode-side gas diffusion layer and / or the cathode-side gas diffusion layer, and the membrane is provided with a centering dam in the edge region on the anode side or the cathode side. The method according to the present invention achieves the same advantages as described above in conjunction with the fuel cell stack according to the present invention. Reference is hereby made to these advantages in full. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention and its improved solutions and advantages are described in detail below with the help of the accompanying drawings. The accompanying drawings schematically show:

[0023] Figure 1 A schematic diagram of a known fuel cell stack, and

[0024] Figure 2 Schematic diagram of a fuel cell stack according to the present invention. DETAILED DESCRIPTION

[0025] Figure 1 It is used to illustrate the problem on which the present invention is based. Figure 1A known fuel cell stack 100 is shown. During assembly of this fuel cell stack 100, it may occur that the membrane CCM is not precisely aligned with the bipolar plates BPP. Problems can arise if the membrane CCM is not aligned with the edge regions of the bipolar plates BPP in the edge regions R of the membrane CCM and in the port region of the fuel cell stack 100. A difference in the height of the membrane CCM relative to the bipolar plates BPP in these edge regions R can lead to short circuits between successive bipolar plates BPP. Furthermore, a difference in the height of the membrane CCM relative to the bipolar plates BPP in the edge regions R can lead to mechanical damage to the membrane CCM and / or the bipolar plates BPP and / or instability of the fuel cell stack 100. However, this problem can generally be overcome if the membrane CCM protrudes sufficiently beyond the edge regions of the bipolar plates BPP. However, the protrusion of the membrane CCM beyond the edge region of the bipolar plate BPP may be disadvantageous in the port region of the fuel cell 101 or in the region of the fuel cell stack 100 used to orient the membrane CCM and the bipolar plate BPP when assembling the fuel cell stack 100 .

[0026] Figure 2 A fuel cell stack 100 according to the invention is shown, which has at least one fuel cell 101 or a plurality of fuel cells 101, wherein the fuel cell or each fuel cell 101 has a membrane CCM separating the anode side A from the cathode side K of the fuel cell 101, an anode side gas diffusion layer GDLA, a cathode side gas diffusion layer GDLK, and a bipolar plate BPP separating the fuel cell 101 from an adjacent fuel cell 101 or a casing (not shown).

[0027] Here, the present invention provides that the diaphragm CCM protrudes beyond the anode-side gas diffusion layer GDLA and the cathode-side gas diffusion layer GDLK in an edge region R located outside the active surface AF of the diaphragm CMM (at least in a direction perpendicular to the channels of the bipolar plate BPP), and the diaphragm CMM has a centering dam 10 in the edge region R on the anode side A or the cathode side K.

[0028] In this case, the closed coolant channels GK of the bipolar plates BPP of the adjacent fuel cells 101 lie on the cathode side K against the membrane CCM.

[0029] exist Figure 2 The centering dam 10 is shown only as an example on the anode side A of the fuel cell 101, wherein it is also possible to form the centering dam 10 on the cathode side K of the fuel cell 101. In the latter case, the bipolar plate BPP of the adjacent fuel cell 101 can be bent in the other direction in the edge region R of the membrane CCM and can abut against the membrane CCM of the adjacent fuel cell 101 on the anode side A of the fuel cell 101.

[0030] The membrane CCM can have two edge regions R on the left and right of the active surface AF. The edge regions R can be oriented parallel or substantially parallel to the coolant channels KK in the bipolar plate BPP.

[0031] The centering dam 10 can therefore be aligned parallel or substantially parallel to the coolant channel KK in the bipolar plate BPP. It is conceivable that the centering dam 10 can be designed in a bulge-like manner.

[0032] By means of the centering dam 10, an optimized edge area R of the diaphragm is provided, which enables improved centering of the diaphragm CMM and the bipolar plate BPP inside the fuel cell stack 100, provides improved leakage protection, and ensures improved sealing of the fuel cell stack 100 (at least in the direction perpendicular to the channel of the bipolar plate BPP).

[0033] The centering dam 10 provides a more rigid region at the edge region R of the diaphragm CMM. The centering dam 10 can thus be used to orient the bipolar plate BPP and to center the diaphragm CCM relative to the bipolar plate BPP. The protruding regions of the diaphragm CCM above the anode-side gas diffusion layer GDLA and the cathode-side gas diffusion layer GDLK can prevent electrical short circuits between successive bipolar plates BPP of adjacent fuel cells 101 and mechanical damage to the successive bipolar plates BPP. If desired, the edge region R of the diaphragm CCM can be designed to align with or protrude beyond the edge regions of the bipolar plates BPP.

[0034] The centering dam 10 can be fixed in a materially bonded manner on the membrane CMM or on a sealing layer SG of the membrane CCM, a so-called subgasket, for example by injection molding, vulcanization or embossing.

[0035] When it is desired to have a sealing layer SG in the entire edge region R of the membrane CCM, the centering dam 10 can be produced by folding the sealing layer SG. The sealing layer SG is usually a thin flat elastic layer that can be folded together or rolled up to form a rigid centering dam 10 with sealing properties.

[0036] As from Figure 2 As can be seen in the figure, the height of the centering dam 10 can be less than the height of the coolant channels KK of the bipolar plate BPP, or in other words, less than the height of the bipolar plate BPP. This makes it possible to compensate for manufacturing tolerances that may occur during the manufacture of the membrane CCM, gas diffusion layers GDLA, GDLK, and / or bipolar plate BPP.

[0037] So external Figure 2 As indicated in , the centering dam 10 can have a height that is 0.5 to 0.99, in particular 0.7 to 0.9 times the height of the coolant channels KK of the bipolar plate BPP.

[0038] As already mentioned above, the bipolar plate BPP according to the invention can have closed coolant channels GK in the edge region R of the membrane CCM. The closed coolant channels GK serve for improved support on the centering dam 10 .

[0039] like Figure 2 As shown, closed coolant channels GK can be formed by bending the two plates 1, 2 of the bipolar plate BPP in the same direction at an angle of between 0° and 90°, in particular between 30° and 60°, preferably 45°, relative to the membrane CMM.

[0040] Advantageously, the centering dam 10 in the edge region R of the diaphragm CCM can be adapted to the geometry of the bipolar plate BPP, in particular the geometry of the closed coolant channels GK of the bipolar plate BPP, in order to center the diaphragm CMM in the fuel cell stack 100 and seal the at least one fuel cell 101. Here, the diaphragm CMM can be centered in the edge region R by placing the centering dam 10 against the inclined surface of the closed coolant channel GK of the bipolar plate BPP. Furthermore, the centering dam 10 on the edge region R of the diaphragm CCM can create a closed and sealed region between the diaphragm CCM and the bipolar plate BPP.

[0041] Within the scope of the present invention, the centering dam 10 can be designed as a trapezoid and / or ridge. Advantageously, the base of the trapezoid rests against the diaphragm CMM or the sealing layer SG of the diaphragm CMM. The sides of the trapezoid resting against the inclined surface of the closed coolant channels GK of the bipolar plate BPP can be oriented parallel to the closed coolant channels GK of the bipolar plate BPP.

[0042] The above description of the drawings describes the present invention only within the scope of examples. Of course, the individual features of the embodiments can be freely combined with one another as long as it makes technical sense, without leaving the scope of the present invention.

Claims

1. A fuel cell stack comprising: at least one fuel cell having a membrane for separating an anode side of the fuel cell from a cathode side of the fuel cell, an anode-side gas diffusion layer, a cathode-side gas diffusion layer, and a bipolar plate for separating the fuel cell from an adjacent fuel cell or a housing, It is characterized in that The membrane protrudes beyond the anode-side gas diffusion layer and the cathode-side gas diffusion layer in an edge region outside the active surface of the membrane, and The diaphragm has a centering dam in the edge region on the anode side or the cathode side, wherein the bipolar plate has closed coolant channels in the edge region of the diaphragm, The closed coolant channel has an inclined surface, and the centering dam rests on the inclined surface.

2. The fuel cell stack according to claim 1, wherein: The centering dam is fixed to the diaphragm in a materially bonded manner.

3. The fuel cell stack according to claim 1, wherein: The centering dam is sprayed, vulcanized or embossed on the diaphragm.

4. The fuel cell stack according to any one of claims 1 to 3, characterized in that In the edge region, the membrane is provided with an elastic sealing layer, wherein the centering dam is fixed to the sealing layer in a materially bonded manner.

5. The fuel cell stack according to claim 4, characterized in that: The centering dam is sprayed, vulcanized or stamped on the sealing layer, or The centering dam is produced by folding the sealing layer.

6. The fuel cell stack according to any one of claims 1 to 3, characterized in that The centering dam has a height that is less than a height of the coolant channel of the bipolar plate.

7. The fuel cell stack according to any one of claims 1 to 3, characterized in that The centering dam has a height that is 0.5 to 0.99 times the height of the coolant channel of the bipolar plate.

8. The fuel cell stack according to any one of claims 1 to 3, characterized in that The closed coolant channels are produced by bending both plates of the bipolar plate in the same direction.

9. The fuel cell stack according to any one of claims 1 to 3, characterized in that: The closed coolant channel is oriented at an angle between 0° and 90° relative to the diaphragm.

10. The fuel cell stack according to any one of claims 1 to 3, characterized in that: The centering dam is adapted to the geometry of the bipolar plate in the edge region of the membrane in order to center the membrane in the fuel cell stack and to seal the at least one fuel cell.

11. The fuel cell stack according to any one of claims 1 to 3, characterized in that: The centering dam is configured in a trapezoidal shape.

12. The fuel cell stack according to claim 11, wherein: The trapezoid has sides that are oriented parallel to the closed coolant channels of the bipolar plates and rest sealingly against the closed coolant channels of the bipolar plates.

13. The fuel cell stack according to claim 7, wherein: The centering dam has a height that is 0.7 to 0.9 times the height of the coolant channel of the bipolar plate.

14. The fuel cell stack according to claim 9, wherein: The closed coolant channel is oriented at an angle of between 30° and 60° relative to the diaphragm.

15. The fuel cell stack according to claim 9, wherein: The closed coolant channel is oriented at an angle of 45° relative to the diaphragm.

16. The fuel cell stack according to claim 11, wherein: The base of the trapezoid rests on the membrane or on the sealing layer of the membrane.

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