Fuel cell comprising at least one stack of bipolar plates having complementary shapes that limit transverse movements

Abstract

Fuel cell comprising at least one stack of bipolar plates having complementary shapes limiting transverse movements. The invention relates to a fuel cell comprising a stack of bipolar plates (22) and electrolytes positioned alternately in transverse planes and compressed against each other, at least the first and second bipolar plates (22) of the stack having complementary shapes that cooperate with each other such that the first and second bipolar plates (22) are immobilized relative to each other in a transverse plane. This simple and inexpensive solution keeps the bipolar plates (22) immobile, which helps maintain optimal fuel cell performance. Figure 3

Description

Title of the invention: Fuel cell comprising at least one stack of bipolar plates having complementary shapes limiting transverse movements

[0001] The present application relates to a fuel cell comprising at least one stack of bipolar plates having complementary shapes limiting transverse movements.

[0002] According to an embodiment shown in [Fig. 1], a fuel cell 10 comprises a stack of bipolar plates 12 and polymer membranes positioned alternately. These bipolar plates 12 are substantially flat and positioned in transverse planes. Because they are flat, they are relatively simple and inexpensive to manufacture. In addition to the stack, the fuel cell 10 includes a compression system configured to compress the bipolar plates 12 by applying forces directed along a longitudinal direction (perpendicular to the transverse planes), in the opposite direction and in the direction of the stack.

[0003] The bipolar plates 12 and the polymer membranes must remain perfectly still in order for the fuel cell 10 to maintain optimal performance.

[0004] During operation, due to shocks, accelerations, decelerations, or vibrations, the bipolar plates 12 can translate relative to each other in a transverse direction, as illustrated in [Fig. 1]. Such deformation of the fuel cell 10 leads to a significant reduction in its performance.

[0005] According to an embodiment visible in [Fig.2], to prevent the bipolar plates 12 from sliding relative to each other in transverse directions, the fuel cell 10 includes four guide systems 14.1, 14.2 in contact with the four edges 12.1, 12.2 of each bipolar plate 12.

[0006] Although this solution keeps the bipolar plates 12 stationary relative to each other, it is not entirely satisfactory because the guidance systems 14.1, 14.2 in contact with the bipolar plates 12 can damage them and cause short circuits. Furthermore, the presence of guidance systems 14.1, 14.2 increases the mass and production costs of the fuel cell 10 and adds complexity to the design.

[0007] The present invention aims to remedy all or part of the drawbacks of the prior art.

[0008] To this end, the invention relates to a fuel cell comprising a stack of bipolar plates and electrolytes positioned in transverse planes and in an alternating manner, and a compression system configured to compress the bipolar plates and electrolytes against each other in a longitudinal direction perpendicular to the transverse planes, each bipolar plate having first and second faces and at least one edge connecting the first and second faces.

[0009] According to the invention, at least the first and second bipolar plates of the bipolar plate and electrolyte stack comprise complementary shapes which cooperate with each other so that the first and second bipolar plates are immobilized relative to each other in a transverse plane.

[0010] This solution makes it possible to obtain a robust fuel cell that maintains optimal performance and has an extended lifespan compared to prior art fuel cells. The bipolar plates are held stationary without the addition of any elements other than the plates, which means that the mass of the fuel cell is not increased and it is not made more complex.

[0011] According to another feature, all the bipolar plates of the stack comprise complementary shapes which cooperate with each other in such a way that all the bipolar plates are immobilized relative to each other in transverse planes.

[0012] According to another feature, each bipolar plate includes at least one deformation which generates a protruding shape on the first face and a recessed shape on the second face.

[0013] According to another feature, the deformation is adjacent to the edge of each bipolar plate.

[0014] According to another feature, each bipolar plate comprises a central flat part positioned in a transverse plane and a curved peripheral border which runs along the edge, forming a truncated pyramid or a truncated cone.

[0015] According to another characteristic, each deformation is distant from the edge of the bipolar plate.

[0016] According to another feature, each bipolar plate includes at least one indentation which generates a protruding shape on the first face and a recessed shape on the second face.

[0017] According to another feature, each bipolar plate is square or rectangular and has four angles as well as four recesses positioned near the angles.

[0018] According to another feature, each indentation comprises a central disc-shaped area, substantially flat and parallel to the first and second faces of the bipolar plate, as well as a frustoconical junction area connecting the central area to the rest of the bipolar plate.

[0019] According to another feature, the electrolytes positioned between the bipolar plates are made of a deformable material configured to allow the electrolytes to deform and adapt to the shapes of the bipolar plates when the stack is compressed.

[0020] According to another characteristic, the electrolytes, in an uncompressed state, have forms complementary to those of the bipolar plates.

[0021] Other features and advantages will become apparent from the following description of the invention, given by way of example only, with reference to the accompanying drawings, among which:

[0022] [Fig-1] is a schematic cross-section of a fuel cell illustrating a mode of realization of prior art,

[0023] [Fig.2] is a schematic cross-section of a fuel cell illustrating another mode of the realization of prior art,

[0024] [Fig.3] is a schematic cross-section of a fuel cell illustrating a mode of realization of the invention,

[0025] [Fig.4] is a cross-section of a bipolar plate of the fuel cell visible on the [Fig.3],

[0026] [Fig.5] is a front view of a bipolar plate of the fuel cell visible on the [Fig.3],

[0027] [Fig.6] is a schematic cross-section of a fuel cell illustrating another mode of the realization of the invention,

[0028] [Fig.7] is a side view of a bipolar plate of the fuel cell visible on the [Fig.6], and

[0029] [Fig.8] is a front view of a bipolar plate of the fuel cell visible on the [Fig.6].

[0030] As illustrated in Figures 3 and 6, a fuel cell 20 comprises a stack of bipolar plates 22 and electrolytes positioned alternately in transverse planes, and a compression system 24 configured to compress the bipolar plates 22 and the electrolytes against each other in a longitudinal direction perpendicular to the transverse planes by exerting forces directed along a longitudinal direction (perpendicular to the transverse planes), in opposite directions and in the direction of the stack. In one design, the electrolytes are polymer membranes.

[0031] With the exception of the bipolar plates 22, the other elements composing the fuel cell 20 are not further described as they may be identical to those of the prior art.

[0032] As illustrated in figures 4, 5, 7 and 8, each bipolar plate 22 comprises first and second faces 26.1, 26.2 as well as at least one edge 26.3 connecting the first and second faces 26.1, 26.2.

[0033] According to one configuration, the edge 26.3 of each bipolar plate 22 describes a square or a rectangle. Of course, the invention is not limited to these geometries for the contour C of the bipolar plates 22. By way of example, the contour C of each bipolar plate 22 could be circular.

[0034] All the bipolar plates 22 have the same contour C and are arranged so that the contours C of the bipolar plates 22 coincide.

[0035] According to a first embodiment visible in figures 3 to 5, each bipolar plate 22 comprises a peripheral border 28 which runs along the edge 26.3 and is curved so that each bipolar plate 22 forms a convex shape at the level of the first face 26.1 and a concave shape at the level of the second 26.2.

[0036] According to this first embodiment, each bipolar plate 22 comprises a central flat part 30 positioned in a transverse plane and a flared peripheral border 28, forming a truncated pyramid or a truncated cone.

[0037] According to this first embodiment illustrated in [Fig. 3], the bipolar plates 22 fit together. When the flat central portions 30 of the bipolar plates 22 are compressed by the compression system 24, the peripheral edges 28 prevent any translational movement of the bipolar plates 22 relative to each other in the transverse direction. To give an order of magnitude, the peripheral edge 28 has a width of between 3 and 10% of the length of one side of the bipolar plate 22 or of its diameter.

[0038] According to a second embodiment visible in figures 6 to 8, each bipolar plate 22 includes at least one recess 32 which generates a protruding shape 32.1 on the first face 26.1 and a recessed shape 32.2 on the second face 26.2.

[0039] According to this second embodiment, when the bipolar plates 22 are compressed by the compression system 24, the protruding shape 32.1 of each bipolar plate 22 fits into the hollow shape 32.2 of another bipolar plate 22, which makes it possible to keep the bipolar plates 22 immobile relative to each other in transverse planes and to prevent them from sliding between each other.

[0040] According to one configuration, in the case of square or rectangular bipolar plates 22 having four angles, each of them includes four recesses 32 positioned near the angles.

[0041] According to one design, each recess 32 comprises a central zone 34 substantially flat and parallel to the first and second faces 26.1, 26.2 of the bipolar plate 22 and a junction zone 36, connecting the central zone 34 to the rest of the bipolar plate 22, which has a flared shape from the central zone 34 towards the first face 26.1. According to one arrangement, the central zone 34 is a disk and the junction zone 36 is frustoconical.

[0042] According to this second embodiment illustrated in [Fig.6], when the bipolar plates 22 are compressed by the compression system 24, the protruding shape 32.1 of each indentation 32 of each bipolar plate 22 fits into the hollow shape 32.2 of the indentation 32 of another bipolar plate 22.

[0043] Of course, the invention is not limited to these two embodiments. Regardless of the embodiment, at least the first and second bipolar plates 22 of the stack of bipolar plates and electrolytes comprise complementary shapes which cooperate with each other so that the first and second bipolar plates 22 are immobilized relative to each other in a transverse plane, in particular when the bipolar plates 22 of the stack are compressed against each other.

[0044] This solution makes it possible to obtain a robust fuel cell 20, which maintains optimal performance and has an extended lifespan compared to prior art fuel cells. The bipolar plates 22 are held in position without the addition of any components, which means that the mass of the fuel cell 20 is not increased and it is not made more complex.

[0045] The fuel cell 20 obtained according to the invention can be used in environments where it is subjected to shocks, accelerations, decelerations or vibrations. Thus, it can be used in the field of transport and equip a vehicle such as an aircraft, for example.

[0046] According to a preferred embodiment, all the bipolar plates 22 of the stack comprise complementary shapes which cooperate with each other so that all the bipolar plates 22 are immobilized relative to each other in transverse planes.

[0047] According to one configuration, each bipolar plate 22 includes at least one deformation which generates a protruding shape on the first face 26.1 and a recessed shape on the second face 26.2.

[0048] The protruding shape corresponds to the flat central part 30 in the case of the first embodiment and to the central area 34 of a recess 32 in the case of the second embodiment. The deformation is adjacent to the edge 26.3 of the bipolar plate 22 in the case of the first embodiment and / or distant from the edge 26.3 of the bipolar plate 22 in the case of the second embodiment.

[0049] According to one operating method, the bipolar plates 22 are deformed by a deformation technique such as stamping for example.

[0050] According to some embodiments, the electrolytes positioned between the bipolar plates 22 are made of a deformable material configured to allow the electrolytes to deform and adapt to the shapes of the bipolar plates 22 when the stack is compressed. Alternatively, the electrolytes, in an uncompressed state, have shapes complementary to those of the bipolar plates 22. Thus, each electrolyte has at least one recessed shape configured to house a protruding shape of an adjacent bipolar plate 22 and / or at least one protruding shape configured to fit into a recessed shape of an adjacent bipolar plate 22.

Claims

Demands

1. Fuel cell comprising a stack of bipolar plates (22) and electrolytes positioned in transverse planes and alternately and a compression system (24) configured to compress the bipolar plates (22) and electrolytes against each other in a longitudinal direction perpendicular to the transverse planes, each bipolar plate (22) having first and second faces (26.1, 26.2) and at least one edge (26.3) which connects the first and second faces (26.1, 26.2); characterized in that at least the first and second bipolar plates (22) of the stack of bipolar plates and electrolytes comprise complementary shapes which cooperate with each other so that the first and second bipolar plates (22) are immobilized relative to each other in a transverse plane.

2. Fuel cell according to the preceding claim, characterized in that all the bipolar plates (22) of the stack comprise complementary shapes which cooperate with each other in such a way that all the bipolar plates (22) are immobilized relative to each other in transverse planes.

3. Fuel cell according to any one of the preceding claims, characterized in that each bipolar plate (22) comprises at least one deformation which generates a protruding shape on the first face (26.1) and a hollow shape on the second face (26.2).

4. Fuel cell according to the preceding claim, characterized in that the deformation is adjacent to the edge (26.3) of each bipolar plate (22).

5. Fuel cell according to the preceding claim, characterized in that each bipolar plate (22) comprises a flat central part (30) positioned in a transverse plane and a curved peripheral border (28) which runs along the edge (26.3), forming a truncated pyramid or a truncated cone.

6. Fuel cell according to claim 3, characterized in that each deformation is distant from the edge (26.3) of the bipolar plate (22).

7. Fuel cell according to the preceding claim, characterized in that each bipolar plate (22) includes at least one indentation (32) which generates a protruding shape (32.1) on the first face (26.1) as well as a recessed shape (32.2) on the second face (26.2).

8. Fuel cell according to the preceding claim, characterized in that each bipolar plate (22) is square or rectangular and has four corners as well as four indentations (32) positioned near the corners.

9. Fuel cell according to any one of claims 7 to 8, characterized in that each indentation (32) comprises a central zone (34), disc-shaped, substantially flat and parallel to the first and second faces (26.1, 26.2) of the bipolar plate (22) and a frustoconical junction zone (36) connecting the central zone (34) to the rest of the bipolar plate (22).

10. Fuel cell according to any one of the preceding claims, characterized in that the electrolytes positioned between the bipolar plates (22) are made of a deformable material configured to allow the electrolytes to deform and adapt to the shapes of the bipolar plates (22) when the stack is compressed.

11. Fuel cell according to any one of claims 1 to 9, characterized in that the electrolytes have, in an uncompressed state, forms complementary to those of the bipolar plates (22).

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