Electrochemical cell and cell stack

Abstract

The invention relates to an electrochemical cell (1), in particular a fuel cell or an electrolysis cell, having a membrane (2) with an active surface and an edge region enclosing the active surface, wherein a gas and / or liquid transporting layer (3) lies against both sides of the active surface of the membrane (2) and the edge region is enclosed at least along one side of the active surface by a frame structure (4) adjacent to the gas and / or liquid transporting layers (3), and wherein at least one elongated opening serving as a media channel (5) is formed in the frame structure (4) and is divided by at least one crosspiece (6) into multiple individual openings (5.1, 5.2,… 5.n). According to the invention, the frame structure (4) has a depression (7), which extends over the entire length (L) of the media channel (5) and connects the individual openings (5.1, 5.2,… 5.n) to one another and also to the adjacent gas and / or liquid transporting layer (3). It is alternatively proposed that the frame structure (4) has connecting channels (8), which respectively extend from an individual opening (5.1, 5.2,… 5.n) to the adjacent gas and / or liquid transporting layer (3) in a fan-like arrangement. The invention also relates to a cell stack, in particular a fuel-cell stack or an electrolysis-cell stack, with at least one electrochemical cell (1) according to the invention.

Description

[0001] Description

[0002] Title:

[0003] Electrochemical cell, cell stack

[0004] The invention relates to an electrochemical cell, in particular a fuel cell or an electrolysis cell. In practice, a plurality of electrochemical cells are connected to form a cell stack, in particular a fuel cell stack or an electrolysis cell stack. The invention therefore further relates to a cell stack comprising at least one electrochemical cell according to the invention.

[0005] The preferred application of the invention is fuel cell stacks and / or electrolyzers. The electrolyzer can be, in particular, a PEM or AEM electrolyzer for producing hydrogen or a CCh electrolyzer.

[0006] State of the art

[0007] Electrochemical cells have a multi-layered structure. The central layer forms a membrane, which is usually coated on both sides with a catalytically active material to form an anode and a cathode. This membrane is often referred to as a membrane-electrode assembly (MEA). On both the anode and cathode sides, a gas and / or liquid transport layer is attached to the membrane, through which the respective reaction medium is supplied to the membrane. The membrane is closed off by bipolar plates arranged on both sides. These are often embossed metal sheets, particularly in fuel cells. These form flow channels running parallel to the cell plane, which serve to connect the respective gas and / or liquid transport layer to at least one supply and / or disposal channel running perpendicular to the cell plane.A gas and / or liquid transport layer is supplied with the respective reaction medium via a supply channel. The respective reaction medium and / or a reaction product is / are removed via a disposal channel.

[0008] The supply and disposal channels are formed by openings in the bipolar plates, which are arranged in opposite edge regions of the cell and thus outside an active area of ​​the membrane. The active area is the area in which the electrochemical reaction takes place. The efficiency of the cell therefore depends - among other things - on the size of the active area. In a cell stack with several electrochemical cells, the openings in the bipolar plates lie one above the other, forming channels that run through the cell stack. The channels are sealed off from the outside by at least one intermediate seal and by bracing the cells together. The seal can be formed by the membrane itself, which for this purpose is extended to the edge regions of the bipolar plates and provided with corresponding openings.However, the seal is often formed by a separate frame structure, also called a "gasket," which encloses the edge areas of the membrane, leaving the active surface exposed, and is arranged between the bipolar plates. In this case, the frame structure is provided with corresponding openings to form the supply and discharge channels. The gas and / or liquid transport layer is arranged within the frame structure, specifically on the active surface of the membrane.

[0009] For optimal connection of the active surface of a cell membrane to a supply or disposal channel formed in a frame structure, the frame structure preferably has an elongated opening that extends over the entire length of the active surface. In cell stacks with a particularly large base area, crossbars can be inserted for stabilization, which divide the elongated opening into several openings. Connecting channels in the form of grooves formed in the frame structure then lead from each opening to the gas and / or liquid transport layer arranged on the active surface. The disadvantage of this design of the frame structure is that there is no connection between the openings and the transport layer in the area of ​​the crossbars. The connection therefore needs to be improved.

[0010] The present invention is concerned with this problem.

[0011] To this end, the electrochemical cell having the features of claim 1 is proposed. Preferred developments of the invention are set forth in the subclaims. Furthermore, a cell stack comprising at least one electrochemical cell according to the invention is specified.

[0012] Disclosure of the invention

[0013] The proposed electrochemical cell, in particular a fuel cell or electrolysis cell, comprises a membrane with an active surface and an edge region enclosing the active surface, wherein a gas and / or liquid transport layer rests on both sides of the active surface of the membrane and the edge region is enclosed, at least along one side of the active surface, by a frame structure adjacent to the gas and / or liquid transport layers. At least one elongated opening serving as a media channel is formed in the frame structure, which opening is divided into several individual openings by at least one transverse web. According to the invention, the frame structure has a depression that extends over the entire length of the media channel and connects the individual openings to one another and to the adjacent gas and / or liquid transport layer.Alternatively, it is proposed that the frame structure has connecting channels which extend in a fan-shaped arrangement from an individual opening to the adjacent gas and / or liquid transport layer.

[0014] Using the lowered frame structure proposed in the first alternative, the adjacent gas and / or liquid transport layer can be connected to the individual openings along its entire length. The interconnection of the individual openings achieved by the lowered frame structure ensures a uniform distribution of the respective reaction medium, provided the media channel is a supply channel. If the media channel serves as a disposal channel, the reaction medium and / or a reaction product formed in the cell during the electrochemical reaction can be fed to the individual openings via the lowered frame.

[0015] The connecting channels of the frame structure proposed according to the second alternative also allow the adjacent gas and / or liquid transport layer to be connected to the individual openings along its entire length, since the connecting channels run not parallel but diagonally to each other, resulting in a fan-shaped arrangement. The fan-shaped arrangement allows the connecting channels of the individual openings separated by the crossbar to be merged in the area of ​​the at least one transverse web, so that this area of ​​the adjacent gas and / or liquid transport layer is also supplied with the respective reaction medium or the reaction medium / reaction product is removed from this area.

[0016] Preferably, the connecting channels are each arranged at a distance a1 in the region of an individual opening and at a distance a2 in the region of the adjacent gas and / or liquid transport layer, wherein the distance a1 is smaller than the distance a2. This results in the fan-shaped arrangement of the connecting channels. In the region of the individual openings, the connecting channels are therefore closer together and then diverge in a fan shape towards the gas and / or liquid transport layer. If the number of connecting channels leading from an individual opening is irregular, the connecting channel arranged centrally with respect to the individual opening runs essentially perpendicular to the adjacent gas and / or liquid transport layer.The additional connecting channels arranged to the sides already run at an angle to this, with the angle between one of these connecting channels and the centrally located connecting channel increasing with increasing distance from the centrally located connecting channel. If the number of connecting channels leading from a single opening is even, the two centrally located connecting channels can still run parallel to each other.

[0017] The angles or distances between the connecting channels are preferably selected such that, in the area of ​​the adjacent gas and / or liquid transport layer, all distances a2 between the connecting channels are equal. This means that the distance between the two connecting channels converging in the area of ​​the at least one transverse web is also equal to the distance a2.

[0018] Furthermore, it is proposed that the connecting channels all be of equal length. This applies in particular if the media channel serves to supply the gas and / or liquid transport layer with a reaction medium, since the equal length of the connecting channels ensures a uniform distribution of the reaction medium. To ensure that all connecting channels are of equal length, the individual openings on the connecting channel side can have a convex boundary wall, so that the individual openings are narrower in the center than in the area of ​​the at least one transverse web. This measure is particularly easy to implement.

[0019] In a further development of the invention, it is proposed that at least one additional connecting channel be formed in the frame structure in the region of the at least one transverse web to interconnect the individual openings. The interconnection of the individual openings enables pressure equalization.

[0020] The same effect can be achieved - even without an additional connecting channel in the crossbar - by lowering the frame structure over the entire length of the media channel according to the proposed first alternative.

[0021] Since the gas and / or liquid transport layer is optimally connected to the individual openings of the media channel via the depression or the connecting channels of the frame structure, the at least one crossbar can be made wider if necessary, for example in order to clamp the electrochemical cell to other cells of a cell stack in the area of ​​the at least one crossbar. For this purpose, an opening for receiving a clamping device, for example a clamping bolt, can be formed in the frame structure in the area of ​​the at least one crossbar. This opening is then preferably circular. By arranging the opening in the area of ​​the at least one crossbar, the frame structure can be made narrower, thereby reducing the external dimensions of the electrochemical cell without having to reduce the active area.

[0022] It is further proposed that a bipolar plate forming flow channels be applied to the frame structure and the adjacent gas and / or liquid transport layer. The flow channels of the bipolar plate serve to distribute the reaction medium over the surface. Preferably, each flow channel is connected to a connecting channel in the frame structure. This ensures that the reaction medium is evenly distributed among the flow channels.

[0023] Furthermore, a cell stack is proposed, in particular a fuel cell stack or an electrolysis cell stack, comprising at least one electrochemical cell according to the invention. Preferably, several electrochemical cells according to the invention arranged one above the other form the cell stack. The advantages of the electrochemical cell according to the invention contribute to an increase in the efficiency of the cell stack. Furthermore, depending on the position of the clamping means for clamping the cells, the dimensions of the cell stack can be reduced without compromising performance.

[0024] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show:

[0025] Fig. 1 is a schematic longitudinal section through an electrochemical cell according to the invention,

[0026] Fig. 2 is a plan view of a frame structure and a gas and / or liquid transport layer of an electrochemical cell according to the invention,

[0027] Fig.3 shows an enlarged section of Figure 2 in the area of ​​two individual openings of the frame structure separated by a crossbar,

[0028] Fig. 4 is a plan view of a second frame structure for an electrochemical cell according to the invention in the region of two individual openings separated by a crossbar,

[0029] Fig. 5 is a plan view of a third frame structure for an electrochemical cell according to the invention in the region of two individual openings separated by a crossbar,

[0030] Fig. 6 is a plan view of a fourth frame structure for an electrochemical cell according to the invention,

[0031] Fig. 7 is an enlarged section of Fig. 6 in the region of an individual opening and Fig. 8 is a plan view of a fifth frame structure for an electrochemical cell according to the invention.

[0032] Detailed description of the drawings

[0033] Figure 1 shows an electrochemical cell 1 according to the invention, which has a membrane 2 arranged between two gas and / or liquid transport layers. In an edge region, the membrane 2 is enclosed by a frame structure 4, which extends up to the gas and / or liquid transport layers 3. Bipolar plates 13 are located on both sides of this frame structure and the gas and / or liquid transport layers 3.

[0034] As can be seen in particular from Figure 2, the frame structure 4 forms a circumferential frame while leaving an active area of ​​the membrane 2 free. In Figure 2, the active area is covered by the gas and / or liquid transport layer 3. Along each of the two long sides, a media channel 5 is formed in the frame structure 4, which is divided into a plurality of individual openings 5.1, 5.2, etc. by transverse webs 6. The two media channels 5 each have a length L that corresponds to the length of the gas and / or liquid transport layer 3. Further out, the frame structure 4 has circular openings 11 that serve to accommodate clamping bolts (not shown).

[0035] In order to improve the connection of the gas and / or liquid transport layer 3 to the individual openings 5.1, 5.2, etc., particularly in the area of ​​the transverse webs 6, the frame structure 4 has a depression 7 extending over the entire length L of the media channel 5 and reaching as far as the gas and / or liquid transport layer 3 (see Figure 1). The reaction medium can be optimally distributed via the depression 7, so that the gas and / or liquid transport layer 3 is evenly supplied with the reaction medium. Flow channels 12 formed in the bipolar plate 13, which are also connected to the depression 7 (see Figure 1), contribute to the reaction medium being distributed over the surface. Since the depression 7 extends over the entire length L of the media channel 5, all individual openings 5.1, 5.2, etc. are also connected to one another via the depression 7. This allows pressure equalization so that in all individual openings 5.1, 5.2 etc.the same pressure prevails.

[0036] In Figure 3, the frame structure 4 with two individual openings 5.1, 5.2 and the depression 7 is shown again as an enlarged section.

[0037] An alternative embodiment, in which the depression 7 is replaced by several connecting channels 8, is shown in Figure 4. To achieve a uniform distribution of the reaction medium, the connecting channels have a fan-shaped arrangement. This means that the connecting channels 8 are arranged at a distance a1 in the area of ​​the individual openings 5.1, 5.2 and at a distance a2 in the area of ​​the gas and / or liquid transport layer 3, where a1 is smaller than a2. The connecting channels thus diverge or converge again in the area of ​​a transverse web 6.

[0038] As shown by way of example in Figure 5, the transverse webs 6 can be made wider, so that the openings 11 for the clamping bolts can be arranged in the area of ​​the transverse webs 6. The frame structure 4 can accordingly be made narrower, thus reducing the external dimensions of the electrochemical cell 1.

[0039] Alternatively, as shown by way of example in Figure 6, the transverse webs 6 can also have additional connecting channels 10, which interconnect the individual openings 5.1, 5.2, etc. Pressure equalization can then be achieved through these channels.

[0040] From Figure 6, in particular the enlarged section of Figure 7, it can be seen that the individual openings 5.1, 5.2, etc., can have a convexly curved boundary wall 9, so that the individual openings 5.1, 5.2, etc., each have a smaller width in their center than at the transverse webs 6. This measure ensures that all connecting channels 8 are of equal length. Figure 7 shows a radius R that describes a circular arc along which the boundary wall 9 runs.

[0041] Figure 8 shows a frame structure 4 designed analogously to Figures 6 and 7. Each connecting channel 8 is also connected to a flow channel 12 of the bipolar plate 13 adjacent to the frame structure 4. The flow channels 12 are shown in dashed lines in Figure 8 because they lie outside the plane of the sheet. The connection to the flow channels 12 ensures a uniform distribution of the reaction medium across the surface.

Claims

Claims 1. An electrochemical cell (1), in particular a fuel cell or electrolysis cell, comprising a membrane (2) with an active surface and an edge region enclosing the active surface, wherein a gas and / or liquid transport layer (3) is in contact with the active surface of the membrane (2) on both sides, and the edge region is enclosed at least along one side of the active surface by a frame structure (4) adjoining the gas and / or liquid transport layers (3), and wherein at least one elongated opening serving as a media channel (5) is formed in the frame structure (4), which opening is divided into a plurality of individual openings (5.1, 5.2, ...5.n) by at least one transverse web (6), characterized in that the frame structure (4) (a) has a depression (7) which extends over the entire length (L) of the media channel (5) and connects the individual openings (5.1, 5.2, ...5.n) to each other and to the adjacent gas and / or liquid transport layer (3), or (b) has connecting channels (8) which extend in a fan-shaped arrangement from an individual opening (5.1, 5.2, ...5.n) to the adjacent gas and / or liquid transport layer (3).

2. Electrochemical cell (1) according to claim 1, characterized in that the connecting channels (8) are each arranged in the region of an individual opening (5.1, 5.2, ...5.n) at a distance (a1) from one another and in the region of the adjacent gas and / or liquid transport layer (3) at a distance (a2) from one another, wherein the distance (a1) is smaller than the distance (a2).

3. Electrochemical cell (1) according to claim 2, characterized in that in the region of the adjacent gas and / or liquid transport layer (3) all distances (a2) between the connecting channels (8) are equal.

4. Electrochemical cell (1) according to one of the preceding claims, characterized in that the connecting channels (8) are all of the same length.

5. Electrochemical cell (1) according to one of the preceding claims, characterized in that the individual openings (5.1, 5.2, ...5.n) have a convex-shaped boundary wall (9) on the side of the connecting channels (8), so that the individual openings (5.1, 5.2, ...5.n) are less wide in the middle than in the region of the at least one transverse web (6).

6. Electrochemical cell (1) according to one of the preceding claims, characterized in that in the frame structure (4) in the region of the at least one transverse web (6) at least one further connecting channel (10) for connecting the individual openings (5.1, 5.2, ...5.n) to one another is formed.

7. Electrochemical cell (1) according to one of the preceding claims, characterized in that an opening (11) for receiving a clamping means, for example a clamping bolt, is formed in the frame structure (4) in the region of the at least one transverse web (6).

8. Electrochemical cell (1) according to one of the preceding claims, characterized in that a bipolar plate (13) forming flow channels (12) is located on the frame structure (4) and the adjacent gas and / or liquid transport layer (3), wherein preferably each flow channel (12) is connected to a connecting channel (8) of the frame structure (4).

9. Cell stack, in particular fuel cell stack or electrolysis cell stack, with at least one electrochemical cell (1) according to one of the preceding claims.

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