Electrochemical cell

Abstract

The invention relates to an electrochemical cell (1), in particular a fuel cell or an electrolysis cell, comprising a membrane (2) which is arranged between two transport layers (3, 4) and, in at least one edge region (5), between two frame parts (6.1, 6.2) of a frame (6), wherein the two frame parts (6.1, 6.2) each abut, in an abutment region (7, 8), the transport layer (3, 4) arranged on the same side of the membrane (2), and the frame parts (6.1, 6.2) are of different widths, such that the abutment regions (7, 8) on both sides of the membrane (2) are offset with respect to one another. According to the invention, the wider frame part (6.2) and a bipolar plate (9) that bears against the outside of the wider frame part (6.2) together delimit a relief space (10) that is situated opposite the abutment region (7) arranged on the other side of the membrane (2).

Description

[0001] Description

[0002] Title:

[0003] Electrochemical cell

[0004] The invention relates to an electrochemical cell, in particular a fuel cell or an electrolysis cell.

[0005] In practice, a large number of electrochemical cells are combined to form a cell stack, in particular a fuel cell stack or an electrolysis cell stack. The preferred application area is therefore fuel cell stacks and / or electrolysis cell stacks. The electrolyzer can, in particular, be 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. A transport layer, through which the respective reaction medium is fed to the membrane, is attached to both the anode and cathode sides of the membrane. Typically, the membrane is enclosed in at least one edge region extending beyond the transport layers by a frame structure. This frame structure supports the membrane and can also function as a seal. The frame structure, which usually consists of two frame sections, is also called a gasket or subgasket.

[0008] During operation of an electrochemical cell, different pressures prevail on the anode and cathode sides. Typically, the pressure on the cathode side is higher than on the anode side. This leads to compressive loading of the membrane perpendicular to the membrane plane, causing the membrane on the side with the lower pressure, usually the anode side, to be pressed against the transport layer and the adjacent frame part. The edges of the transport layer and the frame part can thus cause damage to the membrane.

[0009] In addition, the membrane is subjected to compressive stress by the external bipolar plates, which are clamped together to seal the electrochemical cell from the outside. This tension acts particularly on the frame structure, forcing the two frame sections against the intermediate membrane.

[0010] The present invention aims to reduce the pressure load on the membrane in order to increase its robustness and service life. As a result, the service life of the electrochemical cell containing the membrane is to be increased.

[0011] To achieve this object, the electrochemical cell having the features of claim 1 is proposed. Advantageous developments of the invention can be found in the subclaims.

[0012] Disclosure of the invention

[0013] Proposed is an electrochemical cell, in particular a fuel cell or an electrolysis cell, comprising a membrane arranged between two transport layers and, in at least one edge region, between two frame parts of a frame. The two frame parts each abut in a butt region against the transport layer arranged on the same side of the membrane, wherein the frame parts are designed with different widths, so that the butt regions on both sides of the membrane are offset from one another. According to the invention, the wider frame part and a bipolar plate lying on the outside of the wider frame part jointly delimit a relief chamber arranged opposite the butt region arranged on the other side of the membrane.

[0014] The relief chamber formed on one side of the diaphragm serves to relieve the pressure on the diaphragm. In the area of ​​the relief chamber, the bipolar plate has no contact with the frame part underneath, so that no force can be transferred from the bipolar plate to the frame part in this area. The flow of force towards the diaphragm is thus interrupted by the relief chamber and the pressure on the diaphragm is relieved. Because the relief chamber is formed on the side with the wider frame part and is located opposite the joint area on the other side of the diaphragm, the pressure on the diaphragm is relieved in the joint area. This means that the diaphragm is not pressed against the joint area, or at least the pressure is pressed to a significantly lesser extent. This also reduces the risk of the diaphragm being damaged by the edges of the frame part and the transport layer that border the joint area.Consequently, the robustness and lifetime of the membrane as well as the lifetime of the electrochemical cell increase.

[0015] According to a first preferred embodiment of the invention, the relief space is formed by a recess in the frame part delimiting the relief space. This means that a recess is formed in the wider frame part on the side facing the bipolar plate. Alternatively or additionally, the relief space can be formed by a recess in the bipolar plate. In this case, the recess is arranged on the side of the bipolar plate facing the frame part.

[0016] The recess in the frame part and / or the bipolar plate for forming the relief chamber preferably has chamfered or rounded edges, so that no sharp edges are formed that could press into the adjacent component. This prevents damage to the adjacent component.

[0017] According to a further preferred embodiment of the invention, the relief space is formed by profiling the bipolar plate. Since a bipolar plate is often a stamped sheet, the profiling forming the relief space can be produced particularly easily by stamping during the manufacture of the bipolar plate.

[0018] Preferably, the relief chamber is arranged or formed substantially centrally and / or mirror-symmetrically with respect to the joint area arranged on the other side of the membrane. The central arrangement allows for compensation of small manufacturing and / or assembly tolerances, so that the relief chamber continues to be opposite the joint area on the other side of the membrane. The mirror-symmetrical design of the relief chamber simplifies its manufacture.

[0019] Furthermore, the relief space preferably has a width B that is at least as large as a thickness D of the membrane. In this way, a sufficiently large relief space is created, which leads to the desired relief of the membrane.

[0020] In a further development of the invention, it is proposed that the relief chamber be arranged on the same side of the membrane at a distance a from the joint area that is at least as large as the width B of the relief chamber. Half of the width B plus the distance a then results in the optimal offset between the joint areas arranged on both sides of the membrane.

[0021] It is further proposed that the membrane and / or at least one of the transport layers be coated with a catalytically active material. The membrane can be coated on one or both sides. If one side is uncoated, a transport layer coated with a catalytically active material preferably lies at least on this side. Preferably, both sides of the membrane are coated with a catalytically active material, so that coating the transport layers with a catalytically active material is unnecessary.

[0022] The coatings with catalytically active material lead to the formation of electrodes, with one electrode forming a cathode and the other electrode forming an anode. Since the internal pressure on the membrane is generally higher on the cathode side than on the anode side during operation of an electrochemical cell, the membrane is pressed against the anode-side transport layer and the anode-side joint area. Ideally, the anode-side transport layer is larger than the cathode-side transport layer, so that the anode-side joint area is closer to the edge and the internal pressure does not act directly on the membrane in the joint area. This further relieves the membrane's load.

[0023] The wider frame part is therefore preferably arranged on the cathode side, so that it covers the anode-side joint area. Furthermore, it is proposed that a bipolar plate be applied to each frame part. The two bipolar plates thus form the two outer layers of the electrochemical cell. By bracing the two bipolar plates, a force is generated that presses the two frame parts against the membrane, so that the two frame parts simultaneously function as a seal. Alternatively or additionally, a separate seal can be arranged between at least one frame part and the membrane.

[0024] A preferred embodiment of the invention is explained in more detail below with reference to the accompanying drawing. This shows a schematic longitudinal section through an electrochemical cell according to the invention.

[0025] Detailed description of the drawing

[0026] The electrochemical cell 1 shown in the figure has a membrane 2 which is arranged between two transport layers 3, 4 and in an edge region 5 between two frame parts 6.1, 6.2 of a frame 6. The upper frame part 6.2, which in this case is the cathode-side frame part 6.2, has a width y which is greater than a width x of the lower frame part 6.1 or the anode-side frame part 6.1. This means that between the transport layers 3, 4 and the frame parts 6.1, 6.2, abutment regions 7, 8 are formed which are offset from one another in the plane of the membrane 2. The upper or cathode-side frame part 6.2 thus covers the lower or anode-side abutment region 7.

[0027] Since the internal pressure on the cathode side is generally higher than on the anode side during operation of the electrochemical cell 1, the membrane 2 is pushed toward the anode-side contact area 7. However, due to the offset, the internal pressure on the cathode side is not directly applied to the membrane in the area of ​​the anode-side contact area 7. This means that the membrane 2 is relieved of pressure in the area of ​​the anode-side contact area 7.

[0028] However, an additional compressive load is exerted via external bipolar plates 9, which are clamped together. A compressive force is thus exerted on the two frame parts 6.1, 6.2 via the two bipolar plates 9, so that they are pressed against the membrane 2. The frame parts 6.1, 6.2 thus seal the electrochemical cell 1 from the outside. However, the upper frame part 6.2 presses the membrane 2 against the lower joint area 7, so that the desired relief of the membrane 2 cannot be fully achieved without further measures.

[0029] The additional measures in this case provide a relief chamber 10, which is delimited by the upper frame part 6.2 and the upper bipolar plate 9. The relief chamber 10 is arranged opposite the impact area 7 located on the other side of the membrane 2. The relief chamber 10 interrupts the flow of force from the upper bipolar plate 9 toward the membrane 2, so that the membrane is relieved of stress in the area of ​​the relief chamber 10.

[0030] For this purpose, the relief chamber 10 has a width B that corresponds at least to a thickness D of the membrane 2 and is arranged at a distance a from the joint area 8 on the same side. The distance a is selected to be at least equal to the width B. Since the relief chamber 10 is arranged centrally with respect to the lower joint area 7, half of the width B and the distance a together result in the offset between the joint areas 7, 8 formed on both sides of the membrane 2.

[0031] The relief chamber 10 is formed here by recesses 11 formed in the upper frame part 6.2 and in the bipolar plate 9. However, the relief chamber 10 can also be formed by a recess 11 in the frame part 6.2 or in the bipolar plate 9, thereby making the construction of the relief chamber 10 more cost-effective. Furthermore, the relief chamber 10 can be formed by profiling (not shown) the bipolar plate 9, so that a recess 11 can be omitted entirely.

[0032] If a recess 11 is provided in the frame part 6.2 and / or in the bipolar plate 9, it is preferably defined by chamfered or rounded edges 12. The edges 12 are then less likely to press into the adjacent component.

Claims

Claims 1. An electrochemical cell (1), in particular a fuel cell or electrolysis cell, comprising a membrane (2) arranged between two transport layers (3, 4) and in at least one edge region (5) between two frame parts (6.1, 6.2) of a frame (6), wherein the two frame parts (6.1, 6.2) each abut against the transport layer (3, 4) arranged on the same side of the membrane (2) in a butt region (7, 8), and wherein the frame parts (6.1, 6.2) are of different widths, so that the butt regions (7, 8) on both sides of the membrane (2) are offset from one another, characterized in that the wider frame part (6.2) and a bipolar plate (9) lying on the outside of the wider frame part (6.2) together delimit a relief chamber (10) which is arranged opposite the butt region (7) arranged on the other side of the membrane (2).

2. Electrochemical cell (1) according to claim 1, characterized in that the relief space (10) is formed by a recess (11) of the frame part (6.2) and / or the bipolar plate (9), wherein the recess (11) preferably has chamfered or rounded edges (12).

3. Electrochemical cell (1) according to claim 1, characterized in that the relief space (10) is formed by profiling the bipolar plate (9).

4. Electrochemical cell (1) according to one of the preceding claims, characterized in that the relief space (10) is arranged or formed substantially centrally and / or mirror-symmetrically with respect to the impact region (7) arranged on the other side of the membrane (2).

5. Electrochemical cell (1) according to one of the preceding claims, characterized in that the relief space (10) has a width (B) which is at least as large as a thickness (D) of the membrane (2).

6. Electrochemical cell (1) according to claim 5, characterized in that the relief space (10) is arranged from the impact area (8) on the same side of the membrane (2) at a distance (a) which is at least as large as the width (B) of the relief space.

7. Electrochemical cell (1) according to one of the preceding claims, characterized in that the membrane (2), preferably on both sides, and / or at least one of the transport layers (3, 4) is or are coated with a catalytically active material.

8. Electrochemical cell (1) according to one of the preceding claims, characterized in that the wider frame part (6.2) is arranged on the cathode side.

9. Electrochemical cell (1) according to one of the preceding claims, characterized in that a bipolar plate (9) is in contact with each of the two frame parts (6.1, 6.2).

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