Electrochemical cell

Abstract

The invention relates to an electrochemical cell (1), in particular a fuel cell or an electrolytic 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), the two frame parts (6.1, 6.2) each abut on the transport layer (3, 4) arranged on the same side of the membrane (2) in an abutment region (7, 8), and wherein the frame parts (6.1, 6.2) are designed with different widths such that the abutment regions (7, 8) on both sides of the membrane (2) are arranged offset from one another. According to the invention, the wider frame part (6.2) and the bipolar plate (9) externally resting on the wider frame part (6.2) together delimit an unloading space (10), which is arranged opposite the abutment region (7) arranged on the other side of the membrane (2).

Description

Technical Field

[0001] This invention relates to an electrochemical battery, particularly a fuel cell or an electrolytic battery. Background Technology

[0002] In practice, multiple electrochemical cells are connected to form a battery stack, particularly a fuel cell stack or an electrolysis battery stack. Preferred applications are therefore fuel cell stacks and / or electrolysis battery stacks. Electrolysis devices can be, in particular, PEM or AEM electrolysis battery stacks for hydrogen production, or CO2 electrolysis devices.

[0003] Electrochemical cells have a multi-layered or multi-tiered structure. The intermediate layer forms a membrane, which is typically coated on both sides with a catalytically active material to construct the anode and cathode. A transport layer is attached to the membrane not only on the anode side but also on the cathode side, through which the corresponding reaction medium is supplied to the membrane. Typically, the membrane is surrounded by a frame structure in at least one edge region protruding from the transport layer. This frame structure supports the membrane and can also act as a seal. A frame structure typically consisting of two frame members is also called a gasket or sub-gasket.

[0004] During the operation of an electrochemical cell, different pressures exist on the anode and cathode sides. Typically, the pressure on the cathode side is higher than that on the anode side. This results in a pressure load perpendicular to the membrane plane, causing the membrane to be pressed against the transport layer and adjacent frame members on the side with lower pressure, typically the anode side. The edges of the transport layer and frame members can thus cause damage to the membrane.

[0005] Furthermore, the external bipolar plates also generate a pressure load on the membrane, which clamps together to seal the electrochemical cell externally. The clamping force acts particularly on the frame structure, causing the two frame members to press against the membrane located between them. Summary of the Invention

[0006] This invention addresses the task of reducing the pressure load on membranes to improve their robustness and lifespan. Consequently, the lifespan of electrochemical cells with membranes should be extended.

[0007] To address this task, an electrochemical cell having the features of claim 1 is proposed. Advantageous further extensions of the invention can be derived from the dependent claims.

[0008] An electrochemical cell, particularly a fuel cell or electrolytic cell, is proposed, comprising a membrane disposed between two transport layers and disposed between two frame members of a frame in at least one edge region. The two frame members are respectively abutted in abutment regions onto the transport layers disposed on the same side of the membrane, wherein the frame members are constructed of different widths such that the abutment regions are staggered from each other on both sides of the membrane. According to the invention, the wider frame member and the bipolar plate externally abutting against the wider frame member jointly define an unloading space, which is disposed opposite to the abutment region disposed on the other side of the membrane.

[0009] An unloading space constructed on one side of the membrane is used to unload the membrane. Because the bipolar plate does not contact the frame below it in the region of the unloading space, no force can be transmitted from the bipolar plate to the frame in this region. The force flow towards the membrane is thus interrupted by the unloading space, and the membrane is unloaded. By constructing the unloading space on one side of the frame with a wider section and arranging it opposite the docking area on the other side of the membrane, unloading of the membrane occurs in the docking area. This means that the membrane does not press against the docking area, or at least presses against the docking area to a significantly reduced extent. This also reduces the risk of damage to the membrane from the edges of the docking area, which is the boundary between the frame and the transport layer. Therefore, the robustness and lifespan of the membrane, as well as the lifespan of the electrochemical cell, are improved.

[0010] According to a first preferred embodiment of the invention, the unloading space is constructed by a groove in the frame member that defines the unloading space. This means that a groove is constructed in the wider frame member on the side facing the bipolar plate. Alternatively or supplementarily, the unloading space can be constructed by a groove in the bipolar plate. In this case, the groove is arranged on the side of the bipolar plate facing the frame member.

[0011] The grooves in the frame members and / or bipolar plates used to construct the unloading space preferably have chamfered or rounded edges, so as to avoid the construction of sharp edges that could be pressed into the respective mating members. In this way, damage to the respective mating members is avoided.

[0012] According to another preferred embodiment of the invention, the unloading space is constructed by a profiling portion of the bipolar plate. Since the bipolar plate is typically a pressed plate, the profiling portion constituting the unloading space can be manufactured particularly easily by pressing during the manufacture of the bipolar plate.

[0013] Preferably, the unloading space is arranged or constructed substantially centrally and / or mirror-symmetrically with respect to the docking area on the other side of the diaphragm. The central arrangement allows for compensation for minimal processing and / or installation errors, while also ensuring the unloading space is opposite to the docking area on the other side of the diaphragm. The mirror-symmetrical construction of the unloading space simplifies its manufacturing process.

[0014] Furthermore, the unloading space preferably has a width B, which is at least as large as the membrane thickness D. This creates a sufficiently large unloading space that results in the desired unloading of the membrane.

[0015] In a further extension of the invention, it is proposed that the unloading areas are arranged with a spacing 'a' relative to the abutment areas on the same side of the diaphragm, the spacing being at least as large as the width 'B' of the unloading space. The sum of half the width 'B' and the spacing 'a' yields the optimal offset between the abutment areas arranged on both sides of the diaphragm.

[0016] Furthermore, it is proposed that the membrane and / or at least one transport layer are coated with a catalytically active material. The membrane may be coated not only on one side but also on both sides. If one side is not coated, it is preferable that at least one transport layer coated with a catalytically active material is attached to that side. Preferably, both sides of the membrane are coated with a catalytically active material, thereby eliminating the need to coat the transport layer with a catalytically active material.

[0017] Coating with a catalytically active material results in the formation of electrodes, one configured as a cathode and the other as an anode. Because a greater internal pressure is typically applied to the membrane on the cathode side than on the anode side during electrochemical cell operation, the membrane is pressed against the transport layer and the mating region on the anode side. Ideally, the transport layer on the anode side is larger than the transport layer on the cathode side, causing the mating region on the anode side to be closer to the edge, so that the internal pressure does not act directly on the membrane in this mating region. The membrane is thus further unloaded.

[0018] The wider frame is therefore preferably arranged on the cathode side, so that the frame covers the mating area on the anode side.

[0019] Furthermore, it is proposed that a bipolar plate be attached to each of the two frame members. These two bipolar plates thus constitute the two outer layers of the electrochemical cell. A force is generated by clamping the two bipolar plates, which presses the two frame members against the membrane, causing both frame members to simultaneously act as seals. Alternatively or supplementarily, a separate seal can be arranged between at least one frame member and the membrane. Attached Figure Description

[0020] Preferred embodiments of the invention are further explained below with reference to the accompanying drawings. The drawings schematically show a longitudinal cross-section through an electrochemical cell according to the invention. Detailed Implementation

[0021] The electrochemical cell 1 shown in the accompanying drawings has a membrane 2 arranged between two transport layers 3 and 4 and between two frame members 6.1 and 6.2 of a frame 6 in an edge region 5. The upper frame member 6.2, currently the cathode-side frame member 6.2, has a width y, which is greater than the width x of the lower frame member 6.1 or the anode-side frame member 6.1. This means that mating regions 7 and 8 are formed between the transport layers 3 and 4 and the frame members 6.1 and 6.2, arranged offset from each other in the plane of the membrane 2. The upper or cathode-side frame member 6.2 thus covers the lower or anode-side mating region 7.

[0022] Because the internal pressure on the cathode side is typically higher than that on the anode side during operation of the electrochemical cell 1, the membrane 2 is pressed towards the docking region 7 on the anode side. However, due to this misalignment, the internal pressure on the cathode side is not directly applied to the membrane in the docking region 7 on the anode side. This means that the membrane 2 is unloaded in the docking region 7 on the anode side.

[0023] However, the externally mounted, mutually clamping bipolar plates 9 create an additional pressure load. Therefore, pressure is applied to the two frame members 6.1 and 6.2 via these two bipolar plates 9, causing the two frame members to press against the membrane 2. The frame members 6.1 and 6.2 thus seal the electrochemical cell 1 externally. The upper frame member 6.2, however, presses the membrane 2 against the lower mating area 7, making it impossible to fully unload the membrane 2 without further measures.

[0024] A further measure is the provision of an unloading space 10, which is bounded by the upper frame member 6.2 and the upper bipolar plate 9. The unloading space 10 is positioned opposite the docking area 7 arranged on the other side of the diaphragm 2. The unloading space 10 interrupts the force flow from the upper bipolar plate 9 toward the diaphragm 2, causing the diaphragm to be unloaded in the area of ​​the unloading space 10.

[0025] For this purpose, the unloading space 10 has a width B, which is at least equal to the thickness D of the diaphragm 2, and is arranged to be spaced apart from the docking areas 8 on the same side by a distance a. The distance a is chosen here to be at least as large as the width B. Since the unloading space 10 is currently centered relative to the docking area 7 below, half the width B plus the distance a gives the offset between the docking areas 7 and 8 constructed on both sides of the diaphragm 2.

[0026] The unloading space 10 is currently constructed via a recess 11 formed in the upper frame 6.2 and in the bipolar plate 9. However, the unloading space 10 can also be constructed via only one recess 11 in the frame 6.2 or the bipolar plate 9, thereby reducing the cost of constructing the unloading space 10. Furthermore, the unloading space 10 can be constructed via a molded portion (not shown) of the bipolar plate 9, thus completely eliminating the need for the recess 11.

[0027] If a groove 11 is provided in the frame member 6.2 and / or in the bipolar plate 9, the groove is preferably bounded by a chamfered or rounded edge 12. The edge 12 cannot be pressed into the respective mating members so easily.

Claims

1. An electrochemical cell (1), particularly a fuel cell or electrolytic cell, having a membrane (2) arranged between two transport layers (3, 4) and in at least one edge region (5) between two frame members (6.1, 6.2) of a frame (6), wherein, The two frame members (6.1, 6.2) are respectively mated in mating areas (7, 8) onto the transmission layers (3, 4) arranged on the same side of the diaphragm (2), wherein the frame members (6.1, 6.2) are constructed with different widths such that the mating areas (7, 8) on both sides of the diaphragm (2) are staggered from each other. The feature is that the wider frame member (6.2) and the bipolar plate (9) that is externally attached to the wider frame member (6.2) jointly define the unloading space (10), which is arranged opposite to the docking area (7) arranged on the other side of the diaphragm (2).

2. The electrochemical battery (1) according to claim 1, characterized in that, The unloading space (10) is constructed by a groove (11) in the frame member (6.2) and / or the bipolar plate (9), wherein preferably, the groove (11) has chamfered or rounded edges (12).

3. The electrochemical battery (1) according to claim 1, characterized in that, The unloading space (10) is constructed through the forming part of the bipolar plate (9).

4. The electrochemical battery (1) according to any one of the preceding claims, characterized in that, The unloading space (10) is substantially centered and / or mirror-symmetrically arranged with respect to the docking area (7) arranged on the other side of the diaphragm (2).

5. The electrochemical battery (1) according to any one of the preceding claims, characterized in that, The unloading space (10) has a width (B) that is at least as large as the thickness (D) of the diaphragm (2).

6. The electrochemical battery (1) according to claim 5, characterized in that, The unloading space (10) is arranged to be spaced apart by a distance (a) from the docking area (8) on the same side of the diaphragm (2), the distance being at least as large as the width (B) of the unloading space.

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

8. The electrochemical battery (1) according to any one of the preceding claims, characterized in that, A wider frame member (6.2) is arranged on the cathode side.

9. The electrochemical battery (1) according to any one of the preceding claims, characterized in that, A bipolar plate (9) is attached to each of the two frame components (6.1, 6.2).

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