Fuel cell system and method for manufacturing a fuel cell system

Abstract

The invention relates to a fuel cell system and a manufacturing method for a fuel cell stack arranged in a stacked manner along a stacking direction (z), which fuel cell stack consists of a plurality of plate-shaped components which are arranged in a stacked manner along the stacking direction, wherein the fuel cell has at least one end plate which consists of a plurality of segments.

Description

Technical Field

[0001] This invention relates to a multi-piece fuel cell end plate. Background Technology

[0002] End plates are installed at both ends of the fuel pool system, or "stack structure," to provide stability to the stack structure and apply adapted pressure to the stacked fuel pools. The stack structure or fuel pool stack has fuel pools arranged in a stacked manner along the stacking direction. The fuel pools are each constructed in a plate-like manner and extend along a first transverse direction and a second transverse direction orthogonal to the first transverse direction when viewed orthogonally to the stacking direction.

[0003] Known fuel cell endplates can be composed of multiple parts or sub-segments, which are then fixed into a common mechanical unit or plate. Mechanical force is introduced onto the plate, and thus into the stack and onto the fuel cell, via a tightening or pulling device. Here, the entire endplate is mechanically tightened onto the stack, regardless of how many parts or segments the endplate is composed of.

[0004] The individual fuel cells are stacked along the stacking direction and have the following characteristics:

[0005] - The bipolar half-plate on the anode side has a fuel channel structure for guiding fuel.

[0006] - Gas diffusion layer on the anode side,

[0007] - A membrane electrode assembly (MEA) having an electrolyte membrane and electrode layers arranged on both sides of the electrolyte membrane along a stacking direction, the electrode layers constituting an anode and a cathode for electrochemical reactions of fuel and oxidant.

[0008] - Gas diffusion layer on the cathode side,

[0009] - The bipolar half-plate on the cathode side has an oxidant channel structure for guiding the oxidant.

[0010] For examples of prior art regarding this type of fuel single-pool reactor, see publications EP 2 357 698 B1, EP2 445 045 B1, EP 2 584 635 B1, EP 2 946 431 B1 and EP 3 316 377 A1.

[0011] Fuel single-pool stacks are typically mechanically tightened using clamping bolts or screws and spring elements. Alternatively, a solution exists where a (typically metallic) belt is guided around the stack body, which is then tightened at fastening points and pre-tensioned at the end plates of the stack body; for this, see, for example, US 2006 / 093890 (Steinbroner). An additional solution is tightening based on toothed or wedge-shaped belts, which utilize multiple belts along with multiple tightening units.

[0012] In particular, a large holding or clamping force is required to achieve a uniform force distribution across the active cell area. For this purpose, the mechanical structure of the end plate is partially solid. Because the sealing plane and guide portion of each individual cell must also be mechanically held and clamped, a clamping force is also applied to the active surface.

[0013] The high clamping force on the active surfaces of the stack results in high requirements for the mechanical guides and force receivers in the sealing area. Correspondingly, the structure of the end plates and guide planes is complex. Furthermore, the clamping process places high demands on the aforementioned guide planes, such as stacking aids and sliding guides, as well as on the clamping process itself. The movement of the plates, MEA layers, and seals must be carefully monitored simultaneously. Summary of the Invention

[0014] Therefore, the purpose of this invention is to avoid the problems mentioned above.

[0015] This objective is achieved by a fuel monocell system according to this disclosure and a method for manufacturing a fuel monocell system. Advantageous improvements of the invention are presented in this disclosure.

[0016] The fuel single-pool system according to the invention has a fuel single-pool stack having a plurality of components stacked along a stacking direction and having at least one end plate, wherein the at least one end plate has a plurality of segments.

[0017] The components arranged relative to the stack preferably correspond to the fuel cells described above and are constructed, for example, substantially plate-like. The stack is closed at at least one end, preferably at two opposite ends along the stacking direction, with end plates. Here, the end plate itself can, in principle, form part of the fuel cell, or be directly or indirectly connected to, adjacent to, or placed on such a fuel cell. The term "closed" should be understood broadly in this context and within the framework of this application, and includes the aforementioned variations. According to the invention, the at least one end plate has multiple segments, which are preferably individual parts. The at least one end plate is therefore preferably implemented in multiple parts, wherein the individual parts are not securely connected to each other.

[0018] According to a preferred embodiment of the invention, at least one end plate is implemented in a laterally segmented manner. That is, the end plate consists of multiple discontinuous portions arranged orthogonally to the stacking direction, for example, side-by-side or intermingled with each other. This should enable, when the stack is tightened, the application of forces to different areas of the stack, such as the active single-cell area and the sealing area, as well as to other segments of the single cell, in a spaced-apart manner. This can be achieved, in particular, by intermingled plates that have little or no mechanical contact.

[0019] On the one hand, this solution allows the tightening force to be optimally adapted to the different requirements in the active area, the sealing area, and, if necessary, other mechanically tightened areas. Each individual segment of the end plate can be tightened with the force set for this purpose, thus reducing structural costs in the development of single-pool geometry and optimizing mechanical requirements, such as those on the seal itself.

[0020] On the other hand, segmented endplates enable a sequential tightening process. Here, each layer or segment to be tightened can be pre-tightened and tightened individually as needed. This also reduces the requirements in the stacking process itself, as mechanical holding forces, sealing layers, and active surfaces with contact resistance can be applied in an optimal sequence.

[0021] A fuel cell system can convert the chemical reaction energy of a continuously supplied fuel (e.g., hydrogen) and a continuously supplied oxidant (e.g., oxygen or air) into electrical energy through an electrochemical reaction.

[0022] In the operation of a fuel cell arranged in series via (conductive) bipolar half-plates, the reactants of the electrochemical reaction, namely fuel (e.g., hydrogen) and oxidant (e.g., air), are supplied to the membrane electrode unit within each fuel cell on different sides when viewed along the stacking direction.

[0023] For this purpose, each bipolar half-plate of a fuel cell is often constructed with channel structures on its side facing the membrane electrode unit so that fuel and oxidant can be introduced through these channel structures into the corresponding gas diffusion layer adjacent thereto on the corresponding side of the membrane electrode unit, and thus guided through the corresponding gas diffusion layer to the corresponding electrode layer on the corresponding side of the electrolyte membrane.

[0024] The electrode layer is typically formed of carbon material and coated or doped with a suitable catalyst. Here, the electrode layer on the fuel side forms the anode and the electrode layer on the oxidant side forms the cathode of the membrane electrode unit.

[0025] The products of the electrochemical reactions that take place in each fuel cell, such as water, can be discharged through the fuel cell zone that guides the oxidant (such as air).

[0026] In each fuel cell, the regions that guide the fuel, i.e., the channel structure, gas diffusion layer, and electrode layer (anode) on the anode side, and the regions that guide the oxidant, i.e., the channel structure, gas diffusion layer, and electrode layer (cathode) on the cathode side, must be sealed relative to each other to prevent gas exchange that is detrimental to power efficiency between these regions.

[0027] This specifically means that at least one of these two areas must be sealed relative to the surrounding environment (e.g., the atmosphere) of the fuel pool or fuel pool stack to prevent such exchange through the surrounding environment. In practice, at least the area guiding the fuel is sealed relative to the surrounding environment to prevent fuel from leaking from this fuel pool area into the surrounding environment and to prevent media (e.g., air) from entering this fuel pool area from the surrounding environment.

[0028] Specifically, to construct an air-cooled fuel cell system, the area guiding the oxidant can also be designed to be "open" towards the surrounding environment. For example, the oxidant channel structure provided in each fuel cell can be open at two sides of the fuel cell that are positioned opposite each other when viewed laterally, so that the oxidant (e.g., air) can flow through the fuel cell system in this lateral direction during operation. For this purpose, the oxidant can be driven through the laterally open fuel cell system, for example, by a fan, which also serves to cool it.

[0029] However, in many cases it is more advantageous that not only the fuel-guiding area of ​​the fuel pool reactor but also the oxidizer-guiding area are sealed relative to each other and relative to the surrounding environment.

[0030] Such seals are commonly made separately and placed between the bipolar plate and the diaphragm electrode unit, or, for example, the sealing material is dispensed / sprayed onto the corresponding components (e.g., bipolar plate, diaphragm electrode unit) of the fuel cell during the assembly process, or the components of the fuel cell with seals already formed therein are pre-processed.

[0031] The regions formed orthogonally to the stacking direction are called active regions, where electrochemical reactions occur between the fuel and oxidant. Typically, the active regions of each individual fuel cell extend planarly around the center of the plate-like assembly orthogonally to the stacking direction, while a sealing region surrounds the active regions. In a fuel cell stack, the sealing region thus surrounds the active regions of the stack, for example, in a sheath-like shape. Areas for the delivery / discharge—or distribution—of fuel, oxidant, and, if necessary, coolant can also be surrounded by or included within the sealing region.

[0032] According to a preferred design variant of the fuel single-pool system of the invention, at least one end plate of the stack comprises at least one first segment and at least one second segment. The first segment is associated with a first functional region of the stack, or encloses the first functional region along the stacking direction, and the second segment is associated with a second functional region of the stack, or encloses the second functional region along the stacking direction. Preferably, the first and second segments can be clamped to the stack largely independently of each other. Thus, a first force can be applied to the first functional region of the fuel single-pool stack by clamping via at least one first segment, and a second force can be applied to the second functional region of the fuel single-pool stack by clamping via at least one second segment. The forces applied to the first or second functional region of the stack for compression can thus preferably be set largely independently of each other. In particular, the first force and the second force can be different from each other. The second segment then surrounds the first segment, for example, on its periphery.

[0033] Similarly, implementations with more than two endplate segments are also feasible and are considered in this invention, which are used for targeted force introduction in more than two functional regions of a fuel pool reactor.

[0034] In this application, the functional areas referred to as fuel single-pool reactors are, for example, the areas described above: active areas, sealed areas, and areas for conveying / discharging or distributing fuel, oxidant, and, if necessary, coolant.

[0035] At least one end plate is preferably divided laterally for this purpose. However, the end plate can also be divided horizontally and / or axially in other embodiments.

[0036] In a preferred variation, the end plate is divided such that multiple segments fit together when tightened. This can be achieved, for example, through a step-by-step division.

[0037] The following variation is advantageous, for example, in which the segments are fitted together such that tightening the active area of ​​the stack via the first segment of the end plate also applies a preload to the second segment and thus to the sealing area of ​​the stack. The sealing area can then be subjected to, for example, an even higher compressive force through further tightening via the second segment. Similarly, this can also be conceived in the opposite way, where the preload is applied to the first segment by tightening the second segment.

[0038] In some embodiments, the fuel single-cell system is suitably configured for operation in which hydrogen is used as fuel, for example having an electrolyte membrane configured as a proton-conducting membrane.

[0039] However, alternatively, a design scheme for a single-fuel pool system is also considered, for example, for operation with another fuel, such as an organic compound (e.g., methane or methanol) or natural gas.

[0040] In one embodiment, the fuel single-pool system is suitably constructed for operation with air as the oxidant.

[0041] In one embodiment, the bipolar half-plate is formed of a metallic material. Alternatively, the bipolar half-plate can be formed, in particular, of a carbon material or, for example, of a conductive plastic material (e.g., correspondingly, with added carbon black), or of another conductive material.

[0042] In one embodiment, the bipolar half-plate and end plate provided in this invention are prefabricated separately from each other and are inserted into the stack body accordingly by stacking the individual components during the manufacture of the fuel single-pool system.

[0043] In another aspect, the present invention relates to a method for manufacturing a fuel single-pool system. Attached Figure Description

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments. The following are schematically illustrated:

[0045] Figure 1 A two-piece end plate is shown;

[0046] Figure 2 A one-piece end plate is shown. Detailed Implementation

[0047] Figure 1A fuel pool 100 is shown, having an end plate 110 consisting of two segments 111 and 112. Each fuel pool comprises multiple plate-shaped components arranged in a stacked manner along a stacking direction, with plate-shaped end plates at corresponding ends of the stack. The end plate segments apply forces 121 and 122 to the fuel pool stack or stack structure 130. Specifically, force 121 is applied to the active region 131, and force 122 is applied to the sealing region 132.

[0048] End plates are used to stabilize the stack and are therefore mounted at both ends along the stacking direction. However, more stability is required in the sealed region than in the active region. Generally, the end plates are more mechanically stable than the bipolar plates in the middle of the stack. A larger clamping force is required to achieve a uniform force distribution in the active single-cell region. For this purpose, the mechanical structure of the end plates is partially solid.

[0049] The sealing plane and guide portion of each individual pool are also mechanically held and pressed. A pressing force 122 is also applied to the active surface. Therefore, depending on the requirements, the outer segment 112 can apply more pressure to the sealing area than the inner segment 111, which applies pressure to the active area, or vice versa. The end plates can be interlocked, with the segments having little or no mechanical contact.

[0050] The end plate can consist of two segments or more. Each individual segment of the end plate can be tightened with a set force, thereby reducing structural costs in the development of single-pool geometries. It also optimizes the mechanical requirements of components such as seals or sealing areas.

[0051] Mechanical tightening compresses the entire endplate onto the stack, regardless of the number of parts or segments the endplate comprises. The high tightening force on the active surface of the stack results in higher requirements for the mechanical guides and force receivers in the sealing area. Laterally segmented multi-piece endplates allow for the application of forces to, for example, the active single-cell area, the sealing area, and other segments of the single-cell area. Due to the segmented endplates, a sequential tightening process is also possible. Here, each segment to be tightened is tightened or its tightening force is set individually. This also reduces requirements during the stacking process because mechanical holding forces, the sealing layer, and the active surface with contact resistance can be incorporated into the tightening process in an optimal order.

[0052] In different embodiments of the invention, the segmentation is lateral, axial, or horizontal, or a combination of both. Step-by-step segmentation can also be implemented, with the segments fitting into each other during the compaction process. Stacks with segmented end plates (e.g., at the upper end of the stack) and unsegmented end plates (e.g., at the lower end of the stack) can also be formed.

[0053] The end plates can be made of the same material as the bipolar plates, or they can be made of a different material. Fuel single-pool reactors are typically mechanically tightened by means of clamping bolts or screws and, if necessary, spring elements. Alternatively, there are solutions that guide a strip of typically metal around the stack body, which is then fastened at one or two fastening points and pre-tightened at the end plates of the stack body.

[0054] exist Figure 2 The text depicts a one-piece endplate. Figure 2 A fuel cell 200 with end plates 210 is shown. Each fuel cell consists of multiple plate-shaped components arranged in a stacked manner along the stacking direction, having plate-shaped end plates at the respective ends of the stack. The end plates apply force 220 to the fuel cell stack or stack structure 230, particularly to the active region 231 and the sealing region 232.

[0055] The end plate must be designed to withstand the applied pressure. The end plate can be formed or composed of, for example, steel or another metal. It can also be made of non-conductive materials, such as polymer compounds. However, the required mechanical properties must be ensured.

Claims

1. A fuel single-pool system (100) having a fuel single-pool stack (130) having a plurality of plate-shaped components stacked along a stacking direction (z) and having at least one end plate, wherein, The at least one end plate (110) has multiple segments (111, 112), which are implemented as separate parts. The fuel pool stack has at least one end plate (110) having at least one first segment (111) and at least one second segment (112), the first segment being associated with a first functional region (131) of the fuel pool stack and the second segment being associated with a second functional region (132) of the fuel pool stack, thereby applying a first force (121) to the first functional region (131) of the fuel pool stack (130) by tightening via the at least one first segment (111) and applying a second force (122) to the second functional region (132) of the fuel pool stack by tightening via the at least one second segment (112).

2. The single-pool fuel system according to claim 1, wherein, The at least one end plate (110) is divided laterally.

3. The single-pool fuel system according to claim 1 or 2, wherein, At least one end plate (110) is divided axially or horizontally.

4. The single-pool fuel system according to claim 1 or 2, wherein, At least one end plate (110) is implemented with step-by-step segmentation.

5. The single-pool fuel system according to claim 1 or 2, wherein, At least one end plate (110) consists of segments that fit into each other during the tightening process.

6. The fuel single-pool system according to claim 1 or 2, wherein one end plate is segmented, but the other end plates are not segmented.

7. The single-pool fuel system according to claim 1 or 2, wherein, At least one end plate is composed of segments, and wherein the end plate is made of metal or a non-conductive material.

8. A method for manufacturing a single fuel cell system (100) according to any one of the preceding claims, comprising the steps of: pass: - The fuel pool stacks (130) are arranged in a stacked manner along the stacking direction (z), and - End plates are arranged in a stacked manner at both ends of the fuel pool stack along the stacking direction (z). To form a fuel single-pool system (100). Its features are, At least one end plate (110) has multiple segments (111, 112).

9. The method for manufacturing a fuel single-cell system (100) according to claim 8, wherein, Each segment (111, 112) to be compacted is compacted individually.

10. The method for manufacturing a fuel single-pool system (100) according to claim 8, wherein, The segments to be tightened (111, 112) are loaded with different tightening forces.

11. The method for manufacturing a fuel single-pool system (100) according to claim 8, wherein, Each segment is loaded sequentially or simultaneously with a corresponding, yet-to-be-set, tightening force.

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