Electrochemical system, and method for assembling an electrochemical system
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-01-22
- Publication Date
- 2026-08-13
Smart Images
Figure DE2026100071_13082026_PF_FP_ABST
Abstract
Description
[0001] Electrochemical system and method for assembling an electrochemical system
[0002] The invention relates to an electrochemical system comprising a stack of electrochemical cells, in particular in the form of electrolysis cells, each with a bipolar plate provided for demarcation from adjacent electrochemical cells, and each with an active region comprising a proton- or anion-permeable membrane and fluid-permeable cell materials. The invention further relates to a method for assembling a stack of electrochemical cells.
[0003] A cell stack of an electrochemical system, namely an electrolysis system, as described in DE 102023 109 185 A1, comprises a plurality of bipolar plates arranged parallel to one another, each separating a half-cell of a first electrochemical cell from a half-cell of another electrochemical cell. The bipolar plates have several groups of raised sections that serve both a mechanical support function and a flow-guiding function. The bipolar plates are supported by frames with seals on both the inside and outside.
[0004] German patent DE 1 149027 B discloses a sealing arrangement for a demountable plate heat exchanger. This sealing arrangement comprises softer seals positioned between harder seals, the harder seals defining the distance between parallel plates. The plate heat exchanger is assembled into a rigid plate pack by clamping devices.
[0005] German patent DE 10257964 A1 discloses a separator unit for PEM fuel cells with an integrated inlay. The separator unit is composed of two plates with continuous joints. In the port areas, the plates are profiled to create a sealing groove around the ports. German patent DE 102021 121 404 A1 discloses a bipolar plate and a method for manufacturing a bipolar plate. Coolant ports, media ports, and distribution fields are formed through the bipolar plate. The half-sheets from which the bipolar plate is constructed have a non-uniform embossing depth across their width. Seals are inserted between the bipolar plates and the frame.
[0006] EP 3748750 A1 describes a metallic bipolar plate for fuel cells consisting of an anode plate and a cathode plate, each formed from shaped sheet metal and connected to each other via a sealing frame.
[0007] US patent 2014 / 0287340 A1 discloses a rubber composition suitable for use in an adhesive layer in a fuel cell. Among other things, two halves of a separator plate are joined by means of two adhesive layers and a rubber component, with a coolant passage formed between the halves.
[0008] CN 116544434 A describes a fuel cell unit wherein an anode plate or a cathode plate is provided with an adhesive overflow groove. The cathode plate is connected to a cathode frame. A cathode gas sealing cavity is formed between the cathode plate and the cathode frame. The anode plate is connected to an anode frame. An anode gas sealing cavity is formed between the anode plate and the anode frame. The cathode frame and the anode frame are provided with adhesive overflow channels that penetrate the anode frame and the cathode frame.
[0009] German patent DE 102024 104248 A1 discloses an electrochemical cell stack comprising several cells separated from each other by bipolar plates. A supporting frame surrounding a membrane is also present, forming a stepped shape onto which a sealing arrangement is injection-molded.
[0010] The invention is based on the objective of further developing stacked electrochemical systems compared to the aforementioned prior art, particularly with regard to manufacturing and sealing technology, with the aim of achieving high process reliability under mass production conditions.
[0011] This problem is solved according to the invention by an electrochemical system with the features of claim 1. The electrochemical cell can, in particular, be a cell of an electrolysis system. The problem is also solved by a method designed according to claim 10 for assembling a stack of electrochemical cells, in particular an electrolysis cell stack. The embodiments and advantages of the invention explained below in connection with the assembly method also apply mutatis mutandis to the devices, i.e., the electrochemical cell and the electrochemical system constructed from a plurality of such cells, and vice versa.
[0012] In a basic concept known per se, a bipolar plate separates one electrochemical cell from another. An active region of the electrochemical cell, where the desired electrochemical reactions take place, comprises a proton- or anion-permeable membrane and fluid-permeable cell materials, and is surrounded by an active field frame. In this context, a proton is considered a hydrogen ion. Thus, the membrane is always ion-permeable.
[0013] The bipolar plate is constructed from two half-sheets: one three-dimensionally structured and one flat. A coolant chamber is formed between them. A cooling field frame surrounding the coolant chamber contacts both half-sheets and is sealed against them by at least one gasket attached to the cooling field frame. This seal can be formed with or without additional elements of a defined shape, such as a material-bonded connection between the half-sheets and the cooling field frame. The active field frame is provided with at least one further gasket that seals the active area while maintaining a deformation reserve. A sealing zone is formed that extends from one bipolar plate to the next in the stacking direction of the cell stack.The deformation reserve means that, unlike the seal between the cooling field frame and the half-sheets, a so-called soft stop is present at this point. This combines a soft stop with the hard stop present at the cooling field frame. The term "deformation reserve" implies that further compression of the seal would be possible without impairing its sealing effect; that is, the seal's working range is not exhausted. Compared to standard O-ring seals, the seal located on the active field frame has a relatively large working range. Theoretically, in exceptional cases, the deformation reserve of a seal could be exhausted at individual points within a cell stack. However, this is not the case for the majority of points within a cell stack.
[0014] This combination of different contacting and sealing principles—in one case, a flexible (soft-stop) and in the other, a rigid (hard-stop) design, both referring to the operational state after assembly—results in remarkable tolerance insensitivity combined with excellent sealing performance, even under fluctuating operating conditions. In particular, there is no need for functionally corresponding components in different cells, including plate- and frame-shaped components, to be exactly the same height in all stacked cells of an electrochemical system. Tolerance sorting is unnecessary. The height of the cells is not precisely defined by rigid components such as metal or plastic frames.At least to a very limited extent, it may even be possible to tilt individual components within the stacked electrochemical system without affecting the tightness or the electrical properties.
[0015] Regarding the fundamental possibility of mounting a stack of electrochemical cells with a soft-stop mechanism, reference is made to DE 102024 104248 A1, which relates to a stack of electrolysis cells. In the case of DE 102024 104248 A1, a support frame including an electrically insulating area represents a softer spring compared to an arrangement located in an active field.
[0016] In cases where the hard-stop, meaning the stacked arrangement of half-sheets and the cooling field frame sandwiched between them in a non-significantly compressible manner when fully assembled, is implemented with separate sealing elements, at least one gasket attached to the cooling field frame can be used to seal the half-sheets against the frame. The expansion of this gasket in the installed and compressed state is determined by the shape of the half-sheets and the thickness of the cooling field frame. The term "hard-stop" means that the total thickness of the stacked arrangement of the individual elements—in this case, the cooling field frame and the half-sheets—is determined by the thickness of the respective elements and does not depend on any further compressibility of the gasket.
[0017] The seal located on the cooling field frame, whose compressibility is not fully utilized by the hard stop, can be molded or injection-molded onto the edge of the cooling field frame, particularly in the sense of an "edge bonding" technique. For examples of edge bonding technology, reference is made to DE 102023 111 278 A1 or DE 102022 119 198 A1. In the present case, one of the two half-sheets belonging to the bipolar plate can be contacted on its first side by the seal attached to the cooling field frame, particularly the injection-molded seal, and on its directly opposite side by the seal with which the active field frame is provided.
[0018] According to the invention, the electrochemical system further comprises at least one connecting element that is positively inserted into each bipolar plate and projects through openings in the half-sheets and the cooling field frame arranged between them, as well as through one of the active field frames adjacent to this bipolar plate. In particular, the connecting element is rotationally symmetrical to ensure easy insertion into the bipolar plate. However, other shapes are of course also possible for the connecting element.
[0019] Since the active field frame is subjected to internal pressure from the cell stack, particularly on the surfaces facing the cathode, it must exhibit high strength and stiffness. This is especially true for large, essentially rectangular cell stacks, particularly those 500 cm² and larger. 2Despite the active area, the active field frame, due to the large opening in the active field area, is no longer able to withstand the forces resulting from the internal pressure. Internal pressures in the range of 5 to 100 bar can occur, typically in the range of 30 ± 5 bar. A similar situation applies to the cooling field frame located between the two half-sheets of a bipolar plate. The at least one connecting element secures the bipolar plate, comprising the two half-sheets and the cooling field frame, as well as the active field frame, against displacement relative to each other, thus significantly increasing the operational reliability of the electrochemical system.
[0020] Since the active field frame is equipped with at least one additional seal designed to seal the active area while maintaining a deformation reserve, the friction between the active field frames and the bipolar plates is low or even close to zero. To counteract this, one or more connecting elements are provided, which are positively inserted into the bipolar plate and achieve mechanical stabilization of the cell components relative to each other, as such a connecting element protrudes through the bipolar plate and one of the adjacent active field frames. In this way, the cooling field frame and the active field frame are connected to each other via the plate-shaped half-sheets, which do not have a frame structure with a large central opening and thus each form a mechanically stable plane. This connection enables them to withstand the internal pressure of the cell stack without any displacement relative to each other.
[0021] The connecting element has, in particular, a recess that prevents contact, especially mechanical and / or electrical contact, with an adjacent connecting element. The recess thus serves to maintain a minimum distance to electrically conductive parts that are at different electrical potentials, such as bipolar plates and frames arranged above and below, and thereby ensure electrical insulation. The connecting element is preferably made of metal, in particular steel, or plastic, in particular a thermoplastic or thermoset. This allows it to withstand high forces.
[0022] The active field frame can be equipped with various additional seals, namely a first-type seal extending over the entire height of the active area as measured in the stacking direction, and a second-type seal with a sealing area located only on one side of the membrane—that is, without limiting generality, either on the top or the bottom of the membrane—and thus intended for sealing a half-cell of the electrochemical cell. At least one of the different seals can be located at the edge of a port in the cell stack provided for media passage. In any case, the active field frame can be designed as a formed metal part overmolded with sealing material, that is, in particular, as a sheet metal part.
[0023] Regardless of which frame-shaped part, i.e., the active field frame or the cooling field frame, the seal is attached to, it can be a pressure-activated seal. This means that the sealing effect increases with increasing pressure in the space to be sealed, which contains either a coolant or operating fluid.
[0024] The half-sheets can be made of, for example, sheet steel or titanium. Regardless of the material from which the half-sheets are made, one of the half-sheets is flat and the other is three-dimensionally structured, in particular by means of embossing.
[0025] The method for assembling the electrochemical system according to the invention, as described in the application, generally comprises the following steps:
[0026] - Provision of several pairs of half-sheets, - Provision of cooling field frames, each intended to define a coolant space to be formed between two half-sheets, - Provision of a proton- or anion-permeable membrane per electrochemical cell as well as various fluid-permeable cell materials, which are intended to be arranged on both sides of the membrane in the active area of the electrochemical cell,
[0027] - Assembling the pairs of half-sheets to form a bipolar plate, with the cooling field frame contacting both half-sheets and forming seals between the cooling field frame on the one hand and the half-sheets on the other,
[0028] - Inserting the membrane and the cell materials into an active field frame to which at least one additional seal is attached, - Stacking the bipolar plates, the connecting elements, and arrangements of active field frame, membrane, and cell materials, - Pressing the cell stack formed in the previous step in such a way that the at least one additional seal attached to the active field frame is compressed in the sense of a soft stop while maintaining a deformation reserve, whereas the components delimiting the coolant chamber, half-sheets and cooling field frame, are placed on top of each other in the sense of a hard stop without any further compression possibility.
[0029] The sealing of the coolant chamber, bounded by the half-sheets and the cooling field frame and intended for the later receipt of a coolant, can be carried out either during the upstream assembly of the arrangement comprising the bipolar plate and the cooling field frame, or at a later stage of assembly, namely during the pressing of the entire stack. In the former case, the half-sheets of the bipolar plate can be joined together, for example by welding, before being inserted into the cell stack. Welded or brazed connections between the cooling field frame and the half-sheets are also conceivable.
[0030] In any case, the compression of the cell stack can be stopped depending on the force acting within the stack. Therefore, the compression process—at least as long as predefined tolerances are not exceeded—is not directly dependent on geometric dimensions. The force required for compression can increase significantly with decreasing cell height, especially if further reduction of the cell height would require deforming components that are difficult to compress, such as those forming flow fields.
[0031] After compaction, the stack height can be fixed, for example, mechanically or by a hydraulic device. Particularly when using hydraulic means, automatic readjustment of the stack height during operation of the electrochemical system is also possible. This readjustment can be achieved in such a way that the integration of the active field frames into the stack remains as if it were a soft stop, while the cooling field frames were already installed in the cell stack with a hard stop from the outset. Generally, the active field frames can be considered part of an active cell, while the cooling field frames are components of a cooling cell.
[0032] In principle, the electrochemical system, which comprises multiple electrochemical cells, can be designed for any electrochemical reaction that involves the use of a proton- or anion-permeable membrane. In this context, a proton is considered a hydrogen ion. Thus, the membrane is always ion-permeable. Specifically, this electrochemical system is an electrolysis system for water electrolysis.
[0033] The combined soft-stop and hard-stop design of the cell stack significantly contributes to ensuring that, during intended operation, largely independent of operating conditions, a force always acts on the components in the active area of the cell stack—that is, in the area where the electrochemical reactions take place—even if the cell height varies slightly over time or from cell to cell within the stack. The mechanical stability and tightness of the cell stack are maintained even under high internal pressures and with an area greater than 500 cm². 2 The active area is reliably ensured by the connecting elements.
[0034] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows:
[0035] Fig. 1 shows a section of a stack of electrochemical cells, namely electrolysis cells, in a sectional view.
[0036] Fig. 2 shows a detail of the arrangement according to Fig. 1 ,
[0037] Fig. 3 Components of the cell stack according to Fig. 1 in an exploded view.
[0038] An electrolyzer, designated by reference numeral 1, that is, an electrochemical system, is designed for the production of hydrogen from water, i.e., for water electrolysis, and has a cell stack 2, referred to as a stack, as its main component. The stack 2 is composed of a plurality of electrolysis cells 3, each comprising a first half-cell 4 and a second half-cell 5, with a proton-permeable membrane 6 forming the boundary between the two half-cells 4, 5 of the same electrolysis cell 3. The desired electrochemical reactions, i.e., electrolysis, take place in the two half-cells 4, 5. The half-cells 4, 5, together with the catalytically coated membrane 6, are part of an active cell 15.
[0039] The individual electrolysis cells 3 are separated from each other by bipolar plates 11. In this case, the bipolar plates 11 are each made of two half-sheets 12, 13. These consist of an embossed, i.e., three-dimensionally structured, half-sheet 12 and a flat half-sheet 13. A coolant flows between the half-sheets 12, 13, which is separate from the operating media of the electrolysis cells 3. The half-sheets 12, 13, together with the coolant chamber formed between the half-sheets 12, 13 (designated 16), constitute a so-called cooling cell 17, which, like the active cell 15, is a component of the electrolysis cell 3, referred to simply as the cell.
[0040] The electrolysis cells 3 contain materials generally referred to as cell materials 7, 25. These materials 7, 25 comprise anode-side cell material 7 and cathode-side cell material 25 and can include porous transport layers and / or gas diffusion layers, and may be single- or multi-layered. The areas of the electrolysis cells 3 containing the cell material 7, 25 are generally referred to as active fields 8 or active areas. Each active field 8 is enclosed by a frame 9, i.e., an active field frame, made of plastic or metal. The frame 9 can be a single piece or composed of several superimposed frame elements. In the present case, sketched in Figures 1 to 3, the frame 9 is a formed metal part. Openings in the frame 9 form, among other things, ports 10, which allow the supply of operating or cooling media to the active field 8 or the discharge of such media.Overall, the frame 9, like the active field 8, has a rectangular, elongated shape. The ports 10 are located in a port and feed area designated 14.
[0041] Coolant, in this case cooling water, which is separate from the process water intended for electrolytic decomposition, flows from the port and feed area 14 into cell 3 – more precisely: into the cooling cell 17. The coolant chamber 16 is bounded by the two half-sheets 12, 13 and by a cooling field frame 18. Seals 20, 21 are located on the cooling field frame 18.
[0042] As shown in Figures 1 and 2, the half-sheets 12 and 13 rest on the upper and lower surfaces of the cooling field frame 18. The use of terms like "top" or "bottom" in this text refers only to the figures and does not imply any statement about the actual orientation of components of the electrochemical system 1 in space. In particular, planar components of the electrolyzer 1 may be vertically oriented. The distance between the half-sheets 12 and 13 is fixed by the cooling field frame 18. The cooling field frame 18 is inserted between the half-sheets 12 and 13 in a hard-stop configuration. The seals 20 and 21 have little influence on the distance between the half-sheets 12 and 13. Areas where the half-sheets 12 and 13 overlap are designated 22.In a manner not shown, fixed connections, for example welded or soldered joints, or connections produced by forming, can exist between the half sheets 12, 13.
[0043] The hard stop in the cooling cell 17 is fundamentally different from the soft stop formed at various points in the active cell 15. Figure 1 shows additional seals 19, 23 of different shapes, each serving a specific function within the soft stop. The term "soft stop" implies that, during the assembly of the stack 2, the height of the individual active cells 15 in the fully assembled electrolyzer 1 is not fixed by rigid components with unchanging dimensions. Rather, the assembly process utilizes the fact that individual components, in this case, in particular the cell materials 7, 25, are elastically, and possibly even plastically, deformable. During the compression of the stack 2, the force acting on the stack 2 initially increases moderately and then rapidly. A limiting force is defined at which the compression of the stack 2 is stopped.In this state, the active field frame 9, as a rigid component of the active cell 15, is not in contact on both sides with other rigid components, such as two bipolar plates 11. Rather, further compression of the stack 2 would theoretically be possible at this point. The absence of such further compression characterizes the force-controlled soft stop.
[0044] The tightness of the component arrangements within the active cell 15, which are adjusted by means of the soft-stop mechanism, is achieved by means of the aforementioned seals 19 and 23. Sealing lips are generally designated by 24. The soft-stop seal 19, which is visible in both Figure 1 and Figure 2 and is located on a region of the active field frame 9 adjacent to a connecting element 26, has a sealing area that extends in the stacking direction of the stack 2 from one bipolar plate 11 to the next bipolar plate 11, i.e., over the entire height of the active cell 15. A similarly effective sealing area is also formed in the seal 23. In addition, the seal 23 has a sealing area that is arranged only on one of the two sides of the membrane 6 and is thus intended for sealing exactly one half-cell 4 of the electrochemical cell 3.
[0045] Each seal 19, 23 is designed as a pressure-activated seal. This means, as illustrated in Figure 2, that horizontal forces Fh acting in the active part cell 15 parallel to the surface of the bipolar plate 11 are converted into vertical forces Fv, which enhance the sealing effect.
[0046] Regarding the structure of the stack 2, reference is made to Figure 3. Among other things, this figure shows that the seals 20, 21 are arranged on the edges of the cooling field frame 18 in a so-called "edge bonding" arrangement. Theoretically, since the seals 20, 21, unlike the seals 19, 23 located on the active field frame 9, do not have a compensating function within the operating electrolyzer 1, they could be replaced by metallurgical bonds.
[0047] The connecting elements 26, 26', whose arrangement is shown in Figure 1 and Figure 3, are rotationally symmetrical and have the form of a circular plug, which, in section according to Figure 1, has a recess 26a. Each connecting element 26, 26' is positively engaged in a bipolar plate 11 and projects through openings 12a, 13a in the half-sheets 12, 13, an opening 18a in the cooling field frame 18, and an opening 9a in one of the active field frames 9 adjacent to the bipolar plate 11. The recess 26a prevents adjacent connecting elements 26, 26' from touching each other and thus electrically short-circuiting different adjacent bipolar plates 11. (Related symbols: 1 Electrolyzer, electrochemical system; 2 Cell stack)
[0048] 3 Electrolysis cell, cell
[0049] 4 half-cell
[0050] 5 half-cell
[0051] 6 Membran
[0052] 7 Cell material, anode side
[0053] 8 Active field, active area
[0054] 9 frames, active field frames
[0055] 9a Opening in the active field frame
[0056] 10 ports
[0057] 11 Bipolar plate
[0058] 12 half-sheets, embossed
[0059] 12a Opening in the half sheet 12
[0060] 13 Half-sheet, flat
[0061] 13a Opening in the half-sheet 13
[0062] 14 Port and feed area
[0063] 15 active cell
[0064] 16 Coolant compartment
[0065] 17 refrigerated compartment
[0066] 18 cooling panel frames
[0067] 18a Opening in the cooling field frame
[0068] 19 Seal on the active field frame
[0069] 20 Seal on the cooling field frame
[0070] 21 Seal on the cooling field frame
[0071] 22 Area of overlapping half-sheets 23 Seal on the active field frame
[0072] 24 sealing lip
[0073] 25 cell material, cathode side
[0074] 26, 26' Connecting element
[0075] 26a Indentation
[0076] Fh, Fv Kraft
Claims
Patent claims 1. Electrochemical system (1) comprising a cell stack (2) of electrochemical cells (3), each with a bipolar plate (11) which is provided for demarcation from adjacent electrochemical cells (3), and with each with an active area (8) comprising a proton- or anion-permeable membrane (6) and fluid-permeable cell materials (7, 25), which is surrounded by an active field frame (9), wherein - the bipolar plate (11) is constructed from two half-sheets (12, 13), wherein a three-dimensionally structured half-sheet (12) and a flat half-sheet (13) are present, between which a coolant chamber (16) is formed, wherein a cooling field frame (18) surrounding the coolant chamber (16) contacts both half-sheets (12, 13) and is sealed against the half-sheets (12, 13) by means of at least one seal (20, 21) attached to the cooling field frame (18), - the active field frame (9) is provided with at least one further seal (19, 23) which seals the active area (8) while maintaining a deformation reserve, wherein a sealing area is formed which extends in a stacking direction of the cell stack (2) from one bipolar plate (11) to the next bipolar plate (11), and wherein - at least one connecting element (26) is provided which is positively inserted into each bipolar plate (11) and protrudes through openings (12a, 13a, 18a, 9a) in the half-sheets (12, 13) and the cooling field frame (18) arranged between them, as well as one of the active field frames (9) adjacent to this bipolar plate (11).
2. Electrochemical system (1) according to claim 1, characterized in that the extent of the at least one seal (20, 21) on the cooling field frame (18) in the installed and pressed state is determined by the shape of the half sheets (12, 13) and the thickness of the cooling field frame (18).
3. Electrochemical system (1) according to claim 2, characterized in that the at least one seal (20, 21) is injection molded onto an edge of the cooling field frame (18).
4. Electrochemical system (1 ) according to claim 2 or 3, characterized in that one of the two half-sheets (12, 13) is contacted on one side by the at least one seal (20, 21) attached to the cooling field frame (18) and on the directly opposite side by the seal (19, 23) with which the active field frame (9) is provided.
5. Electrochemical system (1) according to one of claims 1 to 4, characterized in that the active field frame (9) is provided with various further seals (19, 23), namely a seal (19) of the first type, which extends over the entire height of the active area (8), and a seal (23) of the second type, which has a sealing area that is arranged only on one side of the membrane (6) and is thus provided for sealing a half-cell (4, 5) of the electrochemical cell (3).
6. Electrochemical system (1) according to one of claims 1 to 5, characterized in that the active field frame (9) is designed as a formed metal part overmolded with sealing material.
7. Electrochemical system (1) according to one of claims 1 to 6, characterized in that at least one of the seals (19, 20, 21, 23) is designed as a pressure-activated seal.
8. Electrochemical system (1) according to one of claims 1 to 7, characterized in that the connecting element (26) has a recess (26a) which prevents contact with an adjacent connecting element (26').
9. Electrochemical system (1) according to any one of claims 1 to 8, characterized in that the connecting element (26) is made of metal, in particular steel, or plastic, in particular a thermoplastic or thermoset.
10. Method for assembling an electrochemical system (1) according to any one of claims 1 to 9 comprising the following steps: - Provision of several pairs of half-sheets (12, 13), - Provision of cooling field frames (18), each of which is intended to limit the coolant space (16) to be formed between two half-sheets (12, 13), - Provision of the proton- or anion-permeable membrane (6) per electrochemical cell (3) as well as various fluid-permeable cell materials (7, 25) which are provided for arrangement on both sides of the membrane (6) in the active area (8) of the electrochemical cell (3), - Assembling the pairs of half-sheets (12, 13) to form a bipolar plate (11), wherein the cooling field frame (18) contacts both half-sheets (12, 13) and seals are formed between the cooling field frame (18) on the one hand and the half-sheets (12, 13) on the other hand, - Inserting the membrane (6) and the cell materials (7, 25) into each active field frame (9), to which at least one further seal (19, 23) is attached, - Stacking of the bipolar plates (11), the connecting elements (26) and arrangements of active field frames (9), membrane (6) and cell materials (7, 25), - Pressing the cell stack (2) formed in the previous step in such a way that the at least one further seal (19, 23) attached to the active field frame (9) is compressed in the sense of a soft stop while maintaining a deformation reserve, whereas the components limiting the coolant chamber (16) half sheets (12, 13) and cooling field frame (18) are placed on top of each other in the sense of a hard stop without further compression possibility.
11. Method according to claim 10, characterized in that the compression of the cell stack (2) is stopped depending on the force acting in the cell stack (2).