Electrochemical cell stack

Abstract

An electrochemical cell stack (1) comprises a plurality of cells (2), which are separated from one another by bipolar plates (5, 5'), wherein each cell (2) is formed from two half-cells (3, 4) between which a membrane (6), surrounded by a support frame (7), is arranged, and wherein there is a porous transport layer (10, 11) in each half-cell (3, 4). The support frame (7) describes a stepped shape with two adjacent cross-section regions (12, 13), wherein an edge (18) of the membrane (6) lies in a step (17) formed by the cross-section regions (12, 13) and the porous transport layer (10) of a half-cell (3) extends into the step (17), and wherein the support frame (7) comprises at least one sealing arrangement (15) which is injection-moulded onto the support frame (7) and comprises an electrically insulating sealing material, wherein the sealing arrangement (15) comprises three sealing regions (19, 20, 21) each having at least one sealing lip (22, 22'), specifically a first sealing region (19) and a second sealing region (20) which are assigned to the narrower of the two cross-section regions (12, 13) facing the membrane (6) and each of which contact exactly one bipolar plate (5, 5'), and a third sealing region (21) which is on a side of the support frame (7) facing away from the step (17) and borders an opening (9) of the support frame (7) provided for the guiding through of media, and contacts both bipolar plates (5, 5') to which the first and the second sealing region (19, 20) are adjacent.

Description

[0001] Electrochemical cell stack

[0002] The invention relates to an electrochemical cell stack comprising a plurality of electrochemical cells separated from one another by bipolar plates. Each electrochemical cell is formed from two half-cells, between which a membrane surrounded by a support frame is arranged, and each half-cell contains a porous transport layer. The electrochemical cell stack is designed, in particular, as a stack of electrolysis cells for hydrogen production.

[0003] An electrolysis cell stack is known, for example, from WO 2018 / 078157 A1. The known electrolysis cell stack, i.e., electrolyzer, comprises a plurality of bipolar plates arranged in a stacked fashion. Between the bipolar plates, among other things, are membranes and porous transport layers, also commonly referred to as porous transport layers (PTLs). According to WO 2018 / 078157 A1, the bipolar plates each have a layer of Ir, Ru, Rh, Os, their oxides, or mixtures thereof. This layer is intended to function as a corrosion protection layer within the electrochemical system.

[0004] DE 10 2021 203 983 A1 discloses a single-cell arrangement for a fuel cell stack. A framed membrane electrode arrangement comprises an electrochemically active region made of two gas diffusion layers and a catalyst-coated membrane, which are bonded to a frame. Furthermore, the arrangement according to DE 10 2021 203 983 A1 comprises a bipolar plate having flow distribution and guide elements in a flow region corresponding to the electrochemically active region. In an edge region of the bipolar plate surrounding the flow region, a sealing groove for receiving a seal between the frame and the bipolar plate is formed on at least one of the surfaces of the bipolar plate.

[0005] Another membrane assembly, which separates an anode chamber from a cathode chamber within a fuel cell stack, is described in DE 10 2009 039 905 A1. The membrane of the arrangement according to DE 102009039 905 A1 has an elongated rectangular shape, with several channels, generally referred to as ports, for the passage of working gases, i.e., operating media, located on both narrow sides of the rectangular membrane. The membrane is assigned to an MEA plate, which is surrounded by an auxiliary assembly section designed as a dimensionally stable support frame. Within a connecting section, which connects the MEA plate to the support frame, there is, among other things, a seal designed as a sealing bead.

[0006] An arrangement for a fuel cell disclosed in DE 10 2008 028 117 A1 comprises a bipolar plate in the form of a flat component to which a sealing element is positively attached. The sealing element is essentially U-shaped.

[0007] Further design options for seals in stacked arrangements of electrochemical cells can be found, for example, in the documents EP 3 039 734 B1, DE 10 2006 058 335 A1, DE 11 2015 002 427 T5 and WO 2021 / 104812A1.

[0008] EP 3 356 575 B1 discloses a high-pressure or differential-pressure electrolysis cell comprising an electrochemical cell with a high-pressure side and a low-pressure side. The electrochemical cell includes two flow-field plates and a membrane arranged between the flow-field plates and having a first side on the low-pressure side and a second side on the high-pressure side. Furthermore, the electrolyzer according to EP 3 356 575 B1 comprises a first porous support arranged between the first side of the membrane and the first flow-field plate, which is relatively incompressible compared to other materials arranged between the plates. A first seal surrounds the first porous support, forming a gap between the first porous support and the seal. A second seal is arranged between the second side of the membrane and the second flow-field plate.Furthermore, the device according to EP 3356 575 B1 comprises a second porous support arranged on the second side of the membrane, which is more compressible than the first porous support. The electrolyzer according to EP 3 356 575 B1 is intended to operate at a pressure difference between the high-pressure side and the low-pressure side.

[0009] Low pressure side of at least 40 bar.

[0010] DE 10 2022 101 106 A1 describes an electrolysis cell with a cell frame made of insulating plastic between two bipolar plates. At least one sealing element in the form of a flat gasket is provided between the cell frame and each bipolar plate. The flat gasket is integrated into the cell frame using a two-component injection molding process.

[0011] The invention is based on the object of specifying an electrochemical cell stack which is further developed compared to the cited prior art, in particular with regard to manufacturing and sealing technology, for example in the form of a stack of electrolysis cells for hydrogen production, wherein the cell stack should also be operable under a high differential pressure between the cathode side and the anode side.

[0012] This object is achieved according to the invention by an electrochemical cell stack, in particular a stack of electrolysis cells for hydrogen production, having the features of claim 1. The cell stack comprises, in a basic concept known per se, a plurality of electrochemical cells which are separated from one another by bipolar plates, each electrochemical cell being formed from two half-cells between which a membrane surrounded by a support frame is arranged, and each half-cell containing a porous transport layer which is permeable to operating media of the electrochemical system.

[0013] According to the invention, the support frame has a stepped cross-section, with two adjacent, for example rectangular, cross-sectional areas of different widths of the support frame. Generally, this is also referred to as adjacent, different-width areas. The width of these distinguishable areas is measured in the plane in which the support frame and the membrane lie. One edge of the membrane rests on the support frame in a step formed by the two cross-sectional areas.

[0014] The porous transport layer of one of the two half-cells of the electrochemical cell is designed as a compressive force-transmitting element and extends from the active field of the electrochemical cell enclosed by the support frame into the aforementioned step, i.e., beyond the inner edge of the support frame. The compressive forces considered are forces acting in the normal direction to the mutually parallel planes in which the support frames and the bipolar plates are arranged.

[0015] The support frame comprises at least one sealing arrangement made of an electrically insulating sealing material, which is molded onto the support frame. The sealing arrangement comprises at least three sealing regions, each with at least one sealing lip, namely a first sealing region and a second thin sealing region, which are assigned to the narrower cross-sectional region facing the membrane. The thickness of all sealing regions is to be measured in the aforementioned normal direction, i.e., orthogonal to the direction in which the width of the various cross-sectional regions of the support frame is to be measured. Each of the two aforementioned sealing regions contacts exactly one bipolar plate.Furthermore, there is a third sealing area, which is located on a side of the support frame facing away from the step, i.e. on the outer side of the support frame, and borders on an opening of the support frame provided for the passage of media, i.e. on a port, and in this case contacts both bipolar plates against which the first and the second sealing area rest.

[0016] The at least three sealing areas represent integral components of the support frame and, viewed from the active field of the electrochemical cell, are staggered from the inside to the outside, with the first sealing area enclosing the cathode side of the electrochemical cell and representing the innermost seal, i.e., the seal closest to the center of the active field. Accordingly, the active field has a smaller footprint on the cathode side than on the anode side. The membrane of the electrochemical cell rests on the first sealing area. In contrast to unclaimed solutions, the membrane is not supported by another seal at this point. Rather, on the side of the membrane directly opposite the first sealing area on the cathode side, there is a volume section of the anode-side porous transport layer. This volume section is attributable to the previously mentioned element suitable for transmitting compressive forces.From this element, which is in the form of a porous transport layer, the compressive forces can be transferred further into the adjacent bipolar plate.

[0017] Just like the membrane, the porous transport layer on the anode side, designed to transmit compressive forces, extends into the step formed by the two cross-sectional areas of the support frame with different widths. A strip-shaped edge area of ​​the membrane is thus arranged in an area that is hardly usable for electrochemical reactions. The mechanical support of the edge area of ​​the membrane by a similarly strip-shaped area of ​​the support frame makes a significant contribution to preventing leaks from occurring at that point, for example by the membrane being pressed into a gap at its edge. Rather, the strip-shaped edge area of ​​the membrane is also pressed against the step by the pressure prevailing on the anode side.

[0018] The active field of the electrochemical cell is limited on the anode side by the second sealing area located further outward. The anode-side porous transport layer can extend to this second sealing area, whereby this second sealing area, together with other volume sections of the support frame, can be used in addition to the transport layer to transmit compressive forces acting between the bipolar plates.

[0019] The third sealing area encloses the outer edge of the support frame on the side facing away from the step. The third area has at least two sealing lips, which run against the bipolar plate arranged above and below the support frame in the cross-section of the support frame. The sealing material is made of an elastomeric material with a Shore A hardness of 70-90 ShA, particularly at a temperature of 23°C ± 2 K. The Shore A hardness is specified for elastomers after measurement with a needle with a blunt tip. The end face of the truncated cone has a diameter of 0.79 millimeters, and the opening angle is 35°. Contact weight: 1 kg, holding time: 15 s. The material thickness should be at least 6 mm.

[0020] Examples of suitable sealing materials for forming the various sealing areas include FKM (an abbreviation for fluororubber compound or fluorocarbon rubber) and EPDM (ethylene propylene diene rubber). Well-known technologies such as injection molding and edge bonding are suitable for applying the sealing material.

[0021] In principle, the minimum required seal coverage, i.e., the height of a sealing lip above the remaining sealing area, is a function or result of material hardness, design, the tolerance chain, and the system requirements, i.e., the pressure to be sealed in a half-cell. The seal coverage is generally a multiple of the height of any existing support structures (see below).

[0022] Preferably, both the first sealing region and the third sealing region each have at least two annular sealing lips extending parallel to the plane of the membrane at their ends facing away from the support frame, and the second sealing region has at least one annular sealing lip extending parallel to the plane of the membrane. Possible configurations of the sealing lips are shown in Figures 12 and 13.

[0023] One sealing area is preferably designed to be almost as high as it is wide, as seen in cross-section through the frame arrangement. The sealing area thus resembles an O-ring. The sealing function of the second sealing area is primarily based on axial compression of the sealing lip(s). The sealing function of the first and third sealing areas is primarily based on axial compression of the sealing lips and pressure activation, primarily acting horizontally on the sealing area and acted upon by the medium to be sealed. This pressure activation, due to the preferably low compressibility of the sealing material, leads to an additional axial sealing force on the sealing lips.

[0024] The various sealing areas are generally constructed from preferably incompressible materials, particularly elastomers. This creates interactions between loads acting in different directions, for example, horizontal forces occurring in the plane of the support frame and vertical forces acting in the longitudinal direction of the stack, i.e., the cell stack. Such interactions enhance the sealing effect of the support frame. Overall, the support frame represents a highly integrated component embedded in a compact, easy-to-assemble, and robust cell design. Due to the integration of various functions into the support frame and the resulting minimized number of individual components, the issue of assembly tolerances is largely eliminated by design.

[0025] The support frame, which has at least three offset sealing areas in plan view, is suitable, for example, for use in an electrolyzer operating with a pressure difference of 100 bar between the cathode and anode sides. A particular advantage of this application is that separate equipment for compressing the hydrogen, which can be fed into a pipeline network or supplied directly to a consumer, can be largely or even completely eliminated.

[0026] Apart from the sealing areas, metallic or non-metallic materials are generally suitable for manufacturing the support frame. If a core of the support frame is made of metal, a substance located on the core can provide electrical insulation between the two bipolar plates that enclose the support frame. It has proven effective to have at least one electrically insulating area that connects the third sealing area with the second sealing area and / or the second sealing area with the first sealing area. The at least one electrically insulating area has no sealing function but serves solely as electrical insulation. This may be required on the anode side, the cathode side, or both sides of the support frame.

[0027] The at least one electrically insulating region is preferably formed from the electrically insulating sealing material from which the sealing arrangement is made. The electrically insulating region can be formed during the formation of the sealing arrangement. This electrically insulating region can be implemented both in a support frame with a metallic core and in a support frame made entirely of non-metallic materials. However, the at least one electrically insulating region is preferably arranged on a support frame made of electrically conductive material to reduce costs.

[0028] According to a possible further development, elastic support in the electrically insulating region, which is preferably significantly wider than any of the sealing regions, is provided by elastic support structures, such as elastic nubs, webs, grooves, or compression springs. The support structures can be made of any metallic and / or non-metallic materials.

[0029] The elastic resilience of the support structures can be used, in particular, for assembly with a so-called SoftStop. This is based on the assumption that the support frame, including the electrically insulating area, represents a softer spring than the arrangement present in the active field, which, in addition to the membrane, includes, in particular, the porous transport layers in both half-cells.

[0030] A HardStop concept, on the other hand, can be implemented with a support frame that does not have an electrically insulating region made of an elastic material such as the sealing material. In such a case, the adjacent bipolar plates can rest directly on the barely flexible core of the support frame, provided the core is made of an electrically insulating material. Otherwise, electrical insulation can be achieved by an electrically insulating coating located on at least one side of the support frame adjacent to a bipolar plate, forming an electrically insulating region. Suitable electrically insulating coatings include, for example, ceramic coatings, such as Al2O3 and / or SiO2, or polymer coatings.

[0031] If a core element of the support frame is designed as a metal part, particularly a sheet metal part, a single- or multi-layer design of this core element is possible. In the case of a two-layer design, one of the two sheet metal layers of the core element can form the step in the area of ​​its end face with a longer sheet metal layer arranged underneath. The sheet metal layers can be connected to each other, for example, by welding.

[0032] When manufacturing the support frame from sheet metal, particularly steel, a three-dimensional structuring of the sheet offers advantages in terms of mechanical stability while simultaneously utilizing materials economically. For example, the metal core of the support frame, manufactured from sheet metal using a forming process, describes a three-dimensionally formed cross-section. In this case, beads introduced into the sheet metal can run particularly in the longitudinal direction of the frame. After forming the sheet metal, which represents the core element of the support frame, the sheet metal can be overmolded in a single step with an elastomer, which forms all sealing areas. At the same time, electrically insulating areas can be overmolded.

[0033] According to one possible embodiment, the first sealing area is located between one of the two bipolar plates sandwiching the support frame and a layered arrangement designed to absorb compressive forces. This arrangement consists of the membrane of the electrochemical cell, the compressive force-transmitting porous transport layer of the anode-side half-cell, the second bipolar plate, and a cooling field frame, which is mechanically stronger than surrounding elements. Despite the low height of the electrochemical cells, a stable structure of the entire cell stack with highly effective seals both inside and outside the cells is thus possible.

[0034] Several embodiments of the invention are explained in more detail below with reference to a drawing. In the drawings:

[0035] Fig. 1 shows a first embodiment of an electrochemical cell stack in cross section,

[0036] Fig. 2 shows a section of the arrangement according to Figure 1,

[0037] Fig. 3 shows a support frame of the cell stack according to Figure 1 in plan view,

[0038] Fig. 4 - 10 Sections of further electrochemical cell stacks seen in cross section,

[0039] Fig. 11 shows another section of an electrochemical cell stack in cross section, and

[0040] Fig. 12 - 13 possible sealing lips for the sealing areas seen in cross section.

[0041] Unless otherwise stated, the following explanations refer to all exemplary embodiments. Corresponding or essentially equivalent parts are identified by the same reference numerals in all figures.

[0042] An electrochemical cell stack, designated overall by reference numeral 1, is an electrolyzer for producing hydrogen. The cell stack 1 comprises a plurality of electrochemical cells 2, i.e., electrolysis cells, each composed of a first half-cell 3 and a second half-cell 4. Bipolar plates 5, 5' separate a half-cell 3 of a first electrochemical cell 2 from a half-cell 4 of another electrochemical cell 2. The two half-cells 3, 4 of each electrochemical cell 2 are separated from one another by a membrane 6. The membrane 6 is located in a support frame 7, which is sandwiched between two parallel bipolar plates 5, 5'. The outline of the support frame 7 is shown in Figure 3. The support frame 7 encloses an active field 8 of the electrolysis cell 2.Openings 9 arranged outside the active field 8, through which operating media of the cell stack 1 are conducted, are generally referred to as ports. Within the electrolysis cells 2, the operating media flow, among other things, through porous transport layers 10, 11 located in the half-cells 3, 4. As can be seen from all figures with the exception of figure 3, the two half-cells 3, 4 have different widths. Without loss of generality, in the present cases the anode-side half-cell 3 is referred to as the upper half-cell and the cathode-side half-cell 4 as the lower half-cell. The anode-side porous transport layer 10 projects beyond the cathode-side porous transport layer 11 in all cases. Accordingly, the support frame 7, which encloses the active field 8, has a stepped shape in cross-section.

[0043] The section of the support frame 7 considered in the exemplary embodiments borders, on the one hand, a port 9 and, on the other hand, both half-cells 3, 4 of one and the same electrochemical cell 2. In this section, there are two distinguishable, differently wide cross-sectional areas 12, 13. The support frame 7 comprises a single- or multi-part core element 14, which occupies space in at least one of the cross-sectional areas 12, 13, as well as a sealing arrangement designated overall by 15. The sealing arrangement 15, like the core element 14, is assigned to a frame section 16.

[0044] The width of the frame section 16, measured in the plane of the support frame 7, is designated BR. The width of the core element 14, which is smaller in all cases, is designated BK. The height of the support frame 7, designated HR, together with other elements of the cell stack 1, specifies the distance between two adjacent bipolar plates 5, 5'. The sum of the thickness of the cross-sectional area 13 and the thickness of the electrically insulating area 27 results in the height HR of the frame section 16. In these cases, too, the designations "bottom" and "top" refer only to the figures and do not imply any statement about the actual installation position of the components 5, 5', 6, 16 in the cell stack 1. A step 17 is formed between the cross-sectional area 12 and the cross-sectional area 13 on the side of the frame section 16 facing the active field 8.An edge of the membrane 6, designated 18, lies in this step 17, remaining at least slightly spaced from the core element 14 due to the presence of the sealing arrangement 15. The sealing arrangement 15 comprises three distinguishable sealing regions 19, 20, 21. A first sealing region 19 and a second sealing region 20 are distinguishable from a third sealing region 21. The thickness of the first sealing region 19 and the second sealing region 20 each corresponds to the height of a half-cell 3, 4. The third sealing region 21 fills the entire cell height. While the latter third sealing region 21 seals towards the port 9, the two sealing regions 19, 20 seal the active field 8. All sealing areas 19, 20, 21 represent integral components of the support frame 7. In the exemplary embodiments, each sealing area 19, 20, 21 has at least one sealing lip 22.The sealing lips 22 shown in the sectional view each run in a ring shape in the top view of the membrane 6.

[0045] In all the arrangements outlined, the first sealing area 19 has two sealing lips 22, which rest on the lower bipolar plate 5', as well as two further sealing lips 22, on which the membrane 6 rests. The four sealing lips 22 are directed counter to the pressure acting during operation of the cell stack 1, which increases the sealing effect with increasing pressure. Thus, the shape of the sealing lips 22 contributes to the self-sealing effect.

[0046] The porous transport layer 10 located above the membrane 6 represents a force-transmitting element which, together with the first sealing region 19, transmits forces F, i.e., compressive forces, between the bipolar plates 5, 5' arranged parallel to one another. In the exemplary embodiment according to Figures 1 to 2, a force is illustrated acting on a cooling field frame 23 which is inserted into an embossed structure, designated 25, of the bipolar plate 5. Elongated or circular embossed elements of the embossed structure 25 are designated 24, 26. In the exemplary embodiments, the second sealing region 20 has only a single sealing lip 22 resting against the bipolar plate 5. Viewed from the active field 8, the second sealing region 20 is offset outwards relative to the first sealing region 19, i.e., in the direction of the port 9.In the examples outlined, the third sealing region 21 directly adjacent to the port 9 has exactly two sealing lips 22, each of these sealing lips 22 contacting one of the bipolar plates 5, 5', between which the support frame 7 is arranged.

[0047] In the exemplary embodiments according to Figures 1, 2, 4, 5, 6, 7, 8, and 9, there is also an electrically insulating region 27, which connects the second sealing region 20 to the third sealing region 21 and rests against the upper bipolar plate 5 shown in the illustrations. Thus, the sealing regions 20, 21 and the electrically insulating region 27 extend over the entire cross-sectional area 13 in these cases.

[0048] According to Figures 1, 2, 4, 5, 7, 8, 9, a further electrically insulating region 27' is present, which connects the second sealing region 20 to the first sealing region 19.

[0049] The electrically insulating regions 27, 27' are formed according to Figures 1, 2, 4, 5, 7, 8, 9 from the electrically insulating sealing material with which the sealing regions 19, 20, 21 are formed.

[0050] According to Figure 6, an electrically insulating region 27 is formed from an electrically insulating coating 31 which does not correspond to the sealing material.

[0051] The entire support frame 7 is thus given elastic flexibility in the normal direction of the plane in which the support frame 7 lies.

[0052] In the exemplary embodiment according to Figures 1 and 2, the core element 14 of the support frame 7 is made of plastic. The sealing arrangement 15 is integrally connected to the core element 14, so that the support frame 7, which comprises the core element 14 and the sealing arrangement 15, forms a structural unit that is not intended for disassembly. Such a structural unit consisting of the core element 14 and the sealing arrangement 15 is also provided in the design according to Figure 4, wherein in this case the core element 14 is designed as a profiled sheet metal to which the sealing arrangement 15 is injection-molded. As far as the shape of the individual sealing regions 19, 20, 21 and the number of sealing lips 22 are concerned, there are no fundamental differences between the embodiment according to Figure 4 and the embodiment according to Figure 1. In the case of Figure 4, the core element 14, designed as a sheet metal, rests on the lower bipolar plate 5' in several strip-shaped regions.On the left side of the core element 14 in the arrangement according to Figure 4, i.e. the side facing the port 9, an edge strip 28 is formed by the core element 14, which protrudes from the plane that is tangent on the one hand to the lower bipolar plate 5' and on the other hand to the underside of the core element 14, and extends approximately over the entire height HR of the support frame 7. On the opposite, inner side of the core element 14, this runs out in the form of a flat band 29, to which the first sealing region 19 adjoins in the direction of the active field 8.

[0053] The support frame 7 according to Figure 5 differs from the support frame 7 according to Figures 1 and 2 in that several elastic support elements 30, here indicated as helical springs, are located in the electrically insulating region 27, which transmit forces F, as illustrated by arrows in Figure 5, between the bipolar plate 5 and the support frame 7. The core element 14 is made of plastic in the case of Figure 5, as in the case of Figure 1.

[0054] In the embodiment according to Figure 6, the core element 14 is made of metal and thus designed as an electrical conductor. To create electrical insulation between the mutually parallel bipolar plates 5, 5', which enclose the support frame 7 between them like a sandwich, an electrically insulating region 27 in the form of an electrically insulating coating 31 is located on the upper side of the support frame 7, i.e. on the cross-sectional region 13. Elastic deformability of the support frame 7 in the normal direction of the bipolar plates 5, 5' is present to a much lesser extent in the case of Figure 6 than in the cases of Figures 1, 4 and 5. Accordingly, the case of Figure 6 is referred to as a so-called HardStop concept.

[0055] In the case of Figure 7, the support frame 7 has the same external shape as in the embodiment according to Figure 1. In contrast to the embodiment according to Figure 1, in the case of Figure 7, the cross-sectional area 13 is formed by a part of the core element 14 and the electrically insulating area 27. The core element 14 is also located in the cross-sectional area 12. Thus, a distinctive SoftStop concept is realized in the embodiment according to Figure 7.

[0056] In the embodiment according to Figure 8, the core element 14, as in the case of Figure 4, is made of metal. Here, the core element 14 has a toothed profile produced by forming, with grooves 32, i.e., beads, running in its longitudinal direction on the underside of the profile and teeth 33, rectangular in cross-section, visible on the top of the profile. Adapted to the cross-section of the core element 14, the fourth sealing region 27 has a toothed structure 34, not visible from the outside, which provides a particularly stable bond between the core element 14 and the sealing arrangement 15.

[0057] The embodiment shown in Figure 9 also features a metallic core element 14, which here is formed from two unequal-width, welded sheet metal strips 35, 36. The overall cross-sectional shape of the core element 14 of the support frame 7 shown in Figure 9 corresponds to the embodiment shown in Figure 1.

[0058] In the embodiment shown in Figure 10, the plastic core element 14 fills the entire height HR between the two bipolar plates 5. In this case, the sealing arrangement 15 comprises only the two interconnected sealing areas 19, 20 and the sealing area 21 separated from them.

[0059] According to Figure 11, a core element 14 and a sealing arrangement 15 are present, wherein in this case the core element 14 is designed as a profiled sheet metal to which the sealing arrangement 15 is injection-molded. As far as the shape of the individual sealing regions 19, 20, 21 and the number of sealing lips 22 are concerned, there are no fundamental differences between the embodiment according to Figure 4 and the embodiment according to Figure 1. The same reference numerals as in these figures identify the same elements. Only the core element 14 is more delicate in the cross-sectional region 13 and forms a step 17 with the cross-sectional region 12 due to the deformation of the sheet metal. The electrically insulating region 27 between the third sealing region 21 and the second sealing region 20 has support structures 30 which support the bipolar plate 5.The further electrically insulating region 27' between the second sealing region 20 and the first sealing region 19 is formed from sealing material, like the electrically insulating region 27, and is integrally molded onto the core element 14 at the same time as the sealing arrangement 15. The frame arrangement 16 is particularly cost-effective and can be manufactured quickly.

[0060] Figure 12 shows possible designs of sealing lips 22 in the third region 21, which is injection-molded onto an end face of a core element 14 (only partially shown). Shown here from left to right are: two sealing lips 22, each with a triangular basic shape; four sealing lips 22, each with a triangular basic shape; two sealing lips 22, each with a rounded basic shape; four sealing lips 22, each with a step-like, flattened basic shape; four sealing lips 22, two with a triangular basic shape, two with a rounded basic shape.

[0061] Such basic shapes can be combined as desired, and the number of sealing lips 22 can be varied. The sealing lip designs shown for the third sealing area 21 can also be used for the first sealing area 19.

[0062] Figure 13 shows possible designs of a sealing lip 22' in the second region 20, which is molded in the region of the step 17 of a core element 14 (only partially shown). Shown here from left to right are: two sealing lips 22', one with a rounded basic shape and one with a triangular basic shape; two sealing lips 22', each with a step-like, flattened basic shape; one sealing lip 22' with a rounded basic shape; two sealing lips 22', each with a triangular basic shape; one sealing lip 22' with a triangular basic shape. Such basic shapes can be combined as desired, and the number of sealing lips 22' can be varied.

[0063] List of reference symbols for electrochemical cell stacks, electrochemical cell, electrolysis cell

[0064] Half-cell

[0065] Half cell, 5' bipolar plate

[0066] membrane

[0067] support frame

[0068] Active field

[0069] Opening, port 0 Porous transport layer, anode side 1 Porous transport layer, cathode side 2 Cross-sectional area 3 Cross-sectional area 4 Core element 5 Sealing arrangement made of sealing material 6 Frame section 7 Step 8 Edge of the membrane 9 First sealing area on the active field with sealing lips 22 0 Second sealing area on the active field with one-sided sealing lip 22'1 Third sealing area, bordering the port 9 2 Sealing lip 2' Sealing lip 3 Cooling field frame 4 Embossed element 5 Embossed structure 6 Embossed element 7, 27' Electrically insulating area (without sealing function) 8 Edge strip 9 Band 0 Support structures 31 Electrically insulating coating

[0070] 32 grooves

[0071] 33 tooth

[0072] 34 Tooth structure

[0073] 35 metal strips

[0074] 36 metal strips

[0075] BR Width of the frame element

[0076] BK Width of the core element

[0077] F compressive force

[0078] HR Height of the support frame

Claims

Patent claims 1. An electrochemical cell stack (1) comprising a plurality of electrochemical cells (2) separated from one another by bipolar plates (5), each electrochemical cell (2) being formed from two half-cells (3, 4) between which a membrane (6) surrounded by a support frame (7) is arranged, and each half-cell (3, 4) containing a porous transport layer (10, 11), characterized in that the support frame (7), viewed in cross-section, has a stepped shape with at least two adjacent cross-sectional areas (12, 13) of different widths, an edge (18) of the membrane (6) lying in a step (17) formed by the two cross-sectional areas (12, 13), and the porous transport layer (10) of one of the two half-cells (3) extends into the step (17) as a pressure-transmitting element.and wherein the support frame (7) comprises at least one sealing arrangement (15) made of an electrically insulating sealing material, which is injection-molded onto the support frame (7), wherein the sealing arrangement (15) comprises at least three sealing regions (19, 20, 21), each with at least one sealing lip (22, 22'), namely a first sealing region (19) and a second sealing region (20), which are assigned to the narrower of the two cross-sectional regions (12, 13) facing the membrane (6) and each contact exactly one bipolar plate (5, 5'), as well as a third sealing region (21), which is located on a side of the support frame (7) facing away from the step (17) and borders an opening (9) of the support frame (7) provided for the passage of media, and in this case contacts both bipolar plates (5, 5') against which the first and second sealing regions (19, 20) rest.

2. Cell stack (1) according to claim 1, characterized in that at least one electrically insulating region (27, 27') is present which connects the third sealing region (21) to the second sealing region (20) and / or the second sealing region (20) to the first sealing region (19).

3. Cell stack (1) according to claim 2, characterized in that the at least one electrically insulating region (27, 27') is formed from the sealing material or an electrically insulating coating (31).

4. Cell stack (1) according to claim 2 or 3, characterized by a plurality of elastic support structures (30) arranged in at least one electrically insulating region (27, 27').

5. Cell stack (1) according to one of claims 1 to 4, characterized in that a core element (14) of the support frame (7) is made of plastic.

6. Cell stack (1) according to one of claims 1 to 4, characterized in that a core element (14) of the support frame (7) is designed as a metal part, in particular a sheet metal part.

7. Cell stack (1) according to claim 6, characterized in that the support frame (7) is constructed in two layers from sheet metal.

8. Cell stack (1) according to claim 6 or 7, characterized in that both the first sealing region (19) and the third sealing region (21) each have at least two annular sealing lips (22) running parallel to the plane of the membrane (6) at their ends facing away from the support frame (7), and in that the second sealing region (20) has at least one annular sealing lip (22') running parallel to the plane of the membrane (6).

9. Cell stack (1) according to claim 6, characterized in that the support frame (7) has a core element (14) in the form of a metal part three-dimensionally formed from a flat sheet metal strip.

10. Cell stack (1) according to one of claims 1 to 9, characterized in that the first sealing region (19) lies between one of the bipolar plates (5, 5') and a layered arrangement which is formed from the membrane (6), the porous transport layer (10) provided for transmitting compressive force, the further bipolar plate (5) and a cooling field frame (23).

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