Sealing arrangement, cell element of an electrochemical cell, cell stack with a distributor structure, and electrolyser

Abstract

The invention relates to a sealing arrangement (21, 21A, 21B) comprising a flat metal support (23A) and a sealing element (23B) applied to the metal support (23A), wherein the metal support (23) is designed as a thin surrounding frame having an outer edge and an inner edge, and wherein a plurality of openings (31) are introduced into the metal support (23) along an edge and the openings (31) are arranged along a straight line and are aligned flush with respect to the outer edge such that a hole pattern is formed. The hole pattern is designed in such a way that openings (31) of a first type and of a second type are provided, with the longitudinal extent perpendicular to the straight line for an opening (31) of the first type being greater than the longitudinal extent for an opening (31) of the second type, a linear, alternating hole pattern being formed along the straight line, and the sealing element (23B) having an elastomer which is applied to the metal support (23A) at least at the rim of the openings (31). The invention also relates to a cell element having the sealing arrangement (21, 21A, 21B), to a cell stack having a plurality of electrochemical cells, and to an electrolyzer.

Description

[0001] Description

[0002] Sealing assembly, cell element of an electrochemical cell, cell stack with a distributor structure and electrolyzer

[0003] The invention relates to a sealing arrangement and a cell element of an electrochemical cell, in particular an electrolysis cell, with such a sealing arrangement. The invention further relates to a cell stack comprising a plurality of electrochemical cells with a cell element and an electrolyzer, in particular a PEM electrolyzer, comprising a cell stack.

[0004] In cell stacks, such as those found in fuel cells or electrolyzers, cells are stacked on top of each other to increase usable voltage or media throughput. These cells consist alternately of the active component, often called a membrane electrode assembly (MEA) in an electrolysis cell stack, and a media distribution plate, also called a bipolar plate, which in turn can consist of further components. For cost and space reasons, it is advantageous to minimize the material thickness of the respective media distribution plates. This can lead to deformation of the media distribution plate edges during the manufacturing process, transport, or integration into an end system. In extreme cases, such deformation can cause adjacent media distribution plates to touch, resulting in a short circuit in the media distribution plate stack.

[0005] It is known that the respective insulating intermediate layers, such as a so-called "subgasket" or an edge reinforcement, extend beyond the respective media distribution plates of a cell stack to such an extent that a short circuit cannot occur even if the edge of the media distribution plates is bent. The fluid to be distributed during electrolysis can be, in particular, a gas and / or a liquid, especially an electrolyte, a catalyst, an analyst, or a reactant for the operation of the electrochemical cell in question.

[0006] In electrolysis, particularly water (H₂) or CO₂ / CCy electrolysis, as well as in fuel cells, incoming fluid flows must be distributed as evenly as possible across the width of the active cell to enable and maintain the electrochemical reaction across the entire surface, for example, at the ion or proton exchange membrane. This means supplying fresh media and removing spent media. Only a uniform supply and / or removal of media across the entire membrane surface allows for uniform current densities. By adhering to the maximum permissible current density, which depends on the specific membrane, the overall power output of the cell can be maximized without local overload and the associated premature aging.

[0007] In this context, it is particularly advantageous to increase the flow resistance of distribution channels as much as possible, at least downstream in the vicinity of the active cell, in order to prevent or largely reduce electrical parasitic currents.

[0008] In current cell designs, the cell height of an electrolysis cell, for example a PEM electrolysis cell, is limited by the required height of the cell frame and the seals embedded therein, e.g., O-rings. Tolerances are currently compensated for within certain limits by using soft, internal sealing and cell components. This design significantly impairs the cell's efficiency and limits the desired higher power densities per volume, particularly for reducing installation space. Therefore, a particular object of the present invention is to provide an improved, homogeneous media distribution for electrochemical cells that simultaneously enables the most robust and compact design possible for the component containing the cell and facilitates automated industrial mass production.

[0009] This problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent patent claims.

[0010] The invention is based on the understanding that known cell designs for electrolysis cells, particularly PEM electrolysis cells, have certain inherent disadvantages and technical limitations that prevent fundamental improvements in their construction. In these known cell designs, the required contact pressure during assembly and sealing of a membrane electrode assembly (MEA) is achieved by matching the component heights and their stiffnesses. However, this results in a certain sensitivity to manufacturing tolerances. This is mitigated by using appropriately soft materials for the internal sealing and cell components, such as soft carbon fleece as an internal component of a PEM electrolysis cell.The structural integrity of a series arrangement or axial stacking of a large number of electrolysis cells into so-called “stacks” is based on the effect of frictional locking between the current collector, also known as the bipolar plate (BPP), and the cell frame.

[0011] A disadvantage of the known cell design is that reducing the height of the electrolysis cell, and thus further compaction, is limited, in particular, by the required depth of the grooves integrated into the cell frame to accommodate the sealing elements, such as O-rings. These O-rings consist of a ring-shaped elastic material, usually rubber or silicone. Due to their circular or near-circular cross-section, O-rings can seal axially and / or radially. Initial sealing is achieved by compressing the rubber body during installation in the radial and / or axial direction. The sealing pressure results from the superposition of the initial compression during installation and the system pressure to be sealed. Therefore, the sealing pressure in the necessarily provided sealing joint is always higher than the pressure to be sealed by the amount of the initial compression. This is why even very high pressures can be sealed.However, the current cell design results in limited precision of the cell frame, which is always inherent in the construction, due to the use of materials such as plastic and injection molding. This necessitates manual assembly and positioning of the sealing elements in the sealing grooves.

[0012] In contrast, the invention presents a novel and advantageous cell concept. This allows for a reduction in manufacturing and material costs. Fewer components are required, and the production of thinner electrolysis cells is enabled, meaning that significantly more electrolysis cells can be accommodated in the same space compared to a conventional cell design. This directly results in gains in efficiency and performance.

[0013] The advantage of the invention over the prior art lies particularly in the improved possibility of a compact design while simultaneously achieving a largely homogeneous distribution of the fluid across the entire cell width. This, in turn, allows for the realization of more robust electrochemical components with significantly improved power density. Furthermore, the invention offers the advantage of improved manufacturability and the possibility of mechanically supporting or pressing cell stacks with multiple cell elements against each other with particular stability, thereby achieving elasticity, strain tolerance, and flexibility in the construction. Performance is preferably improved by replacing the previously used ECM250 carbon fleece with porous transport layers (PTLs) or gas diffusion layers (GDLs) in the electrolysis cell.These functional layers can be designed in accordance with the respective operating conditions and specifically adapted to the requirements.

[0014] In particular, according to one aspect of the invention, an improved multifunctional and standardized sealing arrangement is provided, thus sealing the cell for fluid transport and its homogeneous distribution across the active area of ​​the membrane electrode assembly (MEA). For this purpose, a robust membrane seal is provided for use in an electrolysis cell, which optionally also enables advantageous differential pressure operation between the anode and cathode compartments. Therefore, the sealing arrangement of the invention provides a sealing function and a transport function for a fluid by forming a fluid channel or a plurality of fluid channels (so-called fluid manifold or distributor structure). The transport function includes the supply and distribution of the media to a cell element, in particular to a half-cell, and the discharge and discharge of the media from a cell element.Thus, the sealing arrangement of the invention simultaneously realizes a media distributor or a distributor structure. This makes the sealing arrangement ideal for use in an electrochemical cell, such as an electrolysis cell, through the interaction of several sealing arrangements by axial stacking, preferably of identical design.

[0015] The sealing arrangement according to the invention comprises a flat metal carrier and a sealing element applied to the metal carrier, wherein the metal carrier is designed as a thin surrounding frame with an outer edge and an inner edge, wherein a plurality of openings are provided in the metal carrier along an edge and the openings are arranged along a straight line and are aligned flush with the outer edge when viewed, such that a hole pattern is formed which is designed such that openings of a first type and a second type are provided, wherein the longitudinal extent perpendicular to the straight line for an opening of the first type is greater than the longitudinal extent for an opening of the second type, wherein a linear, alternating hole pattern is formed along the straight line, and wherein the sealing element comprises an elastomer which is applied at least to the edge of the openings on the metal carrier.

[0016] In a particularly preferred embodiment of the sealing arrangement, the sealing element is applied to the metal carrier as an edge-bonded seal, wherein the elastomer is applied to the edges of the opening as a sealing material.

[0017] In a particularly preferred embodiment, the sealing arrangement comprises a metallic base body onto which an elastomer-based seal is selectively applied as a functional sealing element at local sealing points or sealing areas of the base body. This results in a metal-elastomer seal for an electrolysis cell in the form of a one-piece, flat component similar to a sealing plate. The metal-elastomer seal as a sealing arrangement can be manufactured industrially and serially in any quantity and can be integrated accordingly into an electrolysis cell.

[0018] In this sealing arrangement, the elastomer-based sealing elements preferably protrude from the surface of the metallic base body in a normal direction. In particular, they can be designed as a bead-shaped or lip-shaped structure, or have this form. Due to their normal protrusion from the component surface, the sealing elements achieve not only a sealing effect but also a particularly advantageous elastic effect in the installation situation, thus enabling flexibility for precise series production. This results in an inherent, independent, and flexible adaptation of the sealing arrangement under various operating conditions with respect to the operating pressure. In contrast to conventional designs, no frictional engagement is required.

[0019] Thus, a combination seal is provided. The same sealing arrangement can be used on both the anode and cathode sides, making it a standard component. Furthermore, the cell design facilitates automated industrial mass production. Manually assembled and installed components can therefore be largely eliminated during the manufacturing of the electrolysis cell. In this way, high-performance and particularly efficient electrolyzers can be produced with a large number of fluid-tight, axially stacked electrolysis cells based on the proposed cell design.

[0020] According to a particular aspect of the invention, an electrolysis cell stack is proposed comprising a number of electrolysis cells stacked in an axial direction, in which the electrolysis cells are arranged in pairs, with a first electrolysis cell A and a second electrolysis cell B. The cell pairs A and B are arranged alternately in the stacking direction and interact fluidically. This enables a particularly efficient and uniform flow distribution of the medium or fluid in each of the electrolysis cells. This cell design results in a manifold or distribution structure for the working fluid, in particular a media distribution for the incoming reactant flow and the outgoing anodic and cathodic product flows.

[0021] Preferably, the electrolysis cells are arranged in pairs, with one cell type A and one cell type B. Each electrolysis cell comprises an anode compartment with an anode and a cathode compartment with a cathode. The electrodes are mounted on a proton-conducting membrane, forming a membrane electrode assembly (MEA). The cells are fluidically separated from each other and simultaneously electrically supplied via current distributors or bipolar plates.

[0022] In a particularly preferred embodiment, in a cell pair, the sealing arrangement in a cell of cell type B is offset relative to the sealing arrangement in an adjacent cell of cell type A. The term "offset" in the cell construction implies that the adjacent cell types A and B can also be separated, spaced apart, or set back, so that a flow path across the adjacent cells is formed and provided. The offset is predominantly formed in one direction within the planar cell plane—radially inward or radially outward—so that an overflow channel is formed essentially perpendicular to the cell plane, allowing fluid to flow from cell B to the adjacent cell A.

[0023] The alternating sealing geometry and arrangement proposed here in a particularly preferred embodiment within the cell pairs creates, in addition to its sealing effect, a flow channel which, during operation of adjacent electrolysis cells, establishes a flow path so that a cell of cell type A can be supplied via the adjacent cell of cell type B. Thus, for example, a flow of fluid, such as reactant water, can be effected during PEM electrolysis, which flows from a cell of cell type B to a cell of cell type A on the cathode side of the distributor structure.

[0024] The sealing of the anodic from the cathodic half-cell in an electrolysis cell is achieved with a sealing arrangement, preferably based on a metal-elastomer seal. Typical, readily available flat gaskets can also be used in certain applications. However, a metal-elastomer seal will prove to be more efficient in an electrolysis cell. According to a further aspect of the invention, an electrolysis cell comprising an anodic half-cell and a cathodic half-cell is proposed, in which a sealing arrangement with a sealing element is incorporated in at least one of the half-cells. The sealing arrangement is designed as a metal-elastomer seal and is arranged such that the membrane electrode unit can be sealed against the bipolar plate by the sealing element in a floating or sliding manner.

[0025] Particularly in the assembled state, under a compression of the elastomer of approximately 20% to 30%, a very high sealing effect is already achieved, whereby, characteristically, no frictional connection is provided, unlike in known electrolysis cells. This type of connection can be dispensed with. It has been shown that even with a comparatively low compression, a high sealing effect can be achieved with a proposed combined metal-elastomer seal, e.g., designed as a simple flat gasket.

[0026] Preferably, in a sealing arrangement, a predetermined cell-adapted elastomer profile is provided on a metallic substrate or a metal carrier, which is locally edge-bonded or overmolded with elastomer material.

[0027] To achieve a sealing effect, such an elastomer profile is preferably compressed when installed in an electrolysis cell, so that a seal is specifically created, while the metal support remains dimensionally stable under the pressure.

[0028] Preferably, a gap or space is provided between the metal support of the sealing arrangement and the bipolar plate (BPP) on the one hand and / or the membrane electrode assembly (MEA) on the other, so that a sliding or floating sealing effect is achieved. The floating installation of the sealing arrangement in a half-cell advantageously ensures tolerance compensation of the internal components via a soft, outwardly movable load path.

[0029] A particularly noteworthy feature is that the sealing concept advantageously does not rely on frictional engagement of the cell components and therefore requires a significantly lower clamping force. Consequently, a comparatively low axial compression of the elastomer material of approximately 20%–30% is sufficient to achieve the desired sealing effect while simultaneously allowing for tolerance compensation.

[0030] The concept of paired cells or cell pairs and their supply with working fluid is advantageously enabled by a novel design concept for a sealing arrangement. This allows for the simultaneous implementation of a supply topology to realize a media or fluid distributor when using a multiple of axially stacked, appropriately designed cell pairs.

[0031] Here, the fundamental design concepts can be implemented using a single basic design of a sealing arrangement as the fundamental element. The sealing arrangement is designed so that it can be easily rotated to create the desired flow path. Thus, adjacent sealing arrangements are rotationally symmetrical, preferably with respect to a 180° rotation. This leads to standardization and a significant reduction in the number of components and manufacturing costs.

[0032] Advantageously, the thin, sheet-like or panel-shaped sealing arrangement is provided at its periphery with at least two different types of geometrically shaped openings, which are arranged regularly around the entire circumference. When at least two of the sealing arrangements are stacked, fluid channels are formed that supply axially adjacent electrolysis cells of cell type A and cell type B. With appropriate pairwise stacking and dense packing of a large number of cell pairs ("dual-cell") of cell type A and cell type B, a supply topology or manifold is formed at the periphery for supplying a stack with fluid.

[0033] In a particularly preferred embodiment, the hole pattern or opening pattern of the supply topology is repeated every two cells in the axial stacking direction of the cells; that is, the repetition occurs with the period of a cell pair ("dual cells") comprising one cell of cell type A and one cell of cell type B. The opening or hole can, for example, be an elongated slot. In engineering terms, this refers to an elongated bore or groove. Its narrow sides are closed by semicircles whose diameters correspond to the width of the slot. The long sides of the slot run parallel to each other. However, it is also possible to use other shapes for the openings.

[0034] Preferably, a sealing arrangement may include elongated holes with different longitudinal extents but the same width. In particular, the peripheral hole pattern of the sealing arrangement alternates continuously between elongated holes with shorter longitudinal sides and elongated holes with longer longitudinal sides. Thus, when adjacent sealing arrangements are rotated 180° relative to each other and stacked, an axial fluid channel is created that supplies adjacent cells, whereby a cell of cell type A can be supplied via a cell of cell type B in pairs. This can be repeated as often as necessary until a stack with a multitude of such cell pairs is built up.

[0035] Preferably, the sealing element on the metal carrier is implemented using an edge-bonded seal, meaning an elastomer is applied as a sealing material to selected edges of the metal carrier. Stainless steel is used as the metal carrier. Stainless steel is dimensionally stable and easily machinable, allowing for the simple integration of a predetermined peripheral hole pattern, for example, by drilling, punching, etching, laser processing, or other material-removing machining processes using machine tools. In principle, depending on the application in a specific electrochemical cell, other metals can also be used. Elastomer is locally applied as a sealing material to the desired sealing surfaces on the prepared metal carrier, particularly bonded to the edges. In this way, the sealing arrangement provides a flat gasket as a sealing element based on a composite metal-elastomer seal.

[0036] A fluoroelastomer (FKM) is the preferred choice for this application. This category encompasses a whole group of different synthetic polymer blends, all characterized by the monomer VDF (vinylidene difluoride). The material belongs to the M-group of rubbers, which are distinguished by a saturated carbon backbone. This high-quality material exhibits excellent properties, making it a versatile elastomer. This is due to its combination of good heat and ozone resistance with resistance to a wide range of chemicals.

[0037] In this way, a large number of cell pairs equipped with the appropriate sealing arrangement can be stacked fluid-tight to form a stack of corresponding cell pairs. In particular, a stack of axially stacked electrolysis cell pairs can be provided, which, through the interaction of the sealing arrangements, form an integrated media distributor. Thus, a flow pattern across the cells can be set, enabling a flow pattern and fluid distribution. The incoming fluid is, for example, demineralized water as a reactant in PEM water electrolysis. Similarly, the products from each cell can be discharged and drained. The tandem principle described above is implemented, meaning a paired fluid-technical connection and supply of adjacent cells, which are specifically adapted and designed as cell type A and cell type B.

[0038] Preferably, several fluid distributors are arranged evenly across the entire side of a cell, allowing for a uniform and customized flow distribution across the active area of ​​the catalyst-coated polymer membrane (CCM). A fluid distributor can be provided through a suitably designed opening in the stainless steel metal carrier of the sealing assembly. A plurality of suitably designed fluid distributors are provided at the periphery of the sealing assembly. The sealing assembly can be designed as a thin sheet or panel and may, for example, have a rectangular, square, or polygonal shape. Other formats are possible, including round or elliptical sealing assemblies, depending on the geometry of the electrolysis cell. Thus, fluid distributors are preferably incorporated evenly along each edge of the rectangle, square, or polygon in the form of through-holes at the periphery.The sealing arrangement is designed as a flat, frame-like element or as a frame construction. In other words, the basic form is preferably not a solid sheet or panel, but rather the sealing arrangement has a central recess. This recess can be rectangular, square, or round and contoured according to the hole pattern of the openings on the periphery. This central recess serves as a free surface and is necessary for receiving and providing a membrane coated with an electrode or the membrane electrode assembly. Thus, the active area for the electrochemical reaction is kept clear. In a particularly preferred embodiment of the sealing arrangement, the openings in the peripheral hole pattern are arranged alternately along an edge, such that every second opening has the same shape and opening area – e.g.,The opening is designed as a slot with a longitudinal dimension and a width. Between each pair of identical slotted holes of type 1, a further opening of a different type is incorporated into the sheet metal structure. This opening of type 2 is, for example, circular, elliptical, or stadium-shaped and has a smaller longitudinal dimension and thus a smaller opening area than an opening of type 2, i.e., a slotted hole. Both opening types are flush with the outer edge of the sheet metal. When several identical sealing assemblies are stacked, a bypass is thus achieved for every second cell.

[0039] The hole pattern in the sealing arrangement incorporates rotational symmetry with respect to an axis of rotation parallel to the surface normal of the metal-elastomer sealing sheet. Preferably, the sealing arrangement can be mapped onto itself by a double rotation of 180°, meaning the corresponding axis of rotation is twofold. This is because performing the rotation twice results in a full 360° rotation, thus achieving identity. The twofold axis of rotation is therefore the preferred symmetry element of the sealing arrangement and is designated 02. Conversely, a single rotation of 180° provides the orientation of a sealing arrangement for use in cell type B configurations. In this way, a tandem principle can be implemented with a single component, allowing the cell of cell type A to be supplied via the cell of cell type B during installation and operation.This allows for a particularly uniform flow or crossflow across the respective active area of ​​an anodic or cathodic half-cell. This enables the flow to selectively pass through either the anode compartment and / or the cathode compartment. During operation, a fluid flows as a reactant through the inlet openings at one edge of the sealing arrangement into a half-cell, flows uniformly through the half-cell space, and is at least partially electrochemically converted into a product within that half-cell. Finally, the fluid (product) is discharged as a fluid at the opposite edge. The term "edge" can also refer to a curved line that follows the contour of a round or elliptical sealing arrangement. Thus, the hole pattern can also be incorporated into the metal carrier on a circular or elliptical arc.For example, the metal support can be functionally divided into four 90° segments, analogous to a square or rectangular base shape.

[0040] Preferably the orientation of the stacked sealing arrangements is such that the flow direction of the fluid flow within the anodic half-cell and within the cathodic half-cell is perpendicular to each other.

[0041] For example, a vertical flow from top to bottom can be realized in a cathodic half-cell and a horizontal flow from left to right in an anodic half-cell.

[0042] The crosswise alternating flow pattern, when multiple electrolysis cells are axially stacked, promotes a particularly homogeneous temperature distribution across the stack and avoids thermomechanical stresses between the cells. Furthermore, the design principle ensures that the membrane electrode unit is sealed against the bipolar plate by a floating or sliding sealing element, which also provides inherent flexibility to accommodate thermally induced material expansion during operation.

[0043] Thus, by the design of the sealing arrangement and the interaction of several sealing arrangements in a series connection of several electrochemical cells, in particular electrolysis cells, a distribution structure for supplying or providing a cell element, especially a half-cell, with a fluid is realized. According to one aspect of the invention, a cell element of an electrochemical cell, in particular an electrolysis cell, is therefore proposed with such a sealing arrangement comprising a membrane-electrode unit (MEA) which has as its active surface a membrane coated with an anode and a cathode as well as an edge region, wherein a sealing arrangement is provided on the anode side and on the cathode side respectively, which are stacked tightly on top of each other, wherein the membrane-electrode unit is received centrally and clamped and positioned in the edge region by means of the rubber-elastic sealing elements.

[0044] Furthermore, according to one aspect of the invention, a cell stack with a plurality of electrochemical cells, in particular stacks of electrolysis cells, is proposed, each with a corresponding cell element, which is designed according to a first cell type or according to a second cell type, each having an anode compartment and a cathode compartment, which are separated from each other by a respective membrane, wherein different cell types are stacked alternately one above the other as cell pairs along a stacking axis, wherein the axially stacked sealing arrangements form a distributor structure with a channel structure for supplying a cell element with a fluid, wherein in the cell pairs, in addition to the sealing function, the channel structure is formed, which provides a flow path for adjacent cell types such that a cell of the first cell type is supplied with fluid via the adjacent cell of the second cell type.

[0045] The cell of the second cell type is arranged upstream of the first cell type A in the axial flow direction of the fluid. Thus, a tandem construction or a dual-cell arrangement (twin-cell) is given, with a supplying and upstream cell element and a receiving and downstream cell element. In a particularly preferred embodiment of the cell stack, the sealing arrangement on the membrane electrode assembly (MEA) on the anode side of one cell type is identical in design to a sealing arrangement on the other cell type, but rotated 180° around the stack axis as the axis of rotation.

[0046] A corresponding design is also advantageously implemented on the cathode side of a membrane electrode assembly (MEA) in a cell type A compared to a cell type B.

[0047] In this way, different cell types can be constructed using a single design of the sealing arrangement as a cell element, and when stacked into a cell stack, a distribution structure for the fluid and a tight intake, fixation and positioning of the membrane electrode assembly (MEA) are provided.

[0048] Another aspect of the invention relates to an electrolyzer, in particular a PEM electrolyzer, comprising a cell stack formed from electrolysis cells ( 1 ) with a corresponding distributor structure designed for supplying and distributing a fluid into the cell element and a similarly designed outlet structure for directing fluid ( F) out after flowing through the cell element.

[0049] An electrolyzer according to the invention therefore comprises a distributor structure for supplying the fluid medium to the cell element and a similarly designed, in particular identical, outlet structure for discharging the fluid medium. With respect to the main flow direction in a half-cell, the outlet structure can accordingly preferably be designed or oriented in the opposite direction to guide the fluid from the cell element uniformly back into a possibly central single outlet channel and discharge it. The design principle of the cell and the cell pairs can be applied not only to PEM electrolysis but also to other types of electrolysis, such as AEM electrolysis (AEM: Anion Exchange Membrane) or alkaline electrolysis (AEL). Applications in electrochemical cells such as fuel cells are also possible.

[0050] The chosen design principle and the implementation and design of the media distribution via the sealing arrangement enable a very compact design of an axial stack or an electrolyzer, resulting in a significant saving of installation space compared to conventional electrolyzers. This is achieved, among other things, by completely replacing the previously used cell frame construction with O-ring seal and a frictional connection of the components with a novel, robust sealing concept based on metal-elastomer sealing arrangements, in which the necessary fluid transport properties for supplying the cells are fully integrated.

[0051] Exemplary embodiments of the invention are explained in more detail with reference to a drawing. This drawing schematically and in a highly simplified manner shows the

[0052] FIG 1 shows a cutaway view of a known electrolysis cell for water electrolysis, in particular a PEM electrolysis cell;

[0053] FIG 2 shows a section of a stack of electrolysis cells according to the design of the invention with paired cell arrangement and flow pattern for cell supply;

[0054] FIG 3 shows a sectional view of an electrolysis cell with a sealing arrangement in a decompressed state;

[0055] FIG 4 shows a sectional view of an electrolysis cell with a sealing arrangement in a compressed state; FIG 5 shows a detail view of an electrolysis cell with two sealing arrangements stacked to form a sealing pair;

[0056] FIG 6 shows an exploded view of a cell stack formed from a multitude of stacked electrolysis cells according to FIG 5;

[0057] FIG 7 shows an electrolysis cell according to FIG 5 with flow guidance through adjacent cells;

[0058] FIG 8 shows a section detail of a plurality of axially densely stacked sealing arrangements with a formed channel pattern for flow distribution;

[0059] FIG 9 shows a top view comparing an anodicated half-cell of cell type A and cell type B with flow pattern;

[0060] FIG 10 shows a top view comparing a cathodic half-cell of cell type A and cell type B with flow pattern;

[0061] FIG 11 shows an exploded view of a plurality of axially stacked electrolysis cells with cell components;

[0062] FIG 12 shows a simplified view of an assembled stack of electrolysis cells and connection components.

[0063] Figure 1 shows a sectioned view of a known electrolysis cell 1 for water electrolysis. The section depicts the outer edge region of the electrolysis cell 1 in detail, with a cell frame 3 serving as the supporting structural element. The setup shown is typically significant and applicable to PEM electrolysis. An anode compartment with an anode 5 and a cathode compartment with a cathode 7 are separated by a membrane 9, for example, a proton-conducting polymer membrane, forming a cathodic half-cell 25A and an anodic half-cell 25B. The cathodic half-cell 25A and the anodic half-cell 25B are each delimited and electrically contacted by a current distributor 11. The current distributor 11 is also referred to as a bipolar plate. Grooves 27 are provided in the cell frame, into which a sealing ring 15 is inserted, for example, a Viton O-ring.

[0064] The cathodic half-cell 25A and the anodic half-cell 25B are sealed by a respective sealing ring 15, which is inserted into one of the two opposing grooves 27 of the cell frame 3 in its outer edge region. The sealing effect is achieved by local surface pressure on the contact surface of the respective current distributor 11, whereby the sealing ring 15 is compressed and deformed, thereby creating a frictional connection between the current distributor 11 and the cell frame. Another sealing ring 15 is inserted inwards within the stepped cell frame 3. This sealing ring 15 rests against the membrane 9, thereby securing the membrane 9 and ensuring the necessary mutual sealing of the cell spaces of the two half-cells 25A and 25B.An electrically conductive nonwoven material 13 is inserted into the cathodic half-cell 25A and rests on the membrane 9, thus enabling electrical contact and fluid transport. The nonwoven material 13 is a carbon nonwoven. Electrodes (not shown) are applied to the membrane 9 on both the anode and cathode sides, each containing a catalyst material, such as platinum (Pt) or iridium (Ir). Thus, a membrane electrode assembly (MEA) is realized by a catalyst-coated membrane 9 or CCM (catalyst-coated membrane). The chosen cell structure, with its O-ring-sealed cell frame 3, implies a minimum required cell height H for the electrolysis cell 1, which cannot be reduced further with the current design principle. This minimum structural height is typically approximately H = 13 to 15 mm.As a result, when a large number of such electrolysis cells 1 are stacked axially, the overall length is correspondingly large and the energy density – electrolysis power per volume – is correspondingly limited. Furthermore, the cell frame 3 is manufactured as a plastic component using injection molding, which also limits the dimensional accuracy and reproducibility of an electrolysis cell 1 during serial production. Moreover, in addition to other manufacturing steps, manual insertion and precise alignment of the sealing rings 15 are required, meaning a relatively low level of automation is necessary for industrial production.

[0065] In contrast, FIG. 2 shows a section view of an axially arranged stack of electrolysis cells 1 according to the invention. The stack axis Z corresponds to the vertical direction in FIG. 2. A paired cell arrangement with an integral, cell-spanning flow pattern for cell supply is illustrated. The section view shows a sectional view in the near-edge region of each electrolysis cell 1 in the stack. The electrolysis cells 1 are arranged in pairs, with cell type A and cell type B, which differ structurally. Each electrolysis cell 1 comprises an anode compartment with an anodic half-cell 25B and a cathode compartment with a cathodic half-cell 25A, wherein the anodic half-cell 25A has an anode 5 and the cathodic half-cell 25B has a cathode 5.The electrodes (not shown in detail) are applied to the proton-conducting membrane 9, so that a membrane electrode assembly (MEA) is formed in each of the electrolysis cells 1, separating the half-cells 25A and 25B from each other. Adjacent electrolysis cells 1 are spatially separated from each other and simultaneously electrically supplied via respective current distributors 11 or bipolar plates.

[0066] Of particular importance for the function of the electrolysis cells 1 in the stack is that, in a cell pair, the sealing arrangement 21 in an electrolysis cell 1 of cell type B is offset relative to the sealing arrangement 21 in an adjacent electrolysis cell 1 of cell type A, i.e., they exhibit an offset d from each other. The term "offset" in the cell design here implies that the adjacent cell types A and B can also be separated, spaced apart, or set back, so that a flow path for a fluid F across adjacent cells or cell elements is configured and provided. This creates a media distributor. The flow path and the effect as a media distributor are realized by appropriately designed openings 31 in the periphery or edge region of a sealing arrangement 21.The offset d is configured in one direction within the planar cell plane – radially inwards or radially outwards – such that a channel structure 29 with a flow channel 29B is formed essentially perpendicular to the cell plane, i.e., in the stacking direction of the electrolysis cells 1. This allows fluid F to flow from one electrolysis cell 1 of cell type B to the adjacent electrolysis cell 1 of cell type A. Furthermore, the channel structure 29 has a through-channel 29A that is essentially continuous along the stacking axis Z of the cell stack, which is oriented vertically in FIG. 2. At the outer edge of the cell stack, the openings 29 in the sealing arrangements 21 are flush one above the other along the stacking axis Z, so that the through-channel 29A acts as the main distributor. The openings 29 have a sealing function at their perimeters or are provided with a sealant.The transport function for fluids F realized by the stacking in the channel structure 29 includes the targeted supply and distribution of media to a cell element, in particular to a half-cell 25A, 25B, as well as the media discharge and discharge from a cell element. Thus, a media distributor or distributor structure is simultaneously implemented in an electrolysis cell 1 and a cell stack via the sealing arrangement 21 of the invention. FIG. 3 shows a sectional view of a peripheral section of an electrolysis cell 1 with a sealing arrangement 29 in a decompressed state, i.e., before final assembly. For example, an electrolysis cell 1 of cell type A is realized here. The electrolysis cell 1 has two stacked sealing arrangements 21 that clamp a proton-conducting membrane 9.Thus, the two stacked sealing assemblies 21 provide the function of a surrounding frame or clamping frame for the membrane 9, so that the area within the surrounding frame forms the anode compartment of the anodic half-cell 25B and the cathode compartment of the cathodic half-cell 25A. A membrane electrode assembly (MEA) with an active area for the electrochemical cell reaction is incorporated through the catalyst-coated membrane 9. According to the cell concept of the invention, each of the sealing assemblies 21 has a metal support 23A made of a thin stainless steel sheet and a sealing element 23B. A sealing element 23B is applied locally and around the perimeter of a respective opening 31, e.g., via edge bonding, and is designed as an elastomer. Therefore, the sealing assembly 21 is designed as a metal-elastomer seal.The opening 31 in the metal carrier 23A can be punched into the metal sheet or realized as a bore or slot. A respective metallic, flat current distributor 11 – also referred to as a bipolar plate – delimits and encloses the anode and cathode compartments of the electrolysis cell 1, while simultaneously providing electrical contact and connection options on both the anode and cathode sides. The bead-shaped or raised design of the sealing element 23B creates a characteristic gap 33. This gap allows for assembly tolerances and self-adjustment and alignment during component assembly, thus facilitating automation in manufacturing.The sealing arrangement 21 is designed as a metal-elastomer seal and is arranged such that the membrane electrode unit can be sealed against the bipolar plate 11 by the sealing element 23B in a floating or sliding manner. The gap 33 is created by the beaded or raised shape of the sealing element 23B, so that even in the assembled state the metal support 23A is spaced from the power distributor 11 by the gap 33 and is held and positioned solely by the rubber-elastic sealing element 23B.

[0067] Compared to FIG. 3, FIG. 4 shows a sectional view of a peripheral section of a corresponding electrolysis cell 1 with a sealing arrangement 21 in the compressed state, i.e., in the fully assembled state. Particularly in the assembly state shown in FIG. 4, with a compression of the elastomer of approximately 20% to 30%, a very high sealing effect is already achieved. Characteristically, unlike the electrolysis cells 1 described in FIG. 1, no frictional connection is provided. This type of connection via friction can be completely dispensed with in the proposed cell concept, as can a cell frame 3 and sealing rings 15 (see FIG. 1). Rather, it has been shown that even with a comparatively low compression, a high sealing effect can be achieved with a proposed combined metal-elastomer seal, e.g., designed as a simple flat gasket.A channel structure 29 is designed for targeted fluid distribution within the electrolysis cell 1 and uniform supply to the electrochemically active membrane surfaces 9. Furthermore, in this novel cell design, which significantly reduces the number of parts, the membrane 9 and the entire membrane electrode assembly (MEA) are fixed, aligned, and protected, particularly through the paired use of identical sealing arrangements 21 in an electrolysis cell 1 of a specific cell type (A or B). The compact design of the new cell concept results in a significantly reduced cell height h, approximately only h = 5 mm compared to h = 13 mm in known cell concepts. This leads to significantly higher power densities by a factor of approximately 2.5 for the same installation space, or a corresponding reduction in installation space of 40% for the same electrolysis power.

[0068] Figure 5 shows a section of an electrolysis cell 1 with two sealing arrangements 21A, 21B axially stacked or flush one above the other to form a sealing pair. Each stacked sealing arrangement 21A, 21B has a metal support 23A and a sealing element 23B. The membrane 3, which is clamped between the two sealing arrangements 21A, 21B, is visible in section. An electrode layer 35 – shown in dark in Figure 5 – is applied to the membrane 3 as an active surface and contains a catalyst material. The membrane 3 is clamped between the two sealing arrangements 21A, 21B in a fluid-tight and pressure-tight manner, for example, according to the principle of the construction shown in Figure 4. Additionally, the membrane 9 can be provided with a circumferential clamping structure 37 at the outer edge outside the active area and can optionally be reinforced - shown in light grey in FIG. 5.Sealing elements 23B are each applied to the metal carrier 23A in a beaded fashion at the outer edge of the openings 31 and are made of an elastomer. The openings 31 in the metal carrier 23A are designed as elongated holes with different longitudinal extents along one edge. An elongated hole with a greater longitudinal extent and an elongated hole with a comparatively smaller longitudinal extent are alternately machined into the metal carrier 23A along one edge, so that a characteristic hole pattern is formed for each of the stacked sealing assemblies 21A, 21B. Furthermore, the inner and outer edges of a sealing assembly 21A, 21B are provided with the sealing element 23A following the contour, whereby a wave-like contour results at the inner edge and a straight contour at the outer edge due to the hole pattern.This is a consequence of the alternating elongated holes with different longitudinal extents, arranged flush along a straight line towards the outer edge of the sealing arrangement 21A, 21B. The hole patterns of the first sealing arrangement 21A and the hole pattern of the underlying second sealing arrangement 21B are chosen to be different or complementary, resulting in an offset d. By stacking a plurality of corresponding sealing arrangements 21A, 21B, a desired channel structure 2 9 and a media or fluid distributor for a stack of electrolysis cells 1 can be created. This is illustrated in more detail in FIG. 6.

[0069] FIG. 6 shows a simplified exploded view of a cell stack formed from a plurality of stacked pairs of electrolysis cells 1 as the basic cell element (“dual or twin cell”). Characteristic of the cell concept and the underlying design principle of the invention is that it is a stack of dual or twin cells as the smallest building unit. As shown in FIG. 2, at least the two basic designs, cell type A and cell type B, are configured as dual or twin cells and assembled into a building unit or cell element, with a corresponding plurality of such cell elements successively stacked axially one above the other along the stacking axis Z. When at least two of the sealing arrangements 21A, 21B are stacked, fluid channels are formed that supply axially adjacent electrolysis cells of cell type A and cell type B.With appropriate pairwise stacking and dense packing of a large number of cell pairs ("dual-cell"), which are connected as cell type A and cell type B to form a cell element, a supply topology or manifold is formed at the periphery to supply an extended stack with fluid. This can be repeated as often as necessary to construct an extended stack.

[0070] FIG. 7 illustrates the flow path through adjacent cell spaces, separated by a membrane 3, for an electrolysis cell 1 shown in partial view as in FIG. 5. FIG. 5 shows, by way of example, a cathodic half-cell 25A, shown in the foreground, stacked on top of an anodic half-cell 25B in the background (see also FIG. 2). The flow path is such that the cathodic half-cell 25A, of cell type A (in the foreground), can be supplied by the anodic half-cell 25B (in the background) via cell type B through the channel structure 29. The passage of fluid F, its flow path, and its uniform distribution within a half-cell 25A, 25B on both sides across the surface of the membrane 3 are achieved by the design of the sealing arrangements 21A, 21B with the hole pattern and their stacking.

[0071] FIG. 8 shows a section view of a plurality of sealing assemblies 21 stacked closely one above the other along a stacking axis Z, such that the stacked sealing assembly 21, as a thin and flat component, provides a correspondingly designed distributor structure 17 for flow distribution, e.g., of an electrolysis reactant and / or an electrolysis product. The stacking axis Z is perpendicular to the surface of the sealing assembly 21, which is designed as a flat component. FIG. 8 shows a view from the inside, i.e., the membrane side, of the internal structure of the multiple stacked sealing assemblies 21. The stack of sealing assemblies 21 comprises pairs of essentially identical or structurally identical sealing assemblies 21A, 21B, rotated 180° relative to each other, which are stacked closely one above the other alternately along the selected stacking axis Z and connected or clamped.This results in a particularly simple desired channel structure 29 for media distribution, comprising a through channel 29A and an overflow channel 29B. Thus, a complex distributor structure 17 is realized in a particularly simple manner for fluid distribution, e.g., in an electrolysis cell stack along the stack axis Z. This structure is fundamentally based on an advantageously designed and implemented sealing arrangement 21 as a multi-purpose, elementary component. The distributor structure 17 enables a particularly uniform and comprehensive distribution of a fluid F, as well as homogeneous injection along an entire edge into the anode or cathode compartment. Accordingly, a uniform flow along the active surface of a catalyst-coated membrane 9 is achieved.

[0072] Figure 9 shows a top view of an anodic half-cell 25B of cell type A and, for comparison, of cell type B, each with a fluid flow pattern F across the membrane surface. The anode electrode is a thin electrode layer 35 applied to the membrane 9. A catalyst material, for example iridium, is incorporated into the electrode layer. At the edge, the rectangular or square membrane 9 is not coated but held in place by a corresponding clamping structure 37 and the respective sealing arrangement 21A, 21B. A corresponding sealing arrangement 21A is installed in cell type A, and a sealing arrangement 21B in cell type B.The sealing arrangements 21A and 21B each have a plurality of openings 31, which are configured alternately along an edge as either a through-channel 29A or an overflow channel 29B, thus creating a specific hole pattern for the desired and very uniform fluid distribution, resulting in targeted cross-cell overflow. A cell of cell type A is supplied with fluid F by a cell of cell type B. A characteristic and highly advantageous feature is that the sealing arrangement 21A and the sealing arrangement 21B are identical in construction, and the installation state for cell type A and cell type B is achieved through a simple symmetry operation of the same component. In this case, a rotation of 180° is provided. This also ensures that, in the anodic half-cell 25B, the anode compartment and the membrane 9 are always flowed through in the same direction – in this case, horizontally from left to right.Furthermore, in the axial stacking direction, the alternating arrangement via the through-channel 29A directs the fluid in a bypass such that every second cell is bypassed or overflowed, for example, the cells of cell type A (see FIG. 2). Analogously to the detailed design shown in FIG. 9, FIG. 10 shows an adapted embodiment for a cathodic half-cell 25A. FIG. 10 shows, accordingly, a top view of the membrane 9 of a cathodic half-cell 25A of cell type A and, for comparison, of cell type B, each with a respective flow pattern of a fluid F over the membrane surface. This results in the cathodic half-cell 25B always having a uniform flow pattern through the cathodic space and the membrane 9 in the same direction – in this case, vertically from top to bottom.Otherwise, the same design concept with paired cell supply ("dual-cell") applies analogously to a cathodic half-cell 25A. In a stack with several axially connected anodic and cathodic half-cells 25A, 25B of cell type A and cell type B, an alternating horizontal flow and a vertical flow of the fluid F along the membrane 9 are implemented. This additionally ensures a particularly uniform flow and temperature distribution over the axial length of a large cell stack during operation, and thus a significant reduction in the stress with regard to adverse thermal and thermomechanical effects of a stack.

[0073] FIG. 11 shows an exploded view of a plurality of cell components stacked axially along a stacking axis Z. A sealing arrangement 21 has a sealing element 23B as an edge-bonded elastomer seal, which is mounted on a metal support 23A, for example, a stainless steel sheet. A membrane 9 is arranged between two sealing arrangements 21. The membrane 9 is provided with a clamping structure 37 at its outer edge for pressure- and fluid-tight installation between two stacked sealing arrangements 21 and for precise and uniform positioning. An electrode layer 35, comprising a respective catalyst material, is applied to both sides of the central surface of the membrane 9. Preferably, iridium (Ir) is used as the catalyst material on the anode side and platinum (Pt) on the cathode side.Thus, a membrane electrode assembly (MEA) is provided, which is enclosed between two sealing assemblies 21. A current distributor 11, also referred to as a bipolar plate, is axially attached to each pair of sealing assemblies comprising the membrane electrode assembly (MEA). This forms an electrolysis cell 1 with either cell type A or cell type B, each with an anode compartment and a cathode compartment. The current distributor 11 can optionally be designed and structured for fluid distribution to achieve a desired flow field and fluid transport.Additional porous transport layers or gas diffusion layers – not shown in detail in FIG 11 – may be introduced into the anode compartment and / or the cathode compartment to enable the function of the electrolysis cell 1 with regard to fluid transport of the supplied reactant and removal of the products as well as low-resistance electrical contact to the current distributors 11.

[0074] A characteristic feature of the proposed design is that the metal support 23A of the sealing arrangement 21 is suspended, i.e., held in position with a gap between the current distributor 11 (bipolar plate) and the membrane electrode assembly (MEA) solely by the soft, rubber-like sealing elements 23B made of an elastomer material. This allows for a very precise position in the installation and also prevents buckling of the metal support 23A under pressure. Additionally, a clearly defined load path through the internal components of the electrolysis cell 1 is achieved, as well as a constant contact pressure. Furthermore, tolerances of gas diffusion layers and other components can be automatically compensated for.The internal pressure is maintained by the thickness of the metal support 23A of the sealing arrangement 21, which makes the electrolysis cell 1 ideal for use in pressure electrolysis, achieving an operating pressure of at least 16 bar. The compact design is advantageous, as it does not require a frictional connection, unlike previously known designs.

[0075] The design is further advantageously characterized by reduced compressive force, as there is no cell frame to be compressed. The size of the available active area and the maximum pressure are essentially a function of the width of the metal support 23A of the sealing assembly 21, thus enabling a higher utilization rate and efficiency. The clamping structure 37, or the non-active edge region of the membrane 9, can be dimensioned relatively narrowly. A significant reduction in cell height from H = 13 mm to h = 5 mm is possible, allowing for a very compact design, as exemplified in FIG. 12 below. Furthermore, manual assembly of the sealing assembly 21 is not required, thus enabling a high degree of automation in industrial series production.

[0076] Finally, FIG 12 illustrates, in a simplified view, an assembled electrolysis stack or electrolysis module as a unit with a plurality of vertically stacked square or rectangular electrolysis cells 1. In this example, 100 electrolysis cells 1 are stacked and clamped between two end plates 43. A uniform surface pressure can be applied to the end plates 43 via a plurality of threaded clamping rods 39 using clamping screws, thus pressing the stacked electrolysis cells 1 together and connecting them in a pressure- and fluid-tight manner. Compared to known designs, this requires fewer and smaller clamping rods 39, as well as fewer or even no disc springs. A reactant, such as demineralized water H₂O, can be supplied via appropriate flanges 45, and the anode products, such as oxygen O₂, and the cathode products, such as hydrogen H₂, can be removed from the electrolysis process.To operate the electrolysis process, a direct current is fed in via terminals 41A and 41B, which flows through the electrolysis cells 1 in series. The active area of ​​one cell is approximately 2,500 cm². 2 per cell. A current density of 3.5 A / cm² 2 is achievable. The dimensions (external dimensions) of the stack are typically 800x800x740 mm with a weight of approximately 2,500 - 3,000 kg. Round or elliptical designs are also possible, in which the design principle of the invention can be implemented.

[0077] The advantage of the invention over the prior art lies particularly in the improved possibility of a compact design while simultaneously achieving a largely homogeneous distribution of the fluid across the cell width. This, in turn, allows for the realization of more robust electrochemical components with significantly improved power density. Furthermore, the invention offers the advantage of improved manufacturability and the possibility of mechanically supporting or pressing cell stacks with multiple cell elements against each other with particular stability.

Claims

Patent claims 1. Sealing arrangement (21, 21A, 21B) comprising a flat metal support (23A) and a sealing element (23B) applied to the metal support (23A), wherein the metal support (23) is designed as a thin surrounding frame with an outer edge and an inner edge, wherein a plurality of openings (31) are provided in the metal support (23) along an edge, and the openings (31) are arranged along a straight line and are flush with the outer edge when viewed, such that a hole pattern is formed, which is designed such that openings (31) of a first type and a second type are provided, wherein the longitudinal extent perpendicular to the straight line for an opening (31) of the first type is greater than the longitudinal extent for an opening (31) of the second type, wherein a linear, alternating hole pattern is formed along the straight line, and wherein the sealing element (23B) comprises an elastomer.which is applied at least to the edge of the openings (31) on the metal support (23A).

2. Sealing arrangement (21, 21A, 21B) according to claim 1, wherein the sealing element (23B) is applied as an edge-bonded seal to the metal carrier (23A), wherein the elastomer is applied as a sealing material to the edge of the opening (31).

3. Cell element of an electrochemical cell, in particular an electrolysis cell (1) , with a sealing arrangement (21, 21A, 21B) according to one of claims 1 or 2, comprising a membrane electrode assembly (MEA) which has as an active surface a membrane (9) coated with an anode (5) and with a cathode (7) and an edge region (37), wherein a sealing arrangement (21, 21A, 21B) is provided on the anode side and on the cathode side, which are stacked tightly on top of each other, wherein the membrane electrode assembly (MEA) is received centrally and clamped and positioned in the edge region (37) by means of the sealing elements (23B) in a rubber-elastic manner.

4. Cell stack with a plurality of electrochemical cells, in particular stacks of electrolysis cells (1), each with a cell element according to claim 3, which is designed according to a first cell type (A) or according to a second cell type (B), each having an anode compartment and a cathode compartment separated from each other by a respective membrane (9), wherein cell types (A, B) are stacked alternately one above the other as a cell pair along a stacking axis (Z), wherein the axially stacked sealing arrangements (21, 21A, 21B) form a distributor structure (17) with a channel structure (29) for supplying a cell element with a fluid (F), wherein in the cell pairs, in addition to the sealing function, the channel structure (29) is formed, which provides a flow path for adjacent cell types (A, B) such that a cell of the first cell type (A) is supplied with fluid (F) via the adjacent cell of the second cell type (B).

5. Cell stack according to claim 4, in which, on the anode side of a cell type (A), the sealing arrangement (21A) arranged on the membrane electrode assembly (MEA) is identical in design to a sealing arrangement (21B) arranged on a cell type (B) and is rotated by 180° about the stack axis (Z) as the axis of rotation.

6. Electrolyzer, in particular PEM electrolyzer, comprising a cell stack of electrolysis cells (1) with a distributor structure (17) according to claim 4 or 5, for supplying and distributing a fluid (F) into the cell element and a similarly designed outlet structure for draining fluid (F) after flowing through the cell element.

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