Cell concept with a novel cathode structure and a corresponding cell frame for alkaline water electrolysis

Abstract

The invention provides a cathode structure (1) and a cell frame for an alkaline electrolysis cell (20), wherein the cathode structure (1) comprises a bipolar plate (2) connected to conductor links (3), and wherein the conductor links (3) subdivide an active cell region (6) and are aligned in an electrolyte flow direction (7). The cell frame (10) comprises the cathode structure (1) and has a distributor structure (11), the distributor structure (11) defining an active cell region (6) and being designed to achieve a uniform flow distribution in the cell (20). The invention further provides a process for producing the cell frame (10).

Description

[0001] Description

[0002] Cell concept with a novel cathode structure and a corresponding cell frame for alkaline water electrolysis

[0003] The present invention relates to a cell concept for an electrochemical cell, in particular an alkaline electrolysis cell, wherein the sealing concept comprises an electrode structure and a cell frame. Furthermore, a method for producing the cell frame is the subject of the present invention.

[0004] In light of the energy transition and advancing climate change, very ambitious efforts are underway to significantly increase the installed capacity of water electrolyzers, whether via PEM electrolysis or alkaline electrolysis, in the coming years. This also creates a very strong need to develop new cell concepts, frames, electrodes, membranes, separators, and corresponding sealing components that are characterized, for example, by simpler manufacturing, higher efficiency, higher current density, and the use of improved materials.

[0005] If an electrolysis reaction takes place in the alkaline range, a diaphragm (also called a separator) can be used, or specifically an anion exchange membrane (AEM). If, on the other hand, the electrolysis reaction takes place in the acidic range, a proton exchange membrane (PEM) is used instead.

[0006] The production of green hydrogen from water is now largely carried out electrolytically using the processes mentioned above. This is an electrochemical process in which water is separated into its chemical components, oxygen and hydrogen. The electrochemical

[0007] Cell reactions or operating mode or alkaline

[0008] Electrolysis can be summarized as follows:

[0009] To achieve the political goals, particularly those of the US Department of Energy, of hydrogen production costs below US$2 / kg, technical advances in electrolysis systems are required. In addition to material improvements, significant cost reductions and efficiency gains can be achieved through improvements in manufacturing processes.

[0010] Hydrogen can be produced by electrolysis of water, using the various technologies mentioned above.

[0011] Alkaline water electrolysis (AEL) is an industrially established technology that requires low investment costs, resulting from its market maturity. AEL is also characterized by high long-term stability and the fact that virtually no critical raw materials or complex membrane or electrode materials are required.

[0012] Known (pressure) cell concepts are based, for example, on nickel-coated steel rings or steel frames, which are sealed to each other and electrically separated by PTFE flat gaskets. In addition to common flat gaskets, O-ring or cord seals are also known, which are inserted into corresponding grooves. This sealing variant, however, is limited to plastic cell frames, since electrical insulation between the cells is often not provided in alkaline electrolysis stacks. Known electrolysis cells operate in a pressure range between 30 bar and 40 bar and at a temperature of 60 to 100°C. The sealing material can be exposed to the following media: H2, O2, NaOH (30 wt.%) and / or KOH. This results in special requirements for the sealing material used. Current pressurized AEL systems achieve current densities of 200 to a maximum of 400 mA / cm 2. These systems are therefore only suitable to a limited extent for economic (industrial) application of the technology.

[0013] Sealing concepts for electrolyzers, for example based on fluoroelastomers or PTFE (polytetrafluoroethylene), are known from: EP 0 276 351 Bl, EP 2 734 658 Bl, EP 2 993 254 Al, EP 2 993 254 Bl.

[0014] It is an object of the present invention to solve the problems described above and to provide an improved cell concept for alkaline water electrolysis, which in particular allows the electrolysis to be carried out at significantly higher current densities, ie up to or even more than 1 A / cm 2 , to operate.

[0015] This problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent patent claims.

[0016] One aspect of the present invention relates to an electrode structure, in particular a cathode structure, for an alkaline electrolysis cell, in particular a pressure-operated one.

[0017] The cell is preferably intended for water electrolysis and for the production of green hydrogen from renewable energy.

[0018] The structure of the electrode or cathode structure includes a

[0019] Bipolar plate connected to flow guides. The bipolar plate can, for example, consist of a steel sheet a few millimeters thick. Preferably, the surface of the bipolar plate also roughly defines an active cell region or "active field" of the cell.

[0020] The conductive webs further divide the active cell area and are aligned along an electrolyte flow direction, which preferably occurs during operation of the electrochemical cell.

[0021] In one embodiment, the distance between the guide bars is approximately 7 cm to 10 cm.

[0022] The presented concept of the cathode structure advantageously enables, particularly in conjunction with a suitable cell frame, the cell to be used efficiently and with low wear at particularly high current densities. At current densities of, for example, over 1 A / cm 2 Targeted heat dissipation becomes essential; this can also be ensured in the presented concept by the assembly and dimensioning of the cathode structure.

[0023] In addition, a further aspect of the present invention, namely relating to the production of the corresponding cell frame, advantageously makes it possible to save material and labor costs and to dispense with additional, otherwise required, complex work steps, such as machining steps, in particular for producing sealing grooves in the cell frame.

[0024] The presented cell concept is compatible with steel frame constructions for pressure operation of approximately 30 to 40 bar.

[0025] Furthermore, the described concept enables improved (electrolytic) fluid guidance or media supply and media removal due to the advantageous branching and course of the channels, preferably by means of fluidics integrated into the cell frame or cell (without external "manifolding"), which advantageously makes it possible to dispense with expensive and material-intensive filter press constructions.

[0026] Furthermore, the present concept enables an efficient so-called "zero-gap design" of the electrolysis cell for a particularly high (electrical) system efficiency without excessive ohmic losses.

[0027] The present invention also enables the use of PFAS-free sealing materials, even in pressurized AELs. The concept presented advantageously eliminates the use of PFASs while still achieving sealing functionality that is at least as good or even improved compared to conventional solutions.

[0028] PFAS are so-called per- and polyfluoroalkyl substances. Due to the persistence of PFAS substances or their degradation products in the environment, these substances (also called “forever chemicals”) have a bad reputation and pose serious ecological and health risks. PFAS are particularly suspected of being carcinogenic. Due to the high risk potential of PFAS and in particular the high follow-up costs associated with containing and minimizing damage caused by their spread, for example through contaminated drinking water, far-reaching bans are likely in the near future.

[0029] In one embodiment of the described concept, two adjacent conducting webs define a separate flow plane for a, particularly liquid, electrolyte during operation of a corresponding electrochemical cell. The web concept creates an additional flow plane in which the electrolyte can flow unhindered, thereby ensuring efficient heat and gas removal. This is particularly necessary for or to achieve high current densities. Furthermore, the design enables efficient removal of gas bubbles from the electrode plane. In known "zero-gap systems", gas bubbles must pass through the electrode structure (expanded metals / foams, etc.) in plane, which results in a longer residence time. Since the gas bubbles displace the electrolyte, "gassing" of the electrode leads to a significant increase in cell voltage.By "flowing behind" the electrode structure in the concept described here, an efficient removal is achieved through shorter diffusion lengths.

[0030] In other words, it advantageously prevents gas bubbles from becoming trapped within the electron structure and thus increasing the electrical contact resistance at the corresponding electrode, thereby reducing efficiency. Instead of transporting gas bubbles through the electrode chamber, the conducting webs enable defined and efficient gas kinetics. Because the main flow of the electrolyte (as well as the gas removal) advantageously occurs within the defined flow plane, a vacuum also prevents significant penetration or entrapment of gas bubbles in the actual electrode.

[0031] In one embodiment, the bipolar plate has (only) two, in particular equally long, opposite straight edges, which in particular define a deviation from a round cell geometry. According to this embodiment, the cell or the active cell region is preferably not completely round, but rather has a rounded shape around the circumference, for example only in certain regions (between the straight edges). The design of the bipolar plate with two straight edges advantageously makes it possible to minimize waste during cutting, in particular by means of laser cutting. Furthermore, in certain operating states, a so-called "gas bar" can form in completely round cells, as a result of which the diaphragm loses its blocking effect and gas exchange can occur between the anode and cathode.As a result, safety problems, particularly the risk of explosion, may arise during cell operation, since otherwise less or hardly any alkali or less electrolyte would be present in the "cut-off" areas. This effect can be reliably prevented by the proposed shape of the bipolar plate or the cell.

[0032] In one embodiment, the guide webs are connected at an end facing away from the bipolar plate to a support structure, in particular a welded one, which in turn supports an electrode structure for the cathode. This embodiment enables a particularly suitable geometry and the development of advantageous flow kinetics (cf. the described backflow of the electrode) and electrocatalytic efficiency of the cell.

[0033] In one embodiment, the electrode structure comprises a metal mesh, in particular a nickel mesh, and, preferably in an interior region closest to the separator or diaphragm, a metal mesh, in particular a nickel mesh. This electrode design allows for particularly advantageous electrocatalytic efficiency of the cell to be achieved.

[0034] A further aspect of the present invention relates to a cell frame for alkaline electrolysis, in particular comprising the described cathode structure. In particular, the cathode structure is welded to the cell frame, or vice versa. The cell frame further comprises a distribution structure or distribution bar, which likewise defines the active cell region and is designed to achieve a uniform flow distribution (for the electrolyte) of the cell. The distribution structure can be a diffuser structure, in particular a (slotted) square tube, which in particular seals the cell (see below) and - in particular in interaction with the conducting webs of the cathode structure - significantly increases the electrolyte flow in the cell, but also homogenizes it and thus enables cell operation at the aforementioned high current densities.

[0035] In one embodiment, the guide webs are aligned perpendicular to the distributor structure.

[0036] In one embodiment, the cell frame is a ring construction, in particular comprising a nickel-plated steel ring, with the distribution structure arranged inside the ring. According to this embodiment, the obvious advantages of a (partially) round cell, namely its better mechanical force distribution under pressure, can be utilized while simultaneously avoiding the disadvantages or sealing problems described above.

[0037] In one embodiment, the distributor structure defines or integrates distributor channels for guiding the (liquid) electrolyte, wherein the cell frame is further configured such that a distributor inlet or distributor outlet channel, in particular for the inlet of the electrolyte into the active cell region or for its outlet from the active cell region, is arranged between each two adjacent guide webs.

[0038] In particular, the distribution structure according to the invention prevents the formation of unfavorable flow paths (so-called "z-flow"), for example diagonally and uncontrolled across the active cell region. Such an unguided flow of the electrolyte would otherwise inevitably lead to a lower electrolytic throughput and to the formation of dead zones in the active field.

[0039] A further aspect of the present invention relates to an electrolysis cell, in particular for alkaline water electrolysis, comprising at least at the cathode the described cell frame, wherein the cell is furthermore designed for pressures of 30 bar to 40 bar, temperatures of 80 °C to 100 °C and / or for carrying the media H2, O2 and / or highly concentrated NAOH (e.g. 30 to 35 wt%) or KOH.

[0040] The electrode structure according to the invention is particularly efficient and useful at the cathode of alkaline electrolysis cells, since, for example, twice the amount of alkali or electrolyte must be passed through here; thus, twice the amount of gas is produced than, for example, at the anode. Without limiting its generality, the cathode structure according to the invention can, in principle, also be used at the anode.

[0041] In one embodiment, the electrolysis cell is designed to operate or achieve current densities above 1 A / cm 2 designed .

[0042] In one embodiment, the cell comprises a fluorine-free seal, in particular comprising a PPSU plastic, wherein the seal is designed both to seal the cell as a whole and to seal the cell's diaphragm. Alternatively, the described sealing effect can also be achieved by several fluorine-free individual seals.

[0043] Another aspect of the present invention relates to a

[0044] Stack or cell stack or a stack arrangement with a plurality, for example dozens of such electrolysis cells.

[0045] A further aspect of the present invention relates to an electrolyzer having a plurality of the described stacks.

[0046] Yet another aspect of the present invention relates to a method for producing the cell frame or cell, comprising providing a rectangular profile, in particular a beam profile, and round-bending the rectangular profile in a roll bending device. The round bending can, for example, involve profile bending of the steel profile using a 3-roll configuration.

[0047] The method further comprises in particular cutting out electrolyte channels from the rounded profile by means of plasma cutting, laser cutting, water jet cutting or flame cutting.

[0048] In one embodiment, the method then comprises the cathode-side welding or welding of a bipolar plate into the profile ring, as well as the connecting or welding of the described guide webs, as well as the support structure and the electrode structure, as described above.

[0049] Configurations, features and / or advantages which in the present case relate to the cathode structure or the cell frame also relate to the electrolysis cell itself and the manufacturing process, and vice versa.

[0050] As used herein, the term "and / or" or "respectively," when used in a series of two or more elements, means that any one of the listed elements may be used alone, or any combination of two or more of the listed elements may be used.

[0051] Further details of the invention are described below with reference to the figures. Figure 1 shows a cathode structure according to the invention in a schematic sectional or side view.

[0052] Figure 2 shows a schematic perspective view of the cell frame according to the invention, in particular its cathode side.

[0053] Figure 3 shows a perspective view of the corresponding anode, similar to Figure 4.

[0054] Figure 4 schematically indicates an electrolyzer comprising an electrolysis stack according to the invention.

[0055] Figure 5 shows a schematic view of further details of the electrolysis cell according to the invention.

[0056] Figure 6 shows a diagram of a roll bending device and method steps according to the invention using a schematic flow diagram.

[0057] Figures 7 to 9 each show diagrammatically different parameters, such as in Figure 7 the volume flow of the electrolyte, in Figure 8 the volume flow of a coolant and in Figure 9 the diameter of a half-cell, each as a function of the current density.

[0058] In the exemplary embodiments and figures, identical or equivalent elements may be provided with the same reference numerals. The illustrated elements and their relative sizes are generally not to scale; rather, individual elements may be exaggeratedly thick or oversized for clarity and / or clarity.

[0059] Figure 1 schematically illustrates an electrolysis cell 20. The electrolysis cell 20 is preferably an alkaline cell for water electrolysis, which is particularly designed for pressure operation, particularly at pressures of 30 to 40 bar, and temperatures of 80°C to 100°C.

[0060] One aspect of the present invention now concerns the cathode (not explicitly marked) of the cell 20. For this purpose, a cathode structure 1 is shown in the lower region of Figure 1. For the sake of clarity, an anode 17 is marked opposite the cathode or cathode structure 1, which is separated from the cathode by a separator or a diaphragm 14.

[0061] The cathode structure 1 comprises a bipolar plate 2 (see illustration below). The bipolar plate 2 can, for example, be a bipolar sheet a few millimeters thick, in particular 3 mm.

[0062] Furthermore, the cathode structure 1 comprises conductive webs 3, which are in particular welded onto the bipolar plate 2 or otherwise connected thereto. The webs 3 can, for example, be welded onto the bipolar plate 2 at a distance of 7 cm to 10 cm. The webs 3 can also be made from 3 mm flat steel and have a height (cf. vertical extension in Figure 1) of 10 mm to 20 mm, preferably 15 mm.

[0063] With their longitudinal axis, the webs 3 preferably extend into the plane of the illustration, i.e. along a flow direction (cf. reference numeral 7 in Figure 2) for the electrolyte, which direction is formed during operation of an electrochemical cell 20 comprising the cathode structure.

[0064] The flow guide webs 3 thus divide an active cell region (cf. reference numeral 6 below) into, in particular, equidistant sections, wherein two adjacent guide webs 3 define a separate flow plane for the electrolyte (not explicitly identified by reference numeral in the present case) during operation of the corresponding electrochemical cell 20. Accordingly, the webs 3 can also function as spacers or partitions.

[0065] Although this is not explicitly indicated in the present figures, the webs 3 can be perforated, slotted or structured in some other way.

[0066] The next element of the cathode structure 1 is a support structure 4, which is indicated by the zigzag-like course above the webs 3. The preferably metallic support structure 4 can, for example, have a thickness of 2 mm and be formed from expanded metal. The support structure 4 essentially serves to support or spaced-apart connection of the actual electrode, which is indicated by the reference symbol 5. The electrode or electron structure 5 in the present case comprises a metal mesh, for example approximately 5 mm to 10 mm, in particular 7 mm, thick, in particular a nickel mesh, and further inside, i.e. closer to the separator, a metal fabric, in particular a fine nickel fabric.

[0067] On the far right in the illustration of Figure 1, possible thickness and size ratios of parts of the cathode structure 1 are given in millimeters - merely as an example.

[0068] Figure 2 shows a further aspect of the present invention, namely a cell frame 10 which is designed to be compatible with the described cathode structure 1.

[0069] The cell frame 10 has a round shape and preferably consists largely of a corresponding profile steel or steel ring (see description based on Figure 6 below). A round or partially rounded cell geometry proves to be significantly superior to square or rectangular "cross-sections," particularly with regard to mechanical force ratios, integrity, and tightness.

[0070] In an interior of the ring, the cell frame 2 has two opposing distribution structures 11. The distribution structures 11, or "diffuser strips," essentially define an active cell region 6 laterally. The active cell region 6, in turn, preferably corresponds approximately to the area of ​​the bipolar sheet 2, which preferably also has straight edges along the distribution structures 11, which represents a deviation from the round cell geometry.

[0071] The distribution structures 11 also define, in particular, a deviation of the active cell area 6 from the round or ring-shaped geometry of the frame 10.

[0072] The distribution structures 11 or distribution bars can further consist of a square tube with appropriate slots for the fluid channels or electrolyte flow. In particular, the distribution structures 11 enable uniform flow distribution and also mechanically support the sealing of the cell 20.

[0073] Although the described cathode structure 1 is not completely visible in Figure 2 for the sake of clarity, the guide webs 3 can be seen, which extend essentially perpendicular to the course (longitudinal axis) of the distributor structures 11.

[0074] As a feature of the distribution channels 11, inlet and outlet openings or corresponding channels 12 are also shown in Figure 2, through which the inflow of the electrolyte, in particular NaOH or KOH, during operation of the cell 20, or its outflow can expediently take place at relatively high flow rates. A further channel system (internal "manifolding") is also not explicitly shown in Figure 2 for the sake of clarity. However, the interaction of the openings 12 of the distributor structure 11 with the described cathode structure 1, or its webs 3, is revealed by the position of the channel openings 12. This is because an elongated, approximately oval or crescent-shaped opening 12 (for the inflow or outflow of the electrolyte) is preferably provided between every two webs 3.Without loss of generality, the openings 12 thus provide the cathodic rectilinear flow of the electrolyte, either from front to back or vice versa.

[0075] Using this cell concept according to the invention, the gas throughput and the possible current density of the cell can be increased several times over compared to known concepts. In particular, an electrochemical cell equipped with the cathode structure according to the invention or with the cell frame according to the invention is particularly suitable for current densities of more than 1 A / cm 2 operable .

[0076] Figure 3, similar to Figure 2, shows an anode side of the corresponding cell 20, where a cell frame 10 may also be used. However, the anode is preferably supplied with electrolyte via a different channel or inflow system than on the cathode side. For this purpose, the cell frame 10 has the outer openings 15 in the annular frame.

[0077] On both the cathode and the anode side, inserts or plastic elements, for example made of PPSU, can be provided in the inlet and outlet areas for the fluids or media, which ensure or improve the sealing of the cell 20 and / or the diaphragm 14.

[0078] Figure 4 schematically illustrates an electrolyzer 40 comprising a cell stack 30 of electrochemical cells 20 (see above). The advantages of the present invention, based on the individual cell, are thus multiplied across the stack and the entire electrolysis system.

[0079] Therefore, the present invention enables a significant improvement in the AEL even at industrialized levels and paves the way for the production of green hydrogen (from renewable energy) at particularly high production rates or renewable input power in the gigawatt range.

[0080] The robust, innovative cell concept, which is nevertheless relatively simple and fault-tolerant in terms of manufacturing, allows for particularly high electrolyte flow rates, particularly up to or more than 60 rpm. This electrolyte flow also influences the cooling of the system, which is why the flow rate can only be reduced if cooling is not performed at the anode, but rather by other means, for example, exclusively on the cathode side.

[0081] Figure 5 shows only a portion of the cell 20, namely two seals 13, between which the separator 14 or the diaphragm is arranged, thus sealing it. The seals are essentially annular flat seals, which have recesses in the outer region for the anodic fluid supply (similar to the openings 15 in Figure 3).

[0082] The described seal 13 preferably consists of a PPSU in a single-layer or multi-layer design. The seal 13 can be (hot-) pressed with the diaphragm 14 during the production of the cell 20, for example as a (multi-layer) PPSU foam. This can be done in particular using heated matrices at approximately 215 °C. The "laminate" produced in this way is, in contrast to fluorine-free elastomer seals such as those made of EPDM, completely compatible with the media and advantageously enables mechanical fixing and "padding" of the diaphragm. Compared to PTFE flat seals, the concept described here advantageously exhibits no or significantly less creep behavior under pressure applications. This in turn advantageously reduces the otherwise necessary mechanical re-tensioning of the stacks.

[0083] The cell design described here still allows the use of fluorine-free seals, preferably in combination with pressure-resistant nickel-plated steel ring cells.

[0084] The manufacturing process for the cell frame 10 is further described in more detail with reference to Figure 6. A roller bending device 100 is shown therein in simplified form. This device is preferably intended for the round bending of profile steels.

[0085] The method according to the invention comprises in S 1 the provision of a rectangular profile 10, in particular a steel profile 10.

[0086] The method further comprises, in S2, the round bending of the rectangular profile 10 in a roll bending device 100, and, in S3, the cutting out of electrolyte channels 16 from the round-bent profile 10.

[0087] A profile steel or steel ring, which is later to form the cell frame 10, is preferably bent round from a 3 mm thick rectangular profile with an outer diameter of approximately 1 m or more. This method offers advantageous material and machining costs compared to conventional processes. In known processes for producing steel ring cells, corresponding blanks are cut from tubes and the sealing grooves and media channels are subsequently integrated by machining. The production process described here, in contrast, is based on simple round bending of steel tube profiles. Cutouts for electrolyte channels can be subsequently integrated by plasma cutting, laser cutting, water jet cutting or flame cutting. Cell frames with an outer diameter of over 1 m can preferably be burnt out of heavy plate using flame cutting and deburred.Alternatively, smaller cells can also be manufactured by welding bent sub-segments.

[0088] It is not excluded that profile rings can also be assembled from several bent segments or L-profiles. This is particularly relevant for smaller ring diameters with critical bending radii. Profiles are usually bent with multiple roll passes.

[0089] The bipolar plate 2 (containing, in particular, the other elements of the cathode structure 1) can then be welded into the ring 10. For this purpose, the components are preheated, preferably to at least 180°C. MIG or MAG welding processes with a fast pulsed arc can be used to largely prevent thermal distortion or reworking. Then, during cell production, the webs 3 can be welded onto the bipolar plate 2 on the cathode side.

[0090] According to a modification, after welding the bipolar sheet 2 into the ring, the described support structure 4 as well as the electron structure 5 can also be welded accordingly.

[0091] Furthermore, insulation sections (not explicitly marked here) can be integrated into the steel ring profile. These can be created, for example, by inserting tubes or by filling the structure with epoxy resin.

[0092] The cell design described here particularly advantageously enables the use of cost-effective structural steels and profile steels. The cells constructed in this way exhibit high compressive strength, since the bipolar plate and the welded cross sections largely reliably compensate for the outwardly acting forces. Furthermore, the process according to the invention advantageously significantly reduces material waste compared to conventional manufacturing techniques.

[0093] Figure 7 shows a diagram with exemplary data of the volume flow rate of the electrolyte, plotted against the current density J . From the somewhat proportional curve, it can be deduced that correspondingly high flow rates are required to achieve high current densities, but are also achievable with the presented concept.

[0094] Figure 8 shows a similar dependence as shown in Figure 7 for the cooling flow rate as a function of the current density.

[0095] Figure 9 also shows a similar behavior of the half-cell thickness d of the so-called "catholyte" or the corresponding chamber thickness as a function of the current density. The depicted parameter of the half-cell or catholyte thickness may approximately correspond to the height of the conducting webs 3 (see above).

[0096] All data shown in Figures 7 to 9 correspond to a design of the cell configuration at atmospheric pressure (approx. 1 bar). It can be seen that the desired current densities up to approx. 1 A / cm 2 for the parameters specified, these can therefore already be achieved without the cell being operated under pressure. Accordingly, the cell concept presented is dimensioned quite generously, and it is evident that the advantages according to the invention become even more apparent in pressure operation, for example above 1 bar to 20 bar, or even in a range between 30 bar and 40 bar, although no explicit data are described in this regard. Those skilled in the art will know that pressure operation in particular prevents the formation of large gas bubbles and thus considerably reduces ohmic losses. In other words, the efficiency of the cell is advantageously increased over pressure operation without any significant reduction in service life.

Claims

Patent claims 1. Cathode structure (1) for an alkaline electrolysis cell (20), wherein the cathode structure (1) comprises a bipolar plate (2) which is connected to conducting webs (3), wherein the conducting webs (3) divide an active cell region (6) and are aligned along an electrolyte flow direction (7), and wherein the bipolar plate (2) has two opposite straight edges which in particular define a deviation from a round cell geometry.

2. Cathode structure (1) according to claim 1, wherein each two adjacent guide webs (3) define a separate flow plane for an electrolyte during operation of a corresponding electrochemical cell (20).

3. Cathode structure (1) according to one of the preceding claims, wherein the conductive webs (3) are arranged on one of the bipolar plates (2) are connected to a support structure (4) at its end facing away from it, the support structure (4) carrying an electrode structure (5) for the cathode.

4. Cathode structure (1) according to claim 3, wherein the electrode structure (5) comprises a metal mesh, in particular a nickel mesh, and a metal fabric, in particular a nickel fine fabric.

5. Cell frame (10) for an alkaline electrolysis cell (20), wherein the cell frame (10) comprises the cathode structure (1) according to one of the preceding claims, and a distributor structure (11), wherein the distributor structure (11) defines an active cell region (6) and is designed to achieve a uniform flow distribution of the cell (20).

6. Cell frame (10) according to claim 5, wherein the guide webs (3) are aligned perpendicular to the distribution structure (11).

7. Cell frame (10) according to claim 5 or 6, which is a ring construction, in particular comprising a nickel-plated steel ring, wherein the distribution structure (11) is arranged inside the ring.

8. Cell frame (10) according to one of claims 5 to 7, wherein the distributor structure (11) defines distributor channels for guiding an electrolyte, wherein the cell frame (10) is configured such that a distributor inlet or distributor outlet channel (12) is arranged between each two adjacent guide webs (3).

9. Electrolysis cell (20), in particular for alkaline water electrolysis, comprising a cell frame on the cathode side (10) according to one of claims 5 to 8, wherein the cell (20) is designed for pressures of 30 bar to 40 bar, temperatures of 80 °C to 100 °C, and / or for carrying the media H2, O2, and / or highly concentrated NaOH or KOH.

10. Electrolysis cell (20) according to claim 9, which has a fluorine-free seal (13), in particular comprising a PPSU plastic, wherein the seal (13) is designed both for sealing the cell (20) as a whole and for sealing a diaphragm (14) of the cell (20).

11. Stack arrangement (30) with a plurality of electrolysis cells (10) according to claim 10.

12. Electrolyzer (40) with a plurality of stacks (30) according to claim 11.

13. A method for producing a cell frame (10) according to any one of claims 5 to 8, comprising the steps: - (Sl) providing a rectangular profile (10), in particular a steel profile, - (S2) round bending of the rectangular profile (10) in a roll bending device (100), and - (S3) cutting out electrolyte channels (16) from the rounded profile (10) by means of plasma cutting, laser cutting, water jet cutting or flame cutting.

14. Method according to claim 13, wherein subsequently a Bipolar plate (2) is welded into the profile ring on a cathode side, and subsequently the guide webs (3), and in particular the carrier structure (4) and the electron structure (5) are welded or connected according to one of claims 1 to 4.

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