Electrochemical electrode structure, electrochemical cell, and method for converting a finite-gap electrochemical cell into a zero-gap electrochemical cell.

Abstract

The present invention relates to an electrochemical electrode structure comprising a current collector and at least one electrode element, wherein the at least one electrode element is a two-dimensionally stretched conductive element having an open structure. In this electrochemical electrode structure, the at least one electrode element has at least one end having a hemming rim in which a strip portion of the electrode is hemmed. Furthermore, the present invention relates to an electrochemical cell comprising a first electrode, a second electrode and a separator, wherein either or both of the first electrode or the second electrode are such an electrochemical electrode structure, and further relates to a method for converting a finite-gap electrochemical cell into a zero-gap electrochemical cell using such an electrochemical electrode structure.

Description

Technical Field

[0001] The present invention has been made in the field of electrolytic cells, particularly zero-gap electrolytic cells. The present invention relates to an electrochemical electrode structure comprising a current collector and at least one electrode element, wherein the at least one electrode element is a two-dimensionally extended conductive element having an open structure. The present invention further relates to an electrochemical cell comprising a first electrode, a second electrode, and a separator, wherein the separator is a two-dimensionally extended partially permeable element disposed between the first electrode and the second electrode, and the two-dimensionally extended partially permeable element has two surface sides, and to a method for converting a finite-gap electrochemical cell into a zero-gap type electrochemical cell.

Background Art

[0002] In recent years, there has been a significant increase in interest in using hydrogen as a secondary energy carrier. In particular, this increase in interest is based on the following advantages of hydrogen. That is, hydrogen can be easily produced from water using renewable primary energy, hydrogen is a non-toxic substance with a relatively high energy density per mass, and the chemical energy stored in hydrogen can be easily converted into electrical energy without releasing large amounts of carbon dioxide or other greenhouse gases. In addition, hydrogen can also be used as a starting material in various chemical processes. One important method for producing hydrogen is by electrolysis of water, i.e., a process in which hydrogen is produced in the cathode compartment of an electrolytic cell from an alkaline aqueous solution, an acidic aqueous solution, or a neutral aqueous solution. The cathode compartment and the anode compartment are typically separated from each other by a separator such as a membrane or diaphragm. In many applications, particularly alkaline water electrolysis, has proven to be the most promising process.

[0003] Conventionally, the efficiency of alkaline water electrolysis devices has been limited, as high internal ohmic resistance causes a significant voltage drop across the electrolyte, meaning such devices could only operate at relatively low current densities. Therefore, "zero-gap" electrolytic cells have been established to minimize the voltage drop across the electrolyte, thereby enabling the achievement of higher current densities. In zero-gap designs, electrodes with an open structure (such as perforated or porous electrodes) are employed as anodes and cathodes that are in direct contact with the surface of the membrane with little or no gap, in order to reduce the gap between electrodes and thus the width of the voltage drop between the two electrodes.

[0004] Mechanical damage to the thin film often occurs in the peripheral region of the cell, mostly as a result of direct contact between the outer edge of the metal electrode and the upper surface of the film. To reduce the risk of such damage, European Patent Application Publication No. 3575440 suggests that the electrode should exhibit a zero-gap design only in its central region, while the distance between the electrode and the film increases toward the periphery of the cell, thus giving the electrode a one-sided cushion-like structure with a finite gap that increases toward its edge region.

[0005] Unfortunately, the cushion-like structure introduces several individual drawbacks. Specifically, in the outer regions of the electrochemical cell, the electrodes do not directly contact the membrane, reducing the electrode area where the zero-gap condition is actually realized. Furthermore, in these outer regions, localized voltage drops across the electrolyte occur, resulting in a non-uniform current density distribution across the electrode area, thus hindering the maximum efficiency of hydrogen production. To enable a localized finite-gap design in the outer regions, the electrodes require a certain thickness. However, this results in an increased overall thickness of the electrolytic cell, which may prevent the achievement of the maximum stacking density. While this may not be very relevant when manufacturing new cells, it can become problematic when modifying existing finite-gap electrolytic cells into zero-gap electrolytic cells, as the available space may be limited by the original design, and therefore electrodes of such thickness may not be usable. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] European Patent Application Publication No. 3575440 [Overview of the project]

[0007] Therefore, the object of the present invention is to overcome the above-mentioned drawbacks and provide an electrode arrangement for a zero-gap electrolytic cell that avoids damage to the film by the electrodes and simultaneously enables the highest possible yield, and in addition, it must be possible to convert existing finite-gap electrolytic cells into zero-gap cells even when space is limited. Another object is to provide a suitable electrolytic cell, as well as a method for converting a finite-gap electrochemical cell into a zero-gap electrochemical cell.

[0008] The present invention provides an electrochemical electrode structure comprising a current collector and at least one electrode element, the at least one electrode element being a two-dimensionally stretched conductive element having an open structure. The at least one electrode element has at least one end having a hemming rim, which is formed by hemming a strip portion of the electrode element. According to this solution, by hemming the strip portion of the electrode element, sharp edges are eliminated, preventing damage to the separator. This solution is also applicable when there is not enough space / gap to curve the electrode element away from the separator. Furthermore, since a zero-gap design can be implemented over a larger area compared to when the end of the electrode element is curved away from the separator, higher electrolytic performance can be achieved.

[0009] When the hemming rim has a bending angle between 170° and 180°, particularly between 175° and 180°, and more specifically between 177° and 180°, damage to the separator by the ends of the electrode elements can be more reliably prevented.

[0010] Damage to the separator can be further prevented if at least one electrode element has a further end with a hemming rim, and two ends are provided on both sides of at least one electrode element.

[0011] The electrochemical electrode structure preferably has a support element positioned between at least one electrode element and a current collector, wherein the support element comprises an elastic member adapted to push at least one electrode element away from the current collector. This allows the distance between opposing electrode elements to be reduced to, ideally, substantially zero.

[0012] Preferably, at least one electrode element has four ends, each with a hemming rim. Separator damage can be further prevented.

[0013] Alternatively, at least one electrode element may have two additional ends on either side of the at least one electrode element, which has an inclined rim that is bent and inclined so that the strip portion of the electrode element is separated. The inclined rim may be used to attach the electrode element to a support element.

[0014] The inclined rim may have a bending angle greater than 0° and less than or equal to 70°, and the bending angle is particularly between 15° and 45°, more specifically between 15° and 30°.

[0015] The support element comprises at least one projection extending from at least one end of the support element, each of which has a front side facing at least one electrode element and a rear side facing away from the at least one electrode element, and preferably the strip portion of the electrode element in the inclined rim is fitted to lock the rear side of the at least one projection to secure at least one end of the at least one electrode element to the support element. With this arrangement, the electrode element can be attached to the support element without using a fixing element.

[0016] Damage to the separator can be further prevented if the width of the strip portion of the electrode element within the hemming rim is in the range of 3 mm to 50 mm.

[0017] Electrochemical electrode structures can comprise multiple electrode elements. This facilitates the handling of the electrode elements. Furthermore, the number of electrode elements can be adjusted to suit electrochemical cells of different sizes.

[0018] Electrode elements from multiple electrode elements may be arranged such that the edges of adjacent electrode elements overlap each other, or so that the edges of adjacent electrode elements are joined together. The former may be advantageous in arranging the electrode elements without gaps and thus obtaining the maximum electrode area. The latter may be expected to have a flatter electrode surface.

[0019] Preferably, at least one electrode element is a grid element or an expanded mesh element. The gas generated in front of the electrode element can be discharged to the rear of the electrode element through an opening in the grid element or expanded mesh.

[0020] According to another aspect of the present invention, an electrochemical electrode structure is provided comprising a first electrode element, a second electrode element, and a separator, wherein the separator is a two-dimensionally stretched partially permeable element positioned between the first electrode element and the second electrode element, and the two-dimensionally stretched partially permeable element has two surface sides. Either the first electrode element or the second electrode element, or both the first and second electrode elements, constitute the electrochemical electrode structure according to any one of the above aspects. Each electrode element may be positioned adjacent to one of the two surface sides of the separator such that, at each hemming rim, the electrode element is hemmed and bent away from the surface side of the separator. According to this solution, by hemming the strip portion of the electrode element, sharp edges are eliminated and damage to the separator is prevented. This solution is also applicable when there is not enough space / gap to curve the electrode element away from the separator. Furthermore, since a zero-gap design can be implemented over a larger area compared to cases where the ends of the electrode elements are curved away from the separator, higher electrolytic performance can be achieved.

[0021] Preferably, the electrochemical cell comprises a first compartment and a second compartment, where the first compartment houses a first electrode element and the second compartment houses a second electrode element, and a separator is positioned between the first and second compartments to separate them, and the separator has a first surface side and a second surface side. The first surface side is in contact with the first compartment, and the second surface side is in contact with the second compartment to electrochemically interconnect the first and second compartments.

[0022] According to yet another aspect of the present invention, a method for converting a finite-gap electrochemical cell into a zero-gap type electrochemical cell is provided. The method includes providing a zero-gap type electrochemical cell having at least two electrochemical electrode structures, removing the at least two electrochemical electrode structures, and inserting an electrochemical electrode structure according to any of the above aspects.

Brief Description of the Drawings

[0023] [Figure 1] A schematic diagram of a bipolar electrolytic cell according to the present invention is shown. [Figure 2] A schematic diagram of one of the electrochemical cells in FIG. 1 is shown. [Figure 3] A view along A-A in FIG. 2 is shown. [Figure 4] A cross-section along B-B in FIG. 3 is shown. [Figure 5] Another example of a cross-section along B-B in FIG. 3 is shown. [Figure 6] A plan view of an electrode element is shown. [Figure 7A] A cross-section along C-C in FIG. 6 is shown. [Figure 7B] Another example of a cross-section along C-C in FIG. 6 is shown. [Figure 8] A perspective view of a support element in an electrochemical cell is shown. [Figure 9] A perspective view of another exemplary support element in an electrochemical cell is shown. [Figure 10] A perspective view of another exemplary support element in an electrochemical cell is shown. [Figure 11] A perspective view of another exemplary support element in an electrochemical cell is shown. [Figure 12] Attachment of an electrode element to the support element of FIG. 11 is shown. [Figure 13] A view along D-D in FIG. 12 is shown. [Figure 14] A cross-section along E-E in FIG. 12 is shown.

Modes for Carrying Out the Invention

[0024] One exemplary electrolytic cell to which the present invention may be applied is a bipolar electrolytic cell, such as an ion-exchange membrane process electrolytic cell, in which multiple bipolar electrochemical cell units are arranged in series, and an ion-exchange membrane or diaphragm as a separator is placed between adjacent cell units (Figure 1). Filter press techniques may be used to join adjacent cell units such that there is substantially no gap between the electrode elements on both sides of the separator. However, the electrolytic cell may be a unipolar electrolytic cell in which each cell unit has either a cathode electrode element or an anode electrode element on its side (not shown).

[0025] The electrochemical cell of the present invention may be used for chlorine alkali electrolysis. In another example, the electrochemical cell of the present invention may be used for alkaline water electrolysis (AWE). More generally, the electrochemical cell of the present invention may be applicable to any electrolysis process that uses a first electrode element, a second electrode element, and a separator placed between the first and second electrode elements.

[0026] As described herein, an electrochemical electrode structure may be defined as comprising a current collector and at least one electrode element, the at least one electrode element being a two-dimensionally stretched conductive element having an open structure. The term "current collector" refers to the electrical connection between the active material of the electrode element and the external circuit, and thus may cover the conductive portion of the rear wall / partition wall of an individual electrode cell unit, as well as any support structure protruding therefrom. "Open structure" means a structure having one or more openings that penetrate from one side to the other side of the electrode element.

[0027] In addition, the electrochemical cell comprises a first electrode element, a second electrode element, and a separator, the separator being a two-dimensionally stretched partially permeable element positioned between the first electrode element and the second electrode element, and the two-dimensionally stretched partially permeable element can be defined as having two surface sides.

[0028] Referring now to Figure 1 in light of the above definitions, one electrochemical cell 10 may thus comprise a first electrode element 12A (e.g., cathode) of an electrochemical cell unit 14, a second electrode element 12B (e.g., anode) of another electrochemical cell unit 14 adjacent to the electrochemical cell unit 14, and a separator 16 disposed between these electrode elements 12A, 12B. In other words, one electrochemical cell 10 may consist of two adjacent electrochemical cell units 14, 14. Therefore, it should be noted that the terms electrochemical cell and electrochemical cell unit are not necessarily synonymous in this specification.

[0029] As shown in Figure 2, the electrochemical cell 10 may comprise a first casing 18A defining a first compartment 20A internally, a second casing 18B defining a second compartment 20B internally, current collectors 22A and 22B, a first electrode element 12A, a second electrode element 12B, and a separator 16. The current collectors 22A and 22B may also be referred to as part of the electrode structure. The first and second casings 18A and 18B may include a rear wall or partition wall 24A and 24B. The partition walls 24A and 24B face the separator 16 across the first and second compartments 20A and 20B, and together with the separator 16 define these compartments 20A and 20B.

[0030] The separator 16 has a first surface side and a second surface side, the first surface side in contact with the first compartment 20A, and the second surface side in contact with the second compartment 20B to electrochemically interconnect the first compartment 20A and the second compartment 20B. The separator 16 may be an ion exchange membrane. Alternatively, the separator 16 may be a porous diaphragm, particularly an ion-permeable diaphragm. An ion-permeable diaphragm has an ion exchange function but does not allow gases produced by electrochemical reactions to permeate. The separator 16 may be a polymer porous membrane, an inorganic porous membrane, a woven or nonwoven fabric, or the same.

[0031] Referring to Figure 3, a diagram aligned with AA in Figure 2 can be seen. Each electrochemical cell 10 may be connected to a discharge header and a supply header. Preferably, for each compartment 20A, 20B within the electrochemical cell 10, the liquid to be electrochemically treated is supplied from the bottom of the cell 10 and discharged from the top of the cell 10. For example, in Figure 3, the liquid for the first compartment 20A may be supplied from the bottom inlet 26a on the left side and discharged from the top outlet 26b, which is diagonally opposite to the bottom inlet 26a. Similarly, the liquid for the second compartment 20B may be supplied from the bottom inlet 28a on the right side and discharged from the top outlet 28b, which is diagonally opposite to the bottom inlet 28a.

[0032] In Figure 3, the first electrode element 12A may extend over substantially the entire area of ​​the first compartment 20A, leaving a small space around the first electrode element 12A relative to the first casing 18A. Similarly, although not shown in Figure 3, the second electrode element 12B may extend over substantially the entire area of ​​the second compartment 20B, leaving a small space around the second electrode element 12B relative to the second casing 18B. To increase the surface area used for the electrochemical reaction and to efficiently remove gases generated from the surface of the electrode element 12 during the electrochemical reaction, the electrode element 12 may include one or more openings (open structures). In particular, the electrode element 12 may be a perforated electrode or a porous electrode. Such open structures are advantageous in a zero-gap electrochemical cell because gases generated on the side of the electrode element 12 facing the separator 16 can be removed through the opening toward the other side of the electrode element 12. Examples of such electrode elements 12 include woven mesh, knitted mesh, punched metal, grid elements, expanded metal, metal foam, or the like. More preferably, the electrode element is made from a grid element or expanded metal. The electrode element 12 may also have a highly reactive catalyst layer on the surface of its substrate. The material of the substrate is not limited, but may be steel, stainless steel, nickel, or nickel-based alloy. The width of an example electrode element is 0.1 m to 1.5 m. In an example electrode element, the effective area of ​​the electrode element is 1.0 m wide × 0.5 m high or more.

[0033] The first electrode element 12A may comprise multiple electrode elements 12a as segments, as shown in Figure 3. Similarly, the second electrode element 12B may also comprise multiple electrode elements as segments (not shown).

[0034] Referring to Figure 4, a cross-section along BB in Figure 3 can be seen. If the electrode element 12 has multiple electrode elements 12a, these elements 12a may be arranged to partially overlap each other. Preferably, the width of the overlapping portion is in the range of 1% to 10%, more preferably 3% to 8%, of the width of the individual electrode elements 12a.

[0035] In the modified example shown in Figure 5, the electrode elements 12a do not necessarily have to overlap. The electrode elements 12a may be arranged so that the edges of adjacent electrode elements 12a are joined together. In other words, adjacent electrode elements 12a are arranged so that they are in contact with or close to each other in the width direction of the electrochemical cell 10. This arrangement is expected to have a flatter electrode surface.

[0036] It should be noted that the separator 16 may be damaged due to the zero-gap structure in which the first electrode element 12A and / or the second electrode element 12B are positioned in contact with or close to the separator 16. Specifically, in conventional designs, the separator may be damaged by the sharp edges of the electrode elements. When the electrode element has multiple electrode elements, the central region of the separator may also be damaged by the sharp edges of each electrode element. As mentioned above, European Patent Application Publication No. 3575440 addressed this problem by curving the periphery of the electrode elements away from the film acting as a separator. However, this solution has the drawback that the zero-gap design is implemented only in the central region of each electrode element, and therefore the electrolytic efficiency is reduced accordingly, because the distance between opposing electrode elements increases toward their edges due to the curved edges. This drawback is more pronounced when the electrode element consists of several electrode elements.

[0037] Embodiments of the present invention can solve the above problem by having a first electrode element 12A and / or a second electrode element 12B having at least one edge having a hemming rim 30 which is hemmed and bent away from the separator 16 by a strip portion 30a of the electrode element 12. "Strip portion" means a portion of a predetermined width along the edge of the flat electrode element before hemming and bending. According to this solution, by hemming the strip portion 30a of the electrode element 12, the electrode element 12 will no longer have a sharp edge, preventing damage to the separator 16. This solution is also applicable when there is not enough space / gap to curve the electrode element away from the separator. Furthermore, since a zero-gap design can be implemented over a larger area compared to when the ends of the electrode element are curved away from the separator, as suggested in European Patent Application Publication No. 3575440, higher electrolytic performance can be achieved.

[0038] This is best illustrated in Figures 6 and 7. The hemming rim 30 is unique in its technical sense to the peripheral curve in European Patent Application Publication No. 3575440. Specifically, in European Patent Application Publication No. 3575440, the periphery of the electrode element is curved away from the separator by less than 90 degrees. In contrast, in the hemming bend, the strip portion 30a of the electrode element 12 is folded back by more than 90 degrees (see Figure 7A).

[0039] For more reliable damage prevention, the hemming rim 30 may have a bending angle between 175° and 180°, particularly between 177° and 180°, and more specifically between 170° and 180°. In the example shown in Figure 7B, the bending angle of the hemming rim is 180°. The width 30w of the strip portion 30a of the electrode element 12 in the hemming rim 30 is preferably in the range of 3 mm to 50 mm.

[0040] For more reliable damage prevention, the first and / or second electrode elements 12A, 12B have additional edges with hemming rims 30, the two edges being located on both sides of the first and / or second electrode elements 12A, 12B. In the example shown in Figure 6, all (four) edges of electrode element 12(12a) have hemming rims. However, electrode element 12(12a) may have two hemming rims 30 on its side edges. In a more advantageous example, at least one corner of electrode element 12(12a) has a rounded edge 32. More preferably, all (four) corners of electrode element 12(12a) have a rounded edge 32. Such a rounded edge 32 may be formed by deforming the corner with a hammer or similar object after the formation of the (one or more) hemming rims 30.

[0041] One or more electrode elements 12a, composed of electrode elements 12, may include one or more indicators 34 that indicate alignment positions with other electrode elements to create overlaps between adjacent electrode elements 12a, 12a. A person assembling cell 10 can align the electrode elements 12a with each other based on the indicated overlap width. In Figure 6, the indicators 34 may include notches formed at the free ends of the folded strip portions 30a. In other words, the notches are not present on the outermost edges of the electrode elements 12a. This arrangement is advantageous in preventing damage to the separator 16 caused by notches. In the example in Figure 6, the notches are formed on the top of the electrode elements 12a. Alternatively, the notches may be formed on the bottom, or both the top and bottom.

[0042] Referring to Figure 8, a support element 36 may be seen positioned between the first electrode element 12A and the partition wall 24A or current collector 22A. In addition, or alternatively, the support element 36 may be positioned between the second electrode element 12B and the partition wall 24B or current collector 22B. The support element 36 includes an elastic member 38 adapted to push the electrode element 12 away from the partition wall 24A, 24B or current collectors 22A, 22B, i.e., toward the separator 16. In one example, the elastic member 38 may include one or more leaf springs 40 cut out and raised from the base surface 42 of the support element 36, the base surface 42 extending parallel to the separator 16. In the vertical direction of the electrochemical cell 10, adjacent leaf springs project in alternating directions so as to intersect each other in an X shape. The elastic member 38 is not limited to the example in Figure 8. The elastic member 39 can have any shape as long as it can bring the separator 16 and the electrode element 12 into contact with a given pressure. The elastic member 38 may be thinner and have more leaf springs 38, as shown in Figure 9. The elastic member 38 may have one or more coil springs 44, as shown in Figure 10.

[0043] Referring to Figure 11, another exemplary support element 36' suitable for mounting the electrode element 12 is shown. The support element 36' includes an elastic member 38 with the same leaf spring 40 as in the example of Figure 10. The support element 36' of Figure 11 further comprises at least one projection 46 extending from at least one end of the support element 36'. The projection 46 may be formed at the upper and / or bottom ends of the support element 36'. The projection 46 may have a size and shape that allows it to hook and secure the corresponding end of the electrode element 12 (the inclined rim below). The projection 46 may have a front side 46a facing the electrode element 12 and a rear side 46b (Figure 12) facing away from the electrode element 12.

[0044] Referring to Figure 12, the electrode element 12 is attached to the support element 36' by a projection 46. For this purpose, the electrode element 12 may have a corresponding inclined rim 31, which is bent and inclined so that the strip portion 31a of the electrode element 12 is away from the separator 16. The strip portion 31a of the electrode element 12 within the inclined rim 31 is adapted to lock the rear side 46b of the projection 46 in order to secure the edge of the electrode element 12 to the support element 36'. The inclined rim 31 may be formed at the upper and / or lower end of the electrode element 12. The inclined rim 31 may have a bending angle between 2° and 70°, particularly between 15° and 45°, and more specifically between 15° and 30°, relative to the adjacent flat portion of the electrode element 12.

[0045] Referring to Figure 13, a diagram along DD in Figure 12 can be seen. An inclined rim 31 of the electrode element 12 can be seen, hooked and fixed to the projection 46 of the support element 36'. Preferably, the inclined rim 31 is hooked to the projection 46 using an L-shaped bend 33 at the tip of the inclined rim 31. Preferably, the inclined rim 31 is curved convexly toward the separator 16. For this purpose, the height of the elastic member 38 from the base surface 42 of the support element 36' can be adjusted. Specifically, around the support element 36', the height of the leaf spring 40 from the base surface 42 can be gradually reduced toward the projection 46.

[0046] Referring to Figure 14, a cross-section along EE in Figure 12 is shown. A hemming rim 30 formed on the side edge of the electrode element 12 can be seen. The electrode element 12 no longer has a sharp edge. This prevents damage to the separator 16 caused by the sharp edge of the electrode element. At the same time, the electrode element 12 can be easily attached to the support element 36' by the projection 46 and without additional fixing elements.

[0047] According to one embodiment of the present invention, a method is provided for converting a finite-gap electrochemical cell into a zero-gap electrochemical cell. The method includes the steps of providing a zero-gap electrochemical cell having at least two electrochemical electrode structures, removing at least two electrochemical electrode structures, and inserting electrochemical electrode structures as described above. For example, to convert a finite-gap electrochemical cell into a zero-gap electrochemical cell 10, the electrode elements of the finite-gap electrochemical cell may be replaced with electrode elements 12 having hemming rims 30. [Explanation of Symbols]

[0048] 10 Electrochemical Cells 12A(12) First electrode element 12B(12) Second electrode element 12a Electrode element 14 Electrochemical Cell Unit 16 Separators 18A First casing 18B Second casing 20A Section 1 20B Second Section 22A, 22B current collectors 24A, 24B Partition Wall 30 Hemmingrim 30a Strip portion 31. Inclined Rim 31a Strip portion 32 angles 33 L-shaped curve at the tip 34 Indicators 36, 36' Support elements 38 Elastic members 40 leaf springs 42 Base surface 44 Coil springs 46 Protrusion

Claims

1. The device comprises a current collector (22A, 22B) and at least one electrode element (12A, 12B), wherein the at least one electrode element (12A, 12B) is a two-dimensionally extended conductive element having an open structure. The at least one electrode element (12A, 12B) has at least one edge portion having a hemming rim (30) on which the strip portion (30a) of the electrode element (12A, 12B) is hemmed and bent. An electrochemical electrode structure characterized by the following features.

2. The electrochemical electrode structure according to claim 1, wherein the hemming rim (30) has a bending angle between 170° and 180°, particularly between 175° and 180°, and more specifically between 177° and 180°.

3. The electrochemical electrode structure according to claim 1 or 2, wherein the at least one electrode element (12A, 12B) has a further edge having a hemming rim (30), and two of these edges are provided on both sides of the at least one electrode element (12A, 12B).

4. The electrochemical electrode structure according to any one of claims 1 to 3, wherein the electrochemical electrode structure has support elements (36, 36') disposed between the at least one electrode element (12A, 12B) and the current collector (22A, 22B), and the support elements (36, 36') comprises an elastic member (38) adapted to push the at least one electrode element (12A, 12B) away from the current collector (22A, 22B).

5. The electrochemical electrode structure according to claim 4, wherein each of the at least one electrode elements (12A, 12B) has four edges, each having a hemming rim (30).

6. The electrochemical electrode structure according to claim 4, wherein the at least one electrode element (12A, 12B) has two further edges on both sides of the at least one electrode element (12A, 12B) having an inclined rim (31) such that the strip portion (31a) of the electrode element (12A, 12B) is bent and inclined away from the separator (16).

7. The electrochemical electrode structure according to claim 6, wherein the inclined rim (31) has a bending angle greater than 0° and less than or equal to 70°, and the bending angle is particularly between 15° and 45°, and more specifically between 15° and 30°.

8. The electrochemical electrode structure according to claim 6 or 7, wherein the support element (36') comprises at least one projection (46) extending from at least one end of the support element (36'), each of the at least one projection (46) having a front side (46a) facing the at least one electrode element (12A, 12B) and a rear side (46b) facing away from the at least one electrode element (12A, 12B), and the strip portion (31a) of the electrode element (12A, 12B) within the inclined rim (31a) is adapted to lock the rear side (46b) of the at least one projection (46) to fix the at least one edge of the at least one electrode element (12A, 12B) to the support element (36').

9. The electrochemical electrode structure according to any one of claims 1 to 8, wherein the width (30w) of the strip portion (30a) of the electrode element (12A, 12B) within the hemming rim (30) is in the range of 3 mm to 50 mm.

10. The electrochemical electrode structure according to any one of claims 1 to 9, comprising a plurality of electrode elements (12a).

11. The electrochemical electrode structure according to any one of claims 1 to 10, wherein the electrode elements (12a) from the plurality of electrode elements (12a) are arranged such that the edges of adjacent electrode elements (12a) overlap each other, or the edges of adjacent electrode elements (12a) are joined together.

12. The electrochemical electrode structure according to any one of claims 1 to 11, wherein the at least one electrode element (12A, 12B) is a grid element or an expanded mesh element.

13. An electrochemical cell comprising a first electrode element (12A), a second electrode element (12B), and a separator (16), wherein the separator (16) is a two-dimensionally extended partially permeable element disposed between the first electrode element (12A) and the second electrode element (12B), and the two-dimensionally extended partially permeable element has two surface sides. Either the first electrode element (12A) or the second electrode element (12B), or both of the first and second electrode elements (12A, 12B), is an electrochemical electrode structure according to any one of claims 1 to 12. Each electrode element (12A, 12B) is positioned adjacent to one of the two surfaces of the separator (16) such that, in each hemming rim (30), the electrode elements (12A, 12B) are hemmed and bent away from the surface of the separator (16). An electrochemical cell (10) characterized by the following features.

14. The electrochemical cell (10) comprises a first compartment (20A) and a second compartment (20B), - The first compartment (20A) houses the first electrode element (12A), - The second compartment houses the second electrode element (12B), - The separator (16) is positioned between the first section (20A) and the second section (20B) to separate them. - The separator (16) has a first surface side and a second surface side, the first surface side contacts the first compartment (20A), and the second surface side contacts the second compartment (20B) to electrochemically interconnect the first compartment (20A) and the second compartment (20B). The electrochemical cell (10) according to claim 13.

15. A method for converting a finite-gap electrochemical cell into a zero-gap electrochemical cell, - The step of providing a zero-gap type electrochemical cell having at least two electrochemical electrode structures, - The step of removing at least two electrochemical electrode structures, - The step of inserting the electrochemical electrode structure described in any one of claims 1 to 12, Methods that include...

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