Electrode for electrolysis and electrolytic cell

Abstract

To provide an electrolytic cell technique in which the damage of a diaphragm is suppressed.SOLUTION: At least one of an anode and a cathode used as an electrode for electrolysis is bent so that its end meanders in a cross-sectional view.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an electrode for electrolysis and an electrolytic cell, and in particular to an electrode for an electrolytic cell comprising at least an anode, a cathode and a diaphragm therebetween, and an electrolytic cell using such an electrode. [Background technology]

[0002] Electrolysis is currently used in a variety of industries. Electrolytic cells are used to perform electrolysis, or electrolysis. Electrolytic cells come in a variety of forms depending on their intended use, but they all contain at least an anode and a cathode. For example, electrolytic cells that electrolyze aqueous sodium chloride solutions can extract chlorine, hydrogen, and sodium hydroxide (commonly known as caustic soda), and are used to produce raw materials that form the basis of the chemical industry. They are also used to electrolyze alkaline aqueous solutions used in hydrogen production. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication (WO) No. 2012 / 091051 [Patent Document 2] Patent No. 5108043 [Patent Document 3] Patent No. 5970250 Summary of the Invention [Problem to be solved by the invention]

[0004] Electrolytic cells often have a diaphragm to prevent mixing of the substances produced at the anode and the cathode. The process of electrolyzing a sodium chloride solution using an ion exchange membrane as a diaphragm is also called "ion exchange membrane chlor-alkali electrolysis." It is also used for the electrolysis of alkaline solutions used in hydrogen production.

[0005] There are various types of electrolytic cells used in ion-exchange membrane electrolysis of sodium chloride, but the zero-gap type is the most common. In a zero-gap electrolytic cell, the anode, diaphragm, and cathode are closely attached to each other, reducing the distance between the electrodes and thereby reducing electrolyte resistance and power consumption. A possible "zero-gap" electrolytic cell is one in which one of the anode and cathode is softer and more flexible than the other, while the other is relatively more rigid. More specifically, one electrode could be designed with a soft, flexible structure that can absorb unevenness due to tolerances and deformations of the electrode support frame, while the other electrode could be designed with a rigid structure that minimizes deformation when pressed against the diaphragm. In such a case, by providing a conductive elastic body on the back side of the flexible electrode, the elastic force (i.e., reaction force) of the conductive elastic body can provide the pressure necessary to tightly attach the cathode, diaphragm, and anode to each other.

[0006] The inventors of the present invention have realized that there are still problems to be overcome with conventional electrolytic cells, and have found the need to take measures to address these problems. Specifically, they have found the following problems:

[0007] In an electrolytic cell, damage to the diaphragm not only makes electrolysis operation inefficient, but also may lead to direct contact of the electrolyte between the anode side and the cathode side, which may cause unintended and undesired reactions.

[0008] For example, in the above-mentioned "zero gap" electrolytic cell, the electrodes are in direct contact with the ion exchange membrane, so the ion exchange membrane is easily affected by the electrodes. In particular, the end edges of the electrodes used in such electrolytic cells (more specifically, the outermost edges of the electrodes) often have relatively sharp shapes, which easily damage the ion exchange membrane.

[0009] The present invention has been made in view of the above problems, and a main object of the present invention is to provide an electrolytic cell technology in which damage to the diaphragm is suppressed. [Means for solving the problem]

[0010] The inventors of the present invention attempted to solve the above problems by taking a new approach rather than simply extending the conventional technology, and as a result, they have invented an electrolytic cell electrode that achieves the above-mentioned main object.

[0011] The present invention provides an electrode for an electrolytic cell, comprising: There is provided an electrode for electrolysis in which at least one of the anode and the cathode has an end portion bent in a serpentine manner in cross section.

[0012] The present invention also provides an electrolytic cell comprising at least the above-described electrolysis electrode and diaphragm. [Effects of the Invention]

[0013] According to the present invention, damage to the diaphragm can be suppressed in an electrolytic cell by the specific configuration of the electrode end.

[0014] More specifically, in the present invention, the end of at least one of the anode and cathode electrodes for electrolysis is bent in a serpentine manner, thereby reducing the risk of the diaphragm being damaged by such an electrode. In particular, even when the end edge of the electrode for electrolysis has a relatively sharp shape, damage to the diaphragm due to the "serpentine bending" can be suppressed. Therefore, the present invention provides an electrolytic cell technology in which undesirable events due to damage to the diaphragm are suitably prevented. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram for illustrating the configuration of an electrolytic cell. [Figure 2] FIG. 2 is a perspective view showing an example of a conductive elastic body used in an electrolytic cell. [Figure 3] FIG. 3 is a schematic perspective view for explaining the combination of electrolytic cell units with diaphragms interposed therebetween. [Figure 4] FIG. 4 is a locally enlarged schematic diagram of an expanded metal for explaining the width dimension (W) of the strand. [Figure 5] FIG. 5 is a schematic horizontal cross-sectional view of an electrolytic cell according to an exemplary embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view illustrating an electrolytic cell according to one embodiment of the present invention. [Figure 7] FIG. 7 is a schematic cross-sectional view for explaining bending of the electrode end portion. [Figure 8] FIG. 8 is a schematic cross-sectional view illustrating a state in which a thin plate-like member is clamped between the bent end portions. [Figure 9] FIG. 9 is a schematic cross-sectional view illustrating a state in which a wire member is clamped by the bent end portion. [Figure 10] FIG. 10 is a schematic cross-sectional view illustrating an exemplary embodiment of the positioning of the end edge. [Figure 11] 11(a) to 11(e) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 12] 12(a) to 12(e) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 13] 13(a) to 13(d) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 14] 14(a) to 14(d) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 15] 15(a) to 15(d) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 16] 16(a) to 16(d) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 17] 17(a) and 17(b) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 18] 18(a) to 18(e) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 19]19(a) to 19(e) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 20] 20(a) to 20(e) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 21] 21(a) to 21(g) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 22] 22(a) to 22(g) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 23] 23(a) to 23(d) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 24] 24(a) to 24(j) are schematic diagrams showing various variations of bending of the electrode end portion. [Figure 25] FIG. 25 is a schematic diagram for explaining a sharp electrode end edge. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an electrode for electrolysis and an electrolytic cell according to one embodiment of the present invention will be described in more detail with reference to the drawings. The various elements in the drawings are merely shown schematically and as examples to facilitate understanding of the present invention, and the appearances and dimensional ratios may differ from those of the actual objects.

[0017] In this specification, the term "electrolytic cell" refers, in a broad sense, to an apparatus for performing electrolysis, and in a narrow sense, to an apparatus including at least an anode, a cathode, and a diaphragm disposed between the electrodes. Similarly, in the present invention, the term "electrode for electrolysis" refers, in a broad sense, to an electrode used in an apparatus for performing electrolysis, and in a narrow sense, to an anode and / or cathode used in such an apparatus.

[0018] The directions of "up and down" and "left and right" described directly or indirectly in this specification correspond to the up and down directions and left and right directions, respectively, in the drawings. More specifically, in the embodiment shown in FIG. 7 , the direction along the planar direction of the electrode for electrolysis corresponds to the left and right direction, and the direction perpendicular to this corresponds to the up and down direction. When an electrolytic cell is in operation, the electrode for electrolysis in the embodiment shown in FIG. 7 and the like is often used in an upright orientation as shown in FIGS. 3 and the left side of FIG. 6 (i.e., the electrode for electrolysis is often used with its orientation turned approximately 90° from the state shown in FIG. 7 ). Therefore, the orientation of the cell and its components may differ when the electrolytic cell is in use (particularly when the electrolytic cell is in operation with the units that make up the electrolytic cell combined) and when it is not in use (particularly when it is not in operation before the units that make up the electrolytic cell are combined).

[0019] The various numerical ranges referred to in this specification are intended to include both the lower and upper limits. For example, a numerical range such as 1 to 10 is interpreted as including the lower limit of "1" and the upper limit of "10."

[0020] First, the basic configuration of the electrolytic cell that is the premise of the present invention will be described, and then the features of the present invention will be described. In the following description, electrodes for the electrolytic cell, i.e., electrodes for electrolysis, will be referred to simply as "electrodes," or more specifically as "anodes" or "cathodes."

[0021] [Basic configuration of electrolytic cell] The electrolytic cell of the present invention comprises at least an anode, a cathode, and a diaphragm disposed between the electrodes. The anode and cathode are electrodes for externally applying electrical energy to the electrolyte solution. Typically, the anode is an electrode connected to the positive electrode of an external power source, and is an electrode where an oxidation reaction can occur during operation of the electrolytic cell. On the other hand, the cathode is an electrode typically connected to the negative electrode of the external electrode, and is an electrode where a reduction reaction can occur during operation of the electrolytic cell.

[0022] The diaphragm is typically a member that separates the anode chamber from the cathode chamber. Preferably, the diaphragm is provided to prevent mixing of substances produced at the anode and the cathode. In the present invention, the diaphragm may be one that is conventionally used in electrolysis. For example, the diaphragm is an ion exchange membrane. As just one example, in an electrolytic cell used in the soda industry, a cation exchange membrane may be used as the diaphragm.

[0023] The electrolytic cell may further be provided with a conductive elastic body. The conductive elastic body contributes to the passage of current between the electrodes due to its "conductivity," while also being able to apply a pressing force to the electrodes due to its "elasticity." In other words, the conductive elastic body corresponds to a conductive part in the electrolytic cell that can exert a reaction force, and has at least a structure that can be elastically deformed to provide such a reaction force.

[0024] An exemplary configuration of an electrolytic cell is shown schematically in FIG. 1. As shown in the figure, an electrolytic cell uses a conductive elastic body for an electrode assembly comprising at least an anode, a cathode, and an ion exchange membrane between the electrodes. In such an electrolytic cell, the reaction force of the conductive elastic body is used to press the electrode assembly comprising at least an anode, a cathode, and an ion exchange membrane between the electrodes. Specifically, the conductive elastic body is used in a state in which it is subjected to elastic deformation on the back side of the electrode assembly, and the elastic force (i.e., reaction force) provided by this conductive elastic body applies a pressing force to the electrode assembly. In particular, the conductive elastic body subjected to elastic deformation acts to apply a pressing force from one electrode toward the other electrode, thereby promoting close contact of the electrode assembly. In other words, the presence of the conductive elastic body results in close contact between the anode, the ion exchange membrane, and the cathode, allowing the electrolytic cell to function favorably as a so-called "zero-gap" type.

[0025] The conductive elastic body used in the electrolytic cell may have any form as long as it generates an elastic repulsive force. For example, the conductive elastic body may have various forms, such as an elastic cushion or elastic mat (e.g., a member made of a metal coil, a metal nonwoven fabric, or a knitted or woven fabric made of metal wire), or a leaf spring. As merely one specific example, the conductive elastic body 400 may have a wavy-curved elastic portion 450 as shown in FIG. 2 . The conductive elastic body is used in the electrolytic cell in a state where it has been subjected to elastic deformation to exhibit spring characteristics. More specifically, the conductive elastic body is provided in the electrolytic cell in a state where it has been subjected to deformation such that the wavy curvature of the elastic portion is reduced. A conductive elastic body subjected to such deformation is subjected to stress to restore its original shape, thereby exhibiting a repulsive force as a spring characteristic. In large electrolytic cells, multiple conductive elastic bodies are often provided rather than a single conductive elastic body.

[0026] In the electrolytic cell, the electrodes may be made of, for example, a conductive substrate having liquid permeability. In this regard, it is preferable that at least one of the anode and the cathode has a conductive porous substrate. In other words, at least one of the anode and the cathode may be a mesh electrode having mesh openings. By way of example only, the electrodes may be made of, for example, expanded metal, wire mesh (plain weave mesh, twill weave mesh), or punched metal.

[0027] In a preferred embodiment, both the anode and the cathode may comprise a conductive porous substrate. For example, both electrodes may be comprised of expanded metal or plain weave mesh, or one electrode may be comprised of expanded metal and the other electrode may be comprised of plain weave mesh. That is, both the anode and the cathode may be comprised of expanded mesh or plain weave mesh, or one of the anode and the electrode may be comprised of expanded mesh and the other of plain weave mesh. From the viewpoint of exhibiting corrosion resistance, each of the anode and the cathode may comprise at least one selected from the group consisting of titanium, nickel, stainless steel, tantalum, zirconium, niobium, and the like. Furthermore, each of such anodes and cathodes may be supported with an appropriate catalyst. The aperture ratio of the conductive porous substrate is not particularly limited, but may be approximately 20% to 90%, for example, 30% to 80%, 40% to 75%, or 50% to 75%, etc.

[0028] The electrolytic cell is preferably a zero-gap electrolytic cell, and has characteristics suitable for such a zero-gap electrolytic cell. One such characteristic is that the anode and cathode are characterized by the so-called "hardness" and "softness" of the electrode material, i.e., the rigidity and flexibility of the electrode material. Specifically, it is preferable that one of the anode and cathode is relatively flexible relative to the other, and conversely, the other is relatively rigid relative to the other. This allows the relatively flexible electrode to bend under the reaction force of the conductive elastic body, while the relatively rigid electrode can absorb that bending via the ion exchange membrane. When the anode and cathode are relatively different in this respect, the anode, ion exchange membrane, and cathode are more closely attached to each other, allowing the electrolytic cell to function more effectively as a "zero-gap electrolytic cell." This is particularly true when the electrolytic cell is large. That is, this is particularly true when the electrode main surface, which requires pressure for zero-gap electrolysis, is large, as typified by zero-gap electrolysis.

[0029] To obtain a larger amount of the desired electrolysis product, a larger electrolytic cell is used, and the electrode main surfaces (particularly the main surfaces where the anode and cathode face each other) also become larger accordingly. A large zero-gap electrolytic cell is preferably composed of multiple electrolytic cell units, each of which has large electrode main surfaces on both opposing side surfaces. As an example, a so-called "bipolar" electrolytic cell will be described with reference to FIG. 3. One of the opposing side surfaces of the electrolytic cell unit 100 is provided with a cathode 200A (e.g., a cathode surface made of expanded metal), while the other is provided with an anode 200B (e.g., an anode surface made of expanded metal). In an electrolytic cell, multiple such electrolytic cell units are connected to each other so as to be stacked one on top of the other via ion exchange membranes 300 (especially cation exchange membranes). In particular, adjacent electrolytic cell units are stacked such that the cathode surface of one electrolytic cell unit 100' faces the anode surface of the other electrolytic cell unit 100''. In this way, an electrolytic cell is constructed by combining a plurality of electrolytic cell units via ion exchange membranes. Note that an electrolytic cell constructed from a plurality of electrolytic cell units is not limited to being a "bipolar type" but may be a "monopolar type." In other words, the electrode cell units constituting the electrolytic cell are not limited to being bipolar type electrolytic cell units having an anode portion and a cathode portion on opposite sides, but may be "monopolar type" electrolytic cell units having only an anode portion and only a cathode portion on opposite sides. In such cases, an electrolytic cell can be constructed by combining electrolytic cell units having only an anode portion and electrolytic cell units having only a cathode portion so that they are alternately arranged via ion exchange membranes.

[0030] Electrolytic cells composed of electrolytic cell units have relatively large electrode principal surfaces, which is desirable because the desired electrolytic reaction occurs through these large electrode surfaces. However, maintaining the flatness of the electrode surfaces is difficult. Specifically, the larger the electrode principal surfaces, the more likely it is that the effects of bending due to their own weight become significant. Furthermore, factors such as attachment to the electrode support also have an impact, making it difficult to achieve perfectly flat electrode principal surfaces. For example, in the electrolytic cell unit 100 (100', 100'') illustrated in FIG. 3, the principal surface sizes of the anode and cathode surfaces are on the order of meters rather than on the order of several centimeters. Even if the electrodes are made more rigid to achieve a more suitable flat surface, for the reasons described above, such large electrode principal surfaces have a flatness of, for example, ±0.5 mm to 1.0 mm, making it difficult to achieve perfectly flat surfaces (i.e., a flatness of 0 mm). In other words, in a large electrolytic cell, the main surface of a rigid electrode may appear flat macroscopically, but tends to have localized irregularities when viewed microscopically.

[0031] If electrodes that do not have completely flat surfaces are brought into close contact with each other via an ion exchange membrane, the unevenness may impair the uniformity of current distribution. Therefore, in a preferred electrolytic cell, a rigid electrode is paired with a soft, flexible electrode. This allows the flexible electrode to bend to conform to the unevenness of the rigid electrode surface, even if the electrodes are tightly contacted with each other via the ion exchange membrane, thereby more effectively preventing non-uniformity of current distribution. As an example, the anode may be made of a relatively hard, rigid expanded metal, while the cathode may be made of a relatively soft, flexible expanded metal. A conductive elastic body may be provided on the back side of the flexible expanded metal of the cathode, which is combined with the rigid expanded metal of the anode via the ion exchange membrane. In this case, the flexible expanded metal of the cathode is pressed toward the rigid expanded metal of the anode by the reaction force of the conductive elastic body, and at that time, the flexible expanded metal of the cathode can be locally displaced depending on the flatness of the main surface of the rigid expanded metal of the anode. Therefore, even if the electrolytic cell units are fixed tightly together and conditions are created in which the reaction force of the conductive elastic body acts greatly, the anode, ion exchange membrane, and cathode are in favorable contact with each other, and undesirable phenomena such as non-uniform current distribution are unlikely to occur.

[0032] Although not particularly limited, a relatively rigid expanded metal may have a thickness of preferably about 0.2 to 2.0 mm due to its "relative rigidity," and the width (step width) of the strands 210 forming the perforations, i.e., openings (the portion indicated by "W" in FIG. 4 ) may be preferably about 0.2 to 2.0 mm. Similarly, although not particularly limited, a flexible expanded metal may have a thickness of preferably about 0.1 to 1.0 mm, more preferably about 0.1 to 0.5 mm, due to its "relative flexibility," and the width (step width) of the strands forming the perforations, i.e., openings (the portion indicated by "W" in FIG. 4 ) may be preferably about 0.1 to 2.0 mm, more preferably about 0.1 to 1.5 mm. When a wire mesh or punched metal is used as the flexible electrode, the thickness may be preferably about 0.1 to 1.0 mm, more preferably about 0.1 to 0.5 mm, due to its "relative flexibility." In the case of wire mesh, the wire diameter φ, which means the approximate diameter of the metal fibers that make up the wire mesh, may be preferably about 0.05 to 1.0 mm, more preferably about 0.1 to 0.5 mm.In the case of punched metal, the non-opening length L between adjacent openings may be about 0.1 to 2.0 mm, more preferably about 0.1 to 1.5 mm.

[0033] For a further understanding of the electrolytic cell, Figure 5 is shown. Figure 5 corresponds to a vertical cross-sectional view of an exemplary embodiment of the electrolytic cell. In other words, Figure 5 corresponds to a cross-sectional view of the cell (particularly a combination of electrolytic cell units) shown in Figure 3 taken horizontally. In the embodiment shown in Figure 5, a flexible cathode 200A made of expanded metal, a diaphragm 300, and a rigid anode 200B made of expanded metal are stacked in this order, and a conductive elastic body 400 is provided on the back side of the cathode 200A (i.e., the side opposite to the side where the diaphragm 300 is installed). The conductive elastic body 400 is provided so as to be deformed so as to be constricted between the expanded metal cathode 200A and the cathode base 280 (more specifically, the constriction occurs when the connected electrolytic cell units are clamped together, resulting in deformation of the conductive elastic body), and the elastic force of the conductive elastic body 400 is directly applied to the expanded metal flexible cathode 200A that is in direct contact with the elastic portion of the conductive elastic body 400. As a result, the expanded metal flexible cathode 200A is biased so as to be pressed toward the expanded metal rigid anode 200B, bringing the flexible cathode 200A, the diaphragm 300, and the rigid anode 200B into close contact with each other. Note that the rigid anode itself, which is the electrode that is not in direct contact with the conductive elastic body, is fixed immovably to an electrode support of the electrolytic cell unit or the like, and therefore acts to absorb the elastic force of the conductive elastic body, contributing to close contact.

[0034] [Features of the present invention] The present invention relates to the above-mentioned electrode and an electrolytic cell using such an electrode, and is characterized by the electrode shape. In particular, the present invention is characterized by the shape of the electrode end. Specifically, at least one of the anode and cathode used as the electrolysis electrode has an end bent in a serpentine shape in cross section.

[0035] In the present invention, the electrodes for electrolysis and the electrolytic cell are highly related to each other and can be described in common, so they will be described comprehensively below.

[0036] The shape of the end of the electrode for electrolysis of the present invention is shown schematically in Figures 6 and 7. Figures 6 and 7 show a partial cross section of an electrolytic cell unit, depicting the shape before the electrolytic cell units are combined. That is, Figures 6 and 7 show the state before the spring properties of the conductive elastic body are expressed by fastening the electrolytic cell units together, and before the diaphragm and the electrode are in close contact with each other. As can be seen particularly from Figure 7, the end 250 of the electrode for electrolysis 200 is bent significantly, and in particular, is bent in a meandering manner.

[0037] When the electrode end is bent in a serpentine shape, the effect of suppressing damage to the diaphragm in an electrolytic cell can be achieved. The end edges of the electrodes used in electrolytic cells often have relatively sharp shapes, but the present invention can reduce the effects of the sharp end edges and suppress damage to the diaphragm.

[0038] Electrodes for electrolysis are particularly susceptible to sharpening at their end edges (i.e., the edges forming the outermost edges of the electrodes). This is because electrodes are often porous or open. That is, porous or open electrodes are prone to having sharp end edges. As shown in FIG. 25 , an electrode 200 used in an electrolytic cell may have sharp, "jagged" edges due to the multiple wires forming the pores or openings. In other words, electrodes made of a conductive porous substrate are prone to having sharp end edges due to the wires forming the pores and openings. Sharp end edges are likely to damage the diaphragm, but in the electrode for electrolysis of the present invention, the "serpentine curvature" of the end prevents damage to the diaphragm.

[0039] The effects of the present invention will be described in detail. In the present invention, the "serpentine bending of the electrode end 250" facilitates the positioning of the electrode 200 in the electrolytic cell so that the edge 255 does not come into contact with the diaphragm 300 (see FIG. 7). That is, the bending of the electrode end displaces the position of the electrode edge (particularly the peripheral edge / outer edge of the electrode), reducing the risk of direct contact between the electrode edge and the diaphragm during use of the electrolytic cell. In particular, the bending of the electrode end in a serpentine shape allows the electrode edge to be positioned farther from the diaphragm, thereby more effectively preventing damage to the diaphragm. Furthermore, the bending in a serpentine shape can also apply appropriate stress to the electrode. Preferably, the bending in a serpentine shape can generate stress in the electrode end that promotes close contact of the electrode with the diaphragm, thereby promoting close contact between the anode, ion exchange membrane, and cathode. Therefore, the "serpentine bending" of the electrode end facilitates the electrolytic cell to function more effectively as a "zero-gap" system. As can be seen from the above description, in the present invention, the electrode end is not bent to fix the electrode (especially to fix the electrode to the electrode base), but to reduce the undesirable phenomenon that the electrode edge may cause damage to the diaphragm. Therefore, the "serpentine bending" of the electrode end in the present invention can be called bending to prevent damage to the diaphragm.

[0040] In this specification, the term "serpentine bent" refers to a shape in which the electrode ends extend back and forth in cross section. Therefore, in the present invention, the electrode ends are configured to at least partially overlap each other due to the "serpentine bend."

[0041] In a preferred embodiment, the electrode end is continuously bent. That is, the end of at least one of the anode and cathode is bent several times so that its cross-sectional shape reciprocates. This allows the electrode edge to be more reliably spaced distally from the diaphragm, and also makes it easier for stress to be generated in the electrode end that promotes close contact of the electrode with the diaphragm. This contributes to realizing a zero-gap system in which close contact between the anode, ion exchange membrane, and cathode is promoted, while also more effectively suppressing damage to the diaphragm.

[0042] In other words, the electrode end 250 is bent so that at least two bent portions are formed due to the meandering shape. In the embodiment shown in FIG. 7, the end 250 of the electrode 200 is bent significantly, and is bent twice so that the bent end regions overlap. Bending the electrode end in this manner can more reliably separate the electrode edge from the diaphragm. Furthermore, such bending can also generate stress in the electrode end that preferably promotes close contact of the electrode with the diaphragm.

[0043] The bent portion of the electrode end 250 may have a contour as shown in FIG. 7 . That is, the bent portion 257 of the electrode end 250 may have a curved cross-sectional shape. An electrode end having such a shape can reduce adverse effects that may be caused on the diaphragm due to the bent portion. That is, the cross-sectional contour of the bent portion is relatively smooth, without any sharp edges, and even if the bent portion comes into contact with the ion exchange membrane in the electrolytic cell, it is less likely to damage the diaphragm. Furthermore, if the bent portion of the electrode end were to break or sever the electrode, the diaphragm would be more likely to be damaged. However, in the bent portion curved according to the present invention, even if stress that could cause breakage or severance occurs, stress concentration is less likely to occur, and breakage or severance of the electrode is suppressed.

[0044] In the present invention, the end of at least one of the anode and cathode electrodes is preferably bent away from the diaphragm. This is because the bent electrode end is more distal to the diaphragm. In other words, by bending the electrode end away from the diaphragm, the electrode edge can be more reliably separated from the diaphragm, which increases the effect of suppressing damage to the diaphragm.

[0045] Here, "the end portions are bent toward the side opposite to the side where the diaphragm is located" broadly means that the end edges of the electrodes for electrolysis are bent in a direction away from the diaphragm. In a narrower sense, it means that the end portions of the electrodes for electrolysis are bent so that they overlap each other so that the end edges of the electrodes are more distal to the diaphragm in the electrolytic cell. In the form shown in Fig. 7, the end portions 250 of the electrodes are bent downward to increase the overlap, and therefore the position of the end edge 255 is closer to the electrode base 280 on which the electrode is provided, rather than closer to the diaphragm 300.

[0046] In a preferred embodiment, the electrode end of at least one of the anode and cathode electrodes for electrolysis is bent without straddling the electrode base on which it is provided. As shown in Fig. 7, in a configuration in which a relatively soft electrode 200A (e.g., an electrode 200A made of a conductive porous substrate) is placed on an electrode base 280 together with a conductive elastic body 400, the electrode end 250 does not extend so as to cross the electrode base 280. As can be seen from the illustrated configuration, it can be said that the serpentine bent portion 250' at the end 250 of the electrode for electrolysis is provided on the electrode base 280.

[0047] The electrode base 280 is a conductive member and typically has higher rigidity than the electrode 200A. If a meandering bent portion is provided on the electrode base, more suitable stress is likely to be generated in the electrode end. When the electrolytic cell is in use, the electrode is clamped between the diaphragm and the electrode base, and the end of the electrode for electrolysis that is bent in a meandering manner is more suitably sandwiched between the diaphragm and the electrode base, which may generate a reaction force. In other words, by sandwiching the electrode for electrolysis between the diaphragm and the electrode base so that the electrode end is bent without straddling the electrode base, stress that promotes close contact of the electrode for electrolysis with the diaphragm is likely to be generated in the electrode end.

[0048] As described above, when the electrode 200 for electrolysis is porous or open, the edges of the electrode end are particularly likely to become sharp (see FIG. 25 ), but in the present invention, the effects of sharp edges are suppressed by "serpentine bending" of the electrode end. In other words, the effect of the present invention is likely to become apparent when the electrodes used in the electrolytic cell are made of a conductive porous substrate. More specifically, when at least one of the anode and cathode electrodes for electrolysis is an open-mesh electrode made of, for example, expanded metal, wire mesh (plain weave mesh, twill mesh), or punched metal, and the end of such an open-mesh electrode is bent in a serpentine shape, the effect of suppressing damage to the diaphragm is likely to become apparent.

[0049] Similarly, the effects of the present invention are likely to be evident when the diaphragm used in the electrolytic cell is an ion exchange membrane. Ion exchange membranes used in electrolytic cells are relatively thin, for example, about 0.1 to 0.5 mm, and are often made of a material that is relatively softer than the electrodes (for example, a flexible thin film made of a fluororesin film having cation exchange groups is sometimes used as a cation exchange membrane in an electrolytic cell). Therefore, when an ion exchange membrane is used in an electrolytic cell, the ion exchange membrane is usually prone to being damaged by the electrodes for electrolysis. Therefore, when at least one of the electrodes for electrolysis, the anode and the cathode, is a conductive porous substrate made of metal, and the diaphragm directly facing such an electrode is an ion exchange membrane, the effect of suppressing diaphragm damage is likely to be evident.

[0050] The "serpentine bending of the electrode end" can be formed by any method. For example, a serpentine bending can be formed on the electrode end by using an appropriate pressing means and / or an appropriate gripping means (means for gripping the electrode end, etc.). Typically, the electrode end can be bent into a serpentine shape by applying an external force to the electrode end. In this case, it is preferable to bend the electrode end by applying an external force before the electrolytic cell units are combined together.

[0051] The bending operation performed on the end of the electrode for electrolysis may be at least one time, i.e., at least one bent portion may be formed on the electrode end. Preferably, the bending operation performed on the electrode end is at least two times, i.e., at least two bent portions may be formed on the electrode end. There is no particular upper limit on the number of bends / bending portions, and it may be, for example, 10 times / 10 portions, or more specifically, 3 times / 4 portions. The width dimension of the region of the electrode end that overlaps each other due to bending, i.e., the width dimension of the meandering bent region (for example, the dimension "L" shown in the cross section of Figure 10, which will be referred to later), may be about 1 mm to 3 cm, and more specifically, it may be about 1 mm to 5 mm.

[0052] As described above, the present invention is characterized in that the electrode end portions are bent so that the edges of the electrodes used in the electrolytic cell do not damage the diaphragm. The present invention can be embodied in various forms, which will be described below.

[0053] (Means of members whose ends are clamped) In this embodiment, an additional member is provided so as to be sandwiched between the ends of the electrode for electrolysis. Specifically, a thin plate-like member or a wire-like member is provided so as to be sandwiched between the bent ends. In the embodiment shown in Fig. 8, a thin plate-like member 540 is provided so as to be sandwiched between the end 250 bent in a serpentine shape, and in the embodiment shown in Fig. 9, a wire-like member 560 is provided so as to be sandwiched between the end 250 bent in a serpentine shape.

[0054] The thin plate-like or wire-like member may be made of various materials such as metal or resin, and the manufacturing method is not particularly limited. Preferred materials for the thin plate-like or wire-like member include corrosion-resistant materials such as nickel, stainless steel, and fluororesin. As the name suggests, the term "thin plate-like member" as used herein refers to a member having a thin, elongated plate-like or sheet-like shape. For example, a foil-shaped member may be used as the thin plate-like member. As the name suggests, the term "wire-like member" as used herein refers to a member having a "wire-like" elongated shape. The wire-like member may be, for example, a wire-like member. For example, because the thin plate-like member is a "thin plate," it may be thinner than the thickness of the electrode (e.g., a mesh-opening electrode). Similarly, the thickness (cross-sectional dimension) of the wire-like member may be smaller than the thickness of the electrode (e.g., a mesh-opening electrode). However, the present invention is not necessarily limited to such a dimensional relationship, and the thickness of the thin plate-like member or the diameter of the wire-like member may be greater than the thickness of the electrode (for example, a mesh aperture electrode).

[0055] The thin plate-like or wire-like member may be used to attach the electrode to the electrode base. That is, the electrode and the electrode base may be joined to each other by a thin plate-like or wire-like member clamped between the bent ends. In terms of the arrangement in a plan view, the thin plate-like or wire-like member may be provided on at least one of the sides (i.e., at least one side) that form the outer peripheral edge of the electrode. In such a case, it is preferable that a long thin plate-like or wire-like member is provided along such side.

[0056] For example, a thin plate-like member or a wire-like member may be used for welding. That is, the electrode base and the electrode (especially the bent electrode end) may be welded to each other via the thin plate-like member or the wire-like member. This allows the electrolysis electrode to be fixed to the electrode base with more suitable attachment force. Since the thin plate-like member or the wire-like member is provided locally on the electrode, it can also be said that spot welding can be performed via such a member. When considering "welding," the thin plate-like member or the wire-like member is preferably made of a meltable material that can be melted once using a welding gun or a light beam. In this regard, the thin plate-like member or the wire-like member may be, for example, a metal member. Taking into account corrosion resistance and other factors, the metal used for such a metal member is preferably at least one selected from the group consisting of titanium, nickel, stainless steel, tantalum, zirconium, and niobium. The thin plate-like member may be, for example, a metal foil, such as nickel foil. Similarly, the wire-like member may be, for example, a metal wire, such as nickel wire. Nickel foil or nickel wire is particularly suitable for both corrosion resistance and welding properties.

[0057] The presence of the thin plate-like member or wire-like member can contribute to the suppression of damage to the diaphragm. In other words, the presence of the thin plate-like member or wire-like member facilitates the formation of a configuration in which the end edge of the electrode is further separated or isolated from the diaphragm. As merely one example, in a configuration in which the thin plate-like member is positioned above the end edge of the electrode (not shown), the end edge of the electrode is covered by the thin plate-like member, which is likely to be particularly effective in suppressing damage to the diaphragm. Furthermore, although the wire-like member does not provide as wide a surface area as the thin plate-like member and is therefore unlikely to be used as a member for covering the end edge, its narrow shape can act relatively favorably on products (e.g., gaseous products) generated at the electrodes during operation of the electrolytic cell. Specifically, the thin shape of the wire-like member makes it less likely to obstruct the flow of the product gas generated at the electrodes, making it easier to avoid undesirable retention of such gas. When a wire-like member is used, the number of wire-like members may be one or more.

[0058] Furthermore, the thin plate-like or wire-like member can also be used in the bending operation of the electrode end. In such cases, the bending operation of the electrode end can be assisted by abutting the thin plate-like or wire-like member against the electrode end and sandwiching it inside. In addition to facilitating the bending operation, the thin plate-like or wire-like member can suppress undesirable bending of the electrode end due to its thickness, making it easier to achieve a smoothly curved bent portion.

[0059] (Mode of preferred position of end edge) In this embodiment, the edge is positioned at a more unique position due to the bent end of the electrolysis electrode. As shown in the cross-sectional view of FIG. 10 , the end edge 255 of the electrode 250 is positioned inside the outermost edge 252 of the bent end 250. That is, the end edge 255 of the electrode 250 does not extend beyond the outermost edge 252 of the bent end 250. In this embodiment, the bent end portion 250′ is interposed between the electrode edge 255 and the diaphragm 300, resulting in an interposition form in which the electrode edge 255 is more reliably covered by the bent end portion 250′. Therefore, the electrode edge 255 can be isolated from the diaphragm 300 to further reduce the influence of the electrode edge 255, and the effect of suppressing damage to the diaphragm can be more suitably enhanced.

[0060] For example, the end edge 255 (i.e., the "outer peripheral edge") of the electrode for electrolysis 250 may be positioned approximately in the middle of the serpentine overlapping region. More specifically, as shown in Fig. 10, the end 250 of at least one of the anode and cathode electrodes 200 has a first bent portion 257A and a second bent portion 257B formed by bending in a cross-sectional view, and the end edge 255 may be positioned approximately midway between the first bent portion 257A and the second bent portion 257B in the direction of the electrode surface.

[0061] Here, "approximately halfway" does not necessarily mean that it is completely "halfway" and may be slightly shifted from that. For example, if the distance between first bent portion 257A and second bent portion 257B in a cross-sectional view is L, the position of edge 255 of the electrode end portion in the electrode surface direction ("point a" in FIG. 10) may be in the range of 0.4L to 0.6L from first bent portion 257A ("point b" in FIG. 10). Furthermore, "point a" may be in the range of 0.45L to 0.55L or 0.48L to 0.52L from "point b."

[0062] In this embodiment, even though the "serpentine bending" is relatively simple, such as bending twice, the bent end portion is more reliably interposed between the electrode edge and the diaphragm. In particular, because it is "intermediate," an interposition form is achieved in which the electrode edge 255 is more reliably covered by the bent end portion 250' as shown in FIG. 10, and the influence of the electrode edge 255 can be further reduced. Therefore, the electrode edge can be more reliably isolated from the diaphragm, and the effect of suppressing damage to the diaphragm can be more suitably improved.

[0063] (Aspect specific to the zero-gap type) This embodiment is specific to a zero-gap electrolytic cell. In a zero-gap electrolytic cell, the anode, the ion exchange membrane, and the cathode can be brought into close contact with each other (see FIG. 1 ), but the ion exchange membrane is easily damaged by the electrodes that come into close contact with each other. Therefore, when the electrolytic cell is a zero-gap electrolytic cell (for example, a zero-gap chlor-alkali electrolytic cell), the effects of the present invention are likely to be apparent.

[0064] For example, if one of the anode and cathode used as electrodes for electrolysis is relatively flexible relative to the other electrode, better adhesion between the anode, ion exchange membrane, and cathode is achieved, but this usually means that the ion exchange membrane is more likely to be damaged. In the present invention, even under such tight adhesion conditions, the "serpentine bending" makes it easier to arrange the electrode so that the edge of the electrode does not directly contact the ion exchange membrane, thereby suppressing damage to the ion exchange membrane. In other words, in such a case, one of the anode and cathode is relatively flexible relative to the other electrode, and the one electrode is bent in a serpentine shape.

[0065] From a similar perspective, the provision of a conductive elastic body in an electrolytic cell provides better adhesion between the anode, ion exchange membrane, and cathode, but typically means that the ion exchange membrane is more likely to be damaged. That is, when a conductive elastic body is provided on the back side of one of the anode and cathode electrodes so that the conductive elastic body presses against the other electrode, better adhesion is achieved, but the ion exchange membrane is more likely to be damaged. (For example, when a cathode, particularly a cathode made of a conductive porous substrate, is pressed against the anode via the ion exchange membrane, the conductive porous substrate typically tends to damage the ion exchange membrane.) Even under such conditions, the "serpentine curvature" of the present invention makes it easier to position the electrodes so that their edges do not directly contact the ion exchange membrane, thereby suppressing damage to the ion exchange membrane.

[0066] Finally, a few words about the "electrode base" used in this specification. As can be seen from the above explanation, the electrode base corresponds to the back plate or support plate against which the conductive elastic body is pressed when the electrolytic cell is of a zero-gap (particularly true zero-gap) type. Furthermore, based on the understanding of those skilled in the art, this electrode base corresponds to the base electrode for the flexible electrode in the electrolytic cell, and corresponds to the base cathode when the flexible electrode is a flexible cathode, for example. Furthermore, from the viewpoint of function and structure, the electrode base is preferably a porous plate material that serves as a current collector plate.

[0067] Although the embodiments of the present invention have been described above, they are merely typical examples within the scope of application of the present invention. Therefore, it will be readily understood by those skilled in the art that the present invention is not limited to the above-described embodiments and that various modifications can be made without departing from the spirit and scope of the present invention.

[0068] For example, although the above description has been given of "electrode ends bent in a meandering manner," various other shapes are conceivable. Furthermore, even if the bend is not strictly a meandering shape, it is also conceivable as long as it reduces the effect of the electrode edge on the diaphragm. For example, the electrode end may be bent so that there is only one bent portion in a cross-sectional view.

[0069] Various electrode end configurations for electrolysis electrodes are shown in Figures 11 to 24. Figure 11 shows various exemplary configurations in which the end is bent so as to be pointed in cross section. Figure 12 shows various exemplary configurations in which the bent portion of the electrode end is bent in a U-shape in cross section. Figure 13 shows various exemplary configurations in which the bent portion of the electrode end is bent in an arc-like shape in cross section. Figure 14 shows various exemplary configurations in which the electrode end is bent at an angle of approximately 90° (the angle α shown in the figure is approximately 90° (similar to the subsequent drawings)). Figure 15 shows various exemplary configurations in which the electrode end is bent at an angle less than 90° (the angle α shown in the figure is less than 90° (similar to the subsequent drawings)). Figure 16 shows various exemplary configurations in which the bent portion of the electrode end and the bend from the bent portion to the edge are curved. Figure 17 shows various exemplary configurations in which the electrode end is bent in a spiral shape. FIG. 18 shows exemplary electrode end portions having various variations in the direction of bending, including bent portions that are arc-shaped or curved in cross section. FIG. 19 shows various exemplary electrode end portions, particularly those having bent portions that are arc-shaped or curved in cross section but are bent at approximately 90°. FIG. 20 shows various exemplary electrode end portions, particularly those having bent portions that are curved or non-curved in cross section but are bent less than 90°. FIG. 21 shows exemplary electrode end portions having bent portions that are U-shaped in cross section but are bent at various variations in the direction of bending. FIG. 22 shows various exemplary electrode end portions, including those having U-shaped bent portions in cross section but are bent at approximately 90°. FIG. 23 shows various exemplary electrode end portions having bent portions that are approximately 90° but are bent outward. FIG. 24 shows various exemplary shapes in which the bending is performed randomly while having sharply bent portions. [Industrial Applicability]

[0070] The technology according to the present invention can be applied to various electrolytic cells in which electrolysis, i.e., electrolysis, is performed. For example, but not limited to, the present invention can be applied to electrolytic cells used in the soda industry, and is particularly suitable for electrolytic cells in which damage to the diaphragm by the electrodes is a concern. [Explanation of symbols]

[0071] 100 Electrolyzer Unit 100' Electrolyzer Unit 100'' Electrolyzer Unit 200 Electrode for electrolysis 200A cathode 200B Anode 210 strands 250 Electrode End 250' serpentine bend 252 Outermost edge of bent end 255 Electrode Edge 257 Bending Point 257A First bending part 257B Second bending part 258 Maximum bending displacement part of electrode 280 Electrode base (e.g., cathode base) 300 Diaphragm (e.g., ion exchange membrane) 400 Conductive elastic body 450 Elastic part 540 Thin plate-like members 560 Wire-like members 600 Pressing means

Claims

1. 1. An electrode for an electrolytic cell, comprising: An electrode for electrolysis, wherein at least one of the anode and the cathode has an end portion bent in a serpentine manner in cross section.

2. The electrode for electrolysis according to claim 1 , wherein the end portion has at least two bent portions in a cross-sectional view.

3. The electrode for electrolysis according to claim 1 or 2, wherein the bent portion of the end portion has a curved cross-sectional shape.

4. The electrode for electrolysis according to any one of claims 1 to 3, wherein a thin plate-like member or a wire-like member is provided so as to be sandwiched between the bent end portions.

5. The electrode for electrolysis according to any one of claims 1 to 4, wherein an end edge of the electrode is positioned inside an outermost edge of the bent end.

6. The end portion has a first bent portion and a second bent portion when viewed in cross section due to the bending, 6. The electrode for electrolysis according to claim 5, wherein the end edge is located approximately midway between the first bent portion and the second bent portion in the direction of the electrode surface.

7. The electrode for electrolysis according to any one of claims 1 to 6, wherein the at least one electrode comprises a conductive porous substrate.

8. The electrodes for electrolysis according to any one of claims 1 to 7, wherein one of the anode and the cathode is flexible relative to the other of the anode and the cathode, and the one electrode is bent.

9. An electrolytic cell comprising at least the electrode for electrolysis according to any one of claims 1 to 8 and a diaphragm.

10. 10. The electrolytic cell according to claim 9, wherein the end of the electrode for electrolysis is bent on the side opposite to the side where the diaphragm is located.

11. 11. An electrolytic cell according to claim 9 or 10, wherein the end is bent so as not to straddle an electrode base on which the electrode is provided.

12. 12. The electrolytic cell according to claim 9, wherein a conductive elastic body is provided on a back surface side of one of the electrodes so that the one electrode is pressed against the other electrode by the conductive elastic body.

13. 13. The electrolytic cell according to claim 9, wherein the diaphragm is an ion exchange membrane.

14. The electrolytic cell according to any one of claims 9 to 13, wherein the electrolytic cell is a zero-gap type saline electrolytic cell.

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