Electrode laminate for alkaline water electrolysis cell, and alkaline water electrolysis cell

Abstract

Provided is an electrode laminate for an alkaline water electrolysis cell in which a short circuit due to breakage of a diaphragm is unlikely to occur while having a zero gap structure. The electrode laminate for an alkaline water electrolysis cell comprises: an anode that serves as an oxygen generation electrode; a cathode that serves as a hydrogen generation electrode; and a diaphragm that is interposed between the anode and the cathode and has hydroxide ion conductivity. The electrode laminate has a zero gap structure in which the anode, the diaphragm, and the cathode are laminated so as to be in contact with each other. The anode includes an anode stress relaxation layer, which is deformable by stress, on a surface that is in contact with the diaphragm, and / or the cathode includes a cathode stress relaxation layer, which is deformable by stress, on a surface that is in contact with the diaphragm.

Description

Electrode laminate for alkaline water electrolysis cell and alkaline water electrolysis cell

[0001] This disclosure relates to an electrode laminate for an alkaline water electrolysis cell and an alkaline water electrolysis cell.

[0002] Alkaline water electrolysis is attracting attention as a useful technology for producing green hydrogen using renewable energy. Alkaline water electrolysis uses an anode that generates oxygen, a cathode that generates hydrogen, and a diaphragm that separates the anode and cathode in the electrolytic cell, allowing for the selective passage of ions.

[0003] As such components for alkaline water electrolysis, for example, regarding diaphragms, Patent Document 1 (Japanese Patent No. 7444770) discloses a separator for alkaline water electrolysis comprising a porous support, a first porous polymer layer adjacent to one side of the porous support, and a second porous polymer layer adjacent to the opposite side of the porous support. Furthermore, Patent Document 2 (Japanese Patent Publication No. 2023-531792) discloses a separator for alkaline electrolysis comprising a porous support and a first porous layer and a second porous layer provided on one and the other side of the porous support, characterized in that the porous support has a thickness of 150 μm or less and the thickness of the separator is less than 250 μm. Furthermore, Patent Document 3 (Japanese Patent Publication No. 2024-525620) discloses a separator for alkaline electrolysis comprising a porous support and a porous layer provided on the porous support, characterized in that the lateral bubble point of the separator is at least 0.2 bar.

[0004] Patent No. 7444770 Publication Special Publication No. 2023-531792 Publication Special Publication No. 2024-525620 Publication WO2013 / 118561WO2016 / 076047WO2016 / 067884WO2019 / 069762WO2020 / 255856

[0005] Incidentally, one challenge with alkaline water electrolysis is its low energy efficiency. To address this, it is conceivable to improve power efficiency by reducing liquid resistance and creating a zero-gap structure in the alkaline water electrolysis cell or apparatus, where the distance between the anode and cathode and the diaphragm is zero. However, when an alkaline water electrolysis cell has a zero-gap structure, the anode and cathode are pressed against the diaphragm, which can cause stress concentration at the contact points between the convex surfaces of the anode and cathode and the diaphragm, potentially damaging the diaphragm and increasing the risk of short circuits. Furthermore, while a thinner diaphragm reduces liquid resistance, thinner diaphragms are more prone to damage, thus increasing the risk of short circuits in this case as well.

[0006] The present inventors have now discovered that, in an electrode laminate for an alkaline water electrolysis cell having a zero-gap structure, by employing an anode and / or cathode that includes a stress-relieving layer on the side that contacts the diaphragm and is deformable by stress, it is possible to provide an electrode laminate for an alkaline water electrolysis cell that is less prone to short circuits due to diaphragm damage.

[0007] Therefore, the object of the present invention is to provide an electrode laminate for an alkaline water electrolysis cell that has a zero-gap structure but is less prone to short circuits due to diaphragm damage.

[0008] The following embodiments are provided according to this disclosure: [Embodiment 1] An electrode laminate for an alkaline water electrolysis cell, comprising: an anode as an oxygen-evolving electrode; a cathode as a hydrogen-evolving electrode; and a hydroxide ion conductive diaphragm interposed between the anode and the cathode, wherein the electrode laminate has a zero-gap structure in which the anode, the diaphragm and the cathode are laminated in contact with each other, and the anode includes an anode stress-relieving layer on the side of the anode that is in contact with the diaphragm, which is deformable by stress, and / or the cathode includes a cathode stress-relieving layer on the side of the cathode that is in contact with the diaphragm, which is deformable by stress. [Embodiment 2] The electrode laminate for an alkaline water electrolysis cell according to Embodiment 1, wherein the anode stress-relieving layer and / or the cathode stress-relieving layer are configured to be plastically deformable by stress. [Embodiment 3] The electrode laminate for an alkaline water electrolysis cell according to Embodiment 2, wherein the anode stress-relieving layer and / or the cathode stress-relieving layer include a catalyst and a resin binder. [Aspect 4] The electrode laminate for an alkaline water electrolysis cell according to Aspect 3, wherein the catalyst is conductive, and / or the anode stress relaxation layer and / or the cathode stress relaxation layer further comprises a conductive additive. [Aspect 5] The electrode laminate for an alkaline water electrolysis cell according to any one of Aspects 1 to 4, wherein the thickness of the anode stress relaxation layer and / or the cathode stress relaxation layer is 5 to 100 μm. [Aspect 6] The electrode laminate for an alkaline water electrolysis cell according to Aspect 1, wherein the anode stress relaxation layer and / or the cathode stress relaxation layer is configured to be elastically deformable by stress. [Aspect 7] The electrode laminate for an alkaline water electrolysis cell according to Aspect 6, wherein the anode stress relaxation layer and / or the cathode stress relaxation layer comprises at least one selected from the group consisting of foam, nonwoven fabric, porous film, and mesh. [Aspect 8] The electrode laminate for an alkaline water electrolysis cell according to Aspect 6 or 7, wherein the thickness of the anode stress relaxation layer and / or the cathode stress relaxation layer is 5 to 100 μm. [Aspect 9] An electrode laminate for an alkaline water electrolysis cell according to any one of aspects 1 to 8, wherein the thickness of the diaphragm is 5 to 100 μm.[Aspect 10] An electrode laminate for an alkaline water electrolysis cell according to any one of aspects 1 to 9, wherein, when the anode includes the anode stress relaxation layer, the main anode portion constituting the portion of the anode other than the anode stress relaxation layer has higher rigidity than the anode stress relaxation layer, and when the cathode includes the cathode stress relaxation layer, the main cathode portion constituting the portion of the cathode other than the cathode stress relaxation layer has higher rigidity than the cathode stress relaxation layer. [Aspect 11] An alkaline water electrolysis cell comprising: an electrode laminate according to any one of aspects 1 to 10; an electrolyte; and a partition wall that divides the internal space containing the electrode laminate and the electrolyte.

[0009] This is a schematic cross-sectional view showing an example of an electrode stack for an alkaline water electrolysis cell according to the present invention. This is a schematic cross-sectional view showing another example of an electrode stack for an alkaline water electrolysis cell according to the present invention. This is a schematic cross-sectional view showing another example of an electrode stack for an alkaline water electrolysis cell according to the present invention. This is a schematic cross-sectional view showing an example of an alkaline water electrolysis cell using the electrode stack for an alkaline water electrolysis cell according to the present invention.

[0010] Figures 1 to 3 show three typical embodiments of the electrode laminate 10 for alkaline water electrolysis cells of the present disclosure. In each embodiment, the electrode laminate 10 for alkaline water electrolysis cells comprises an anode 12 as an oxygen generation electrode, a cathode 14 as a hydrogen generation electrode, and a hydroxide ion conductive diaphragm 16 interposed between the anode 12 and the cathode 14. The electrode laminate 10 has a zero-gap structure in which the anode 12, the diaphragm 16 and the cathode 14 are stacked in contact with each other. As shown in Figures 1 and 3, the anode 12 includes a stress-deformable anode stress relaxation layer 12a on the side that contacts the diaphragm 16, and / or the cathode 14 includes a stress-deformable cathode stress relaxation layer 14a on the side that contacts the diaphragm 16, as shown in Figures 2 and 3. Thus, in the electrode laminate 10 for an alkaline water electrolysis cell having a zero-gap structure, by employing an anode 12 and / or cathode 14 that includes an anode stress relaxation layer 12a and / or cathode stress relaxation layer 14a that can be deformed by stress on the surface that contacts the diaphragm 16, it is possible to provide an electrode laminate 10 for an alkaline water electrolysis cell that is less prone to short circuits due to damage to the diaphragm 16. In particular, even when a thin diaphragm 16 is used to lower the liquid resistance, the diaphragm 16 can be made less prone to damage. By making the diaphragm 16 less prone to damage in this way, the risk of short circuits is reduced, and it is thought that crossovers in which gases such as hydrogen and oxygen permeate through the diaphragm 16 are less likely to occur. As a result, the advantages of a zero-gap structure, such as reduced liquid resistance and improved power efficiency, can be enjoyed to the fullest extent. Furthermore, the electrode laminate 10 for alkaline water electrolysis cells can be used for water electrolysis using an alkaline electrolyte (for example, one with a pH greater than 7). In addition to general alkaline water electrolysis (where the pH of the electrolyte used is 14 or higher), it can also be used for non-polar pH water electrolysis (where the pH of the electrolyte used is around 9 to 11). Therefore, "alkaline water electrolysis" using the electrode laminate 10 for alkaline water electrolysis cells typically refers to water electrolysis using an electrolyte with a pH of 9 or higher.

[0011] In other words, as mentioned above, one of the challenges of alkaline water electrolysis is its low energy efficiency. To address this, it is conceivable to improve power efficiency by lowering the liquid resistance and making the alkaline water electrolysis cell or apparatus a zero-gap structure, where the distance between the anode and cathode and the diaphragm is zero. However, when an alkaline water electrolysis cell has a zero-gap structure, the anode and cathode are pressed against the diaphragm, which can cause stress concentration at the contact point between the convex surface shapes of the anode and cathode and the diaphragm, potentially damaging the diaphragm and increasing the risk of short circuits. Furthermore, while a thinner diaphragm results in lower liquid resistance, a thinner diaphragm is more prone to damage, thus increasing the risk of short circuits in this case as well. These problems are successfully solved according to the present invention. Specifically, the electrode laminate 10 for alkaline water electrolysis cells of the present invention includes an anode stress relaxation layer 12a and / or a cathode stress relaxation layer 14a that can be deformed by stress, thereby making it less likely for short circuits to occur due to damage to the diaphragm 16. Here, the mechanism by which stress concentration occurs, which should be addressed in the present invention, is presumed to be as follows. That is, in an alkaline water electrolysis cell, in order to maintain a zero-gap structure, a force is applied from the outside by tightening with screws or the like, which presses the anode and cathode against the diaphragm. In this case, the contact surface between the anode and cathode and the diaphragm is structured such that, microscopically, the protrusions on the surfaces of the anode and cathode are in contact with the diaphragm, so the force applied from the outside may concentrate on the protrusions on the surfaces of the anode and cathode. In contrast, in the present invention, by providing an anode stress relaxation layer 12a and / or a cathode stress relaxation layer 14a that can be deformed by stress on the surface that contacts the diaphragm 16, the stress concentration on the diaphragm 16 is mitigated or avoided by the deformation of the anode stress relaxation layer 12a and / or cathode stress relaxation layer 14a, making the diaphragm 16 less likely to be damaged.

[0012] As described above, the anode 12 and / or cathode 14 include an anode stress relaxation layer 12a and / or cathode stress relaxation layer 14a that are deformable by stress on the surface that contacts the diaphragm 16. Therefore, as shown in Figure 1, the anode 12 may include an anode stress relaxation layer 12a provided on the surface that contacts the diaphragm 16 and an anode main portion 12b that constitutes the part of the anode 12 other than the anode stress relaxation layer 12a, or as shown in Figure 2, the cathode 14 may include a cathode stress relaxation layer 14a provided on the surface that contacts the diaphragm 16 and a cathode main portion 14b that constitutes the part of the cathode 14 other than the cathode stress relaxation layer 14a. Alternatively, as shown in Figure 3, the anode 12 may include an anode stress relaxation layer 12a provided on the side in contact with the diaphragm 16 and a main anode portion 12b that constitutes the portion of the anode 12 other than the anode stress relaxation layer 12a, and the cathode 14 may include a cathode stress relaxation layer 14a provided on the side in contact with the diaphragm 16 and a main cathode portion 14b that constitutes the portion of the cathode 14 other than the cathode stress relaxation layer 14a. In any case, the anode stress relaxation layer 12a and the cathode stress relaxation layer 14a may not only relieve stress concentration but also have the functions of the anode 12 and cathode 14, respectively. For this reason, the anode stress relaxation layer 12a and the cathode stress relaxation layer 14a may each contain the same material as the anode 12 and cathode 14, respectively.

[0013] The stresses mentioned with respect to the anode stress relaxation layer 12a and the cathode stress relaxation layer 14a refer to the stress (e.g., 0.5 MPa) that may occur on the contact surface with the diaphragm 16 when the alkaline water electrolysis cell is incorporated and operated in a normal operating manner, and do not refer to excessive stresses that are intentionally applied to deform the anode stress relaxation layer 12a or the cathode stress relaxation layer 14a, deviating from such a normal operating manner. Therefore, whether a layer is the anode stress relaxation layer 12a or the cathode stress relaxation layer 14a can be determined by whether or not the layer deforms when the stress (e.g., 0.5 MPa) expected in a normal operating manner is applied to the contact surface of that layer with the diaphragm 16.

[0014] According to a first preferred embodiment of the present disclosure, the anode stress relaxation layer 12a and / or the cathode stress relaxation layer 14a may be configured to be plastically deformable by stress. In this way, the anode stress relaxation layer 12a and / or the cathode stress relaxation layer 14a can plastically deform in response to changes in the surface roughness of the current collector at the electrode, thereby effectively mitigating stress concentration on the diaphragm 16.

[0015] In a first preferred embodiment, the anodic stress relaxation layer 12a and / or cathode stress relaxation layer 14a, which are configured to be plastically deformable by stress, are not particularly limited as long as they can alleviate stress concentration on the diaphragm 16 by plastic deformation, but preferably include a catalyst and a resin binder. Examples of such an anodic stress relaxation layer 12a and / or cathode stress relaxation layer 14a include a catalyst coating layer and a catalyst-containing film. The catalyst coating layer can preferably be formed by coating the diaphragm 16 with a resin binder in which the catalyst is dispersed. Preferred examples of the resin binder include fluororesins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), aromatic hydrocarbon resins such as polyethylene terephthalate, polybutylene naphthalate, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene sulfone, polyacrylate, polyetherimide, polyimide, and polyamideimide. Examples of catalysts that may be included in the anode stress relaxation layer 12a include platinum group metals such as platinum, palladium, ruthenium, and iridium, platinum group oxides, valve metal oxides, iron group oxides, lanthanide group metal oxides, nickel, nickel alloys, spinel-type cobalt-containing oxides, perovskite-type composite oxides such as lanthanum cobaltate and lanthanum nickelate, and layered double hydroxides. Examples of catalysts that may be included in the cathode stress relaxation layer 14a include platinum group metals, platinum group oxides, nickel, nickel alloys, sulfide-based materials such as Raney nickel and nickel sulfide, and hydrogen storage alloy-based materials.

[0016] In a first preferred embodiment, when the anodic stress relaxation layer 12a and / or cathode stress relaxation layer 14a, which are plastically deformable by stress, contain a catalyst and a resin binder, it is preferable that the anodic stress relaxation layer 12a and / or cathode stress relaxation layer 14a are conductive in order to efficiently carry out the water electrolysis reaction. For this reason, it is preferable that the catalyst is conductive and / or that the anodic stress relaxation layer 12a and / or cathode stress relaxation layer 14a further contain a conductive additive. Examples of conductive catalysts that can be used in the anodic stress relaxation layer 12a include (i) platinum group metals, (ii) ruthenium and iridium oxides, (iii) nickel, (iv) nickel alloys, (v) perovskite-type composite oxides, etc., while examples of conductive additives for the anodic stress relaxation layer 12a include graphite, acetylene black, Ketjenblack, carbon materials such as carbon nanotubes, etc. Examples of conductive catalysts that can be used in the cathode stress relaxation layer 14a include (i) platinum group metals, (ii) ruthenium and iridium oxides, (iii) nickel, (iv) nickel alloys, (v) Raney nickel, (vi) sulfide-based materials, (vii) hydrogen storage alloy-based materials, etc. On the other hand, examples of conductive additives for the cathode stress relaxation layer 14a include graphite, acetylene black, Ketjenblack, carbon materials such as carbon nanotubes, etc.

[0017] In a first preferred embodiment, the thickness of the stress-deformable anode stress relaxation layer 12a is preferably 5 to 100 μm, more preferably 5 to 80 μm, even more preferably 5 to 60 μm, and particularly preferably 5 to 40 μm. The thickness of the stress-deformable cathode stress relaxation layer 14a is preferably 5 to 100 μm, more preferably 5 to 80 μm, even more preferably 5 to 60 μm, and particularly preferably 5 to 40 μm.

[0018] In a first preferred embodiment, the porosity of the anode stress relaxation layer 12a, which is plastically deformable by stress, is preferably 10 to 90%, more preferably 20 to 80%, and even more preferably 30 to 70%. The porosity of the cathode stress relaxation layer 14a, which is plastically deformable by stress, is preferably 10 to 90%, more preferably 20 to 80%, and even more preferably 30 to 70%. The porosity is measured as follows: After polishing the cross-sections of the stress relaxation layers 12a and 14a with CP (cross-section polisher) polishing, the stress relaxation layers 12a and 14a are observed with SEM at a magnification of 1000x, and the obtained SEM images are binarized to calculate the porosity.

[0019] According to a second preferred embodiment of the present disclosure, the anode stress relaxation layer 12a and / or cathode stress relaxation layer 14a may be configured to be elastically deformable by stress. In this way, the anode stress relaxation layer 12a and / or cathode stress relaxation layer 14a elastically deform in response to changes in the surface roughness of the current collector at the electrode, thereby effectively mitigating stress concentration on the diaphragm 16.

[0020] In a second preferred embodiment, the anode stress relaxation layer 12a and / or cathode stress relaxation layer 14a, which are configured to be elastically deformable by stress, are not particularly limited as long as they can alleviate stress concentration on the diaphragm 16 by elastic deformation, but preferably include at least one selected from the group consisting of foam, nonwoven fabric, porous film, and mesh, and more preferably be foam and / or nonwoven fabric. Preferred examples of foam include metal foam and resin foam. Preferred examples of nonwoven fabric include metal nonwoven fabric and resin nonwoven fabric. Preferred examples of porous film include porous resin film and porous rubber sheet. Preferred examples of mesh include metal mesh and resin mesh. The metals, resins, rubbers, etc. that constitute these materials are not particularly limited as long as they can withstand alkaline electrolytes, but examples of metals include nickel, titanium, platinum, etc., examples of resins include PE (polyethylene) and PPS (polyphenylene sulfide), and examples of rubber include fluororesins and EPDM (ethylene propylene diene rubber). However, the anode stress relaxation layer 12a and / or cathode stress relaxation layer 14a, which are elastically deformable under stress, may be made of a non-conductive material. This allows for minimizing short circuits even if the anode stress relaxation layer 12a and / or cathode stress relaxation layer 14a are pushed by the current collector and puncture the diaphragm 16.

[0021] In a second preferred embodiment, the thickness of the anode stress relaxation layer 12a, which is elastically deformable by stress, is preferably 5 to 100 μm, more preferably 5 to 80 μm, even more preferably 5 to 60 μm, and particularly preferably 5 to 40 μm. The thickness of the cathode stress relaxation layer 14a, which is elastically deformable by stress, is preferably 5 to 100 μm, more preferably 5 to 80 μm, even more preferably 5 to 60 μm, and particularly preferably 5 to 40 μm.

[0022] The first and second preferred embodiments are not mutually exclusive, and a combination of the first and second preferred embodiments may be used. For example, in the embodiment shown in Figure 3, the anode stress relaxation layer 12a may be configured to be plastically deformable by stress, while the cathode stress relaxation layer 14a may be configured to be elastically deformable by stress. Alternatively, the cathode stress relaxation layer 14a may be configured to be plastically deformable by stress, while the anode stress relaxation layer 12a may be configured to be elastically deformable by stress.

[0023] In both the first and second preferred embodiments, if the anode 12 includes an anode stress relaxation layer 12a, it is preferable that the anode main portion 12b, which constitutes the portion of the anode 12 other than the anode stress relaxation layer 12a, has higher rigidity than the anode stress relaxation layer 12a. Similarly, if the cathode 14 includes a cathode stress relaxation layer 14a, it is preferable that the cathode main portion 14b, which constitutes the portion of the cathode 14 other than the cathode stress relaxation layer 14a, has higher rigidity than the cathode stress relaxation layer 14a. Typically, the high rigidity of the anode main portion 12b and / or the cathode main portion 14b can be ensured by the anode main portion 12b and / or the cathode main portion 14b including a current collector. Thus, by having a two-layer structure with different rigidities, the anode stress relaxation layer 12a and / or cathode stress relaxation layer 14a can effectively alleviate stress concentration on the diaphragm 16 by following changes in the surface roughness of the current collector (main anode portion 12b and / or main cathode portion 14b) at the electrode.

[0024] The anode 12 functions as an oxygen generation electrode. Therefore, the main part 12b of the anode is the part that bears the main function as an oxygen generation electrode, but the anode stress relaxation layer 12a may also have the function as an oxygen generation electrode. It is preferable that the main part 12b of the anode also serves as a current collector. This current collector itself may function as an oxygen generation electrode, or the function as an oxygen generation electrode may be imparted or improved by supporting a catalyst on the current collector. On the other hand, the cathode 14 functions as a hydrogen generation electrode. Therefore, the main part 14b of the cathode is the part that bears the main function as a hydrogen generation electrode, but the cathode stress relaxation layer 14a may also have the function as a hydrogen generation electrode. It is preferable that the main part 14b of the cathode also serves as a current collector. This current collector itself may function as a hydrogen generation electrode, or the function as a hydrogen generation electrode may be imparted or improved by supporting a catalyst on the current collector. As shown in the following reaction equations, in alkaline water electrolysis, at the anode 12 as an oxygen generation electrode, OH ２ is oxidized to O ２ while at the cathode 14 as a hydrogen generation electrode, H ２ O is reduced to H ２ . Anode: 4OH － →O ２ +2H ２ O + 4e － Cathode: 4H ２ O + 4e － →2H ２ +4OH －

[0025] Therefore, as long as the above reaction occurs in alkaline water electrolysis, the form and material of the anode main part 12b and the cathode main part 14b are not particularly limited, but examples of forms include perforated metal, expanded metal, foam, nonwoven fabric, etc. Examples of constituent materials for the anode 12 (especially the anode main part 12b) include metallic materials such as nickel, titanium, and platinum, and composite materials on which catalysts such as platinum group metals, platinum group oxides, valve metal oxides, iron group oxides, lanthanide group metal oxides, nickel and nickel alloys, spinel-based cobalt-containing oxides, perovskite-type composite oxides, and layered double hydroxides are supported. These constituent materials may also be included in the anode stress relaxation layer 12a. Examples of constituent materials for the cathode 14 (especially the main cathode portion 14b) include metallic materials such as nickel, nickel alloys, and nickel-plated iron, as well as composite materials on which catalysts such as platinum group metals, platinum group oxides, nickel, nickel alloys, Raney nickel, sulfide-based materials, and hydrogen storage alloy-based materials are supported. These constituent materials may also be included in the cathode stress relaxation layer 14a. As described above, when an alkaline water electrolysis cell has a zero-gap structure, the anode and cathode are pressed against the diaphragm, causing stress concentration at the contact points between the convex surfaces of the anode and cathode and the diaphragm, which can damage the diaphragm and increase the risk of short circuits. For example, when perforated metal or expanded metal is used as a current collector, the hard current collector is pressed against the diaphragm, which can damage the diaphragm and cause a short circuit. In contrast, by introducing an anode stress relaxation layer 12a and / or a cathode stress relaxation layer 14a between the current collector (which may be included in the main anode portion 12b and / or the main cathode portion 14b) and the diaphragm 16, the anode stress relaxation layer 12a and / or the cathode stress relaxation layer 14a can follow the irregularities in the thickness direction of the current collector, thereby suppressing short circuits caused by damage to the diaphragm 16. For example, when foam or nonwoven fabric is used as the current collector, the width of the structure in the microstructure of the foam or nonwoven fabric is at the level of several hundred micrometers, so it cannot follow the surface roughness of the diaphragm (at the level of several micrometers), and stress concentrates on the diaphragm. As a result, the diaphragm may be damaged and a short circuit may occur.In contrast, by introducing an anode stress relaxation layer 12a and / or a cathode stress relaxation layer 14a between the current collector (which may be included in the main anode portion 12b and / or the main cathode portion 14b) and the diaphragm 16, the anode stress relaxation layer 12a and / or the cathode stress relaxation layer 14a, which are more easily deformable than the current collector (porous material) used in the electrodes, can deform and release stress, thereby suppressing short circuits caused by damage to the diaphragm 16.

[0026] The thickness of the main anode portion 12b is preferably 0.1 to 1.6 mm, more preferably 0.1 to 1.3 mm, and even more preferably 0.1 to 1.0 mm. The thickness of the main cathode portion 14b is preferably 0.1 to 1.6 mm, more preferably 0.1 to 1.3 mm, and even more preferably 0.1 to 1.0 mm.

[0027] The diaphragm 16 is interposed between the anode 12 and the cathode 14 and has hydroxide ion conductivity. As described above, a thinner diaphragm results in lower liquid resistance, but the thinner the diaphragm, the more easily it is damaged, thus increasing the risk of short circuits. On the other hand, in the electrode laminate 10 for alkaline water electrolysis cells of the present invention, by including an anode stress relaxation layer 12a and / or a cathode stress relaxation layer 14a that can be deformed by stress, the diaphragm 16 can be made less susceptible to damage. Therefore, the electrode laminate 10 for alkaline water electrolysis cells is particularly advantageous in that it can use a relatively thin diaphragm 16. From this viewpoint, the thickness of the diaphragm 16 is preferably 5 to 100 μm, more preferably 5 to 80 μm, and even more preferably 5 to 60 μm.

[0028] The diaphragm 16 can be any type of diaphragm usable in an alkaline water electrolysis cell, and it is preferable that it has hydroxide ion conductivity, low gas permeability, and alkali resistance. Examples of such diaphragms 16 include commercially available polymer microporous membranes, alkaline water electrolysis separators disclosed in Patent Documents 1 to 3, hydroxide ion conductive separators as described later, and ZrO ２ A separator containing (for example, ZrO on both sides of a resin substrate) ２Examples include separators with a contenting layer formed on them. Examples of polymer microporous membranes include microporous membranes made of polyolefins such as polyethylene and polypropylene.

[0029] A hydroxide ion conductive separator is not particularly limited as long as it is a separator capable of separating the anode 12 and cathode 14 in a way that allows hydroxide ions to conduct, but typically it is a separator that contains a hydroxide ion conductive solid electrolyte and selectively passes hydroxide ions by exclusively utilizing its hydroxide ion conductivity. A preferred hydroxide ion conductive solid electrolyte is a layered double hydroxide (LDH) and / or an LDH-like compound. Therefore, it is preferable that the hydroxide ion conductive separator is an LDH separator. In this specification, "LDH separator" is defined as a separator containing LDH and / or an LDH-like compound that selectively passes hydroxide ions by exclusively utilizing the hydroxide ion conductivity of the LDH and / or LDH-like compound. In this specification, "LDH-like compound" is a hydroxide and / or oxide with a layered crystalline structure similar to LDH, which may not be called LDH, and can be considered an equivalent of LDH. However, in a broader sense, "LDH" can also be interpreted as encompassing not only LDH but also LDH-like compounds. The LDH separator is preferably compounded with a porous substrate. Therefore, the LDH separator is preferably compounded with the porous substrate in a form in which LDH and / or LDH-like compounds fill the pores of the porous substrate. That is, in a preferred LDH separator, the LDH and / or LDH-like compounds block the pores of the porous substrate so as to exhibit hydroxide ion conductivity and gas impermeability (and thus function as an LDH separator exhibiting hydroxide ion conductivity). The porous substrate is preferably made of a polymer material, and it is particularly preferable that the LDH is incorporated throughout the entire thickness direction of the polymer material porous substrate. For example, known LDH separators such as those disclosed in Patent Documents 4 to 8 can be used. The thickness of the LDH separator is preferably 5 to 100 μm, more preferably 5 to 80 μm, even more preferably 5 to 60 μm, and particularly preferably 5 to 40 μm.

[0030] As shown in Figure 4, the electrode stack 10 for the alkaline water electrolysis cell can be incorporated into the alkaline water electrolysis cell 20. The alkaline water electrolysis cell 20 comprises the electrode stack 10, the electrolyte 22, and a partition wall 24. The partition wall 24 divides the internal space that houses the electrode stack 10 and the electrolyte 22. The alkaline water electrolysis cell 20 with this configuration uses an electrode stack 10 for alkaline water electrolysis cells that has a zero-gap structure but is less prone to short circuits due to damage to the diaphragm 16. Therefore, by using the alkaline water electrolysis cell 20 in an alkaline water electrolysis device, energy efficiency can be improved. The electrolyte 22 can be appropriately selected from known compositions suitable for the anode 12 and cathode 14 used, and may be, for example, an aqueous solution of alkali metal hydroxide such as potassium hydroxide aqueous solution or sodium hydroxide aqueous solution. The partition wall 24 can be made of an alkali-resistant material commonly used in alkaline water electrolysis cells, and is not particularly limited.

[0031] Preferably, the alkaline water electrolysis cell 20 is equipped with a sealant (gasket) 26, and the diaphragm 16 is fixed by embedding the end of the diaphragm 16 in the sealant (gasket) 26, and the partition walls 24 are joined together via the sealant (gasket) 26. The sealant (gasket) 26 can be an insulating resin material such as polypropylene, polytetrafluoroethylene, or PFA resin, and is not particularly limited.

[0032] The present invention will be further described in detail by the following examples. However, the present invention is not limited to the following examples.

[0033] Example 1 (1) Preparation of the diaphragm A commercially available polyethylene microporous membrane with a thickness of 20 μm (arithmetic mean surface roughness Ra: 0.5 μm) was prepared as the diaphragm 16 and cut to a size of 5.0 cm × 5.0 cm.

[0034] (2) Formation of stress relaxation layer A diaphragm 16 was fabricated by applying a resin binder (PTFE) in which a conductive catalyst (iridium oxide) was dispersed to the surface of the diaphragm 16 that is in contact with the anode 12, thereby forming a catalyst coating layer. This catalyst coating layer is an anode stress relaxation layer 12a that is configured to be plastically deformable by stress, and its thickness was 15 μm.

[0035] (3) Preparation of Anode Current Collector A titanium punching metal with a thickness of 0.6 mm without a catalyst was prepared as the anode current collector and cut into a size of 4.0 cm × 4.0 cm. This anode current collector was used as the anode main part 12b.

[0036] (4) Preparation of Cathode Current Collector A nickel punching metal with a thickness of 0.6 mm carrying a platinum catalyst was prepared as the cathode current collector and cut into a size of 4.0 cm × 4.0 cm. This cathode current collector was used as the cathode main part 14b.

[0037] (5) Assembly of the Electrode Stacked Body Cell for Alkaline Water Electrolysis As schematically shown in FIG. 1, the anode 12 including the anode stress relaxation layer 12a and the anode main part 12b, the separator 16, and the cathode main part 14b as the cathode 14 were laminated so as to contact each other, thereby assembling the electrode stacked body 10 for a monopolar alkaline water electrolysis cell having a zero-gap structure. A total of 40 such electrode stacked bodies 10 for alkaline water electrolysis cells were produced.

[0038] (6) Evaluation of Short-Circuit Risk An alkaline water electrolysis cell 20 was assembled using the electrode stacked body 10 for an alkaline water electrolysis cell, a 30 wt% potassium hydroxide aqueous solution was introduced as the electrolyte, and after leaving it for 1 hour, the resistance value of the alkaline water electrolysis cell 20 was measured using a tester. If the measured resistance value was 1 kΩ or less, it was judged to be short-circuited. Similarly, the number of short-circuited cells 20 among the alkaline water electrolysis cells 20 assembled using 40 electrode stacked bodies 10 for alkaline water electrolysis cells was counted, and this was divided by the total number of alkaline water electrolysis cells 20 and then multiplied by 100 to calculate the short-circuit rate (%). If the short-circuit rate was 20% or less, it was judged that short-circuit due to damage of the separator 16 was unlikely to occur, that is, the short-circuit risk was low. The results were as shown in Table 1.

[0039] Example 2 1) In the above (2), a non-woven fabric made of resin (polyethylene) with a thickness of 20 μm, which is configured to be elastically deformable by stress, was laminated on the surface of the anode 12 of the diaphragm 16 on the side in contact therewith, and 2) In the above (3), except that a titanium punching metal with a thickness of 0.6 mm carrying an iridium oxide catalyst was prepared as the anode current collector, an electrode laminate 10 for an alkaline water electrolysis cell was produced in the same manner as in Example 1, and the risk of short circuit was evaluated. The results were as shown in Table 1.

[0040] Example 3 Except that a Ni non-woven fabric with a thickness of 0.6 mm without a catalyst was prepared as the anode current collector in the above (3), an electrode laminate 10 for an alkaline water electrolysis cell was produced in the same manner as in Example 1, and the risk of short circuit was evaluated. The results were as shown in Table 1.

[0041] Example 4 Except that a Ni non-woven fabric with a thickness of 0.6 mm carrying an iridium oxide catalyst was prepared as the anode current collector in the above (3), an electrode laminate 10 for an alkaline water electrolysis cell was produced in the same manner as in Example 2, and the risk of short circuit was evaluated. The results were as shown in Table 1.

[0042] Example 5 1) In the above (2), a Ni non-woven fabric with a low density (the density of Ni is 0.1 g / cm ３ ) and a thickness of 50 μm, which is configured to be elastically deformable by stress, was laminated on the surface of the anode 12 of the diaphragm 16 on the side in contact therewith, and 2) In the above (3), except that a Ni non-woven fabric with a thickness of 0.6 mm carrying an iridium oxide catalyst was prepared as the anode current collector, an electrode laminate 10 for an alkaline water electrolysis cell was produced in the same manner as in Example 2, and the risk of short circuit was evaluated. The results were as shown in Table 1.

[0043] Example 6 Except that a Ni foam (foam) with a thickness of 0.4 mm without a catalyst was prepared as the anode current collector in the above (3), an electrode laminate 10 for an alkaline water electrolysis cell was produced in the same manner as in Example 1, and the risk of short circuit was evaluated. The results were as shown in Table 1.

[0044] Example 7 An electrode laminate 10 for an alkaline water electrolysis cell was fabricated in the same manner as in Example 2, except that a 0.4 mm thick Ni foam (foamed material) supporting an iridium oxide catalyst was prepared as the anode current collector, as in (3) above, and the risk of short circuits was evaluated. The results are shown in Table 1.

[0045] Example 8 1) In (2) above, the anodic stress relaxation layer 12a is configured to be elastically deformable by stress and has a low density (the density of Ni is 0.1 g / cm³). ３ An electrode laminate 10 for an alkaline water electrolysis cell was fabricated in the same manner as in Example 2, except that 2) a 50 μm thick Ni foam (foam) was laminated on the side of the diaphragm 16 that contacts the anode 12, and 2) in (3) above, a 0.4 mm thick Ni foam (foam) supporting an iridium oxide catalyst was prepared as the anode current collector. The short-circuit risk was then evaluated. The results are shown in Table 1.

[0046] Example 9 (Comparison) An electrode laminate 10 for an alkaline water electrolysis cell was fabricated in the same manner as in Example 1, except that 1) the stress relaxation layer described in (2) above was not used, and 2) in (3) above, a 0.6 mm thick Ti perforated metal supported with iridium oxide catalyst was prepared as the anode current collector. The short-circuit risk was then evaluated. The results are shown in Table 1.

[0047] Example 10 (Comparison) An electrode laminate 10 for an alkaline water electrolysis cell was fabricated in the same manner as in Example 1, except that 1) the stress relaxation layer described in (2) above was not used, and 2) in (3) above, a 0.6 mm thick Ni nonwoven fabric supporting iridium oxide catalyst was prepared as the anode current collector. The short-circuit risk was then evaluated. The results are shown in Table 1.

[0048] Example 11 (Comparison) An electrode laminate 10 for an alkaline water electrolysis cell was fabricated in the same manner as in Example 1, except that 1) the stress relaxation layer described in (2) above was not used, and 2) in (3) above, a 0.4 mm thick Ni foam (foamed material) supporting iridium oxide catalyst was prepared as the anode current collector. The short-circuit risk was then evaluated. The results are shown in Table 1.

[0049] Example 12 An electrode laminate 10 for an alkaline water electrolysis cell was fabricated in the same manner as in Example 9, except that 1) the same catalyst coating layer (anode stress relaxation layer 12a) as in (2) above was formed as the cathode stress relaxation layer 14a on the surface of the diaphragm 16 that is in contact with the cathode 14, as schematically shown in Figure 2, and 2) nickel perforated metal with a thickness of 0.6 mm that does not support a catalyst was used as the cathode current collector in (4) above, and the short-circuit risk was evaluated. The results are shown in Table 1.

[0050]

[0051] 10: Electrode laminate for alkaline water electrolysis cell, 12: Anode, 12a: Anode stress relaxation layer, 12b: Main part of anode, 14: Cathode, 14a: Cathode stress relaxation layer, 14b: Main part of cathode, 16: Diaphragm, 20: Alkaline water electrolysis cell, 22: Electrolyte, 24: Partition wall

Claims

1. An electrode laminate for an alkaline water electrolysis cell, comprising: an anode as an oxygen-generating electrode; a cathode as a hydrogen-generating electrode; and a hydroxide ion conductive diaphragm interposed between the anode and the cathode, wherein the electrode laminate has a zero-gap structure in which the anode, the diaphragm and the cathode are laminated in contact with each other, and the anode includes an anode stress-relieving layer on the side in contact with the diaphragm that is deformable by stress, and / or the cathode includes a cathode stress-relieving layer on the side in contact with the diaphragm that is deformable by stress.

2. The electrode laminate for an alkaline water electrolysis cell according to claim 1, wherein the anode stress relaxation layer and / or the cathode stress relaxation layer are configured to be plastically deformable by stress.

3. The electrode laminate for an alkaline water electrolysis cell according to claim 2, wherein the anode stress relaxation layer and / or the cathode stress relaxation layer comprises a catalyst and a resin binder.

4. The electrode laminate for an alkaline water electrolysis cell according to claim 3, wherein the catalyst is conductive, and / or the anode stress relaxation layer and / or the cathode stress relaxation layer further comprises a conductive additive.

5. The electrode laminate for an alkaline water electrolysis cell according to claim 2, wherein the thickness of the anode stress relaxation layer and / or the cathode stress relaxation layer is 5 to 100 μm.

6. The electrode laminate for an alkaline water electrolysis cell according to claim 1, wherein the anode stress relaxation layer and / or the cathode stress relaxation layer are configured to be elastically deformable by stress.

7. The electrode laminate for an alkaline water electrolysis cell according to claim 6, wherein the anode stress relaxation layer and / or the cathode stress relaxation layer comprises at least one selected from the group consisting of foam, nonwoven fabric, porous film, and mesh.

8. The electrode laminate for an alkaline water electrolysis cell according to claim 6, wherein the thickness of the anode stress relaxation layer and / or the cathode stress relaxation layer is 5 to 100 μm.

9. The electrode laminate for alkaline water electrolysis cell according to claim 1, wherein the thickness of the diaphragm is 5 to 100 μm.

10. The electrode laminate for an alkaline water electrolysis cell according to claim 1, wherein, if the anode includes the anode stress relaxation layer, the main anode portion constituting the portion of the anode other than the anode stress relaxation layer has higher rigidity than the anode stress relaxation layer, and if the cathode includes the cathode stress relaxation layer, the main cathode portion constituting the portion of the cathode other than the cathode stress relaxation layer has higher rigidity than the cathode stress relaxation layer.

11. An alkaline water electrolysis cell comprising: an electrode stack according to any one of claims 1 to 10; an electrolyte; and a partition wall that divides the internal space containing the electrode stack and the electrolyte.

Images