Water electrolysis stack

Abstract

To provide a water electrolysis stack enabled to suppress the deterioration of the sealing property thereof.SOLUTION: The water electrolysis stack structured by laminating a plurality of water electrolysis cells one after another to generate hydrogen by feeding water and applying electric power thereto, comprises a plurality of sealing property improving laminated members, i.e., members not introducing water thereinto, each laminated on a predetermined position of the laminated water electrolysis cells.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a water electrolysis stack in which water electrolysis cells are stacked. [Background technology]

[0002] Patent Document 1 discloses a high pressure-resistant structure for the sealing members at the ends of the water electrolysis cells in the planar direction, which is required to boost the pressure of hydrogen produced by water electrolysis within the water electrolysis stack before supplying it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-123906 Summary of the Invention [Problem to be solved by the invention]

[0004] In a water electrolysis stack, as the internal pressure of the hydrogen electrode increases, the centers of the multiple water electrolysis cells arranged between the end plates bulge, as shown in Figure 16. The water electrolysis cell closest to the end plate warps significantly, causing deformation as shown in the dotted circle, which may reduce the sealing performance of the sealing members arranged at the ends. This reduced sealing performance may make it impossible to sufficiently increase the hydrogen pressure or may cause hydrogen leakage.

[0005] In view of the above problems, an object of the present disclosure is to provide a water electrolysis stack that can suppress deterioration in sealing performance. [Means for solving the problem]

[0006] The present application discloses a water electrolysis stack configured by stacking a plurality of water electrolysis cells, which generates hydrogen by supplying water to the water electrolysis cells and applying electric power to them, in which a sealing property-improving lamination member, which is a member that prevents water from being introduced into the stacked water electrolysis cells, is stacked at a predetermined position on the stacked water electrolysis cells.

[0007] The sealing property-improving laminated member may be configured to have a first exterior body having the same shape as an anode separator provided in the water electrolysis cell, a second exterior body having the same shape as a cathode separator provided in the water electrolysis cell, a core material disposed between the first exterior body and the second exterior body, and a frame disposed between the first exterior body and the second exterior body to bond the first exterior body and the second exterior body together.

[0008] The device may be configured to have a communication hole that connects the space between the first exterior body and the second exterior body to the outside.

[0009] The sealing property improving laminated member may be a plate-like member that is less likely to bend than the water electrolysis cell. [Effects of the Invention]

[0010] According to the present disclosure, the use of a sealing performance improving laminate member can reduce the number of water electrolysis cells that are significantly deformed, thereby suppressing a decrease in the sealing performance within the water electrolysis stack. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a plan view of a water electrolysis cell 10. [Figure 2] FIG. 2 is a conceptual diagram illustrating the layer structure in the water electrolysis region 10a of the water electrolysis cell 10. [Figure 3] FIG. 3 is a conceptual diagram illustrating the layer structure in the oxygen electrode outlet-side distribution region 10d and the oxygen electrode outlet region 10e of the water electrolysis cell 10. As shown in FIG. [Figure 4] FIG. 4 is a conceptual diagram illustrating the structure of the water electrolysis stack 30. [Figure 5] FIG. 5 is a diagram illustrating the stack structure of the water electrolysis cells 10 in the water electrolysis stack 30. [Figure 6] FIG. 6 is another diagram illustrating the stack structure of the water electrolysis cells 10 in the water electrolysis stack 30. [Figure 7]FIG. 7 is a conceptual diagram illustrating the structure of the water electrolysis stack 40. [Figure 8] FIG. 8 is a plan view of the sealing performance improving laminated member 41. As shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view of the sealing performance improving laminated member 41. As shown in FIG. [Figure 10] FIG. 10 is another cross-sectional view of the sealing performance improving laminated member 41. As shown in FIG. [Figure 11] FIG. 11 is a diagram illustrating a first modification of the sealing property improving laminated member 41. In FIG. [Figure 12] FIG. 12 is a diagram illustrating a second modification of the sealing property improving laminated member 41. In FIG. [Figure 13] FIG. 13 is a diagram illustrating a third modification of the sealing property improving laminated member 41. In FIG. [Figure 14] FIG. 14 is a conceptual diagram illustrating the structure of the water electrolysis stack 50. [Figure 15] FIG. 15 is a plan view of the sealing performance improving laminated member 51. As shown in FIG. [Figure 16] FIG. 16 is a diagram illustrating warpage of a water electrolysis cell in a water electrolysis stack. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1. Basic configuration of water electrolysis stack The water electrolysis stack of the present disclosure is characterized by the arrangement of a sealing property-improving laminate member. First, a basic configuration of the water electrolysis stack in which the sealing property-improving laminate member is arranged will be described. Then, the sealing property-improving laminate member and the water electrolysis stack in which the sealing property-improving laminate member is arranged will be described.

[0013] 1.1. Water electrolysis cell A water electrolysis stack comprises a plurality of stacked water electrolysis cells, which constitute the main part of the stack. FIG. 1 illustrates the structure of one embodiment of a water electrolysis cell 10. The water electrolysis cell 10 is a unit element for decomposing pure water into hydrogen and oxygen, and a plurality of such water electrolysis cells 10 are stacked to form a water electrolysis stack. FIG. 1 shows a plan view of the water electrolysis cell 10 (the stacking direction of the plurality of water electrolysis cells 10 is toward the front / rear of the page). In FIG. 1, part of the internal structure of the water electrolysis cell 10 (particularly the oxygen electrode side) is indicated by a dotted line to illustrate the internal structure of the water electrolysis cell 10.

[0014] The water electrolysis in the water electrolysis cell 10 is well known, but the outline thereof is as follows. Pure water flows into the oxygen electrode introduction region 10b through the oxygen electrode introduction hole (oxygen electrode side inlet manifold) 14d. The pure water is then distributed uniformly in the oxygen electrode introduction side distribution region 10c, and reaches the water electrolysis region 10a, where water electrolysis occurs. However, water electrolysis may also occur in the oxygen electrode introduction side distribution region 10c. In the water electrolysis region 10a, a portion of the pure water is decomposed into oxygen and hydrogen by a water electrolysis membrane electrode assembly (described later), and the decomposed oxygen and the remaining pure water are discharged through the respective flow paths. The generated oxygen and the remaining pure water pass through the oxygen electrode outlet-side distribution region 10d, are collected by the oxygen electrode outlet flow path 10e, and are discharged from the oxygen electrode outlet hole (oxygen electrode-side outlet manifold) 14e. Meanwhile, the generated hydrogen migrates to the electrode (hydrogen electrode) opposite the electrode (oxygen electrode) through which pure water flows, across the water electrolysis membrane electrode assembly, and passes through a separate flow path (not shown) before being discharged from the hydrogen electrode outlet hole (hydrogen electrode-side outlet manifold) 14f. The oxygen electrode and the hydrogen electrode are both provided within the water electrolysis cell 10, but apart from the water electrolysis region 10a, separate flow paths are formed between the oxygen electrode and the hydrogen electrode, partitioned by a sealing member (not shown) to prevent the generated hydrogen and oxygen from mixing. As with the unit cells of a fuel cell, another pair of manifolds may be arranged between adjacent water electrolysis cells to allow a fluid to flow, and in this case, it is desirable to allow the generated hydrogen to flow through these manifolds.

[0015] The structure of the water electrolysis cell 10 is described below. Fig. 2 is a partial cross-section taken along the line A-A in Fig. 1, illustrating the layer structure of the water electrolysis region 10a in the water electrolysis cell 10, where water electrolysis is mainly performed. Fig. 3 is a cross-section taken along the line B-B in Fig. 1, illustrating the layer structure of a portion of the oxygen electrode lead-out hole (oxygen electrode side outlet manifold) 14e, the oxygen electrode lead-out region 10e, the oxygen electrode lead-out side distribution region 10d, and a portion of the water electrolysis region 10a.

[0016] The water electrolysis cell 10 is made up of multiple layers, one of which is an oxygen electrode (anode) and the other of which is a hydrogen electrode (cathode) sandwiching a solid polymer electrolyte membrane 11 therebetween. In the water electrolysis region 10a, as shown in FIG. 2 , the anode includes an anode catalyst layer 12, an anode gas diffusion layer 13, and an anode separator 14 stacked in this order from the solid polymer electrolyte membrane 11 side. On the other hand, the cathode includes a cathode catalyst layer 15, a cathode gas diffusion layer 16, and a cathode separator 17 stacked in this order from the solid polymer electrolyte membrane 11 side. Here, the water electrolysis membrane electrode assembly refers to a stack of the solid polymer electrolyte membrane 11, the anode catalyst layer 12 arranged on the anode side of the solid polymer electrolyte membrane 11, and the cathode catalyst layer 15 arranged on the cathode side of the solid polymer electrolyte membrane 11. The thickness of the water electrolysis membrane electrode assembly is typically about 0.4 mm, and the thickness of the water electrolysis cells 10 in the water electrolysis region 10a is typically about 1.3 mm. As shown in FIG. 3, the water electrolysis cell 10 is provided with frames 18 on both ends of the water electrolysis region 10a. First, the mode of each layer will be described, and then the layer structure in each region will be described.

[0017] 1.1.1. Aspects of each layer The layers included in the water electrolysis cell 10 may have the following configurations, for example: However, the water electrolysis cell of the present disclosure is not limited to these configurations.

[0018] [Solid polymer electrolyte membrane] The solid polymer electrolyte membrane 11 is one embodiment of an electrolyte membrane having proton conductivity. In this embodiment, the material (electrolyte) constituting the solid polymer electrolyte membrane 11 is a solid polymer material, such as a proton-conductive ion exchange membrane formed from a fluorine-based resin or a hydrocarbon-based resin material. This exhibits good proton conductivity (electrical conductivity) in a wet state. More specifically, a membrane made of Nafion (registered trademark), a perfluoro-based electrolyte, is exemplified. The thickness of the solid polymer electrolyte membrane 11 is not particularly limited, but is 200 μm or less, preferably 100 μm or less, and more preferably 30 μm or less.

[0019] [Anode catalyst layer] The anode catalyst layer (oxygen electrode catalyst layer) 12 is a catalyst layer containing at least one of a noble metal catalyst such as Pt, Ru, Ir, etc. and its oxides. More specifically, the catalyst may be Pt, iridium oxide, ruthenium oxide, iridium ruthenium oxide, or a mixture thereof. Examples of iridium oxides include iridium oxide (IrO2, IrO3), iridium tin oxide, and iridium zirconium oxide. Examples of ruthenium oxides include ruthenium oxide (RuO2, Ru2O3), ruthenium tantalum oxide, ruthenium zirconium oxide, ruthenium titanium oxide, and ruthenium titanium cerium oxide. Examples of iridium ruthenium oxides include iridium ruthenium cobalt oxide, iridium ruthenium tin oxide, iridium ruthenium iron oxide, and iridium ruthenium nickel oxide.

[0020] The anode catalyst layer 12 may contain an ionomer. The inclusion of an ionomer not only improves coating properties, but also facilitates the permeation of water supplied during water splitting due to its hydrophilicity. Examples of the ionomer that may be contained include ionomers containing perfluorinated electrolytes, which are electrolytes used in solid polymer electrolyte membranes.

[0021] [Anode gas diffusion layer] The anode gas diffusion layer 13 is a gas diffusion layer disposed on the anode side, and may be made of a material having gas permeability and conductivity, although known materials may be used. Specific examples include porous conductive materials made of a sintered body of metal fibers (e.g., titanium fibers) or metal particles (titanium particles).

[0022] [Anode separator] The anode separator 14 is a member (separator) having a flow path (water supply flow path) 14a through which pure water, decomposed oxygen, and residual water flow to be supplied to the anode gas diffusion layer 13. In this embodiment, the anode separator 14 is a plate-like member formed into a corrugated shape in the water electrolysis region 10a, with repeated projections and depressions, and the depressions 14c are placed in contact with the anode gas diffusion layer 13, thereby forming the water supply flow path 14a between the anode gas diffusion layer 13 and the projections 14b. The anode separator 14 can be produced by press-molding a titanium thin film, for example, and its thickness is typically 0.1 mm to 0.2 mm, and the height of the projections and recesses is typically about 0.5 mm.

[0023] As shown in FIG. 1 and described above, the anode separator 14 is provided with an oxygen electrode-side inlet manifold 14d, which is an inlet for pure water, an oxygen electrode-side outlet manifold 14e, which is an outlet for the generated oxygen and remaining water, and a hydrogen electrode-side outlet manifold 14f, which is an outlet for the generated hydrogen and produced water.

[0024] Furthermore, as shown in FIG. 3, the anode separator 14 of this embodiment is provided with a constricted portion 14g in the oxygen electrode lead-out region 10e so as to be convex toward the cathode separator 17 side.

[0025] In this embodiment, grooves may be provided on the surface of the anode separator 14 facing the cathode separator 17 in the oxygen electrode lead-side distribution region 10d and the oxygen electrode lead-out region 10e connected thereto.

[0026] Furthermore, to reduce electrical contact resistance, a conductive layer may be provided on the front and back surfaces of the anode separator 14 at a location corresponding to the water electrolysis region 10a. The conductive layer may be made of any conductive material, such as platinum.

[0027] [Cathode catalyst layer] The cathode catalyst layer 15 is a catalyst layer containing a catalyst, and the catalyst contained in the cathode catalyst layer 15 can be a known catalyst, such as platinum, platinum-coated titanium, platinum-supported carbon, palladium-supported carbon, cobalt glyoxime, nickel glyoxime, etc. The cathode catalyst layer 15 may contain an ionomer. The inclusion of an ionomer can improve coating properties. Examples of the ionomer that can be contained include ionomers made of perfluoro-based electrolytes, which are electrolytes used in solid polymer electrolyte membranes.

[0028] [Cathode gas diffusion layer] The cathode gas diffusion layer 16 is a gas diffusion layer disposed on the cathode side, and may be made of a material having gas permeability and conductivity, such as a porous material such as carbon cloth or carbon paper.

[0029] [Cathode separator] The cathode separator 17 is a member having flow paths 17a through which hydrogen generated by the reduction of hydrogen ions and water (produced water) accompanying the hydrogen ions as they permeate the solid polymer electrolyte membrane 11 arrive. In this embodiment, the cathode separator 17 is a plate-like member formed into a corrugated shape in the water electrolysis region 10a, with repeated projections and depressions, and the recesses 17c are arranged in contact with the cathode gas diffusion layer 16, thereby forming flow paths 17a for discharging hydrogen between the cathode gas diffusion layer 16 and the projections 17b. The cathode separator 17 can be produced by press-molding a titanium thin film, for example, and the thickness thereof is typically 0.1 mm to 0.2 mm, and the height of the projections and recesses is typically about 0.5 mm.

[0030] As shown in FIG. 1 and described above, the cathode separator 17 is provided with an oxygen electrode side inlet manifold (not shown) that overlaps with the oxygen electrode side inlet manifold 14d, an oxygen electrode side outlet manifold (not shown) that overlaps with the oxygen electrode side outlet manifold 14e, and a hydrogen electrode side outlet manifold (not shown) that overlaps with the hydrogen electrode side outlet manifold 14f.

[0031] To reduce electrical contact resistance, a conductive layer may be provided on the front and back surfaces of the cathode separator 17 at a location corresponding to the water electrolysis region 10a. The conductive layer may be made of any conductive material, such as platinum.

[0032] Frame The frame 18 is disposed between the anode separator 14 and the cathode separator 17 at the outer periphery of the water electrolysis cell 10, and functions as a sealing member that seals the inside of the cell and separates the oxygen electrode side from the hydrogen electrode side to form the necessary flow paths. Therefore, the frame 18 surrounds the water electrolysis region 10a, the oxygen electrode introduction region 10b, the oxygen electrode introduction side dispersion region 10c, the oxygen electrode outlet side dispersion region 10d, and the oxygen electrode outlet region 10e, and is disposed so as to be sandwiched between the anode separator 14 and the cathode separator 17. 3, the frame 18 is not sealed in that portion because it allows generated oxygen and residual water to flow from the water supply channel 14a of the anode separator 14 through the oxygen electrode outlet-side distribution region 10d and the oxygen electrode outlet region 10e to the oxygen electrode-side outlet manifold 14e. On the other hand, in the cross section of FIG. 3, it is sealed to block the flow of hydrogen from the channel 17a of the cathode separator 17 to the oxygen electrode-side inlet manifold 14e. In this way, the frame 18 adjusts its contact (seal) with the anode separator 14 and the cathode separator 17 to ensure appropriate fluid flow.

[0033] The frame 18 is made of a thermoplastic resin material that is electrically insulating, airtight, and has a relatively high melting point. Examples of such materials include engineering plastics, such as polyethylene naphthalate resin (PEN), polyphenylene sulfide resin (PPS), and polyphenylsulfone resin (PPSU). The thickness of the frame is not particularly limited, but is preferably 0.05 mm or more and 0.25 mm or less. Adhesives are placed on the front and back of the frame 18, and the anode separator 14 and cathode separator 17 parts that come into contact with these adhesives are adhered to each other.

[0034] 1.1.2. Layer composition of water electrolysis region 2, the layer structure of the water electrolysis region 10a is such that the anode comprises an anode catalyst layer 12, an anode gas diffusion layer 13, and an anode separator 14 stacked in this order from the solid polymer electrolyte membrane 11 side. On the other hand, the cathode comprises a cathode catalyst layer 15, a cathode gas diffusion layer 16, and a cathode separator 17 stacked in this order from the solid polymer electrolyte membrane 11 side. The anode separator 14 has a flow path (water supply flow path) 14a through which pure water and decomposed oxygen flow to be supplied to the anode gas diffusion layer 13. In this embodiment, the anode separator 14 is a plate-like member formed in a corrugated shape in the water electrolysis region 10a, with repeated projections and depressions, and the depressions 14c are disposed in contact with the anode gas diffusion layer 13, thereby forming the water supply flow path 14a between the anode gas diffusion layer 13 and the projections 14b. The cathode separator 17 has a flow path 17a through which hydrogen generated by the reduction of hydrogen ions and water (associated water) that accompanies the hydrogen ions as they pass through the solid polymer electrolyte membrane 11 reach. In this embodiment, the cathode separator 17 is a plate-like member formed in a corrugated shape in the water electrolysis region 10a, with repeated projections and depressions, and the depressions 17c are arranged in contact with the cathode gas diffusion layer 16, forming the flow path 17a for discharging hydrogen between the cathode gas diffusion layer 16 and the projections 17b.

[0035] 1.1.3. Configuration of other areas Other regions include the oxygen electrode inlet region 10b, the oxygen electrode inlet-side distribution region 10c, the oxygen electrode outlet-side distribution region 10d, the oxygen electrode outlet region 10e, and a hydrogen electrode outlet-side distribution region and a hydrogen electrode outlet region (not shown). Here, the oxygen electrode outlet-side distribution region 10d and the oxygen electrode outlet region 10e shown in Figures 1 and 3 will be used as examples.

[0036] The oxygen electrode outlet distribution region 10d and the oxygen electrode outlet region 10e are regions through which the oxygen produced in the water electrolysis region 10a and the remaining water pass before being discharged to the oxygen electrode side outlet manifold 14e. As can be seen from FIG. 3 , the oxygen electrode outlet-side distribution region 10d has end faces of a solid polymer electrolyte membrane 11, an anode catalyst layer 12, an anode gas diffusion layer 13, a cathode catalyst layer 15, and a cathode gas diffusion layer 16. The end face of the anode gas diffusion layer 13 is formed slightly recessed from the other end faces. A frame 18 is laminated on the anode catalyst layer 12 and extends from the end face of the anode gas diffusion layer 13. The frame 18 reaches into the oxygen electrode outlet region 10e and extends to the oxygen electrode outlet manifold 14e. In the oxygen electrode outlet-side distribution region 10d, the cathode separator 17 is bent in the thickness direction (the stacking direction of the layers) until it contacts the surface of the frame 18, sealing the hydrogen electrode side. In the oxygen electrode lead-out region 10e, a constricted portion 14g is formed so that the anode separator 14 is bent toward the frame 18, and the flow path is narrowed in the thickness direction. However, because generated oxygen and remaining water must flow through this portion, a flow path is formed at a predetermined interval that leads to the oxygen electrode-side outlet manifold 14e.

[0037] Although the fluid flows in different directions in the oxygen electrode inlet region 10b and the oxygen electrode inlet-side distribution region 10c, the oxygen electrode inlet region 10b can be considered to be the same as the oxygen electrode outlet region 10e, and the oxygen electrode inlet-side distribution region 10c can be considered to be the same as the oxygen electrode outlet-side distribution region 10d.

[0038] The hydrogen electrode outlet-side distribution region and the hydrogen electrode outlet region are regions in which flow paths are formed to guide hydrogen and produced water generated on the hydrogen electrode side from the water electrolysis region 10a to the hydrogen-side outlet manifold 14f. These regions can be configured in a manner in which the above-described oxygen electrode outlet-side distribution region 10d and oxygen electrode outlet region 10e are applied to the hydrogen electrode side.

[0039] 1.1.4. Effect etc. The water electrolysis cell 10 operates, for example, as follows. When pure water is supplied from the oxygen electrode side inlet manifold 14d, it passes through the oxygen electrode introduction region 10b and the oxygen electrode introduction side distribution region 10c and reaches the water electrolysis region 10a. In the water electrolysis region 10a, pure water (HO) supplied to the anode (oxygen evolving electrode) from the water supply channel 14a is converted into oxygen, electrons, and protons (H + ). At this time, the protons pass through the solid polymer electrolyte membrane 11 and move to the cathode catalyst layer 15. Meanwhile, the electrons separated in the anode catalyst layer 12 pass through an external circuit and reach the cathode catalyst layer 15. Then, the protons receive the electrons in the cathode catalyst layer 15, generating hydrogen (H2), which then reaches the cathode gas diffusion layer 16. In the cathode gas diffusion layer 16, produced water is present along with the generated hydrogen gas.

[0040] The hydrogen gas and produced water present in the cathode gas diffusion layer 16 reach the cathode separator 17, flow through the flow path 17a, pass through the hydrogen electrode outlet side distribution area and the hydrogen electrode outlet area (not shown), and are discharged from the hydrogen electrode side outlet manifold 14f (hydrogen electrode outlet hole).

[0041] On the other hand, oxygen generated in the anode catalyst layer 12 and unused residual water return to the anode separator 14, pass through the hydrogen supply flow channel 14a, pass through the oxygen electrode outlet-side distribution region 10d and the oxygen electrode outlet region 10e, and are discharged from the oxygen electrode outlet manifold 14e.

[0042] 1.2.Water electrolysis stack The water electrolysis stack 30 is a member formed by stacking a plurality of (approximately 50 to 400) of the above-described water electrolysis cells 10, and generates hydrogen and oxygen by passing electricity through the plurality of water electrolysis cells 10. An outline of the configuration is shown in Figure 4. The water electrolysis stack 30 includes a stack case 31, end plates 32, and a plurality of water electrolysis cells 10.

[0043] The stack case 31 is a housing that houses a plurality of stacked water electrolysis cells 10 and the biasing member 33. In this embodiment, the stack case 31 is a rectangular cylinder with one open end and the other closed end, and a plate-like piece protrudes along the edge of the opening to the opposite side to the opening, forming a flange 31a.

[0044] The end plate 32 is a plate-shaped member that closes the opening of the stack case 31 and has a manifold connection portion for the oxygen and hydrogen inlet / outlet portion. The end plate 32 is fixed to the stack case 31 with bolts, nuts, etc. at the overlapping portion with the flange 31a of the stack case 31 so as to cover the stack case 31. The stacked water electrolysis cells 10 are sandwiched at both ends in the stacking direction between the end plates 32 and the stack case 31. In this case, the portions of the stack case located at the ends in the stacking direction of the water electrolysis cells also function as end plates, so that the stack of the water electrolysis cells 10 is sandwiched at both ends in the stacking direction by the end plates.

[0045] The water electrolysis cell 10 is as described above. A plurality of such water electrolysis cells 10 are stacked. In this embodiment, as can be seen from Fig. 4, the water electrolysis cells 10 are stacked horizontally, and each water electrolysis cell 10 is arranged such that the direction in which the water supply channels 14a are aligned and the direction in which the channels 17a are aligned are vertical, as shown in Fig. 1. Additionally, the overlapping of the oxygen electrode side inlet manifolds 14d of the water electrolysis cells forms a flow path for supplying water, the overlapping of the oxygen electrode side outlet manifolds 14e forms a flow path for discharging oxygen and residual water, and the overlapping of the hydrogen electrode side outlet manifolds 14f forms a flow path for discharging hydrogen and produced water.

[0046] If necessary, a biasing member (not shown) may be provided to press the stack of water electrolysis cells in the stacking direction. The biasing member is housed inside the stack case 31 and applies a pressing force to the stack of water electrolysis cells 10 in the stacking direction. An example of the biasing member is a disc spring.

[0047] 2.2.Layer structure of water electrolysis cell As described above, the water electrolysis stack 30 is formed by stacking a plurality of water electrolysis cells 10. Fig. 5 shows a cross section of a portion of the water electrolysis region 10a of three of the stacked water electrolysis cells 10. Fig. 6 shows a cross section of a portion of the end (the oxygen electrode lead-out side distribution region 10d and the oxygen electrode lead-out region 10e) of three of the stacked water electrolysis cells.

[0048] 5 and 6 , when the water electrolysis cells 10 are stacked, the cathode separator 17 of one water electrolysis cell 10 overlaps with the anode separator 14 of the other adjacent water electrolysis cell 10. More specifically, the protrusion 17b of the cathode separator 17 of one water electrolysis cell 10 and the protrusion 14b of the anode separator 14 of the other water electrolysis cell 10 come into contact with each other and overlap with each other.

[0049] 6, an inter-cell seal member 33 is disposed between adjacent water electrolysis cells 10 at the ends of the water electrolysis cells 10 (throttled portions 14g in this embodiment). The inter-cell seal member 33 provides a seal to prevent leakage of fluid from each of the manifolds.

[0050] 2. Water electrolysis stack of the present disclosure 2.1.Form 1 Fig. 7 illustrates a water electrolysis stack 40, one embodiment of a water electrolysis stack according to the present disclosure. Fig. 7 is a view taken from the same perspective as Fig. 4. As can be seen from Fig. 7, the water electrolysis stack 40 according to embodiment 1 includes, in addition to the water electrolysis stack 30, one or more sealing-improving laminate members 41 laminated at each end of the stacking direction of the multiple water electrolysis cells 10. The water electrolysis stack 40 can be considered to be the same as the water electrolysis stack 30 except for the sealing-improving laminate members 41, and therefore the same reference numerals are used and their description will be omitted here.

[0051] 8 to 10 are diagrams illustrating the configuration of the sealing performance improving laminate member 41 included in this embodiment. FIG. 8 is a plan view of the sealing performance improving laminate member 41 (as viewed from the direction in which the lamination direction with the water electrolysis cell 10 faces the back / front of the page). FIG. 9 is a cross-section of the portion indicated by CC in FIG. 8. FIG. 10 is a cross-section of the portion indicated by DD in FIG. 8. As can be seen from FIGS. 8 to 10, the sealing performance improving laminate member 41 in this embodiment has a similar configuration to the water electrolysis cell 10 described above, and its external shape is generally the same as that of the water electrolysis cell 10. However, the sealing performance improving laminate member 41 is not intended for water electrolysis, and is configured so that feed water does not flow through its interior. The sealing performance improving laminated member 41 is made up of a plurality of layers, and has a core material 42 , a first exterior plate 43 , a second exterior plate 44 , and a frame 45 .

[0052] 2.1.1. Aspects of each layer The layers provided in the sealing property improving laminated member 41 have, for example, the following configurations.

[0053] [Core material] The core material 42 is a plate-shaped member disposed between the first exterior body 43 and the second exterior body 44, and serves as the core of the sealing performance improving laminated member 41. The material constituting the core material 42 is not particularly limited as long as it is conductive and has a certain level of strength and cushioning properties. In this embodiment, from these viewpoints, the above-described cathode gas diffusion layer 16 is laminated to form two layers. From the viewpoint of electrical conductivity and load transmission, the thickness of the core material 42 is preferably approximately the same as the thickness of the laminate disposed between the anode separator 14 and the cathode separator 17 in the water electrolysis cell 10.

[0054] [First exterior body] The first exterior body 43 is a plate-like member having a configuration similar to that of the above-described anode separator 14. Therefore, in this embodiment, the first exterior body 43 is a member in which the plate-like member is formed in a wavy shape in the region 41a where the core material 42 is arranged, so that recesses and projections are repeated, and the recesses 43c are arranged in contact with the core material 42, so that cavities 43a are formed between the core material 42 and the projections 43b. The first exterior body 43 can be produced by press-molding a titanium thin film, for example, in the same manner as the anode separator 14, and the thickness thereof can be set to 0.1 mm to 0.2 mm, and the height of the projections and recesses can be set to about 0.5 mm.

[0055] The first exterior housing 43 is provided with a first hole 43d corresponding to the oxygen electrode side inlet manifold 14d, a second hole 43e corresponding to the oxygen electrode side outlet manifold 14e, and a third hole 43f corresponding to the hydrogen electrode side outlet manifold 14f. When the sealing property improving laminate member 41 is laminated on the water electrolysis cell 10, these holes overlap with the corresponding manifolds.

[0056] Furthermore, as shown in FIG. 10, in this embodiment, first exterior body 43 is provided with a narrowed portion 43g that is convex toward frame 45.

[0057] Furthermore, as described above, the sealing property-improving laminated member 41 is not intended to perform water electrolysis and does not need to supply water to its interior. Therefore, it does not have regions corresponding to the oxygen electrode lead-out side distribution region 10d and the oxygen electrode lead-out region 10e continuous therewith, which were provided in the anode separator 14, and is sealed so as to be in contact with the frame 45.

[0058] [Second exterior body] The second exterior body 44 is a plate-like member having a configuration similar to that of the above-described cathode separator 17. Therefore, in this embodiment, the second exterior body 44 is a member in which the plate-like member is formed in a wavy shape in the region 41a where the core material 42 is arranged, and has repeated projections and depressions, and the depressions 44c are arranged in contact with the core material 42, thereby forming cavities 44a between the core material 42 and the projections 44b. Similar to the anode separator 14, the second exterior body 43 can be produced by press-molding a titanium thin film, for example, and the thickness thereof can be set to 0.1 mm to 0.2 mm, and the height of the irregularities can be set to about 0.5 mm.

[0059] The second exterior body 43 also has a first hole corresponding to the oxygen electrode side inlet manifold 14d, a second hole corresponding to the oxygen electrode side outlet manifold 14e, and a third hole corresponding to the hydrogen electrode side outlet manifold 14f (all not shown). These holes overlap with the corresponding manifolds when the sealing property improving laminate member 41 is laminated on the water electrolysis cell 10.

[0060] Furthermore, as described above, the sealing performance improving laminated member 41 is not intended to perform water electrolysis and does not need to supply water to its interior. Therefore, the laminated member 41 does not have a hydrogen electrode lead-side distribution region (not shown) and a hydrogen electrode lead-out region (not shown) continuous therewith, which are provided in the cathode separator 17, and is sealed so as to be in contact with the frame 45.

[0061] Frame The frame 45 is disposed between the first exterior body 43 and the second exterior body 44 at the outer periphery of the sealing property improving laminated member 41, and functions as a sealing member that seals the inside thereof. Therefore, the frame 45 is arranged and bonded to the outer periphery of the sealing property improving laminated member 41 so as to be sandwiched between the first exterior body 43 and the second exterior body 44 . In the cross section of Figure 10, for example, the frame 45 is sealed between the area 41a where the core material 42 is arranged and the second hole 43e, with the first outer body 43 in contact on one side and the second outer body 44 in contact on the other side.

[0062] The frame 45 is made of a thermoplastic resin material that is electrically insulating, airtight, and has a relatively high melting point. Examples of such materials include engineering plastics. Examples of engineering plastics include polyethylene naphthalate resin (PEN), polyphenylene sulfide resin (PPS), and polyphenylsulfone resin (PPSU). The thickness of the frame is not particularly limited, but is preferably 0.05 mm or more and 0.25 mm or less. The frame 45 has adhesive disposed on the front and back sides thereof, and is bonded to the parts of the first exterior body 43 and the second exterior body 44 that come into contact with this adhesive.

[0063] 2.1.2. Layer structure of the area where the core material is placed 9, the layer structure of region 41a where core material 42 is disposed is such that first exterior body 43 is disposed on one surface of core material 42 and second exterior body 44 is disposed on the other surface. A cavity 43a is formed between first exterior body 43 and core material 42, and a cavity 44a is formed between second exterior body 44 and core material 42.

[0064] 2.1.3. Configuration of other areas In other regions, as described above, the sealing property improving laminated member 41 is not intended for water electrolysis inside, and therefore there is no need to supply water to the inside. Therefore, as shown in FIG. 10 , the first exterior body 43 and the second exterior body 44 are sealed in contact with the frame 45.

[0065] 2.1.4. Effects, etc. As described above, in the water electrolysis stack 40 including the sealing property-improving laminated member 41, as described with reference to Fig. 16, the central portions of the water electrolysis cells arranged between the end plates bulge, causing significant warpage in the water electrolysis cell closest to the end plate, which may result in reduced sealing property at the end portions. In response to this issue, if the most warped portion is replaced with a sealing property-improving laminated member 41 that is not intended for water electrolysis and to which water for water electrolysis is not supplied, the number of water electrolysis cells that are significantly deformed (warped) can be reduced, thereby preventing a reduction in sealing property within the water electrolysis stack. Because a reduction in sealing property can be achieved, leakage can be prevented and the hydrogen pressure can be increased.

[0066] In the above description, one sealing performance improving laminate member 41 is disposed on each end of the water electrolysis cell 10 in the stacking direction, but this is not limited thereto, and it is also possible to dispose one on either end, or three or more sealing performance improving laminate members 41. In this case, since warping increases toward the end plates as described above, it is preferable to dispose the sealing performance improving laminate members 41 in positions close to the end plates.

[0067] 2.1.5. Variations The modified examples will be described below. Because the modified examples are modifications of the sealing performance improving laminated member 41, only the sealing performance improving laminated member 41 will be described, and descriptions of the other members will be omitted. As described above, the inside of the sealing performance improving laminate member 41 is sealed by the frame 45, and therefore the gas sealed in the cavities 14a and 17a may expand due to load or heat, and the resulting pressure may place a load on the sealing performance improving laminate member 41. For this reason, in this modified example, communication holes are provided that connect the cavities 14a and 17a to the outside. These communication holes allow the gas in the cavities 14a and 17a to escape, reducing the pressure (load).

[0068] 11 is a diagram showing Modification 1. In this modification, a notch 46 is provided as a communication hole in region 41a where the core material is arranged, and cavity 14a, cavity 17a communicate with the outside through this notch 46.

[0069] 12 is a diagram showing Modification 2. In this modification, a portion 47 where frame 45 is not bonded to second exterior body 44 is provided in a part of the surface of frame 45 that is in contact with second exterior body 44. This non-bonded portion 47 functions as a communication hole, connecting cavity 14a, cavity 17a with the outside.

[0070] 13 is a diagram showing Modification 3. In this modification, a hole 48 that communicates between the inside and outside of the sealing performance improving laminate member 41 is provided in a part of the frame 45. This hole 48 functions as a communication hole, and communicates between the cavity 14a, the cavity 17a and the outside.

[0071] 2.2.Form 2 Fig. 14 illustrates a water electrolysis stack 50, one embodiment of the water electrolysis stack according to the present disclosure. Fig. 14 is a view taken from the same perspective as Fig. 4. As can be seen from Fig. 14, the water electrolysis stack 50 according to embodiment 2 includes, in addition to the water electrolysis stack 30, sealing performance-improving laminated members 51 laminated between the water electrolysis cells 10. The water electrolysis stack 50 can be considered to be the same as the water electrolysis stack 30 except for the sealing performance-improving laminated members 51, and therefore the same reference numerals are used and their description will be omitted.

[0072] Fig. 15 is a diagram illustrating the configuration of the sealing performance improving laminated member 51 included in this embodiment. Fig. 15 is a plan view of the sealing performance improving laminated member 51 (as viewed from the direction in which the lamination direction with the water electrolysis cell 10 faces the back / front of the page). In this embodiment, the sealing performance improving laminated member 51 is a flat plate-shaped member.

[0073] The flat material constituting the sealing performance-improving laminated member 51 is not particularly limited as long as it is conductive and less likely to bend than the water electrolysis cell, but examples thereof include stainless steel. The thickness of the plate is also not particularly limited, but is preferably similar to that of the water electrolysis cell 10, e.g., 0.8 mm to 1.5 mm. The degree of bendability can be compared by a bending test. The sealing performance improving laminate member 51 also has a first hole 41d corresponding to the oxygen electrode side inlet manifold 14d, a second hole 51e corresponding to the oxygen electrode side outlet manifold 14e, and a third hole 51f corresponding to the hydrogen electrode side outlet manifold 14f. When the sealing performance improving laminate member 51 is laminated on the water electrolysis cell 10, these holes overlap with the corresponding manifolds.

[0074] The number and positions of the sealing performance improving laminated members 51 to be arranged are not particularly limited, but it is preferable that there are multiple sealing performance improving laminated members 51, and that the multiple sealing performance improving laminated members 51 are arranged at predetermined intervals.

[0075] As described above, with the water electrolysis stack 50 including the sealability-improving laminated member 51, as described with reference to Fig. 16, the central portions of the water electrolysis cells arranged between the end plates may bulge, causing significant warpage in the water electrolysis cell closest to the end plate, potentially reducing the sealability at the ends. In contrast, by using the sealability-improving laminated member 51, which is not intended for water electrolysis and to which water for water electrolysis is not supplied, and is therefore less likely to deform (high strength and rigidity), the number of water electrolysis cells that undergo significant deformation (warpage) can be reduced, thereby minimizing the reduction in sealability within the water electrolysis stack. Minimizing the reduction in sealability reduces leakage and also increases the hydrogen pressure. [Explanation of symbols]

[0076] 10...water electrolysis cell, 10a...water electrolysis region, 10b...oxygen electrode inlet region, 10c...oxygen electrode inlet side distribution region, 10d...oxygen electrode outlet side distribution region, 10e...oxygen electrode outlet region, 11...solid polymer electrolyte membrane (electrolyte membrane), 12...anode catalyst layer (catalyst layer), 13...anode gas diffusion layer (oxygen electrode gas diffusion layer), 14...anode separator (oxygen electrode separator), 14a...supply flow path, 14d...oxygen electrode side inlet manifold ( oxygen electrode inlet hole), 14e...oxygen electrode side outlet manifold (oxygen electrode outlet hole), 14f...hydrogen electrode side outlet manifold (hydrogen electrode outlet hole), 14g...throttling portion (structure for generating turbulence), 15...cathode catalyst layer (catalyst layer), 16...cathode gas diffusion layer (hydrogen electrode gas diffusion layer), 17...cathode separator (hydrogen electrode separator), 18...frame, 30, 40, 50...water electrolysis stack, 41, 51...laminated member for improving sealing performance

Claims

1. A water electrolysis stack configured by stacking a plurality of water electrolysis cells, which generates hydrogen by supplying water to the water electrolysis cells and applying electric power thereto, a sealing property-improving lamination member, which is a member that prevents the water from being introduced into the stacked water electrolysis cells, is laminated at a predetermined position of the stacked water electrolysis cells; Water electrolysis stack.

2. The sealing property improving laminated member is a first exterior body having the same shape as an anode separator of the water electrolysis cell; a second exterior body having the same shape as a cathode separator of the water electrolysis cell; a core material disposed between the first exterior body and the second exterior body; and a frame disposed between the first exterior body and the second exterior body to bond the first exterior body and the second exterior body together, The water electrolysis stack according to claim 1 .

3. The water electrolysis stack according to claim 2 , further comprising a communication hole that connects a space between the first exterior body and the second exterior body with the outside.

4. The water electrolysis stack according to claim 1 , wherein the sealing property improving laminated member is a plate-shaped member that is less likely to bend than the water electrolysis cells.

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