Cell stack and hydrogen production device

Abstract

This cell stack is provided to a hydrogen production device. The cell stack comprises a plurality of sub-stacks. Each of the plurality of sub-stacks comprises: a laminate in which a plurality of electrolytic cells are laminated; and current collector plates which are respectively disposed on two sides of the laminate. Each of the plurality of electrolytic cells has an anode, an ion exchange membrane, and a cathode.

Description

Cell stack and hydrogen production device

[0001] The present disclosure relates to a cell stack and a hydrogen production device. This application claims priority from Japanese Patent Application No. 2024-056507, filed March 29, 2024. The entire contents of the Japanese application are incorporated herein by reference.

[0002] Patent Document 1 discloses a water electrolysis device that generates hydrogen by electrolyzing an alkaline aqueous solution. The water electrolysis device includes a stack of electrolytic cells, which are electrolysis cells. Each electrochemical cell includes an anode, a cathode, an anion exchange membrane disposed between the anode and the cathode, an anode separator, and a cathode separator. The anode includes an anode catalyst and an anode power supply. The cathode includes a cathode catalyst and a cathode power supply. Each electrochemical cell for water electrolysis is configured by stacking the anode power supply, anode catalyst, an anion exchange membrane, cathode catalyst, and cathode power supply in this order.

[0003] The anode separator and cathode separator have the same structure. The anode separator will be described as a representative example. The anode separator has an anode supply manifold, an anode discharge manifold, and an anode flow path connecting the anode supply manifold and the anode discharge manifold. The anode flow path has a first communication path connected to the anode supply manifold, a second communication path connected to the anode discharge manifold, and an electrode passing flow path connecting the first communication path and the second communication path. The alkaline aqueous solution is supplied to the anode through the anode supply manifold, the first communication path, and the electrode passing flow path. The alkaline aqueous solution that has passed through the anode is discharged from the anode discharge manifold through the second communication path. The alkaline aqueous solution is also supplied to the cathode through the cathode supply manifold, the first communication path, and the electrode passing flow path. The alkaline aqueous solution that has passed through the cathode is discharged from the cathode discharge manifold through the second communication path.

[0004] In an electrochemical cell for water electrolysis, oxygen is generated at the anode and hydrogen is generated at the cathode by applying a voltage between the anode and the cathode while an alkaline aqueous solution is supplied to the anode and the cathode.

[0005] JP 2023-73782 A

[0006] The cell stack of the present disclosure is provided in a hydrogen production device. The cell stack includes a plurality of sub-stacks. Each of the sub-stacks includes a stack of a plurality of electrolysis cells and current collector plates disposed on both sides of the stack. Each of the electrolysis cells includes an anode, an ion exchange membrane, and a cathode.

[0007] 1 is a side view showing an outline of a hydrogen production apparatus according to an embodiment, and FIG. 2 is a partial cross-sectional view of an electrolysis cell provided in the hydrogen production apparatus according to an embodiment.

[0008] [Problem to be Solved by the Present Disclosure] It is desirable to uniformly flow a fluid through an electrolytic cell. To achieve uniform flow of the fluid, it is conceivable to use a thick supply pipe. Connecting a thick supply pipe to the electrolytic cell increases the size of the electrolytic cell.

[0009] When an electrolyte such as an alkaline aqueous solution is supplied to each electrolytic cell in parallel from a common supply source, and the anode flow path and cathode flow path are filled with the electrolyte, a self-discharge current flows through the electrolyte in the anode flow path and the cathode flow path in accordance with the potential difference between each electrolytic cell. This self-discharge current is called a shunt current. When a shunt current flows, the loss rate increases. The thicker the supply pipe, the more likely the shunt current is to increase. The larger the shunt current, the greater the loss rate. Furthermore, the loss rate increases as the number of electrolytic cells increases. When the number of electrolytic cells is increased to increase the amount of hydrogen produced, the loss rate increases.

[0010] One of the objects of the present disclosure is to provide a cell stack that can be made compact.

[0011] [Advantages of the Present Disclosure] The cell stack of the present disclosure can be made compact.

[0012] <Description of Embodiments of the Present Disclosure> First, embodiments of the present disclosure will be listed and described.

[0013] (1) A cell stack according to one aspect of the present disclosure is provided in a hydrogen production device. The cell stack includes a plurality of sub-stacks. Each of the sub-stacks includes a stack of a plurality of electrolysis cells and current collector plates disposed on both sides of the stack. Each of the electrolysis cells includes an anode, an ion exchange membrane, and a cathode.

[0014] When the total number of electrolysis cells included in the cell stack is constant, the cell stack (1) including multiple stacks can shorten the length of one fluid flow section compared to a cell stack with one stack. This allows the fluid to flow uniformly through the electrolysis cells without making the supply pipes excessively thick. The use of thin supply pipes makes it easier to make the cell stack compact.

[0015] The cell stack of (1) above can utilize a thin supply pipe as described above, and therefore tends to have a small shunt current when the supplied fluid is an electrolyte. When the total number of electrolysis cells provided in the cell stack is constant, the cell stack of (1) above can reduce the loss rate due to the shunt current compared to a cell stack with a single laminate, as will be explained in detail in the trial calculation example below. Therefore, the cell stack of (1) above can be used to construct a hydrogen production device that can efficiently produce hydrogen.

[0016] The cell stack of (1) above is excellent in manufacturability in that a plurality of sub-stacks can be manufactured in parallel and that the cell stack can be transported in units of sub-stacks.

[0017] (2) In the cell stack of (1) above, the number of the plurality of sub-stacks may be two.

[0018] The cell stack of (2) above has two laminates. When the total number of electrolysis cells included in the cell stack is constant, the cell stack of (2) above can reduce the loss rate compared to a cell stack with one laminate. The cell stack of (2) above can be made smaller than a cell stack with three or more cell stacks because the length along the stacking direction of the laminates can be made shorter.

[0019] (3) In the cell stack of (1) or (2) above, the number of the electrolysis cells in each of the sub-stacks may be 15 or more and 100 or less.

[0020] A cell stack in which the number of electrolytic cells in each substack is 15 or more can increase the amount of hydrogen produced. A cell stack in which the number of electrolytic cells in each substack is 100 or less can easily reduce the loss rate. By having 100 or less electrolytic cells in each substack, the length of the substack, and therefore the length of the stack in the cell stack, can be shortened.

[0021] (4) In any one of the cell stacks (1) to (3) above, the ion exchange membrane may be an anion exchange membrane.

[0022] The fluid supplied to the cell stack (4) equipped with an anion exchange membrane is an electrolyte such as an alkaline aqueous solution. On the other hand, the fluid supplied to the cell stack equipped with a proton exchange membrane is pure water. The alkaline aqueous solution promotes water electrolysis more than pure water. Therefore, the cell stack (4) can be used to construct a hydrogen production device that can produce hydrogen more efficiently than a cell stack equipped with a proton exchange membrane.

[0023] (5) The cell stack of any one of (1) to (4) above may include a supply / discharge plate and piping connected to the supply / discharge plate. The supply / discharge plate supplies a fluid containing water to the electrolysis cells and discharges gas produced by electrolysis of the water in the electrolysis cells. The piping includes a supply pipe through which the fluid supplied to the anode flows, a first discharge pipe through which oxygen gas from the anode flows, and a second discharge pipe through which hydrogen gas from the cathode flows.

[0024] The cell stack of (5) above is provided with a supply / discharge plate and a supply pipe, which makes it easy to supply fluid to the anode. The cell stack of (5) above is provided with a supply / discharge plate and a first discharge pipe, which makes it easy to discharge oxygen gas from the anode. The cell stack of (5) above is provided with a supply / discharge plate and a second discharge pipe, which makes it easy to discharge hydrogen gas from the cathode. If the cell stack of (5) above does not have a supply pipe for supplying fluid to the cathode, the amount of fluid present at the cathode is small, so it is easy to discharge low-humidity hydrogen gas from the second discharge pipe.

[0025] (6) The cell stack of (5) above may include a folding plate that folds back the fluid supplied from the supply / discharge plate and returns it to the supply / discharge plate.

[0026] Unlike the supply and discharge plates, the turn-back plates are not connected to pipes. Therefore, the cell stack of (6) above can reduce the number of pipes. The cell stack of (6) above can reduce the number of parts, thereby shortening the manufacturing time.

[0027] (7) In the cell stack of any one of (1) to (6), each of the electrolysis cells may include a separator disposed at both ends of the electrolysis cells. The separator includes a conductive plate. The conductive plate is formed of a composite material containing a conductive material and a resin.

[0028] When the total number of electrolysis cells in a cell stack is constant, the cell stack of (7) above can reduce the shunt current compared to a cell stack with one stack because it has multiple stacks.

[0029] (8) A hydrogen production device according to one aspect of the present disclosure includes a cell stack according to any one of (1) to (7) above.

[0030] When the total number of electrolysis cells in the cell stack is constant, the hydrogen production device of (8) can reduce the loss rate by including multiple stacks in the cell stack compared to when the number of stacks is one. Therefore, when the amount of hydrogen produced is constant, the hydrogen production device of (8) can reduce power consumption. Furthermore, when the amount of power consumed is constant, the hydrogen production device of (8) can increase the amount of hydrogen produced.

[0031] <Details of the Embodiments of the Present Disclosure> Specific examples of the cell stack and hydrogen production device of the present disclosure will be described below with reference to the drawings. The same reference numerals in the figures indicate the same objects. The shapes, sizes, positional relationships, etc. shown in each figure are expressed for the purpose of clarifying the description and do not necessarily represent the actual shapes, sizes, positional relationships, etc. The present invention is not limited to the configurations shown in the embodiments, but is defined by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

[0032] <<Embodiment>> [Hydrogen Production Apparatus] A hydrogen production apparatus 1 according to an embodiment will be described with reference to FIGS. 1 and 2. The hydrogen production apparatus 1 produces hydrogen by electrolyzing water contained in a supplied fluid. The hydrogen production apparatus 1 generates oxygen in addition to producing hydrogen through water electrolysis. The hydrogen production apparatus 1 can also be used as an apparatus for producing oxygen. The hydrogen production apparatus 1 includes a cell stack 2 having multiple electrolysis cells 20. One of the features of the hydrogen production apparatus 1 is that the cell stack 2 includes multiple sub-stacks 2s. In FIG. 1, only the exterior of the separator 3 of the electrolysis cell 20 is shown. For ease of explanation, the separator 3, first current collector plate 41, second current collector plate 42, supply / discharge plate 5, folding plate 6, first end plate 91, and second end plate 92 of the electrolysis cell 20 are hatched in FIG. 1.

[0033] [Cell Stack] The cell stack 2 of this example includes a plurality of substacks 2s, a first end plate 91, a second end plate 92, and a clamping mechanism 93. The cell stack 2 is configured by sandwiching the plurality of substacks 2s between the first end plate 91 and the second end plate 92 on both sides in the stacking direction of the plurality of substacks 2s, and clamping the first end plate 91 and the second end plate 92 with the clamping mechanism 93. The cell stack 2 has a plurality of fluid flow sections that are independent of each other. The cell stack 2 of this example further includes a supply / discharge plate 5 and a folding plate 6, which will be described later. In this example, one flow section is provided between one supply / discharge plate 5 and one folding plate 6.

[0034] (Substack) Each substack 2s is an assembly of a stack 2a in which a plurality of electrolysis cells 20 are stacked, and a first current collector 41 and a second current collector 42 arranged on both sides of the stack 2a in the stacking direction. That is, each substack 2s is a section sandwiched between the first current collector 41 and the second current collector 42. Each substack 2s forms one of the flow sections. The flow sections of each substack 2s are independent of each other.

[0035] The number of substacks 2s is not particularly limited and can be selected appropriately. The number of substacks 2s may be two or three or more. In this example, the number of substacks 2s is two. That is, the number of stacks 2a is two. When the total number of electrolysis cells 20 included in the cell stack 2 is constant, the cell stack 2 can reduce the shunt current compared to a cell stack with one stack 2a. Therefore, the cell stack 2 can reduce the loss rate due to the shunt current. A cell stack 2 with two substacks 2s has fewer stacks 2a, first current collector plates 41, second current collector plates 42, and supply / discharge plates 5 than a cell stack with three or more substacks 2s. This allows the length of the stacks 2a along the stacking direction to be shorter, making it easier to make the cell stack smaller. A cell stack 2 with two substacks 2s has fewer piping 7, as described below, compared to a cell stack with three or more substacks 2s, and therefore reduces the manufacturing time.

[0036] The number of electrolytic cells 20 in each substack 2s is not particularly limited and can be selected appropriately. The greater the number of electrolytic cells 20 in each substack 2s, the greater the amount of hydrogen produced. However, the greater the number of electrolytic cells 20 in a substack 2s, the greater the loss rate due to shunt current. The number of electrolytic cells 20 in each substack 2s is, for example, 15 to 100. A cell stack 2 in which the number of electrolytic cells 20 in each substack 2s is 15 or more can increase the amount of hydrogen produced. A cell stack 2 in which the number of electrolytic cells 20 in each substack 2s is 100 or less can reduce the loss rate. Furthermore, a cell stack 2 in which the number of electrolytic cells 20 in each substack 2s is 100 or less can easily reduce the length of the substacks 2s, and therefore the length of the stack 2a in the cell stack 2, along the stacking direction, is likely to be short, and therefore can easily be made compact. The number of electrolytic cells 20 in each substack 2s may be 30 to 80 or 40 to 60.

[0037] <Electrolytic Cell> As shown in FIG. 2, each electrolytic cell 20 includes an ion exchange membrane 21, an anode 22, and a cathode 23.

[0038] The ion exchange membrane 21 is disposed between the anode 22 and the cathode 23. The ion exchange membrane 21 may be a known anion exchange membrane (AEM) or proton exchange membrane (PEM). That is, the hydrogen production device 1 is an AEM-type or PEM-type hydrogen production device. The ion exchange membrane 21 in this example is an anion exchange membrane. That is, the hydrogen production device 1 is an AEM-type hydrogen production device. The fluid supplied to the cell stack 2 of this example equipped with an anion exchange membrane is an electrolyte solution such as an alkaline aqueous solution. Unlike this example, the fluid supplied to the cell stack equipped with a proton exchange membrane is pure water. The alkaline aqueous solution promotes water electrolysis more rapidly than pure water. Therefore, the cell stack 2 of this example can be used to construct a hydrogen production device 1 that can produce hydrogen more efficiently than a cell stack equipped with a proton exchange membrane.

[0039] The anode 22 includes an anode catalyst 221 and an anode diffusion layer 222. The cathode 23 includes a cathode catalyst 231 and a cathode diffusion layer 232. Known materials can be used for the anode catalyst 221, anode diffusion layer 222, cathode catalyst 231, and cathode diffusion layer 232. Each electrolysis cell 20 is configured by laminating the anode diffusion layer 222, anode catalyst 221, ion exchange membrane 21, cathode catalyst 231, and cathode diffusion layer 232 in this order. The stack 2 a may be a catalyst coated membrane (CCM) in which the anode catalyst 221, the ion exchange membrane 21, and the cathode catalyst 231 are bonded together to form an integrated structure, or a membrane electrode assembly (MEA) in which the anode diffusion layer 222, the anode catalyst 221, the ion exchange membrane 21, the cathode catalyst 231, and the cathode diffusion layer 232 are bonded together to form an integrated structure. All of the electrolysis cells 20 in each stack 2 a are electrically connected in series.

[0040] As shown in FIG. 2 , each electrolytic cell 20 includes separators 3 disposed at both ends of the electrolytic cell 20. That is, the separators 3 are disposed on both sides of an assembly in which the anode 22, the ion exchange membrane 21, and the cathode 23 are stacked. The separators 3 separate adjacent assemblies. When the first current collector 41 is the cathode, the separators 3 are disposed between adjacent assemblies, between the cathode 23 located at one end of the stacking direction of the laminate 2a and the first current collector 41, and between the anode 22 located at the other end of the stacking direction of the laminate 2a and the second current collector 42. One separator 3 is disposed between each of the assemblies. One assembly is provided between adjacent separators 3. At the intermediate position in the stacking direction of the laminate 2a, the anode 22, the ion exchange membrane 21, the cathode 23, and the separator 3 are repeatedly stacked in this order.

[0041] The separator 3 at the end adjacent to the first current collector 41 of one substack 2s arranged on the right side in Fig. 1, the separator 3 at the end adjacent to the second current collector 42 of one substack 2s, and the intermediate separator 3 located between these end separators 3 all have the same configuration. The separator 3 at the end adjacent to the first current collector 41 of the other substack 2s arranged on the left side in Fig. 1, the separator 3 at the end adjacent to the second current collector 42 of the other substack 2s, and the intermediate separator 3 located between these end separators 3 all have the same configuration.

[0042] The separator 3 may be composed of a conductive plate and a frame that supports the outer peripheral edge of the conductive plate, or may be composed of only the conductive plate. Although not shown in the figure, the separator 3 in this example is composed of a conductive plate and a frame.

[0043] The conductive plate may be formed of, for example, a first conductive material or a composite material. The conductive plate may be a coated conductive plate. The coated conductive plate includes a substrate and one or more coating layers covering the surface of the substrate. The substrate is formed of a first conductive material. The coating layer is formed of a second conductive material. The composite material includes a first conductive material and a resin. The first conductive material may be a metal or a non-metal. The metal may be, for example, one or more selected from the group consisting of iron alloys, titanium, titanium alloys, copper, copper alloys, nickel, nickel alloys, aluminum, aluminum alloys, and zinc. The iron alloy may be, for example, steel. The steel may be various steels such as stainless steel, silicon chromium steel, or carbon steel. The non-metal may be a carbon material or a conductive ceramic. The carbon material may be, for example, graphite, carbon black, or diamond-like carbon. The second conductive material may be, for example, a material that has better oxidation resistance to an electrolyte than the first conductive material. The second conductive material is, for example, one or more metals selected from the group consisting of platinum group metals, gold, silver, and nickel. The resin in the composite material is, for example, one selected from the group consisting of polyethylene resin, polypropylene resin, polytetrafluoroethylene resin, perfluoroalkoxyalkane resin, perfluoroethylenepropene copolymer, and polyphenylene sulfide resin.

[0044] When the conductive plate of this example is formed of a composite material containing a carbon material and a resin, the cell stack 2 of this example can reduce the shunt current, thereby reducing oxidation of the carbon material due to the shunt current. Therefore, the cell stack 2 of this example may use a separator 3 having a conductive plate made of a composite material containing a carbon material.

[0045] The frame is formed of a resin. The resin forming the frame is, for example, a resin having electrical insulation properties. An electrically insulating resin is a resin that has electrical insulation properties against an electrolyte solution. By forming the frame of a resin, the outer peripheral surface of the laminate 2a is also formed of a resin. Therefore, the electrical insulation of the laminate 2a against the rod 94 described below is likely to be high. The frame may be formed of a resin that has at least one of alkali resistance and heat resistance in addition to electrical insulation properties. An alkali-resistant resin is a resin that is resistant to an electrolyte solution with a pH of 8 or higher. A heat-resistant resin is a resin that is heat-resistant to temperatures of 80°C or lower. The resin may also be a resin that is resistant to temperatures of 50°C or higher. The resin contained in the frame is, for example, one selected from the group consisting of vinyl chloride resin, polypropylene resin, polyethylene resin, fluororesin, epoxy resin, acrylonitrile-butadiene-styrene resin, vinylidene chloride resin, polyamide resin, polyester resin, polystyrene resin, acrylic resin, polyvinyl alcohol resin, diacetate resin, triacetate resin, polyphenylsulfone resin, and polycarbonate resin.

[0046] Although not shown, the separator 3 has a first supply manifold, a first supply slit, a first exhaust manifold, a first exhaust slit, a second exhaust manifold, a second exhaust slit, and a seal groove. When the separator 3 is composed of a conductive plate and a frame, as in this example, these manifolds and slits are provided in the frame. When the separator 3 is composed of only a conductive plate, as in this example, these manifolds and slits are provided in the conductive plate.

[0047] The first supply manifold is a supply port for fluid to the stack 2a. The first supply manifold is a through hole that penetrates the first and second main surfaces of the frame. The first main surface of the frame faces the same direction as the first main surface of the conductive plate. The first main surface of the conductive plate faces the anode 22. The second main surface of the frame is the surface opposite to the first main surface of the frame and faces the same direction as the second main surface of the conductive plate. The second main surface of the conductive plate is the surface opposite to the first main surface of the conductive plate and faces the cathode 23.

[0048] The first supply slit is a flow path for circulating the fluid supplied from the first supply manifold. The first supply slit is a flow path for guiding the fluid from the first supply manifold to the inner peripheral edge of the frame. The first supply slit is a groove having a bottom surface. The first supply slit is provided on the first main surface of the frame so as to connect the first supply manifold and the inner peripheral edge of the frame.

[0049] The first exhaust manifold is an outlet for a first fluid, which includes oxygen gas generated by electrolysis of water, as described below. The first exhaust manifold is a through-hole that penetrates the first main surface and the second main surface of the frame.

[0050] The first discharge slit is a flow path that allows the first fluid to flow toward the first discharge manifold. The first discharge slit is a flow path that guides the first fluid from the inner peripheral edge of the frame to the first discharge manifold. The first discharge slit is a groove having a bottom surface. The first discharge slit is provided on the first main surface of the frame so as to connect the inner peripheral edge of the frame and the first discharge manifold.

[0051] The second exhaust manifold is an outlet for the second fluid, which includes hydrogen gas produced by electrolysis of water, and is a through-hole that penetrates the first main surface and the second main surface of the frame.

[0052] The second discharge slit is a flow path that allows the second fluid to flow toward the second discharge manifold. The second discharge slit is a flow path that guides the second fluid from the inner peripheral edge of the frame to the second discharge manifold. The second discharge slit is a groove having a bottom surface. The second discharge slit is provided on the second main surface of the frame so as to connect the inner peripheral edge of the frame and the second discharge manifold.

[0053] Unlike this example, when the separator 3 is made of a conductive plate, i.e., when it does not have a frame body, each slit is provided on the first main surface or the second main surface of the conductive plate so as to connect each manifold to an area of ​​the conductive plate that overlaps with the anode catalyst 221 or the cathode catalyst 231.

[0054] The seal groove is provided near the outer peripheral edge of at least one of the first and second main surfaces of the frame. The seal groove is provided in an annular shape so as to surround all of the manifolds and all of the slits. Each manifold and each slit is located in the area between the inner peripheral edge of the seal groove and the inner peripheral edge of the frame. A seal member is arranged in the seal groove. The seal member prevents fluid from leaking outside the stack 2a. The seal member is, for example, an annular elastic member.

[0055] In this example, the frame does not have a second supply manifold and a second supply slit, but may have a second supply manifold and a second supply slit. The second supply manifold is a fluid supply port. The second supply manifold is a through hole penetrating the first main surface and the second main surface of the frame. The second supply slit is a flow path for circulating the fluid supplied from the second supply manifold. The fluid supplied from the second supply manifold is the same fluid as the fluid supplied from the first supply manifold. The second supply slit is a flow path for guiding the fluid from the second supply manifold to the inner peripheral edge of the frame. The second supply slit is a groove having a bottom surface. The second supply slit is provided on the second main surface of the frame so as to connect the second supply manifold and the inner peripheral edge of the frame.

[0056] Unlike the present example, when the separator 3 is composed of a conductive plate, i.e., when a frame is not provided, each electrolysis cell 20 may include a frame-shaped insulating member that insulates between the conductive plate and the ion exchange membrane 21. The insulating member prevents direct contact between the conductive plate and the ion exchange membrane 21 and also functions to mechanically protect the ion exchange membrane 21. The insulating member may be formed of rubber or resin that has at least one of alkali resistance and heat resistance in addition to electrical insulation. An alkali-resistant rubber or resin is a rubber or resin that is resistant to an electrolytic solution with a pH of 8 or higher. A heat-resistant rubber or resin is a rubber or resin that is heat-resistant to temperatures of 80°C or lower.

[0057] Examples of the rubber include natural rubber, styrene-butadiene rubber, chloroprene rubber, butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, fluororubber, isobutylene-isoprene rubber, urethane rubber, and chlorosulfonated polyethylene rubber. For the resin forming the insulating member, see the description of the resin forming the frame of the separator 3. Other examples of the resin forming the insulating member include polyamide-imide resin, polyisobutylene resin, polyoxymethylene resin, polyphenol resin, polyethylene terephthalate resin, polytetrafluoroethylene resin, polyvinyl acetate resin, polyacetal resin, furan resin, polyurethane resin, melamine resin, polyether ether ketone, diallyl phthalate resin, unsaturated polyester resin, ethylene-vinyl acetate copolymer resin, polymethylpentene resin, cellulose acetate, and nylon resin.

[0058] <First Current Collector Plate and Second Current Collector Plate> The first current collector plate 41 and the second current collector plate 42 cause water electrolysis, as described below, when a voltage is applied between the two current collector plates 41, 42 from a power source (not shown). In one substack 2s located on the right side in FIG. 1 , the first current collector plate 41 is disposed between the laminate 2a and the first end plate 91, and the second current collector plate 42 is disposed between the laminate 2a and the folding plate 6. In the other substack 2s located on the left side in FIG. 1 , the second current collector plate 42 is disposed between the laminate 2a and the second end plate 92, and the first current collector plate 41 is disposed between the laminate 2a and the folding plate 6. Each of the first current collector plates 41 and each of the second current collector plates 42 is formed of a metal. The metal forming each of the first current collector plates 41 and each of the second current collector plates 42 is, for example, copper or a copper alloy.

[0059] (Supply / Discharge Plate) The supply / discharge plate 5 supplies fluid to the plurality of electrolytic cells 20 and discharges fluid from the plurality of electrolytic cells 20. For this purpose, the supply / discharge plate 5 is connected to a pipe 7, which will be described later. The supplied fluid is a fluid containing water, and in this example, is an electrolytic solution such as an alkaline aqueous solution. The discharged fluid is the first fluid and the second fluid.

[0060] In this example, the supply and discharge plate 5 is arranged between the substack 2s and the first end plate 91, and between the substack 2s and the second end plate 92. In this example, the supply and discharge plate 5 is not arranged between adjacent substacks 2s. In this example, a folding plate 6, which will be described later, is arranged between adjacent substacks 2s. One supply and discharge plate 5 is adjacent to the first current collector plate 41 and the first end plate 91. The other supply and discharge plate 5 is adjacent to the second current collector plate 42 and the second end plate 92. The folding plate 6 is adjacent to the first current collector plate 41 and the second current collector plate 42. In the cell stack 2 of this example, the first end plate 91, supply and discharge plate 5, substack 2s, folding plate 6, substack 2s, supply and discharge plate 5, and second end plate 92 are arranged in this order.

[0061] Although not shown, the supply / discharge plate 5 in this example has first supply communication holes, first discharge communication holes, and second discharge communication holes that communicate with the first supply manifold, the first discharge manifold, and the second discharge manifold, respectively. These communication holes penetrate the first and second main surfaces of the supply / discharge plate 5. The first main surface of the supply / discharge plate 5 in each substack 2s is the surface that faces the substack 2s. The second main surface of the supply / discharge plate 5 in one substack 2s is the surface opposite the first main surface and faces the first end plate 91. The second main surface of the supply / discharge plate 5 in the other substack 2s is the surface opposite the first main surface and faces the second end plate 92.

[0062] In this example, the supply / discharge plate 5 does not have a second supply passage communicating with the second supply manifold because the separator 3 does not have a second supply manifold. Unlike this example, if the separator 3 has a second supply manifold, the supply / discharge plate 5 may have a second supply passage. The second supply passage penetrates the first main surface and the second main surface of the supply / discharge plate 5.

[0063] The material of the supply / discharge plate 5 is resin. The resin forming the supply / discharge plate 5 is an electrically insulating resin. A supply / discharge plate 5 formed from such a resin is likely to have high electrical insulation with respect to the first end plate 91 and the second end plate 92. The resin forming the supply / discharge plate 5 may be formed from a resin that has at least one of alkali resistance and heat resistance in addition to electrical insulation. For the resin forming the supply / discharge plate 5, refer to the description of the resin forming the frame of the separator 3. The resin forming the supply / discharge plate 5 may be the same as or different from the resin forming the frame of the separator 3.

[0064] (Folding Plate) The folding plate 6 folds the fluid supplied from the supply / discharge plate 5 back to the supply / discharge plate 5. The piping 7, which will be described later, is not connected to the folding plate 6. The folding plate 6 is not the supply / discharge plate 5 that supplies the fluid and discharges the gas generated by the electrolysis of water contained in the fluid. The folding plate 6 does not have a hole through which the fluid is supplied from outside the cell stack 2, or a hole through which the gas and fluid are discharged to outside the cell stack 2. In this example, one folding plate 6 is disposed between adjacent substacks 2s. The folding plate 6 has a first main surface and a second main surface. The first main surface is a surface facing the second current collector plate 42 of one of the substacks 2s. The second main surface is a surface opposite to the first main surface and facing the first current collector plate 41 of the other substack 2s. The first and second main surfaces each have a flow path that guides the first fluid to the first discharge manifold or a flow path that guides the second fluid to the second discharge manifold. The folding plate 6 may include a conductive plate (not shown) and a frame body, similar to the separator 3. The flow paths (not shown) are provided on the first and second main surfaces of the frame body.

[0065] The resin forming the frame of the folding plate 6 is an electrically insulating resin. This tends to increase the electrical insulation of the frame of the folding plate 6 against the first current collector plate 41 and the second current collector plate 42. The resin forming the frame of the folding plate 6 may be formed from a resin that is electrically insulating and has at least one of alkali resistance and heat resistance. For the resin forming the frame of the folding plate 6, refer to the description of the resin forming the frame of the separator 3. The resin forming the frame of the folding plate 6 may be the same as or different from the resin forming the supply / discharge plate 5. Unlike this example, the folding plate 6 may not have a conductive plate and may be formed from a resin.

[0066] (Piping) The cell stack 2 includes a distribution system, which includes a pipe 7 and a pump (not shown).

[0067] The piping 7 includes a supply pipe connecting a supply source (not shown) to the cell stack 2, and a discharge pipe connecting the cell stack 2 to a storage tank (not shown). The supply source has a first supply source that stores a fluid. In this example, the supply source does not have a second supply source that stores a fluid, but may further have a second supply source. The storage tank has a first storage tank that stores the generated oxygen gas and a second storage tank that stores the generated hydrogen gas.

[0068] The supply pipes in this example include a first supply pipe 71 but no second supply pipe. The first supply pipe 71 carries a fluid supplied to the anode 22. The first supply pipe 71 passes through first supply holes in a first end plate 91 and a second end plate 92 (described later) and connects a first supply source to the first supply hole in the supply / discharge plate 5. The second supply pipe carries a fluid supplied to the cathode 23. The second supply pipe passes through second supply holes in the first end plate 91 and the second end plate 92 and connects a second supply source to the second supply hole in the supply / discharge plate 5. Each second supply hole communicates with the second supply hole in the supply / discharge plate 5. A second supply pipe is inserted through each second supply hole. In this example, the separator 3 does not have a second supply manifold, and the supply / discharge plate 5 does not have a second supply hole. Therefore, neither first end plate 91 nor second end plate 92 has a second supply passage, and therefore the supply pipe does not have a second supply pipe. However, if separator 3 has a second supply manifold and supply / discharge plate 5 has a second supply passage, the supply pipe may have a second supply pipe.

[0069] The discharge pipes include a first discharge pipe 72 and a second discharge pipe 73. For convenience of explanation, FIG. 1 shows the first discharge pipe 72 and the second discharge pipe 73 arranged in parallel in the up-down direction, but the first discharge pipe 72 and the second discharge pipe 73 are actually arranged in parallel in the depth direction of the paper in FIG. 1 . The first fluid flows through the first discharge pipe 72. The first discharge pipe 72 passes through first discharge communication holes in a first end plate 91 and a second end plate 92 (described later) to connect the first discharge communication hole in the supply / discharge plate 5 to the first storage tank. The second discharge pipe 73 passes through second discharge communication holes in the first end plate 91 and the second end plate 92 (described later) to connect the second discharge communication hole in the supply / discharge plate 5 to the second storage tank.

[0070] The connection points of the first supply pipe 71, the first discharge pipe 72, and the second discharge pipe 73 with the supply / discharge plate 5 may be formed as cylindrical portions that are integrated into the supply / discharge plate 5 in advance. In a structure in which separately prepared piping is connected to this cylindrical portion, it is easy for an operator to handle long piping, and the connection work is therefore easy.

[0071] The pump pressure-feeds the fluid to the plurality of electrolysis cells 20. The pump is provided midway along the first supply pipe 71.

[0072] (First End Plate / Second End Plate) The first end plate 91 and the second end plate 92 sandwich the multiple substacks 2s from the outside of the substacks 2s on both ends. The first end plate 91 and the second end plate 92 are made of metal. The first end plate 91 and the second end plate 92 are made of metal and have higher rigidity than end plates made of resin. This makes it easier to maintain the clamped state of the multiple stacks 2a, and therefore the multiple substacks 2s, for a long period of time. The metal forming the first end plate 91 and the second end plate 92 is, for example, steel or nickel. The steel may be various types of steel, such as stainless steel or carbon steel.

[0073] Although not shown, the first end plate 91 and the second end plate 92 in this example have first supply communication holes, first discharge communication holes, and second discharge communication holes. The first supply communication holes, first discharge communication holes, and second discharge communication holes penetrate the first and second main surfaces of each end plate 91, 92. The first supply communication holes of each end plate 91, 92 communicate with the first supply communication holes of the supply / discharge plate 5. The first supply pipes 71 are inserted through the first supply communication holes of each end plate 91, 92. The first discharge communication holes of each end plate 91, 92 communicate with the first discharge communication holes of the supply / discharge plate 5. The first discharge pipes 72 are inserted through the first discharge communication holes of each end plate 91, 92. The second discharge communication holes of each end plate 91, 92 communicate with the second discharge communication holes of the supply / discharge plate 5. The second discharge pipe 73 is inserted through the second discharge communication hole of each end plate 91, 92.

[0074] (Clamping Mechanism) The clamping mechanism 93 clamps the first end plate 91 and the second end plate 92 toward each other. Clamping the first end plate 91 and the second end plate 92 by the clamping mechanism 93 maintains the stacked state of the multiple electrolysis cells 20 and the stacked state of the multiple substacks 2s. The clamping mechanism 93 in this example includes multiple rods 94 and, although not shown, nuts attached to both ends of each rod 94. Tightening both nuts narrows the gap between the first end plate 91 and the second end plate 92. Each rod 94 penetrates the first end plate 91 and the second end plate 92. In this example, each rod 94 does not penetrate any components disposed between the first end plate 91 and the second end plate 92. Unlike this example, each rod 94 may penetrate at least one of the components disposed between the first end plate 91 and the second end plate 92. In this case, the size of the member through which the rod 94 passes, as viewed from the stacking direction of the stack 2a, is larger than the size of the member that the rod 94 does not pass through, as viewed from the stacking direction of the stack 2a. Each rod 94 and each nut is made of metal. The metal forming each rod 94 and each nut is, for example, steel or titanium. The steel may be any of various types, such as stainless steel.

[0075] [Fluid] The fluid in this example is an electrolyte such as an alkaline aqueous solution. The alkaline aqueous solution may be, for example, potassium hydroxide (KOH) or sodium bicarbonate (NaHCO ３ ) dissolved in water. When the fluid is an alkaline aqueous solution, the electrolysis of water is promoted compared to when the fluid supplied to the electrolysis cell 20 is pure water. The concentration of the electrolyte in the alkaline aqueous solution is, for example, 0.1 mass% or more and 10 mass% or less, when the entire alkaline aqueous solution is taken as 100 mass%. The concentration of the electrolyte in the alkaline aqueous solution may be 0.5 mass% or more and 8 mass% or less, or 1.0 mass% or more and 6.0 mass% or less. The pH value of the alkaline aqueous solution is, for example, 8 or more and 15 or less. The pH value of the alkaline aqueous solution may be 10 or more and 14.3 or less. The electrical conductivity of the alkaline aqueous solution is, for example, 0.003 mS / cm or more and 500 mS / cm or less. The electrical conductivity of the alkaline aqueous solution may be 0.01 mS / cm or more and 400 mS / cm or less, or 0.02 mS / cm or more and 300 mS / cm or less.

[0076] [Electrolysis] An electrolyte is supplied to each anode 22 through the first supply pipe 71. In this example, no electrolyte is supplied to each cathode 23 from the first supply pipe 71. Water moves from each anode 22 side to each cathode 23 through the ion exchange membrane 21. When a voltage is applied between the first current collector plate 41 and the second current collector plate 42 by a power source (not shown), the following electrochemical reaction occurs: Anode: 4OH － →2H ２ O+O ２ +4e － Cathode: 4H ２ O+4e － →2H ２ +4OH －

[0077] At each anode 22, hydroxide ions (OH －) generates water and oxygen and releases electrons. At each cathode 23, water and electrons combine to generate hydrogen and hydroxide ions. In this example, the ion exchange membrane 21 is an anion exchange membrane, so the generated hydroxide ions pass through the ion exchange membrane 21 and move from the cathode 23 to the anode 22. Oxygen gas generated at the anode 22 is discharged from the cell stack 2 through the first discharge pipe 72. Hydrogen gas generated at the cathode 23 is discharged from the cell stack 2 through the second discharge pipe 73. The fluid discharged from the first discharge pipe 72 may contain water generated at the anode 22 and unreacted electrolyte solution supplied to the anode 22. The fluid discharged from the second discharge pipe 73 may contain unreacted water that has moved to the cathode 23.

[0078] Unlike this example, the cell stack 2 may be any of the following forms (A) to (E): (A) Neither supply / discharge plate 5 nor the folding plate 6 is provided. (B) Both supply / discharge plates 5 are provided, but the folding plate 6 is not provided. (C) Neither supply / discharge plate 5 is provided, but the folding plate 6 is provided. (D) One supply / discharge plate 5 is provided, but the other supply / discharge plate 5 and folding plate 6 are not provided. (E) One supply / discharge plate 5 and folding plate 6 are provided, but the other supply / discharge plate 5 is not provided.

[0079] In the case of the above-mentioned configuration (A), the separator 3 at the end adjacent to the first current collector 41 of one substack 2s (right side in FIG. 1 ) (hereinafter referred to as the first separator 3) and the separator 3 at the end adjacent to the second current collector 42 of the other substack 2s (left side in FIG. 1 ) (hereinafter referred to as the fourth separator 3) also serve as supply and discharge plates. The separator 3 at the end adjacent to the second current collector 42 of one substack 2s (hereinafter referred to as the second separator 3) and the separator 3 at the end adjacent to the first current collector 41 of the other substack 2s (hereinafter referred to as the third separator 3) also serve as folding plates. Pipes 7 are directly connected to the frame of the first separator 3 and the frame of the fourth separator 3. That is, the pipes 71, 72, and 73 may be directly connected to the frame of the first separator 3 and the frame of the fourth separator 3 so that the inside of the first supply pipe 71 is in communication with the first supply manifold, the inside of the first discharge pipe 72 is in communication with the first discharge manifold, and the inside of the second discharge pipe 73 is in communication with the second discharge manifold. The pipes 71, 72, and 73 may be welded to the frame using, for example, an organic solvent. The second separator 3 and the third separator 3 are provided with flow paths that prevent the fluid supplied to each substack 2s from crossing between the substacks 2s and that turn back toward each end plate 91, 92. Between the first end plate 91 and the first current collector 41, between the second end plate 92 and the second current collector 42, and between the first current collector 41 and the second current collector 42 of adjacent substacks 2s, it is preferable to provide insulating material that electrically insulates the first end plate 91 and the first current collector 41, the second end plate 92 and the second current collector 42, and the first current collector 41 and the second current collector 42 of adjacent substacks 2s.

[0080] In the case of the above-mentioned form (B), the second separator 3 and the third separator 3 also serve as folding plates. The second separator 3 and the third separator 3 are provided with a flow path that prevents the fluid supplied to each substack 2s from passing between the substacks 2s and folds back toward each end plate 91, 92. The above-mentioned insulating material may be provided between the first current collector plate 41 and the second current collector plate 42 of adjacent substacks 2s.

[0081] In the case of the above-mentioned form (C), the first separator 3 and the fourth separator 3 also serve as supply and discharge plates. The piping 7 is directly connected to the frame of the first separator 3 and the frame of the fourth separator 3. The above-mentioned insulating material may be provided between the first end plate 91 and the first current collector plate 41, and between the second end plate 92 and the second current collector plate 42.

[0082] In the case of the above-mentioned configuration (D), the first separator 3 or the fourth separator 3 also serves as a supply / discharge plate, and the second separator 3 and the third separator 3 also serve as folding plates. The piping 7 is directly connected to the frame of the first separator 3 or the frame of the fourth separator 3. The second separator 3 and the third separator 3 are provided with flow paths that prevent the fluid supplied to each substack 2s from crossing between the substacks 2s and that fold back toward each end plate 91, 92. The above-mentioned insulating material may be provided between the first end plate 91 and the first current collector plate 41 or between the second end plate 92 and the second current collector plate 42, and between the first current collector plate 41 and the second current collector plate 42 of adjacent substacks 2s.

[0083] In the case of the above-mentioned form (E), the first separator 3 or the fourth separator 3 also serves as a supply / discharge plate. The pipe 7 is directly connected to the frame of the first separator 3 or the frame of the fourth separator 3. The above-mentioned insulating material may be provided between the first end plate 91 and the first current collector plate 41 or between the second end plate 92 and the second current collector plate 42.

[0084] <<Experimental Calculation Example>> In the exemplary calculation, differences in the loss rate based on the shunt current due to differences in catalyst area, the number of stacked electrolysis cells, and the electrical resistance value of the first supply slit were investigated.

[0085] [Model No. 1 to Model No. 25] The catalyst area, current density, number of stacked electrolytic cells, and electrical resistance value of the first supply slit for each model are as shown in Table 1. In Table 1, the number of stacked electrolytic cells is shown as "number of stacked electrolytic cells," and the electrical resistance value of the first supply slit is shown as "electrical resistance value." The catalyst area is the area of ​​each of the anode catalyst and the cathode catalyst. The electrical resistance value of the first supply slit is the value obtained by dividing the length of the first supply slit by the cross-sectional area of ​​the first supply slit, and then dividing the result by the conductivity of the electrolytic solution flowing through the first supply slit.

[0086] The power, loss based on shunt current, and loss rate based on shunt current for each model are shown in Table 1. The power for each model is the product of the catalyst area, current density, voltage, and the number of stacked electrolysis cells. The voltage in this example was 1.8 V. The loss for each model is calculated as Ik ２ ×Rs. Ik=[(k−(N+1) / 2){Va+Vc+I(Rcon+Rct+Rdif)}] / Rs where Ik: shunt current flowing from the kth electrolytic cell to the first supply manifold, N: number of electrolytic cells, Va: anode voltage, Vc: cathode voltage, I: current flowing through all electrolytic cells, Rcon (conduction resistance): conductive resistance, Rct (charge transfer resistance): charge transfer resistance, Rdif (diffusion resistance): diffusion resistance, Rs: electrical resistance of the first supply slit. The loss rate for each model is the loss divided by power, expressed as a percentage.

[0087]

[0088] Models with the same number of electrolysis cells stacked and the same electrical resistance value of the first supply slit but different catalyst areas were compared. That is, Models No. 1 to No. 5 were compared, Models No. 6 to No. 10 were compared, Models No. 11 to No. 15 were compared, Models No. 16 to No. 20 were compared, and Models No. 21 to No. 25 were compared. These comparisons revealed that the larger the catalyst area, the smaller the loss rate. Specifically, doubling the catalyst area reduced the loss rate by half, and increasing the catalyst area by five times reduced the loss rate by one-fifth.

[0089] Models with the same catalyst area and the same number of stacked electrolysis cells but different electrical resistance values ​​of the first supply slit were compared. That is, Model No. 11, Model No. 16, and Model No. 21 were compared; Model No. 12, Model No. 17, and Model No. 22 were compared; Model No. 13, Model No. 18, and Model No. 23 were compared; Model No. 14, Model No. 19, and Model No. 24 were compared; and Model No. 15, Model No. 20, and Model No. 25 were compared. These comparisons revealed that the loss rate decreased as the electrical resistance value of the first supply slit increased. Specifically, it was found that when the electrical resistance value of the first supply slit increased threefold, the loss rate decreased by one-third, and when the electrical resistance value of the first supply slit increased tenfold, the loss rate decreased by approximately one-tenth.

[0090] Models with the same catalyst area and the same electrical resistance value of the first supply slit but different numbers of stacked electrolytic cells were compared. That is, Model No. 6 was compared with Model No. 11, Model No. 7 with Model No. 12, Model No. 8 with Model No. 13, Model No. 9 with Model No. 14, and Model No. 10 with Model No. 15. These comparisons revealed that the fewer the number of stacked electrolytic cells, the smaller the loss rate. Specifically, it was found that when the number of stacked electrolytic cells was halved, the loss rate was reduced to 1 / 4. This result showed that, for example, a configuration in which the cell stack includes two substacks, each including a stack of 50 stacked electrolytic cells, can reduce the loss rate, specifically, reduce the loss rate to 1 / 4, compared to a configuration in which the cell stack includes a stack of 100 stacked electrolytic cells, even though the total number of electrolytic cells is the same.

[0091] REFERENCE SIGNS LIST 1 Hydrogen production device 2 Cell stack, 2s Substack, 2a Stack 20 Electrolysis cell, 21 Ion exchange membrane 22 Anode, 221 Anode catalyst, 222 Anode diffusion layer 23 Cathode, 231 Cathode catalyst, 232 Cathode diffusion layer 3 Separator 41 First current collector plate, 42 Second current collector plate 5 Supply and discharge plate, 6 Folding plate 7 Piping 71 First supply pipe, 72 First discharge pipe, 73 Second discharge pipe 91 First end plate, 92 Second end plate 93 Clamping mechanism, 94 Rod

Claims

1. A cell stack provided in a hydrogen production device, the cell stack comprising a plurality of sub-stacks, each of the plurality of sub-stacks comprising: a stack in which a plurality of electrolysis cells are stacked; and current collector plates arranged on both sides of the stack, and each of the plurality of electrolysis cells comprising an anode, an ion exchange membrane, and a cathode.

2. The cell stack according to claim 1, wherein the number of the plurality of sub-stacks is two.

3. The cell stack according to claim 1 or 2, wherein the number of the electrolysis cells in each of the sub-stacks is 15 or more and 100 or less.

4. The cell stack according to any one of claims 1 to 3, wherein the ion exchange membrane is an anion exchange membrane.

5. A cell stack according to any one of claims 1 to 4, comprising: a supply and discharge plate that supplies a fluid containing water to the plurality of electrolysis cells and discharges gas produced by electrolysis of the water in the plurality of electrolysis cells; and piping connected to the supply and discharge plate, the piping comprising: a supply pipe through which the fluid supplied to the anode flows; a first discharge pipe through which oxygen gas from the anode flows; and a second discharge pipe through which hydrogen gas from the cathode flows.

6. The cell stack according to claim 5, further comprising a folding plate that folds back the fluid supplied from the supply / discharge plate and returns it to the supply / discharge plate.

7. A cell stack according to any one of claims 1 to 6, wherein each of the plurality of electrolytic cells comprises a separator disposed on both ends of each of the plurality of electrolytic cells, the separator having a conductive plate, and the conductive plate being formed of a composite material containing a conductive material and a resin.

8. A hydrogen production device comprising the cell stack according to any one of claims 1 to 7.

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