Water electrolyzer stack with a set of half-cell frames

Abstract

A water electrolyzer stack has a set of half-cell frames, each half-cell frame enclosing one of the anode or cathode process chambers, and the half-cell frames are arranged in an array and aligned between a near-end current injection / current collector and a far-end current injection / current collector, wherein each half-cell frame includes an embedded trench channel adapted to deliver electrolyte from the inside of the stack into a manifold channel to the corresponding anode or cathode reaction chamber, and an embedded trench channel adapted to deliver electrolyte and gas from the corresponding anode or cathode reaction chamber to the corresponding internal manifold channel of the stack, wherein each embedded trench channel includes at least one fluid and / or gas trapping section.

Description

Technical Field

[0001] The present invention relates to a water electrolyzer stack having a set of half-cell frames. Background Technology

[0002] In existing designs of pressure-filter alkaline electrolyzers, each independent half-cell has its own dedicated flow path, allowing ions to flow through the alkaline solution even when the solution is stationary and not circulating (e.g., when the pump is not running). The ion connectivity formed between cathodes, anodes, and between cathodes allows for rapid discharge currents during periods of power de-energization (no applied potential). This can drive electrode degradation and shorten the lifespan of the electrolyzer.

[0003] Existing technical references: Abdel Haleem, Ashraf et al., "The Influence of Operating and Shutdown Parameters and Electrode Materials on Reverse Current Phenomenon in Alkaline Water Electrolysis Devices", *Journal of Power Supply*, Vol. 535, July 2022. This paper (https: / / doi.org / 10.1016 / j.jpowsour.2022.231454) investigates the aforementioned problem and quantitatively analyzes the reverse current causing electrode degradation under conditions of pump operation and pump shutdown in an electrolytic cell model. The results show that keeping the gas stagnant within the electrolytic cell can suppress the generation of degradation current.

[0004] This invention seeks to utilize these findings by redesigning the conduits serving the individual half-cells in an electrolyzer stack suitable for alkaline and potentially pressurized water electrolysis for hydrogen and oxygen production. Invention Summary

[0005] The water electrolyzer stack has a set of half-cell frames, each of which encloses either an anode reaction chamber or a cathode reaction chamber. The half-cell frames and half-cell reaction chambers are arranged in an array and aligned between the near-end current injection / collector plate and the far-end current injection / collector plate. Thus, the inflow manifold channels for the cathode electrolyte and anode electrolyte for the two electrolytes are provided in the form of through openings on the half-cell frames. Furthermore, the outflow manifold channels for the two electrolytes and their corresponding product gases are also provided in the form of through openings on the half-cell frames. Each half-cell frame also includes an embedded groove channel suitable for conveying electrolyte from the inflow manifold channel within the half-cell frame to the corresponding anode reaction chamber or cathode reaction chamber, and an embedded groove channel suitable for conveying electrolyte and gas from the corresponding anode reaction chamber or cathode reaction chamber to the corresponding manifold channel within the half-cell stack.

[0006] According to the present invention, each embedded groove channel is provided with at least one fluid and / or gas interception section.

[0007] The novel piping design traps gas within the stagnant fluid when the pump stops. Gas dissolved in the electrolyte forms bubbles, which rise into the trapping section and create a gas pocket. With the gas trapped, the conductivity of the gas-filled piping section decreases significantly, cutting off or greatly limiting ion connectivity between electrodes, thereby slowing electrode degradation. Furthermore, the interruption of ion connectivity allows for the application of a protective bias potential without gas generation. In existing designs, ion connectivity between half-cells is achieved through liquid-filled conduits, resulting in a potential drop in the manifold. Each electrode is within this potential drop, making attempts to apply a protective bias inappropriate because some electrodes will begin to generate hydrogen or oxygen, which can pass through the diaphragm and increase the risk of forming an explosive hydrogen-oxygen mixture inside the tank when the electrolyte flow is low or nonexistent. The design of this invention isolates the electrodes from the potential drop, eliminates gas generation, and makes protective bias control feasible.

[0008] In embodiments of the invention, the fluid and / or gas trapping section is positioned within the half-cell frame near the through-hole. This ensures that the conduit length between the gas trapping structure and the inflow distributor is maximized, allowing as much gas as possible to be trapped in the embedded grooved channels, thereby maximizing the resistance formed by the gas trapped within the trapping structure. It should be understood that the inner surface of the gas-filled channel portion is wetted by the electrolyte, thus forming a current path; however, this current path is much smaller (with higher resistance) than the current path represented by electrolyte-filled channels in the prior art.

[0009] In an embodiment of the invention, any embedded grooved channel has at least two generally vertically extending grooved channel segments near its connection with the internal manifold channel of the channel stack, and the grooved channel segments are interconnected in pairs by generally horizontal grooved channel segments.

[0010] Each pair of such interconnected trench channels can form a U-shaped or inverted U-shaped trench channel, thus ensuring the formation of an effective gas trap section whether the trench channel connects the internal manifold channel of the cell to the higher outflow distributor in the half-cell, or to the lower inflow distributor in the half-cell constituting the anode or cathode process chamber. "Approximately vertical" means that when fluid flow stops, any precipitated bubbles can move within a given channel in a preferred direction from lower to higher positions, and "approximately horizontal" means that when there is no fluid flow in any direction, bubbles in the fluid will remain at their formation location and will not move in any direction within the channel.

[0011] In this embodiment, each fluid flow channel within the battery frame is arranged as a branchless flow channel.

[0012] This ensures that only a single flow path is provided between the manifold channel and the designated half-cell process chamber, eliminating the need to consider short circuits caused by trapped gases and / or liquids. It is important to note that the inflow distributor and outflow collector, located within the half-cell frame, can be shaped as manifold components. These manifold components are not considered part of the embedded grooved flow channels within each half-cell, but rather as part of the internal flow channels within each cell.

[0013] In an embodiment, when the cell stack arrangement is used for production, the embedded trench channels suitable for conveying electrolyte from the anolyte manifold channel or the cathode electrolyte manifold channel inside the cell stack to the corresponding half-cell, and the embedded trench channels suitable for conveying electrolyte and gas from the half-cell to the electrolyte and gas manifold channel inside the cell stack, are all located in the same vertical half-plane of a given half-cell frame.

[0014] By arranging two trench channels within the same half-plane of the half-cell frame, which can be easily positioned to provide inlets and outlets for the anode or cathode process chambers during assembly by remaining stationary or rotating 180 degrees around the stack axis, the half-cell frame can be easily used. Using the same cell frame design throughout the stack offers production advantages; however, it requires a symmetrical design in locations where fluid inflow and outflow to individual process chambers might be unfavorable.

[0015] In an embodiment, when the cell stack arrangement is used for production, it is suitable for conveying electrolyte from the anolyte manifold channel or the cathode electrolyte manifold channel inside the cell stack to the embedded trench channel of the corresponding half cell, and for conveying electrolyte and gas from the half cell to the embedded trench channel of the electrolyte and gas manifold channel inside the cell stack, arranged in a vertical half plane opposite to any specified half cell frame.

[0016] This embodiment does not allow for the design of a half-cell frame that can provide inflow and outflow channels for both the cathode and anode reaction chambers simply by rotating and alternating the half-cell frame within the tank stack, because the rotation of the half-cell frame cannot switch the connection between the anode and cathode electrolyte manifold channels. However, dedicated half-cell frames specifically adapted to serve as anode and cathode reaction chambers allow for embedded grooved channels to accommodate the anode and cathode electrolyte flows separately. This also allows for the configuration of a dedicated inflow distributor, different from the outflow distributor, which is advantageous.

[0017] In an embodiment, at least one fluid and / or gas trapping section inside the groove channel is duckbill-shaped.

[0018] The duckbill valve is essentially a check valve. Simultaneously, when the electrolyte pump is off and there is no fluid inflow or outflow from the half-cell, these valves can cut off the direct conductive path between the reaction chamber and the corresponding manifold inflow channel, which supplies cathode and anolyte to the reaction chamber respectively. Furthermore, the duckbill valve can also serve as a gas trapping structure, causing gas to accumulate in front of the valve and preventing gas leakage back into the higher-positioned anolyte or cathode electrolyte manifold channels inside the tank.

[0019] It should be emphasized that the terms "comprising / including / consisting of" as used in this specification are intended to limit the presence of the stated features, integers, steps, or components, but do not exclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. Attached Figure Description

[0020] The invention will now be described in more detail with reference to the embodiments illustrated in the accompanying drawings. It should be emphasized that the illustrated embodiments are for illustrative purposes only and should not be used to limit the scope of protection of the invention.

[0021] Figure 1 shows a plan view of an embodiment of the battery frame according to the present invention, with gas trapped inside the flow channel; Figure 2 shows the embodiment in Figure 1, in which the flow channel is filled with electrolyte; Figure 3 is a plan view of an embodiment with a dedicated anode and cathode cavity half-cell frame; Figure 4 illustrates the embodiment in Figure 3, which has a further reinforced fluid / gas trapping structure; Figure 5 illustrates the embodiment in Figure 4, which sets up the fluid flow in a mirror layout; Figure 6 shows a three-dimensional cross-sectional view of the electrolytic cell stack; Figure 7 is an enlarged view of a portion of Figure 6; Figure 8 is a 3D view of a cell stack with some components removed to show the battery frame of the prior art; Figure 9 shows a three-dimensional and cross-sectional view of a set of battery frames inside the cell stack; Figure 10 is an enlarged cross-sectional view of the battery frame portion of the disclosed cell stack, schematically showing the separator, bipolar plates, and electrodes. Detailed Implementation

[0022] It should be noted that the accompanying drawings and the above description illustrate exemplary embodiments in a concise schematic form. Numerous specific mechanical details are not shown, but such details are well known to those skilled in the art and would only unnecessarily complicate the description. For example, specific materials and molding processes used are not described in detail because it is generally believed that those skilled in the art can select suitable materials and processes to manufacture the battery frame according to the present invention.

[0023] To better understand the background of the present invention, an example of a pressurized electrolytic cell stack is shown here with reference to Figures 6 to 10.

[0024] Figure 6 shows the three-dimensional structure of the electrolytic cell stack 1 in cross-sectional view. The stack has two end plates 12 and 12.1, namely the proximal end plate 12 and the distal end plate 12.1. The proximal end plate 12 also has two inflow channels 20 and two outflow channels 21, while the distal end plate 12.1 has no inflow or outflow channels. The inflow and outflow channels can penetrate either the proximal or distal end plate as needed. The inflow channels 20 receive cathode electrolyte and anolyte from external supply lines (not shown), respectively, and transport the fluids to the internal cathode electrolyte manifold channel 27 and the internal anolyte manifold channel 25 shown in Figure 8, respectively. The outflow channel 21 discharges the cathode electrolyte / hydrogen mixture and anolyte / oxygen mixture originating from each half-cell to the outside of the tank stack via the anolyte / oxygen manifold channel 26 and the cathode electrolyte / hydrogen manifold channel 28 inside the tank stack, as shown in Figure 8. Typically, the outflow channel 21 is positioned above the inflow channel 20 because the gas generated within the half-cell has buoyancy, thus an upward flow within the half-cell is preferred.

[0025] It should be noted that during the assembly of the slot stack 1, the slot stack 1 is usually placed with its slot stack axis 29 vertical and supported on an end plate 12. However, during use, the slot stack should be located in the horizontal position shown in Figures 6 and 8, where the slot stack axis 29 is horizontal.

[0026] A pull rod 30 is arranged at the edge of each end plate 12, 12.1, extending through opposing holes in the end plate and fastened by a simple nut 31, thereby pulling the two end plates 12, 12.1 toward each other to allow pressurized fluid and gas to be contained within the tank stack. Near each of the two end plates 12, 12.1, an insulating plate 13 (best visible in Figure 7) is first provided, followed by distal and proximal current injection / current collectors 14, 14.1; and between the two current injection / current collectors 14, 14.1, a series of individual cells are arranged, each comprising two half-cells 2.1, these individual cells arranged in a row flat against each other and precisely aligned.

[0027] Each half-cell 2.1 shall include an external so-called single-cell frame 2, which performs at least four different and somewhat independent functions: 1. The battery frame 1 serves as a pressure maintaining device; 2. They hold the internal components of the battery in place, namely the separator 35 and the bipolar plate 36 with accompanying electrodes, namely the cathode electrode 37 and the anode electrode 38 (see Figure 10). 3. They ensure that the two different electrolytes, as well as the electrolytes containing different amounts of the product gases hydrogen and oxygen, are separated and prevented from mixing within the electrolytic cell stack 1; and 4. These constitute an electrolyte and electrolyte / gas distribution network between the tank outlet channel 20 and the tank inlet channel 21 for the two electrolytes and the electrolyte / gas mixture.

[0028] Referring to Figure 9, the pressure-bearing characteristics of the half-cell frames 2 will now be described. The half-cell frames 2 are made of injection-molded electrically insulating polymer, and they require reinforcement to withstand high pressure; therefore, a metal reinforcing ring 33 is provided on the outermost side of each cell frame 2. Furthermore, to prevent any leakage, an O-ring 34 or similar gasket device is provided in a circumferential groove 32 suitable for accommodating an O-ring 34, such that high pressure can be maintained inside the O-ring 34 when the individual half-cell frames 2 are pressed together between end plates 12, 12.1.

[0029] Figure 10 shows an enlarged cross-sectional view of the cell and half-cell frame 2. Each bipolar plate 36 is electrically connected to a cathode electrode 37 on one side and to an anode electrode 38 on the opposite side, and the bipolar plates 36, together with the separator 35, are schematically shown in the figure. Each electrode 37, 38 is typically positioned adjacent to the separator 35. The separator 35 serves to separate the gas (oxygen) generated at the anode electrode 38 and the gas (hydrogen) generated at the cathode electrode 37 from each other, while allowing ions / electrons to pass through the separator between the two adjacent half-cells. An anode process chamber 3 or a cathode process chamber 4 is defined in the space between the bipolar plates 36 and the adjacent separator 35, the space being defined at its periphery by the half-cell frame 2 and along the electrolyzer stack axis by the separator 35 and the bipolar plates 36.

[0030] As shown in Figure 8, each process chamber has an inlet at the bottom, including an inflow distributor 15. At the top of each process chamber, an outflow collector 16 is provided. The inflow distributor 15 and the outflow collector 16 help ensure that the fluid is uniformly distributed across the half-cell region between the bipolar plates and the separator.

[0031] As shown in Figure 8, the inflow distributor 15 and the outflow collector 16 are each connected to their dedicated embedded trench channels 10. As shown in Figures 9 and 10, the dedicated channels 10 are configured as embedded trenches 10 located on a first side of each half-cell frame 2. When the trench is pressed against the back of the next half-cell frame in the cell stack, the trench 10 will take the form of a channel, which opens at one end to the collector 16 or distributor 15, and at the other end to one of the cell stack internal manifold channels 25, 26, 27, 28. Leading out from the anode reaction chamber, two dedicated embedded trench channels 10 are connected to the cell stack internal anolyte manifold channel 25 and the cell stack internal anolyte and oxygen manifold channel 26. Similarly, two dedicated trench channels 10 extend from the cathode reaction chamber and connect to the internal cathode electrolyte manifold channel 27 and the internal cathode electrolyte and hydrogen manifold channel 28, respectively. Therefore, each half-cell frame 2 shown in Figure 8 comprises four through-holes: one part of the internal anode electrolyte manifold channel 25, one part of the internal cathode electrolyte manifold channel 27, one part of the internal anode electrolyte and oxygen manifold channel 26, and one part of the internal cathode electrolyte and hydrogen manifold channel 28. Typically, only one type of battery frame design is used throughout the entire cell stack assembly process, and the same battery frame is placed next to the battery frame seen in Figure 10. However, the adjacent battery frame is rotated 180 degrees around the length axis 24 of the cell stack, so that the anolyte manifold channel 25 / anolyte and oxygen manifold channel 26 inside the cell stack and the catholyte manifold channel 27 / catholyte and hydrogen manifold channel 28 inside the cell stack are alternately connected through the corresponding dedicated embedded groove channel 10, thereby equipping the anode reaction chamber or the cathode reaction chamber with supply and outflow devices.

[0032] Figures 1 and 2 show cross-sectional views of a cell stack 1 including a half-cell 2.1 according to the present invention. In Figure 1, the cell stack 1 is in a shutdown mode, such that the fluid flow pumps (not shown) for the anolyte and catholyte are not in operation; however, some gas 5 from the electrolyte within the half-cell process chamber 2.1 and the embedded trench channel 10 will separate from the fluid, and as the lighter of the two components, the gas will permeate or flow into or into the higher portions of the half-cell and trench channel 10, which will then be filled with gas. The upper part of the half-cell is always connected to the outflowing embedded trench channel 10 with a downward direction (downward orientation), which itself forms a gas trap, as can also be seen in FIG8; however, the inflowing embedded trench channel 10 in the prior art half-cell does not contain any such gas trap (see the lower half of the cell stack in FIG8), and any gas released in the inflowing embedded trench channel of the prior art half-cell will simply flow out of the cell through the internal anode electrolyte manifold channel 25 or the internal cathode electrolyte manifold channel 27. However, with the fluid trapping structure disclosed in FIG1 and FIG2 in place, the gas released in the inflowing embedded trench channel 10 will be trapped by the downward orientation portion 17 of the inflowing embedded trench channel 10, which forms the upper gas pocket 5. It should be noted that the anode or cathode process chamber of the half-cell is itself a "downward-facing portion 17" of the flow channel, and together with the downward-facing portion 17 of the corresponding outflowing embedded grooved flow channel 10, a gas trapping section as described above will exist. Also as seen in Figures 1 and 2, multiple downward-facing flow portions 17, such as the portion indicated by reference numeral 3, are arranged adjacent to each other along the grooved flow channel 10. This, together with the half-cell (as described above, even though the gas-generating reaction also occurs here, the half-cell itself is also a flow channel), effectively provides four downward-facing flow portions 17 side-by-side. If the downward-facing flow portions 17 and their adjacent downward-facing flow portions 17 are interconnected to form an inverted U-shaped flow channel, then one such inverted U-shaped flow channel is sufficient to ensure a gas trapping section, which will prevent direct contact between the fluid portions within the flow channel on each side of the inverted U-shaped flow channel.

[0033] In the embodiment of the invention shown in Figure 3, two mirror-designed half-cell frames are required to serve two consecutive half-cells because rotation of the frames would prevent the cathode electrolyte and hydrogen manifold channels inside the stack from establishing a fluid connection with the inflow distributor at the top of the half-cell or the cathode process chamber. Furthermore, only one inverted U-shaped channel section is shown in Figure 3.

[0034] In the embodiment shown in Figure 4, the downward-facing portion 17 of the inflow channel to each half-cell comprises three downward-facing flow portions 17 and exposes an inverted U-shaped portion filled with gas 5. Figure 5 shows a half-cell frame immediately adjacent to the half-cell frame in Figure 4, and this needs to be a mirror representation of the battery frame in Figure 4 to provide inflow and outflow connections for adjacent half-cells. Such mirrored half-cell frames will each require their own dedicated injection tools during production.

[0035] List of reference numerals in the attached diagram: 1. Tank stack 2. Half-cell frame 2.1 Half-cell 3 Anode process chamber 4. Cathode process chamber 5. Gases separated from electrolyte fluids 10 Embedded grooved flow channels 11 Fluid and / or gas trapping section 12 Proximal endplate 12.1 Far end plate 13 Insulation Board 14. Proximity Current Injection / Collider 14.1 Remote Current Injection / Collider 15. Inflow Distributor 16 Outflow Collector 17. Downward-facing portion of the grooved flow channel 20 Inflow channel 21 Outflow channel 25. Anode electrolyte manifold flow channel inside the tank stack 26. Anode electrolyte and oxygen manifold flow channels inside the stack 27. Internal cathode electrolyte manifold flow channel of the cell stack 28-cell internal cathode electrolyte and hydrogen manifold flow channels 29. Trenches and stacks axis 30 pull rod 31 Nuts 32 circumferential grooves 33 Metal Reinforcing Ring 34 O-rings 35 Diaphragm 36 Bipolar Plate 37 Cathode electrode 38 Anode electrode

Claims

1. A water electrolyzer stack (1) having a set of half-cell frames (2), each of the half-cell frames forming one of an anode process chamber (3) or a cathode process chamber (4), the half-cell frames (2) being arranged in an array and aligned between a near-end current injection / collector plate (14) and a far-end current injection / collector plate (14.1), whereby the cathode electrolyte and the anode electrolyte for the two electrolytes are provided in the half-cell frames (2) in the form of through openings in the internal manifold channels (25, 27) of the stack, and wherein, The internal manifold channels (26, 28) for each of the two electrolytes and the corresponding product gas are also provided in the half-cell frame (2) in the form of through openings, and wherein each of the half-cell frames further includes an embedded groove channel (10) adapted to transport electrolyte from the internal manifold channels (25, 27) in the half-cell frame (2) to the corresponding anode or cathode reaction chamber (3, 4), and an embedded groove channel (10) adapted to transport electrolyte and gas from the corresponding anode or cathode reaction chamber (3, 4) to the corresponding internal manifold channels (26, 28), characterized in that each of the embedded groove channels (10) includes at least one fluid and / or gas trapping section (11).

2. The water electrolysis cell stack (1) according to claim 1, wherein, The fluid and / or gas trapping section (11) is disposed in the embedded groove channel (10) within the half-cell frame (2), close to the corresponding internal manifold channel (25,26,27,28) of the cell stack.

3. The water electrolysis cell stack (1) according to claim 2, wherein, Each of the embedded grooved channels (10) includes at least two generally vertically extending grooved channel segments (17) near its connection with the internal manifold channels (25, 26, 27, 28) of the channel stack, the channel segments being interconnected in pairs by generally horizontal grooved channel segments.

4. The water electrolysis cell stack according to any one of claims 1 to 3, wherein, Each of the embedded fluid channel grooves (10) within the half-cell frame is arranged as a branchless channel.

5. The water electrolysis cell stack according to any one of claims 1 to 4, wherein, When the cell stack arrangement is used for production, the embedded grooved channels (10) adapted to transport electrolyte from the anolyte or catholyte manifold channels (25, 27) inside the cell stack to the corresponding half-cell, and the embedded grooved channels (10) adapted to transport electrolyte and gas from the half-cell to the electrolyte and gas manifold channels (26, 28) inside the cell stack, are arranged in the same vertical half-plane of any given half-cell frame.

6. The water electrolysis cell stack according to any one of claims 1 to 4, wherein, When the cell stack arrangement is used for production, the embedded grooved channels (10) adapted to transport electrolyte from the anolyte or catholyte manifold channels (25, 27) inside the cell stack to the corresponding half-cell, and the embedded grooved channels (10) adapted to transport electrolyte and gas from the half-cell to the electrolyte and gas manifold channels (26, 28) inside the cell stack, are arranged in the relative vertical half-plane of any given half-cell frame.

7. The water electrolysis cell stack according to claim 5 or 6, wherein, The at least one fluid and / or gas trapping section (11) in the grooved flow channel (10) is duckbill-shaped.

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