Expandable and contractible flow field for electrochemical cells and method for rapidly producing the same

Abstract

This application relates to a flow field for an electrolytic cell comprising one or more sheets of porous material having a corrugated structure. The electrolytic cell comprises a membrane, an anode, a cathode, an anode reinforcing layer, a cathode reinforcing layer, an anode flow field, a cathode flow field, and a bipolar plate assembly having an embedded hydrogen seal. The anode flow field comprises one or more porous sheets having at least one linear edge, at least one of the porous sheets having a corrugated pattern with multiple peaks and valleys, the axes of which are substantially aligned with one linear edge of the sheet. The geometric shape of the anode flow field simultaneously provides elasticity for efficient mechanical compression of the cell and well-distributed mechanical support for the anode reinforcing layer adjacent to the anode flow field.

Description

[Technical Field]

[0001] Incorporation by reference to related patent applications This application claims the benefit of priority under 35 U.S.SC § 119(e) to U.S. Provisional Application No. 63 / 483,658, filed on 7 February 2023, and all its contents are incorporated herein by general reference.

[0002] Field of Invention This disclosure relates to electrochemical cells and stacks, and more particularly to components designed for scalable active regions for electrochemical cells and stacks, and to the rapid manufacturing of the same. [Background technology]

[0003] An electrochemical cell is a device that uses electricity to induce a chemical reaction or uses a chemical reaction to generate electricity. When electricity is the output, the cell can be considered a fuel cell or an expander cell, depending on the chemical product. When electricity is the input, the cell can be considered an electrolytic cell, a compressor cell, or a purifier cell, depending on the chemical product. For example, an electrolytic cell takes in electrical energy and stores it in a fuel such as hydrogen by breaking down water into its components. In contrast, a fuel cell can essentially be thought of as an electrolytic cell running in the reverse direction, where hydrogen and oxygen are supplied to the cell, and these molecules are then combined to form water, releasing electrical energy in the process. Other chemical reactions, such as the reduction of carbon dioxide to carbon monoxide, ethylene or ethylene glycol, the reduction of nitrogen to ammonia or related compounds, the formation of hydrogen peroxide from water and oxygen, or the extraction of lithium from a lithium brine solution, can be facilitated by the use of an electrochemical cell or a stack of cells. The basic elements of these devices are two electrodes, an ion-conducting electrolyte, and an ion-permeable layer separating the two electrodes, although it is also possible to operate electrolytic cells or fuel cells in a membrane-less configuration. Electrochemical cells may also include separators between electrodes to prevent the products from mixing inside the cell. In the case of solid electrolytic cells, the membranes and separators may be combined into an integrated solid ion-conducting layer. A complete electrochemical cell may also include one or more impermeable separator plates, also called bipolar plates, for a flow field to deliver reactants to the electrodes, seals to isolate the reactants from each other and from the environment, and for isolating one cell from adjacent cells in a stack, and in some embodiments for housing a separate cooling fluid for thermal management of the cell.

[0004] Various electrolytes can be used in electrochemical cells, including proton exchange membranes, anion exchange membranes, solid oxide ceramic membranes, and liquid alkaline solutions such as potassium hydroxide and sodium hydroxide. Different electrolytes require different operating conditions, and each has its own advantages and limitations. Advantages of proton exchange membrane electrolytes and anion exchange membrane electrolytes include relatively low operating temperatures and the ability to construct cells using unitized layers of electrolyte / membrane. Electrolyzers using such membranes have a clear advantage over other electrolyzers in that they can operate using relatively pure liquid water as the feedstock, rather than caustic solution or water vapor, thereby significantly simplifying the system balance. Relatively pure water can be defined as water that contains more than 1% by weight of elements other than hydrogen and oxygen. Such electrolyzers can also operate without liquid water on the cathode, allowing for the production of hydrogen in a gas phase with a non-zero vapor-phase moisture content. A non-zero vapor-phase moisture content can be defined as a gas containing more than one part per million of water vapor by volume.

[0005] The impact of carbon dioxide on global climate change is well-documented. As societal efforts to address global climate change accelerate, the need to deeply decarbonize a large or all of human energy use is becoming clear and urgent. Using hydrogen as a carbon-free energy carrier is essential to reaching certain human-industrial sectors where direct decarbonization with electricity is difficult or impossible. Examples of such sectors include steel production, fertilizer manufacturing, construction, and heavy transport such as trucking, sea transport, and air transport. In addition to these sectors, hydrogen's energy density and stable storage properties make it a most promising candidate for establishing seasonal-scale energy storage and power grids using only renewable electricity. This would be necessary to completely transform energy use to carbon-free sources. These and other advantages have attracted a high level of interest in the production of “green hydrogen.”

[0006] Hydrogen is given the "green" label when it is produced by electrolysis from renewable electricity (wind, solar, hydro, etc.). Other "colors" of hydrogen have traditionally been assigned to other energy sources. The scale required to meet the potential demand for green hydrogen in the future global energy system is enormous. Electrolyzer production capacity needs to increase by orders of magnitude over the next decade to meet such demand, and their costs need to decrease by more than tenfold. Until now, the manufacture of hydrogen electrolyzers has been a niche industry with small systems and limited deployment, based on cells and stacks designed for research and development. Little consideration has been given to the production speed required to manufacture and assemble cells and stacks at a pace that matches society's ultimate need. [Overview of the Initiative]

[0007] Recognizing the urgent need for innovative electrolytic technology to combat climate change, this application covers flow fields for expandable electrolytic cells and stacks, expandable electrolytic cells and stacks, expandable stack compression systems, and methods for rapid manufacturing. Embodiments of this application cover the design and manufacture of key elements for these cells and stacks, namely fluid flow fields. A flow field is a component within a cell assembly that provides the open space necessary for reactants and products to continuously enter and exit the working cell and stack. Such a flow field may provide other functions within the cell, such as a uniform mechanical load distribution to the membrane and electrode layers, as well as electrical conduction through the cell. This disclosure includes innovative arrangements of the geometric shape and dimensions of flow field elements that facilitate advantages related to the assembly and compression of cells in electrochemical stacks. This disclosure also includes improved geometric shapes and dimensions for electrolytic cells with smaller overall thickness compared to the prior art. This disclosure also includes innovative arrangements of the geometric shape and dimensions of flow field elements that facilitate advantages related to the generation and removal of bubbles generated during reactions on the liquid flow side of the cell. This disclosure also includes innovative methods for manufacturing flow field elements at faster speeds compared to the prior art. The following explanation focuses on water electrolysis for hydrogen production for clarity, but may be applied to other electrochemical processes by those skilled in the art.

[0008] The basic process of water electrolysis involves supplying water to a positively charged anode and conducting ions between the anode and a negatively charged cathode. Oxygen gas is produced at the anode and hydrogen gas at the cathode. The specific ions conducted between the anode and cathode depend on the electrolyte used. In an acidic cell, positively charged hydronium ions (H3O) are produced. + ) conducts from the anode to the cathode. In an alkaline cell, negatively charged hydroxide ions (OH) are conducted. -Current is conducted from the cathode to the anode. In both systems, the entire reaction is the same: (2)H2O(l) → (2)H2(g) + O2(g). Electricity must be supplied to drive the reaction. The open-circuit or thermally neutral voltage for the basic reaction of hydrogen to liquid water is 1.481, and therefore, in order to proceed the reaction, a voltage higher than 1.481 must be applied to the hydrogen electrolytic cell supplied with liquid water (as discussed below, overpotential is usually required for the reaction to proceed at an acceptable rate). The size of the cell (i.e., the active region) determines the rate of hydrogen / oxygen production from one cell at a given applied voltage. The total current required for a particular applied voltage can be proportional to the active region of the cell. In practical systems, multiple cells can be "stacked" on top of each other to increase production capacity. This stacking of cells necessitates applying higher voltages (integer multiples of the number of cells) to drive the reaction. For example, 1000 cm² 2 A single cell in the active region is 500 cm². 2 It can generate the same hydrogen flow as two stacked cells, but this 500cm 2 The stack requires inputs of twice the voltage and half the current. Flexibility in selecting the required voltage and current can be a crucial consideration in the design and cost of the total electrolytic system. For example, power supplies for higher current and lower voltage may be more expensive than those for higher voltage and lower current due to the size of the conductors required and the additional materials needed for their configuration. Therefore, the easily expandable and contractible active area of ​​the cells is a significant advantage for deployment cost and flexibility.

[0009] The components of a hydrogen electrolysis stack may include a stack of repeating components (configured as repeating "cells") and a system of non-repeating components for holding the cells together in the stack configuration. As the name suggests, repeating components are those whose quantity increases or decreases with the stack height and typically include membranes / electrolytes, anode and cathode electrodes, anode and cathode electrode reinforcement layers, water and hydrogen flow fields, water and hydrogen seals, and bipolar cell separator plates. Non-repeating components may typically include end units and mechanical systems for maintaining compression on the stack of repeating components ("stack core"), along with power terminals, electrical insulators, fluid distribution and / or drain / purge manifolds. The stack compression system may include compliant elements such as tension members, springs, and adjustable members (rods, bolts, wedges, etc.) to generate and maintain compressive loads within the stack core. This compression of the stack core may be essential to ensure both electrical contact and fluid sealing between individual cells and end units. In a typical electrolytic cell stack, this compliance element may be located outside the stack core because the core itself can be relatively "rigid" mechanically. In this case, a relatively "soft" or compliant compression system outside the stack core may be needed to maintain a continuous compressive load as the stack height changes with time, temperature, or pressure. These external elements can be large, and / or expensive, and / or difficult to handle for manufacturing. Alternatively, by using repeating components with built-in compliance, designers can significantly minimize or eliminate the need for external springs, rods, bolts, etc., resulting in advantages in cost, size, and assembly speed for the stack. In this context, compliance can be defined as the reciprocal of the effective elastic spring constant along the z-axis (the axis along which the cells are stacked) (i.e., the change in "z" per unit quantity of applied force [kgf] [mm]).

[0010] This disclosure relates to a novel structure for fluid flow fields in expandable electrolytic cells and stacks. The flow field is an element of the cell that provides an open space for cell reactants (e.g., water) delivered to the cell active region and cell products (e.g., hydrogen, oxygen) collected from the cell active region. In conventional electrolytic cells, the flow field may include a series of channels formed in a bipolar plate. Flow fields like channels present significant challenges in electrolysis due to their lack of scalability and the need for relatively large thicknesses to maintain reasonable water pressure losses through the small channels formed. In this disclosure, the flow field comprises a three-dimensionally continuous open space ("open flow field" or "OFF") formed using a porous material to maintain the separation of electrodes from adjacent cells under a compressive load applied to the cell. The OFF can also conduct electricity through the open space between the electrodes and adjacent cells.

[0011] Conventional structures for off-cells (OFFs) for electrolytic cells consist of metal foam, sintered metal frit, flat wire mesh, expanded metal mesh, and perforated sheets of various configurations. These OFFs are flat structures with low porosity and, like channels, require large-thickness cells to provide reasonable water pressure loss. These cells are relatively rigid (non-compliant) along the z-axis and may require large, expensive, and cumbersome compression systems to maintain contact and sealing between cells throughout the lifetime of a stack of such cells. Conventional approaches to OFFs in fuel cells include molded porous sheets, such as thin flat sheets that have been corrugated or dimpled, thereby providing larger volume and lower pressure drop for gas flows within these devices. However, fuel cells do not have the bubble management problems present in electrolytic cells, and therefore the flow fields of these prior arts are not suited to two-phase flow and bubble evacuation. Conventional approaches to OFFs have significant limitations in terms of size, cost, flow resistance, cell performance, and manufacturability, and this disclosure aims to overcome these limitations.

[0012] In some embodiments, the disclosure provides an expandable / contractable flow field that can be used as an anode flow field, which can be combined with a bipolar plate assembly that includes an expandable / contractable cathode flow field further comprising an embedded hydrogen seal. In this configuration, the porous cathode flow field provides both mechanical reinforcement for the hydrogen seal and an open space for collecting the hydrogen gas flow and directing it away from the active region of the cell. The hydrogen seal can be fully embedded within the porous structure of the porous cathode flow field, forming an airtight seal for the hydrogen gas in the cathode, while also physically bonding together with the components of the bipolar plate assembly. In this configuration, by matching the hydrogen seal with the porous flow field along the z-axis, the cathode flow field can be made very thin. Minimizing the thickness of each iterative cell in the stack core may be important for achieving small stacks with high power (i.e., high power density). Essentially, thin components (i.e., short “springs”) are stiffer than thicker components, so achieving integration responsiveness in very thin iterative components can be challenging. The material and geometric shape of the anode flow field can be important for developing a stack core with proper conformability, as this component can be relatively thicker compared to other layers within each cell containing the cathode flow field.

[0013] In some embodiments, the disclosure may include an expandable / contractable flow field, in conjunction with a selected electrode reinforcing material, that enables an improvement in the compressive load distribution to the membrane and electrode. The application of a uniform compressive load to the electrode and membrane may be important for the performance and lifespan of the cell. One or more corrugated layers may have dimensions selected to minimize bending of the electrode reinforcing material under load, resulting in a more uniform transfer of mechanical load to the electrode and membrane through the reinforcing material. The interpeak dimension (i.e., "corrugated pitch") of layers adjacent to the electrode reinforcing material may be selected based on the elastic properties and thickness of the reinforcing material in order to achieve this function.

[0014] In some embodiments, the present disclosure can include a scalable flow field configured to provide relatively high compliance along the z-axis, thereby enabling the use of a compact, low-cost, and convenient stack compression system with minimal requirements for spring functionality.

[0015] For convenience, a Cartesian coordinate system with perpendicular x-y-z axes can be defined, where "x" is parallel to the general direction of water flow through the stack, "y" is perpendicular to x but within the same plane defined by a single cell, and "z" is generally parallel to the stack direction of the cells. In this context, the compression system generally acts to apply a compressive load along the z-axis, holding the cells and their various repeating components in contact with each other. The compliance of the stack core can then be measured along the z-axis and is defined as such.

[0016] When an electrolytic cell is in operation, water is consumed and hydrogen + oxygen gas is produced; therefore, water must be continuously supplied to the cell to sustain the reaction. Stoichiometry is a term relating to the "balance" of a chemical reaction. In an electrochemical cell, the term "stoichiometry" or "stoich" refers to the ratio of reactants supplied to the cell to the amount necessary to precisely balance the entire reaction. For example, an electrolytic cell operating with 2 water stoichs has twice the amount of water as its input required to produce the hydrogen and oxygen leaving the cell. If we conserve the mass of the system with 1 stoich, we can see that 1 kg of hydrogen production per hour is related to approximately 8 kg of oxygen production per hour and approximately 9 kg of water consumption per hour. Typically, an electrolytic cell can be operated with a minimum water stoich greater than 1 to ensure the appropriate reactants at every point in the cell. For example, when the water flow stoich is 1, all the water supplied to the cell is converted to oxygen at the anode, and the oxygen fraction at the cell outlet is 100% (i.e., no water leaves the cell). This condition can be unstable and may lead to damage due to anode deficiency in the cell near the outlet. Furthermore, it can result in high fluid velocity and pressure loss at the outlet, as everything exiting the cell is in the gas phase. Therefore, process conditions can be selected to maintain the oxygen gas phase fraction at the cell outlet below a given threshold. For example, an outlet oxygen fraction of less than 40% can increase the flow field velocity from the water inlet to the outlet by less than twofold. Maintaining an oxygen fraction below 40% may require more than 100 water stoichiometry units. The material and geometry selected for the anode flow field, which delivers water and removes oxygen from the cell, can also be important for maintaining high performance and low pressure drop. Geometry and dimensions that minimize velocity while promoting convection of oxygen bubbles from the anode electrode can offer such advantages.

[0017] The electrolysis process is not 100% efficient, and as a result, a portion of the input electricity is converted into heat within the cell rather than chemical energy stored as hydrogen. This results in a voltage greater than the thermoneutral voltage (1.481 V) required for a practical hydrogen output flow rate. The energy efficiency of this system can be shown to be such that the fraction of power supplied to the hot cell (voltage × current) can be equal to [1-(1.481 / V cell )]. Practical electrolysis cells can operate at 1.8 V, and as a result, [1-(1.481 / 1.8)] =~18% of the power is sent to the cell and converted into heat rather than hydrogen. Thus, practical electrolysis cells require cooling during operation, and an efficient way to achieve this cooling could be to utilize the process water itself to cool the cell. Depending on the operating conditions of the cell, a relatively high flow rate of water may be required to ensure that the peak temperature of the cell is maintained below an acceptable threshold and that the temperature gradient within the cell is also acceptable. This flow rate can also represent a water stoichiometry much greater than 1. For example, in a cell operating at 1.8 V, releasing 18% of the input energy as heat and operating at 2.7 W / cm 2 , a water stoichiometry greater than 100 may be required to maintain a temperature rise of less than 10°C across the cell. From the design considerations described above, the flow rate of water to the cell is determined by the higher of either the need for appropriate reactants or the need for appropriate temperature control.

[0018] Therefore, managing the water supplied to the hydrogen electrolysis cell / stack can be a major consideration for the overall hydrogen production system. Flow rate, pressure, temperature, and composition must all be adjusted to meet the requirements of the cell and stack. A typical system may include a liquid-gas separator, heat exchanger, pump, and purification / deionization system connected in a loop to the anode side of the cell / stack, allowing the water to be recirculated at the required flow rate. One "stoichiometer" of water is consumed as the system produces hydrogen and oxygen. The consumed water (i.e., "makeup water") can be added to the system by injecting one stoichiometer of new water into the system loop from a source of acceptable quality (e.g., demineralized water, desalination water, "buffer water," or tap water). Given the scale of the electrolysis plant, the required water flow consumed by the cell / stack may be proportional to the plant capacity. Regardless of scale, it may be desirable to keep other process parameters (pressure, temperature, composition) uniform, as this can greatly simplify the selection of system components, overall system control, and engineering, procurement, and construction (EPC) costs at the deployment site. For example, water pumps are generally available commercially in a wide range of flow rates for a given pressure capacity. Therefore, it can be advantageous to have a basic cell / stack that minimizes water flow resistance and is independent of cell or stack size. Larger systems can then be built modularly from more cells and / or more stacks, without the need to change the water pump technology and basic pressure rating for the system and plant. Given the high water flow rates required by these considerations, the material and geometric shape of the anode flow field represent important considerations for minimizing pressure loss, allowing for changes in the active region without altering pressure loss, and thereby reducing the cost of water pumps for electrolytic systems.

[0019] In some embodiments, the disclosure may include an expandable flow field configured to have substantially equal resistance to the water flow, equal temperature rise, and equal outlet oxygen fraction at a given operating voltage, regardless of the selected active region. In some embodiments, the flow field may be substantially rectangular and characterized by dimensions along the x-axis selected according to the roll web width (w) of the flow field material used in its manufacture. In some embodiments, the desired roll web width (w) may be selected on the basis of maintaining process parameters for the operating cell within a target threshold. For example, it may be desirable to keep the water pressure drop of the cell below the pumping pressure limit of the system in which the cell may be installed. Alternatively, it may be desirable to keep the water flow temperature rise along the x-axis below the stack temperature gradient limit to ensure acceptable performance and lifespan. Alternatively, it may be desirable to keep the temperature gradient along the z-axis within the cell below the cell temperature gradient limit, which may require the cell to be as thin as possible to facilitate effective internal heat transfer. Alternatively, it may be desirable to keep the oxygen volume fraction at the cell outlet below a limit to ensure stable performance and lifespan of the cell. Alternatively, the desired roll web width (w) may be selected based on the available raw materials for constructing the flow field. For example, it may be desirable to select a roll web width that minimizes waste when converting rolls into flow field pieces during assembly. In this case, the desired roll web widths for membranes, electrodes, and flow fields may be the same or different. If they are different, the selected roll web width can be chosen based on the most expensive membrane, electrode, or flow field, and other material rolls can be selected with a web width (w) that is consistent with the other rolls. Here, "consistency" means a roll web width (w) that improves manufacturing speed and / or total cost. Furthermore, cells of various active regions can be constructed by varying the dimensions only along the y-axis, which greatly simplifies the material procurement and manufacturing process of coils with a fixed web width.

[0020] In some embodiments, the disclosure may include variable cells achieved using a scalable flow field by adjusting the length of the cell along the y-axis. Water distribution windows may be positioned parallel to the y-axis along the leading edge of the anode flow field, and each window may be associated with a unit length along a y-axis of the anode flow field (abbreviated as "ULAFF"). The leading edge of the anode flow field may be defined as the edge through which water enters the anode flow field. The area of ​​each water distribution window, or effective diameter (the diameter of a circle whose area is equal to the diameter of the window), may be selected to maintain the water velocity along the z-axis through the window below a predetermined threshold, with a water flow stoichiometry selected to maintain one or more of the cell temperature rise or the oxygen volume fraction at the outlet below a target threshold. The ULAFF associated with each water distribution window may be selected to maintain the water velocity along the x-axis at the leading edge of the anode flow field below a predetermined threshold. Next, the number of water distribution windows can be selected to achieve the overall target hydrogen production rate of the cell while maintaining the water flow pressure loss, water temperature rise, and oxygen volume fraction at the outlet below target thresholds.

[0021] In some embodiments, the present disclosure may include an expandable flow field comprising one or more metal meshes, expanded metal sheets, or perforated sheets, at least one of which is corrugated into a wavy pattern to effectively increase its thickness along the z-axis. This geometric shape can provide a larger volume for a given amount of flow field material and effectively increases the porosity and thickness of the flow field compared to a non-corrugated sheet, thereby reducing the water flow velocity and further lowering the pressure drop. Multiple corrugated layers can be combined to adjust the pressure drop, bubble discharge, compressive load application, and mechanical obedience along the z-axis within the cell. Further configurations of both the material and geometric shape for the flow field layers enable highly obedient electrolytic cells with smaller thicknesses while simultaneously providing lower pressure drop than the prior art.

[0022] Simultaneously satisfying the requirements of flow restriction, bubble discharge, mechanical load distribution, and elastic compliance is particularly difficult for electrolytic devices utilizing open flow fields and solutions, and is not obvious to those skilled in the art.

[0023] It should be understood that both the general description above and the detailed description below are illustrative and descriptive only and do not limit the disclosure as set forth in the claims. Further objectives, features, and advantages of this application will become apparent from the detailed description of preferred embodiments set forth below, when considered together with the drawings. [Brief explanation of the drawing]

[0024] The accompanying drawings are incorporated herein and constitute part of this specification. The drawings illustrate only specific embodiments of this disclosure and, together with the above and below descriptions, illustrate the principles of this disclosure. Wherever possible, the same identification numbers are used to indicate common or similar components across different figures.

[0025] [Figure 1] Figure 1 shows a cross-sectional view of a preferred embodiment of the layers of the expandable electrolytic cell of the present disclosure.

[0026] [Figure 2] Figure 2 shows an isometric view of a preferred embodiment of a expandable electrolytic cell including an expandable flow field of the present disclosure.

[0027] [Figure 3] Figure 3 shows flow fields of several conventional technologies used in electrolytic devices and fuel cells.

[0028] [Figure 4] Figure 4 shows an isometric view of a scalable bipolar plate assembly ("BPA") containing an embedded hydrogen seal.

[0029] [Figure 5]Figure 5 shows a cross-sectional view of the BPA in Figure 4, illustrating how the embedded hydrogen seal fully penetrates the cathode flow field to form a reinforced seal that is airtight with minimal thickness along the z-axis.

[0030] [Figure 6] Figure 6 shows the mathematical model output for the oxygen volume fraction versus water stoichiometric value at the outlet, with respect to exemplary cell operating pressure and an illustrative oxygen volume fraction threshold.

[0031] [Figure 7] Figure 7 shows the mathematical model output for water temperature rise versus water stoichiometric value with respect to the operating voltage values ​​and graphical water temperature rise threshold of two exemplary cells.

[0032] [Figure 8] Figure 8 shows published scientific results on the structure of fluid flowing through a channel and illustrates the effect of channel dimensions on vortices within the channel.

[0033] [Figure 9] Figure 9 shows an isometric view of a preferred embodiment of an expandable and contractible flow field and associated electrode reinforcement, illustrating the orientation of the water flow and the associated hydrodynamic properties of the flow field elements, thereby minimizing water flow pressure loss while simultaneously promoting bubble discharge from the anode electrode.

[0034] [Figure 10] Figure 10 shows a cross-sectional view of a preferred embodiment of an expandable flow field and associated electrode reinforcement, as shown in Figure 8, illustrating the relative geometric dimensions of various elements that promote a uniform distribution of compressive loads to the electrodes and membranes and facilitate hydrodynamics for efficient bubble removal from the anode electrode.

[0035] [Figure 11ABC] Figures 11A, 11B, and 11C show cross-sections of a preferred embodiment of an expandable and contractible flow field illustrating the elastic deformation of the flow field when subjected to a compressive load along the z-axis.

[0036] [Figure 12] Figure 12 shows a preferred embodiment of an expandable and contractible flow field illustrating the unitization of multiple layers by spot welding.

[0037] [Figure 13] Figure 13 shows a preferred high-speed continuous manufacturing method for an expandable and contractible flow field.

[0038] [Figure 14AB] Figures 14A and 14B show a comparison between a conventional stack compression system (Figure 14A) and an efficient stack compression system made possible by various embodiments of a compliant flow field (Figure 14B).

[0039] [Figure 15AB] Figures 15A and 15B show the results of a load uniformity test comparing a preferred embodiment of the present invention with the prior art.

[0040] [Figure 16] Figure 16 shows the results of finite element simulations calculated for a series of exemplary corrugated porous sheet shapes. The compressive modulus "E" can be defined by conventional engineering convention as the ratio of measured stress to measured strain in a material subjected to a compressive load.

[0041] [Figure 17] Figure 17 shows the characteristic flow resistance [millibars / cm, mb / cm] versus water flow velocity [cm / sec, cm / sec] measured for several exemplary flow fields. [Modes for carrying out the invention]

[0042] Detailed description of the drawing Herein, a detailed description of several preferred embodiments is given with reference to the accompanying drawings. Although the description relates to water electrolysis, it will be understood by those skilled in the art that the described features, components, and methods are applicable and adaptable to other electrochemical techniques, including the reduction of carbon dioxide to carbon monoxide, ethylene or ethylene glycol, the reduction of nitrogen to ammonia or related compounds, the formation of hydrogen peroxide from water and oxygen, or the extraction of lithium from lithium brine solutions, hydrogen compressors, hydrogen purifiers and fuel cells.

[0043] Figure 1 shows a schematic cross-section of a typical electrolytic cell (102) according to the present disclosure. The layers are shown in relative positions to each other, arranged generally in the xy-plane and stacked along the z-axis (101). Each layer may be thicker or thinner along the z-axis than other layers in the cell. Layer (111) represents the anode flow field, which may include two or more layers (a), (b), etc. (only two layers, a and b, are shown). Layer (112) represents an optional anode electrode reinforcement layer. Layer (113) represents the anode electrode layer. Layer (114) represents an electrolyte membrane layer or liquid electrolyte. Layer (115) represents the cathode electrode layer. Layer (116) represents an optional cathode electrode reinforcement layer. Layer (117) represents the cathode flow field layer. Layer (118) represents the bipolar separator plate layer.

[0044] Figure 2 shows a 3D isometric view (202) of the cell layer depicted in Figure 1, with the addition of several components. Component (217) represents the hydrogen seal. Component (221) represents the cell frame. Component (222) represents the water seal. Component (214) represents the internal seal. In this embodiment, the anode flow field (111) is represented as a two-layer corrugated laminate (111a, 111b), as shown in detail figure (203). During operation, the anode flow field (111) can function to deliver and distribute water as a reactant to the cell active region, deliver and distribute water as a coolant to the cell active region, and collect and remove oxygen gas from the active region as a product. During operation, hydrogen gas can be generated, collected, and removed across the active region by the cathode flow field (117). The fluid in the cathode flow field can be predominantly gaseous, with a non-zero water vapor content, due to the evaporation of water transported from the anode through the membrane. Due to the relatively low flow rate of fluid in the cathode flow field compared to the anode flow field, the cathode flow field can be designed with relatively thin dimensions along the z-axis. For example, the cathode flow field (117) can have a thickness of less than 2 mm, less than 1 mm, less than 0.5 mm, or less than 0.25 mm along the z-axis. While the relatively thin z-axis dimensions of the cathode flow field can advantageously contribute to a thin overall cell thickness, it may also result in mechanical stiffness (non-compliantness) along the z-axis. This non-compliantness inherent in thin cathode flow fields can impose an additional burden on the design of an anode flow field with proper compliantness, which will be further discussed below with respect to Figure 11. The width "w" (231) of the anode flow field (111) is located along the x-axis (201), and the length "l" (232) is located along the y-axis (201). Expansion of the anode flow field and other repeating components can be achieved by increasing their dimensions along the y-axis (233).

[0045] Figure 3 shows some examples of conventional flow fields used in electrolyzers and fuel cells. In addition to flow fields in the form of channels (not shown) directly formed on bipolar separator plates in some prior art, separate spacer components include flat wire mesh, expanded and perforated metal sheets, and three-dimensionally formed versions thereof. The object of this disclosure is to overcome the limitations of conventional configurations for electrolytic applications by providing a relatively thin electrolytic cell that simultaneously provides high mechanical obedience along the z-axis to electrodes and membranes, a uniform compressive load distribution, and a favorable geometric shape for bubble evacuation from electrodes. The disclosed cell allows for simplification of the associated stack compression system by providing the required mechanical obedience along the z-axis within the cell's core stack, thereby eliminating the need for springs and other obedience members in the external compression system.

[0046] Thin electrolytic cells allow for stacking more cells in a single stack, resulting in higher power density (kilowatts per liter, kW / L) for such stacks. Thin electrolytic cells can have dimensions of less than 5 mm, less than 3 mm, less than 2 mm, or less than 1.75 mm along the z-axis. Thus, thinner cells can be used with thinner flow fields, thereby resulting in better flow field design and a higher "figure of merit - FoM" for the design.

[0047] High mechanical compliance along the z-axis can be defined by the "compliance ratio", which is the ratio of the compressive elastic modulus along the z-axis of the corrugated porous sheet "E0" to the compressive elastic modulus along the z-axis of the corrugated porous sheet "E1" made of the same material (compliance ratio - E0 / E1). When the compliance ratio is greater than 2:1, greater than 5:1, greater than 10:1, greater than 25:1, or greater than 100:1, it can provide an advantageous compressive load distribution and an advantageous simplification of the requirements for the mechanical compression system outside the cells and the stack. Therefore, a larger compliance ratio can result in a better flow field design and a higher "FoM" for the design. The compressive elastic modulus "E" can be defined as the ratio of the measured stress to the measured strain in the material exposed to the compressive load, according to the conventional engineering convention. When the compliance ratio is large, when exposed to mechanical loads up to 5 kgf / cm 2 , 10 kgf / cm 2 , 15 kgf / cm 2 , 30 kgf / cm 2 , 45 kgf / cm 2 , or 100 kgf / cm 2 , a change in the thickness of the corrugated sheet may occur that is greater than 0.05%, greater than 0.25%, greater than 1%, or greater than 3%.

[0048] The uniformity of the load distribution in the cell region can be defined by comparing the exposed mechanical pressure [kgf / cm 2 ] at any point within the cell region with the average over a circular region of 10 mm 2 centered on that point ("point average load measurement"). The uniformity of the load distribution can be expressed using the "uniformity coefficient" (see Equation 3-1).

[0049]

Equation

[0050] Here, U L is the uniformity coefficient, and f maxis the maximum point-average load measurement at any location within the cell, and f avg This is the average load for the entire cell. L This value can range from 0 to 1, and ideally it is 1. Therefore, a larger uniformity coefficient can lead to better flow field design and a higher "FoM" for design.

[0051] The bubble discharge measurement can be defined as the period during which no liquid reactants are present in a given volume within the flow field. A suitable volume for measurement is 1 mm³. 3 , 5mm 3 , 10mm 3 This is possible. The favorable bubble evacuation period from this volume may be less than 60 minutes, less than 1 minute, less than 10 seconds, or less than 1 second. Alternatively, the evacuation measurement can also be characterized as the reciprocal of the evacuation period, and as a result, the evacuation frequency B f (Hz) is obtained, and for operational stability, a higher frequency is desired. Therefore, a higher discharge frequency can lead to a better flow field design and a higher "FoM" for the design.

[0052] To maximize the efficiency of a system that pumps water through cells or stacks, it is sometimes desirable to minimize the water flow resistance through the cells. Flow resistance can be characterized by the pressure loss experienced by the water flow per unit length of the anode flow field ("characteristic flow resistance" - millibars / centimeter, mb / cm). The material and geometric shape selected for the anode flow field, including corrugation pitch, height, porosity, and thickness of the material, can all affect the characteristic flow resistance. Therefore, a smaller characteristic flow resistance can lead to a better flow field design and a higher "FoM" for the design.

[0053] Referring to Figure 3, the factor described above can be formulated into the excess figure of merit "FoM" equation, as shown in Equation 3-2.

[0054]

number

[0055] Here, (E0 / E1) is the obedience ratio, U L is the uniformity coefficient, B f θ is the bubble removal frequency [Hz], h is the total thickness of the anode flow field [cm], and DP is the characteristic flow resistance of that flow field [mb / cm]. The resulting engineering unit of FoM is Hz per millibar [Hz / mb], which can be interpreted as the rate of bubble removal for a given input energy. This bubble removal efficiency is then weighted by important mechanical properties of docility, load uniformity, and thickness to yield the overall FoM for design. A FoM greater than 1, greater than 5, greater than 10, or greater than 25 is favorable.

[0056] Figure 4 shows an isometric view of a preferred embodiment of a bipolar plate assembly comprising a porous sheet (117) into which a hydrogen seal (217) can be embedded using screen printing, liquid distribution, injection, compression molding, or other suitable process. In this configuration, the porous sheet (117) can provide the function of a cathode flow field, providing both mechanical reinforcement for the hydrogen seal (217) and an open space for collecting the hydrogen gas flow from the active region of the cell. The porous sheet (117) may be relatively thin, while also providing precise thickness control of the bipolar plate assembly during pressing and curing of the hydrogen seal (217) and frame (221). A relatively thin porous sheet (117) may not significantly contribute to the desired compliant function throughout the cell, thereby placing an additional burden on other cell components, including the anode flow field, to provide this function.

[0057] Figure 5 shows a cross-sectional view (502) of Figure 4 with the cathode electrode reinforcement (116), cathode electrode (115), membrane (114), anode electrode (113), anode electrode reinforcement (112), anode flow field (111), internal seal (214), and water seal (222) added. After assembly and curing, the hydrogen seal (217) is completely embedded within the porous structure of the porous sheet (117), forming an airtight seal for hydrogen gas in the cathode flow field, and simultaneously allowing the bipolar plate (118) to be physically bonded to the porous sheet (117) and frame (221). The porous sheet (117) acts as a reinforcement for the hydrogen seal, increasing its strength and enabling sealing under high hydrogen gas pressure. The sheet (117) can be selected from one or more of the following: foam, felt, woven screen, expanded metal, perforated metal, or sintered metal frit. The sheet (117) may include iron, steel, stainless steel, titanium, nickel, nickel-chromium, Inconel, feclaloy, or alloys of these materials, and may also be coated with suitable coatings such as platinum, gold, tin, nickel, carbon, or combinations thereof. The porous sheet (117) may be relatively thin and contribute to the thin overall cell thickness "tc" (503).

[0058] Figure 6 shows the mathematical model results for the volume fraction of oxygen (621) at the anode flow field outlet as a function (622) of the stoichiometric value of the supplied water. The electrolysis process splits water into hydrogen on the cathode side and oxygen on the anode side. Once oxygen is formed on the anode, it may mix as a gas with the discharged liquid water, resulting in a two-phase flow in the anode flow field. The volume fraction of oxygen at the anode outlet may indicate the operational stability, performance, and / or durability of the electrolytic cell, and a target threshold for this parameter can be set by the designer. Conserving mass for the cell can lead to an equation for the volume fraction of oxygen at the outlet, as specified in Equation 6-1, where ρ O2 ρ is the density of oxygen gas at the anode outlet. H2Ois the density of liquid water at the anode outlet, and St is the water stoichiometry supplied to the cell. Plot (602) shows the results of this model over a range of anode pressures (611) of the electrolytic cell, along with an exemplary oxygen volume fraction threshold (612), above which the cell cannot operate stably or enduranceously, or above which the electrolytic system cannot operate efficiently. The oxygen volume fraction threshold can be used to determine a lower limit threshold (613) for water stoichiometry. To maintain stable and endurance operation of the electrolytic cell, it may be advantageous to select water stoichiometry that maintains the oxygen volume fraction below 80%, below 60%, below 50%, below 40%, or below 30%. This stoichiometry value can be greater than 50, or greater than 75, or greater than 100, thereby requiring careful consideration of the geometric shape of the anode flow field to ensure that an acceptable flow limit is achieved during operation. Furthermore, as oxygen gas is generated, the volume fraction may become a function of the operating pressure (611a~e), and the size of the bubbles formed may also be a function of the volume fraction. Therefore, careful consideration of the flow dynamics in the anode flow field is important to ensure the effective removal of bubbles from the electrodes and reinforcing layers, which can directly affect the operating performance and / or durability of the cell.

[0059]

number

[0060] Figure 7 shows the mathematical model results for the water temperature rise [°C] as a function of the stoichiometric value of the supplied water. The heat released during electrolytic cell operation may also be a function of efficiency, which may then be a function of the operating cell voltage. Saving energy in the cell can lead to the water temperature rise equation specified in Equation 7-1 (below), where V is the operating cell voltage, V0 is the thermal neutral cell voltage [1.481V], HHV is the higher heat output of hydrogen [141.79MJ / kg], c pis the specific heat capacity of water [4.182 kJ / kg°C], and St is the water stoichiometer supplied to the cell. Plots (711a) and (711b) show the results of this model at two possible operating voltages representing exemplary values ​​for the start [BoL] and end [EoL] of the electrolytic cell's life. Also shown is an exemplary water temperature rise target threshold (712), beyond which the electrolytic cell may not operate stably or enduringly, or beyond which the electrolytic system may not operate efficiently. The temperature rise threshold can be used in conjunction with the EoL voltage limit to define a lower limit threshold (713) for the water stoichiometer. It may be advantageous to select the water stoichiometer to maintain the water temperature rise at the end of life below 100°C, below 50°C, below 25°C, below 15°C, or below 10°C to maintain stable and enduring operation of the electrolytic cell. This stoichiometric value can be greater than 50, greater than 75, or greater than 100, and thereafter, the geometric shape of the anode flow field must be carefully considered to ensure that an acceptable flow limit is achieved during operation.

[0061]

number

[0062] Figure 8 shows published diagrams relating to the fluid dynamics when a fluid flows over a cavity, and to the formation of instability and fluid vortices. During the operation of an electrolytic cell, liquid water is supplied to the anode, generating oxygen gas. Crucial to this process is the rapid and effective removal of oxygen gas from the electrode and reinforcing material, which allows additional reactants (i.e., water) to reach the active site and enables the reaction to continue with minimal resistance. Therefore, insufficient removal of oxygen bubbles can result in poor cell performance, potentially leading to higher voltages or lower currents than desired for operation. The anode flow field can play a significant role in bubble removal. The geometric shape of the anode flow field can define fluid streamlines near the anode electrode reinforcing material and generate dynamic structures (instability, vortices, shear layers, etc.) that can facilitate effective convection of bubbles away from the electrode. As shown in Figure 8(802), fluid flow over a cavity is one way of generating such dynamic structures. Here, the cavity can be defined by depth "D" (811) and length "L" (812). The ratio L / D(816) can be an important parameter in establishing a desired flow pattern within the cavity. As shown, an L / D of less than 10 can generate a vortex pattern inside the cavity that promotes fluid vortices from the bottom to the top (813, 814) of the cavity. In contrast, an L / D greater than 10 can establish smaller vortices on both sides of the cavity (815) that do not reach the top of the cavity. In an electrolytic cell, the bottom of the cavity may represent the anode electrode reinforcing surface, and the top of the cavity may represent the main water flow through the anode. One or more cavities can be formed by the appropriate geometric shape of a corrugated porous sheet, specifically by arranging the peaks and troughs of the corrugation along the y-axis perpendicular to the flow direction along the x-axis (801) to provide the cavities. Thus, it may be advantageous to position the geometric shape of the corrugated porous sheet to mimic the geometric shape of the illustrated cavity (802).

[0063] Figure 9 shows a preferred flow configuration (902) that can provide low water flow resistance in the anode flow field (111a, 111b) while simultaneously generating instability and vortices (913, 916) near the electrode reinforcement layer (112) to promote convection of bubbles away from the electrode. As shown, the anode flow field consists of two corrugated layers. One layer (111b) is positioned closest to the anode electrode reinforcement and is oriented to have peaks and valleys oriented along the y-axis (901) substantially perpendicular to the water flow through the cell (911). This first layer can be formed from a porous sheet having a peak-to-peak pitch "p1" (915) and a thickness "t1" (925). The second layer (111a) is positioned furthest from the anode electrode reinforcement and is oriented to have peaks and valleys oriented along the x-axis (901) substantially parallel to the water flow through the cell (911). This second layer can be formed from a porous sheet having a peak-to-peak pitch "p2" (914) and a thickness "t2" (924). Since both sheets are porous, liquids and gases can move freely along any of the three axes in the space defined by the two layers. Most of the water flow can flow along relatively straight streamlines either above (911) or below (912) the second layer (111a). Streamlines below the second layer (111a) can act like a flow over a cavity shown in Figure 8. In this case, the cavity is generally defined by the wavy pattern of the first layer (111b), which can induce flow instability (913) and convective vortices (916), facilitating the effective transport of bubbles from the electrode-reinforced layer (112) to the main flow (912). As illustrated in Figure 8, to maximize the effectiveness of bubble removal, it may be advantageous to configure layer 1 (111b) such that the cavity ratio L / D (816) is less than 10, less than 5, or less than 2.5. One or more porous layers of the anode flow field (111) can be selected from one or more of the following: foam, felt, woven screen, expanded metal, perforated metal, or sintered metal frit.The porous material used for (111) may include iron, steel, stainless steel, titanium, nickel, nickel-chromium, Inconel, feclaloy, or alloys of these, and may also be coated with a suitable coating such as platinum, gold, tin, nickel, carbon, or a combination thereof. The porous layer may be processed before corrugating (e.g., by calendering between rollers) to achieve a desired thickness ("t1", "t2") and / or to achieve a desired mechanical property such as yield strength, hardness or elasticity.

[0064] Figure 10 shows a cross-sectional view (1002) of Figure 9 (902), further illustrating the potential hydrodynamic structures that can be generated by the present invention. In this description, bubbles (1031) emerging from the electrode reinforcement layer (112) are moved away by convection of vortices (1016) along the z-axis (1001). Bubbles (1032) can then move through layer 1 (111b) and be moved further away by convection of vortices (916) along the z-axis. Bubbles (1033) can finally enter the main water flow (912) to be removed from the cell. The corrugated structure of layer 1 (111b), having peaks and valleys perpendicular to the main water flow (112), can facilitate the generation of oscillating streamlines (913) flowing through the porous structure of layer 1 (111b). This configuration of layer 1 (111b) can further facilitate the generation of oscillating streamlines (1012) adjacent to the porous structure. The net result of the combination of oscillating streamlines is the generation of instability that removes bubbles attached to the electrode reinforcement (112) or the layers themselves (111b, 111a), which can then be transported by convection into the main water flow (912) through the aforementioned dynamic structure. It may be advantageous to construct layer 1 (111b) with a height "h1" (1022) to pitch "p1" (915) ratio, mimicking ratios less than 10, less than 5, or less than 2.5, which can promote a favorable dynamic pattern as shown in Figure 8 (816). With a waveform aligned along the y-axis perpendicular to the flow streamlines (912), layer 1 (111b) may exhibit greater fluid flow resistance than layer 2 (111a) with a waveform aligned along the x-axis parallel to the streamlines. Therefore, in order to minimize the overall flow resistance through the anode flow field, it may be advantageous to construct layer 2 (111a) having a height "h2" (1023) greater than or equal to the height of layer 1 ("h1", 1022), resulting in a preferred ratio of h2 / h1 ≥ 1.

[0065] Figures 11A, 11B, and 11C illustrate the dimensional response of a preferred embodiment of the present invention to an externally applied compressive load [kgf] (1111) oriented along the z-axis. Figure 11A shows the dimensions before load application, Figure 11B shows the dimensions during load application, and Figure 11C shows the dimensions after load application. The elastic response can be defined as the anode flow field returning to within 0.5% of its original height ("h1" + "h2") when the applied load is removed. The elastic response can further be defined as the corrugated porous sheet being able to withstand an applied compressive load of at least 20 kilograms-force per square centimeter without permanent deformation when applied along the z-axis. Obedience can be defined as the reciprocal of the effective elastic spring constant along the z-axis (i.e., the change in "z" per unit quantity of applied force [kgf] [mm]). Greater obedience results in a greater elastic change in thickness with respect to a given load, making the component behave like an acting spring. The preferred obedience of the anode flow field can be defined as a reduction of 3% to 15% in height ("h1" + "h2") when exposed to a load of 10 to 100 kilograms force / cm². The height "h0" (1021) of the electrode reinforcement layer (112) is relatively thin and may be rigid (i.e., non-obedient) to the other layers shown. Therefore, the height "h0" may not change significantly with the addition of load (1111). Due to the geometric shape and material properties of corrugated layers 1 (111b) and 2 (111a), their respective heights "h1a" (1022) and "h2a" (1023) may change significantly with the application of load (1111) ("h1b", 1122 and "h2b", 1123). Furthermore, the material properties of the corrugated structures (111b, 111a), including yield strength, hardness, or elasticity, as well as the geometric shape, including thicknesses "t1" (925) and "t2" (924), can be configured to elastically respond to the application of a load such that, when the load is removed, the respective heights of each layer return to approximately within ±5% of their original values ​​("h1c", 1132 and "h2c", 1133). A uniform distribution of the compressive load (1111) over the active region of the cell may be important for the effective operation of the cell.Therefore, a uniform distribution of applied loads through layer 2 (111a), layer 1 (111b), and electrode reinforcement (112) can be favored by the selection of the geometric shapes of these layers (e.g., thickness "t", height "h", and pitch "p"). To achieve this goal, it may be important to minimize the bending of each layer in the xy plane. Since bending in such a structure can be greatly influenced by the ratio of unsupported length to layer height, it may be advantageous to limit the ratio of unsupported length to layer height in each layer within the cell. For example, the pitch "p1" of layer 1 (111b) defines the unsupported length of electrode reinforcement layer (112) having height "h0" (1021). It may be advantageous to limit the ratio p1 / h0 ≤ 10, or p1 / h0 ≤ 5, or p1 / h0 ≤ 2.5. Similarly, the pitch "p2" (914, Figure 9) of layer 2 (111a) defines the unsupported length of layer 1 (111b) having height "h1" (1022, Figure 10). It may be advantageous to limit the ratio p2 / h1 ≤ 10, or p2 / h1 ≤ 5, or p2 / h1 ≤ 2.5. Since conformability within layers 1 (111b) and 2 (111a) is desirable, bending of the peaks and valleys of the corrugation is necessary. This bending can be substantially controlled by the geometric shape and material properties of the layers. In particular, the thickness of the porous layer ("t", 925, 924) relative to the corrugation dimensions ("h" and "p") can significantly affect the overall conformability once the corrugated structure is formed. It may be advantageous to limit the ratio p1 / t1 ≤ 15, or p1 / t1 ≤ 10, or p1 / t1 ≤ 5. It may be advantageous to restrict the ratio p2 / t2 ≤ 15, or p2 / t2 ≤ 10, or p2 / t2 ≤ 5. It may be advantageous to restrict the ratio h1 / t1 ≤ 10, or h1 / t1 ≤ 5, or h1 / t1 ≤ 2.5. It may be advantageous to restrict the ratio h2 / t2 ≤ 10, or h2 / t2 ≤ 5, or h2 / t2 ≤ 2.5.

[0066] Figure 12 shows a flow field (1202) in which two layers (111a, 111b) are joined at multiple spots (1211a-1211f) to facilitate alignment and handling as a unitized component having multiple layers. In this way, two or more layers can be joined. The joining points can be distributed across the surface of the layers in the xy plane (1201) at intervals along the x axis (1212) and along the y axis (1213). The intervals along the different axes may be the same or different. The number of joining points (1211a-1211f) along the different axes may be different. Joining can be achieved by welding, brazing, diffusion bonding, adhesive bonding, or any other known method.

[0067] Figure 13 shows a preferred embodiment of the system (1302) for continuous high-speed manufacturing of the anode flow field of Figure 12. Two coils (1311a, 1311b) of porous material may be mounted at the start of the process with their coil axes aligned with the x-axis. The two materials may be the same or different and may be pre-treated to achieve a desired thickness "t" (1332a, 1332b). The web widths "w" (1331a) of coil (1311a) and "w" (1331b) of coil (1311b) may be equal within ±5%. The web from coil (1311a) can be directed through a forming roller (1312a), which has forming teeth oriented parallel to the roller axis to emboss a corrugated pattern onto the web material, thereby increasing its length in the z-axis direction. The corrugated pattern of coil (1311a) can be oriented to have peaks and valleys substantially aligned along the x-axis. The web from coil (1311b) can be oriented through a forming roller (1312b), which has forming teeth substantially arranged circumferentially around the roller to emboss the corrugated pattern into the web material, thereby increasing its length in the z-axis direction. The corrugated pattern of coil (1311b) can be oriented to have peaks and valleys substantially aligned along the y-axis. The corrugated patterns of each coil may be substantially the same or different. Next, the corrugated web (1311a) can be passed over roller (1313) and directed toward the corrugated web (1311b), where both webs can be brought adjacent to each other via roller (1314). Then, the two-layer web (1321) can be passed between welding rollers (1315) positioned on either side of the two-layer web. The welding roller (1315) can be connected to an AC or DC power supply configured to weld two layers into a single web, as shown in Figure 12. The welding may be continuous or periodic, thereby producing separate spot welds, as shown in Figure 12. The spacing along the x-axis (1212) can be determined by the spacing of the wheels on the roller (1315).The spacing along the y-axis (1213) can be determined by dividing the period [seconds] of the welding pulse supplied to the welding roller by the rotational speed [cm / second] of the web moving along the y-axis. The number of welding wheels on the roller and the period of the welding pulse can be determined to ensure proper bonding between layers. In this way, it is also possible to process three or more layers. After welding, the unitized web can be cut into individual part pieces (1202) using known cutting methods that can cut multiple layers of porous material. Such methods may include laser cutting, die stamping, roller die cutting, water jet cutting, shearing, slitting, or any other known method.

[0068] Figures 14A and 14B show a prior art stack (1402a) and a stack (1402b) including components of a preferred embodiment of the present disclosure. The prior art stack (1402a) requires many large springs (1411) to maintain a compressive load on the core cells (1412) within the stack. These springs occupy considerable volume, consist of many parts, and can be inefficient or inconvenient to assemble during stack manufacturing. On the other hand, the stack (1402b) does not require large external springs, and compression can be carried out using a simple wrap (1421) of a thin sheet. The wrap (1421) can provide minimal spring function for compressing the stack. Thus, the compressive load can be maintained by the inherent obedience of the core cells (1422) within the stack. This obedience is imparted to the cells by a flow field disclosed in various embodiments of the present disclosure. In particular, the anode flow field (111) can be configured to have substantial obedience along the z-axis, thereby facilitating the maintenance of compression over time and during changes in temperature, pressure or other process conditions, and the stack can be exposed in combination with a stack compression wrap (1421) with minimal obedience. The anode flow field can further provide the necessary obedience within the core cell (1422) in the stack when combined with a relatively thin cathode flow field (117) with minimal obedience, thereby enabling the mechanical functionality of the relatively thin cell. According to preferred embodiments of the present disclosure, cells having a total thickness of tc ≤ 5.0 mm, or tc ≤ 3.0 mm, or tc ≤ 2.5 mm can be enabled.

[0069] Figures 15A and 15B show pressure paper test results that quantify the uniformity of compressive load in the active region of an electrolytic cell, comparing the prior art anode flow field (Figure 15A) with a preferred embodiment of the present disclosure (Figure 15B). The assembly in Figure 15A included an anode flow field comprising three layers of flat stainless steel wire mesh. The assembly in Figure 15B included an anode flow field comprising a combination of one layer of flat stainless steel wire mesh and one layer of corrugated stainless steel wire mesh having a geometric anode flow field consistent with the present disclosure. Although the overall flow field and cell thickness were the same in both tests, the prior art assembly clearly lacked compliance due to the highly non-uniform pressure (1511) exposed to the active region compared to the cell boundary region (1512). In contrast, the compliance inherent in the assembly of the preferred embodiment allows the load to be substantially equal in both the active region (1521) and the boundary region (1522) of the cell. These results confirm the advantages of a compliant flow field structure in achieving a more uniform load distribution for thin electrolytic cells.

[0070] Figure 16 shows the results of finite element simulations (1602) calculated for a series of exemplary corrugated porous sheet shapes. The compressive modulus "E" can be defined, by conventional engineering convention, as the ratio of measured stress to measured strain in a material subjected to a compressive load. A typical compressive modulus "E0" (1613) was used for uncorrugated stainless steel woven wire mesh of two different thicknesses: 150 mm (1621) and 250 mm (1622). 30 kgf / cm² 2The external load was applied to models with various corrugated pitch-to-height ratios (1612). The calculated deflections obtained were converted to the compressive modulus "E1" (1614). The responsiveness ratio E0 / E1 (1611) was then plotted against the pitch-to-height ratio (1612), and data (1621, 1622) were obtained for two thicknesses, respectively. Least-squares curve fitting for the two datasets (1631, 1632) shows that the responsiveness ratio can be significantly influenced by the choice of pitch-to-height ratio, and that responsiveness ratio values ​​of 2, 5, 10, 25, or greater than 100 can be achieved. These magnitudes of responsiveness ratios can provide a favorable compressive load distribution across the cell area (as shown in Figure 15), and further allow for a favorable simplification of the design requirements for external cell and stack mechanical compression systems. A large responsiveness ratio is 5 kgf / cm². 2 , 10 kgf / cm 2 , 15 kgf / cm 2 , 30 kgf / cm 2 , 45 kgf / cm 2 , or 100 kgf / cm² 2 When exposed to mechanical loads up to a certain point, changes in the thickness of the corrugated sheet may occur by more than 0.05%, more than 0.25%, more than 1%, and more than 3%.

[0071] Figure 17 (1702) shows the characteristic flow resistance [millibars / centimeter, mb / cm] (1711) versus water flow velocity [centimeters / second, cm / second] (1712) measured for several exemplary flow fields (1721). Mathematical model results (1731) for the exemplary flow fields are also shown. Anode flow fields exhibiting characteristic flow resistance-convection velocity curves of such magnitude may be advantageous in minimizing the pumping energy consumed in systems using stacks of cells containing flow fields with these features.

[0072] Exemplary Embodiments A. An electrolytic cell comprising a film, an anode, a cathode, an anode reinforcing layer, a cathode reinforcing layer, an anode flow field, a cathode flow field, and a bipolar plate assembly, The anode flow field includes one or more porous sheets having at least one linear edge, An electrolytic cell comprising at least one porous sheet having a corrugated pattern with multiple peaks and valleys, the axes of which are generally aligned with one straight edge of the sheet, and which protrude by a height "h" along the z-axis which is generally aligned with the thickness dimension of the sheet.

[0073] B. The anode flow field is configured such that its thickness decreases by 3% to 15% when exposed to a load of 10 to 100 kilograms per square centimeter. The electrolytic cell described in A, wherein the anode flow field returns to within 0.5% of its original thickness when the exposed load is removed.

[0074] C. The electrolytic cell described in A, wherein at least one corrugated porous sheet can withstand a compressive load of at least 20 kilograms-force / square centimeter applied along the z-axis, which is roughly aligned with the thickness of the sheet, without permanent deformation.

[0075] D. An electrolytic cell as described in A, in which one or more porous sheets are calendered to a thickness selected to achieve a target yield strength, hardness, or modulus of elasticity.

[0076] E. The anode flow field includes two or more porous sheets, The electrolytic cell described in A, wherein two or more porous sheets are spot-welded to form a single flow field structure.

[0077] F. The anode flow field includes a corrugated porous sheet adjacent to the anode reinforcement layer. The electrolytic cell described in A, wherein the ratio of the corrugated pitch "p1" of this porous sheet to the height "h0" of the anode reinforcement layer is less than 10, less than 5, or less than 2.5.

[0078] G. The anode flow field contains a porous sheet with exactly two waveforms. The electrolytic cell as described in A, wherein the ratio of the waveform pitch "p2" of the sheet furthest from the anode electrode to the height "h1" of the sheet closest to the electrode is less than 10, less than 5, or less than 2.5.

[0079] H. The anode flow field includes at least one porous sheet of waveform, The electrolytic cell described in A, wherein the ratio of the wave pitch to the sheet thickness p / t is 15 or less, 10 or less, or 5 or less.

[0080] I. The anode flow field includes at least one porous sheet of waveform, The electrolytic cell described in A, wherein the ratio of the wave height to the sheet thickness h / t is 10 or less, 5 or less, or 2.5 or less.

[0081] J. The anode flow field contains a porous sheet with exactly two waveforms. The waveform pitch "p1" of the sheet closest to the anode electrode is 0.4 mm to 2.0 mm. The electrolytic cell described in A has a waveform pitch "p2" of the sheet furthest from the anode electrode of 0.5 mm to 2.5 mm.

[0082] K. The anode flow field contains a porous sheet with exactly two waveforms. The height "h1" of the sheet closest to the anode electrode is 0.1 mm to 1.0 mm. The height "h2" of the sheet furthest from the anode electrode is 0.2 mm to 2.0 mm, as described in A for the electrolytic cell.

[0083] L. The anode flow field contains a porous sheet with exactly two waveforms. The electrolytic cell described in A, wherein the waveform pitch "p1" of the sheet closest to the anode electrode is less than or equal to the waveform pitch "p2" of the sheet furthest from the anode electrode.

[0084] M. The anode flow field contains a porous sheet with exactly two waveforms. The electrolytic cell described in A, wherein the height "h1" of the sheet closest to the anode electrode is less than or equal to the height "h2" of the sheet furthest from the anode electrode.

[0085] N. The anode flow field contains a porous sheet with exactly two waveforms. The electrolytic cell according to A, wherein the sheet located furthest from the anode electrode is oriented such that its peak and valley axes are substantially parallel to the flow direction of the anode reactant.

[0086] O. The anode flow field contains a porous sheet with exactly two waveforms. The electrolytic cell according to A, wherein the sheet positioned closest to the anode electrode is oriented such that its peak and valley axes are substantially perpendicular to the flow direction of the anode reactant.

[0087] P. All of the above one or more porous sheets are corrugated. The electrolytic cell described in A, wherein the waveform peaks of adjacent sheets are oriented almost perpendicular to each other.

[0088] Q. The electrolytic cell according to A, wherein one or more of the porous sheets are selected from stainless steel, titanium, nickel, and nickel-chromium materials.

[0089] R. The electrolytic cell according to A, wherein the one or more porous sheets are selected from wire mesh, expanded foil, and perforated sheets.

[0090] S. The cathode flow field includes a porous sheet containing an embedded hydrogen seal. The electrolytic cell according to A, wherein the porous sheet provides both mechanical reinforcement for embedded hydrogen seals and an open space for hydrogen gas flow from the active region of the electrolytic cell to the cell outlet.

[0091] T. An electrolytic stack comprising one or more electrolytic cells, each electrolytic cell comprising a film, an anode, a cathode, an anode reinforcing layer, a cathode reinforcing layer, an anode flow field, a cathode flow field, and a bipolar plate assembly, The anode flow field includes one or more porous sheets having at least one linear edge, At least one of the porous sheets has a corrugated pattern with multiple peaks and valleys, the axes of which are generally aligned with one straight edge of the sheet, and they protrude by a height "h" along the z-axis which is generally aligned with the thickness dimension of the sheet. The above stack is an electrolytic stack comprising a compression system including a structural wrap that includes one or more wrap layers that surround at least a portion of the electrolytic cell stack, which includes multiple cells, in the circumferential direction.

[0092] U. The anode flow field is configured such that its thickness decreases by 3% to 15% when exposed to a load of 10 to 100 kilograms per square centimeter. The electrolytic stack described in T has an anode flow field that returns to within 0.5% of its original thickness when the exposed load is removed.

[0093] V. The electrolytic stack described in T, wherein at least one corrugated porous sheet can withstand a compressive load of at least 20 kilograms-force / square centimeter applied along the z-axis, which is roughly aligned with the thickness of the sheet, without permanent deformation.

[0094] W. The anode flow field includes a corrugated porous sheet adjacent to the anode reinforcement layer. The ratio of the waveform pitch "p1" of this porous sheet to the height "h0" of the anode reinforcement layer is less than 10, less than 5, or less than 2.5, as described in the electrolytic stack T.

[0095] X. The anode flow field contains a porous sheet with exactly two waveforms. The electrolytic stack described in T, wherein the ratio of the waveform pitch "p2" of the sheet furthest from the anode electrode to the height "h1" of the sheet closest to the electrode is less than 10, less than 5, or less than 2.5.

[0096] Y. The anode flow field contains a porous sheet with exactly two waveforms. The electrolytic stack described in T, wherein the average thickness of the cells in the stack core is less than 5 mm, less than 3 mm, or less than 2.5 mm.

[0097] Z. The structural wrap acts as a tension element in the compression system. The electrolytic stack described in T, wherein one or more wrap layers are essentially flat sheets of material having essentially uniform thickness.

[0098] AA. The electrolytic stack described in T is determined by the total thickness of one or more wrap layers, and the maximum allowable operating pressure of the electrolytic cell stack.

[0099] BB. The reactants entering the anode flow field include liquid water containing more than 1% by weight of elements other than hydrogen and oxygen. The products emanating from the cathode flow field have a non-zero water vapor content. The anode flow field includes one or more porous sheets having at least one linear edge, An operating method and electrolytic cell wherein at least one porous sheet has a corrugated pattern having multiple peaks and valleys, the axes of which are generally aligned with one straight edge of the sheet, and they protrude by a height "h" along the z-axis which is generally aligned with the thickness dimension of the sheet.

[0100] CC. A method for producing an anode flow field for an electrolytic cell, A continuous process of wave processing and lamination is performed. A web from one coil of flat porous material ("web1") is guided through a pair of rollers configured to corrugate the web so that it has multiple peaks and valleys with a corrugated pitch of "p1". The waveform axis of "web1" is roughly aligned with the coil axis. The waveform height "h1" of "web1" extends along the z-axis, which is roughly aligned with the thickness dimension of "web1". The web from a second coil of flat porous material ("web2") is guided through a pair of rollers configured to corrugate the web so that it has multiple peaks and valleys with a corrugated pitch of "p2". The axes of the "web2" waveform are roughly aligned in the direction of the "web2" expansion. The waveform height "h2" of "web2" extends along the z-axis, which is roughly aligned with the thickness dimension of "web2". After passing through the corrugated roller, "web1" and "web2" are transported so that they are adjacent to each other. The two layers are spot-welded to each other periodically across the web width and along the length in the coil deployment direction. Individual anode flow field components are cut from the laminated web by laser cutting, roller die cutting, or punching. [Explanation of symbols]

[0101] 101 z-axis 102 Electrolytic Cells 111a,b Anode flow field 112 Anode electrode reinforcement material 113 Anode electrode 114 Electrolytes 115 Cathode electrode 116 Cathode electrode reinforcement material 117 Cathode flow field 118 Bipolar Separator Plate 214 Internal seal 217 Hydrogen Seal 221 Cell Frame 222 Water Seal

Claims

1. film, anode, Cathode, Anode reinforcement layer, Cathode reinforcement layer, Anode flow field, Cathode flow field, and An electrolytic cell comprising a bipolar plate assembly, The anode flow field includes one or more porous sheets having at least one linear edge, An electrolytic cell comprising at least one porous sheet having a corrugated pattern with multiple peaks and valleys, the axes of which are generally aligned with one straight edge of the sheet, and which protrude by a height "h" along the z-axis which is generally aligned with the thickness dimension of the sheet.

2. The anode flow field is configured such that its thickness decreases by 0.05% to 5% when exposed to a load of 10 to 100 kilograms per square centimeter. The electrolytic cell according to claim 1, wherein the anode flow field returns to within 0.05% of its original thickness when the exposed load is removed.

3. The electrolytic cell according to claim 1, wherein at least one corrugated porous sheet can withstand a compressive load of at least 20 kilograms-force / square centimeter applied along the z-axis, which is roughly aligned with the thickness of the sheet, without permanent deformation.

4. The electrolytic cell according to claim 1, wherein one or more porous sheets are calendered to a thickness selected to achieve a target yield strength, hardness, or modulus of elasticity.

5. The anode flow field includes two or more porous sheets. The electrolytic cell according to claim 1, wherein the two or more porous sheets are spot-welded to form a single flow field structure.

6. The anode flow field includes a corrugated porous sheet adjacent to the anode reinforcement layer. The electrolytic cell according to claim 1, wherein the ratio of the corrugated pitch "p1" of the porous sheet to the height "h0" of the anode reinforcement layer is less than 10, less than 5, or less than 2.

5.

7. The anode flow field contains two precisely two waveform porous sheets. The electrolytic cell according to claim 1, wherein the ratio of the waveform pitch "p2" of the sheet furthest from the anode electrode to the height "h1" of the sheet closest to the electrode is less than 10, less than 5, or less than 2.

5.

8. The anode flow field includes at least one porous sheet of waveform, The electrolytic cell according to claim 1, wherein the ratio of the wave pitch "p" to the sheet thickness "t" is less than 15, less than 10, or less than 5.

9. The anode flow field includes at least one porous sheet of waveform, The electrolytic cell according to claim 1, wherein the ratio of the waveform height "h" to the sheet thickness "t" is less than 10, less than 5, or less than 2.

5.

10. The anode flow field contains two precisely two waveform porous sheets. The waveform pitch "p1" of the sheet closest to the anode electrode is 0.2 mm to 2.0 mm. The electrolytic cell according to claim 1, wherein the waveform pitch "p2" of the sheet furthest from the anode electrode is 0.25 mm to 2.5 mm.

11. The anode flow field contains two precisely two waveform porous sheets. The height "h1" of the sheet closest to the anode electrode is 0.1 mm to 1.0 mm. The electrolytic cell according to claim 1, wherein the height "h2" of the sheet furthest from the anode electrode is 0.2 mm to 2.0 mm.

12. The anode flow field contains two precisely two waveform porous sheets. The electrolytic cell according to claim 1, wherein the waveform pitch "p1" of the sheet closest to the anode electrode is less than or equal to the waveform pitch "p2" of the sheet furthest from the anode electrode.

13. The anode flow field contains two precisely two waveform porous sheets. The electrolytic cell according to claim 1, wherein the height "h1" of the sheet closest to the anode electrode is less than or equal to the height "h2" of the sheet furthest from the anode electrode.

14. The anode flow field contains two precisely two waveform porous sheets. The electrolytic cell according to claim 1, wherein the sheet located furthest from the anode electrode is oriented such that its peak and valley axes are substantially parallel to the flow direction of the anode reactant.

15. The anode flow field contains two precisely two waveform porous sheets. The electrolytic cell according to claim 1, wherein the sheet positioned closest to the anode electrode is oriented such that its peak and valley axes are substantially perpendicular to the flow direction of the anode reactant.

16. All of the above one or more porous sheets are corrugated. The electrolytic cell according to claim 1, wherein the waveform peaks of adjacent sheets are oriented substantially perpendicular to each other.

17. The electrolytic cell according to claim 1, wherein the one or more porous sheets are selected from stainless steel, titanium, nickel, and nickel-chromium materials.

18. The electrolytic cell according to claim 1, wherein the one or more porous sheets are selected from wire mesh, expanded foil, and perforated sheets.

19. The cathode flow field includes a porous sheet containing an embedded hydrogen seal. The electrolytic cell according to claim 1, wherein the porous sheet provides both mechanical reinforcement for embedded hydrogen seals and an open space for hydrogen gas flow from the active region of the electrolytic cell to the cell outlet.

20. Electrolytic stack containing one or more electrolytic cells: Here, each electrolytic cell is: film, anode, Cathode, Anode reinforcement layer, Cathode reinforcement layer, Anode flow field, Cathode flow field, and Includes a bipolar plate assembly, The anode flow field includes one or more porous sheets having at least one linear edge, At least one of the porous sheets has a corrugated pattern with multiple peaks and valleys, the axes of which are generally aligned with one straight edge of the sheet, and they protrude by a height "h" along the z-axis which is generally aligned with the thickness dimension of the sheet. The above stack includes a compression system that includes a structural wrap, which includes one or more wrap layers that surround at least a portion of an electrolytic cell stack containing multiple cells in the circumferential direction.

21. The anode flow field is configured such that its thickness decreases by 0.05% to 5% when exposed to a load of 10 to 100 kilograms per square centimeter. The electrolytic stack according to claim 20, wherein the anode flow field returns to within 0.05% of its original thickness when the exposed load is removed.

22. The electrolytic stack according to claim 20, wherein at least one corrugated porous sheet can withstand a compressive load of at least 20 kilograms-force / square centimeter applied along the z-axis, which is roughly aligned with the thickness of the sheet, without permanent deformation.

23. The anode flow field includes a corrugated porous sheet adjacent to the anode reinforcement layer. The electrolytic stack according to claim 20, wherein the ratio of the corrugated pitch "p1" of the porous sheet to the height "h0" of the anode reinforcement layer is less than 10, less than 5, or less than 2.

5.

24. The anode flow field contains two precisely two waveform porous sheets. The electrolytic stack according to claim 20, wherein the ratio of the waveform pitch "p2" of the sheet furthest from the anode electrode to the height "h1" of the sheet closest to the electrode is less than 10, less than 5, or less than 2.

5.

25. The anode flow field contains two precisely two waveform porous sheets. The electrolytic stack according to claim 20, wherein the average thickness of the cells in the stack core is less than 5 mm, less than 3 mm, or less than 2.5 mm.

26. The structural wrap acts as a tension element in the compression system. The electrolytic stack according to claim 20, wherein one or more wrap layers are essentially flat sheets of material having essentially uniform thickness.

27. The electrolytic stack according to claim 20, wherein the total thickness of one or more wrap layers is determined by the x-axis dimension of the cell stack and the maximum allowable operating pressure of the electrolytic cell stack.

28. The reactants entering the anode flow field include liquid water containing more than 1% by weight of elements other than hydrogen and oxygen. The products emanating from the cathode flow field have a non-zero water vapor content. An operating method and electrolytic cell comprising one or more porous sheets having at least one linear edge, at least one of the porous sheets having a corrugated pattern with multiple peaks and valleys, the axes of which are substantially aligned with one linear edge of the sheet, and which protrude by a height "h" along the z axis substantially aligned with the thickness dimension of the sheet.

29. A method for producing an anode flow field for an electrolytic cell, A continuous process of wave processing and lamination is performed. A web from one coil of a flat porous material ("web1") is guided through a pair of rollers configured to corrugate the web so that it has multiple peaks and valleys with a corrugated pitch of "p1". The axis of the waveform in "web1" is roughly aligned with the axis of the coil. The height "h1" of the waveform "web1" extends along the z-axis, which is roughly aligned with the thickness dimension of "web1". The web from a second coil of flat porous material ("web2") is guided through a pair of rollers configured to corrugate the web so that it has multiple peaks and valleys having a corrugated pitch of "p2". The axes of the "web2" waveform are roughly aligned in the direction of the "web2" expansion. The height "h2" of the "web2" waveform extends along the z-axis, which is roughly aligned with the thickness dimension of "web2". After passing through the corrugated roller, "web1" and "web2" are transported so that they are adjacent to each other. The two layers are spot-welded to each other periodically across the web width and along the length in the coil deployment direction. Individual anode flow field components are cut from the laminated web by laser cutting, roller die cutting, or punching.

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