Retractable flow fields for electrochemical cells and methods of making them at high speed

Abstract

The application relates to a flow field for use in an electrolytic cell comprising one or more porous sheets having a corrugated structure. The electrolytic cell comprises a membrane, an anode, a cathode, an anode reinforcement layer, a cathode reinforcement layer, an anode flow field, a cathode flow field, and a bipolar plate assembly comprising an embedded hydrogen seal. The anode flow field includes one or more porous sheets having at least one straight edge, and wherein at least one of the porous sheets has the form of a corrugated pattern having a plurality of peaks and valleys whose axes are substantially aligned with one straight edge of the sheet. The anode flow field geometry simultaneously provides elasticity for efficient mechanical compression of the cell and well distributed mechanical support for anode reinforcement layers adjacent the anode flow field.

Description

[0001] Related Patent Applications Incorporated by Reference

[0002] This application is based upon and claims the benefit of priority to U.S. Provisional Application No. 63 / 483,658, filed on February 7, 2023, under 35 U.S.C. §119(e), the entire contents of all of which are incorporated herein by reference in their entirety. Field of the Invention

[0003] The present disclosure relates to electrochemical cells and stacks, and more particularly, to components for electrochemical cells and stacks designed for scalable active area and high-speed manufacturing.

[0004] background

[0005] An electrochemical cell is a device used to generate electricity by inducing a chemical reaction using electricity or by using a chemical reaction. If electricity is the output, the cell can be considered a fuel cell or expander cell, depending on the chemical product. If electricity is the input, the cell can be considered an electrolyzer, compressor cell, or purifier cell, depending on the chemical product. For example, an electrolyzer captures electrical energy and stores it in a fuel, such as hydrogen, by breaking water into its component elements. In contrast, a fuel cell can be considered essentially an electrolyzer operating in reverse, where hydrogen and oxygen are supplied to the cell, which then combines these molecules to form water, releasing electrical energy in the process. Other chemical reactions can be facilitated by using an electrochemical cell or stack of cells, such as reducing carbon dioxide to carbon monoxide, ethylene, or ethylene glycol, reducing nitrogen to ammonia or related compounds, forming hydrogen peroxide from water and oxygen, or extracting lithium from an aqueous lithium brine solution. 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 an electrolyzer or fuel cell in a membraneless configuration. The electrochemical cell may also include a separator between the electrodes to prevent the products from mixing inside the cell. In the case of a solid electrolytic cell, the membrane and separator may be combined into an integrated solid ionically conductive layer. The complete electrochemical cell may also include a flow field for transporting reactants to the electrodes, a seal for isolating the reactants from each other and from the environment, and one or more impermeable separator plates (also referred to as bipolar plates) for isolating one cell from adjacent cells in the stack, and in certain embodiments, for accommodating a separate cooling fluid for thermal management of the cell.

[0006] 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 electrolyte has its own benefits and limitations. The advantages of proton and anion exchange membrane electrolytes may include relatively low operating temperatures and batteries that can use integrated layer electrolyte / membrane structures. Electrolyzers using such membranes have significant advantages over other electrolyzers in that they can operate using relatively pure liquid water rather than caustic solutions or water vapor as raw materials, thereby greatly simplifying the system balance in practice. Relatively pure water can be defined as water containing no more than 1% by weight of other elements except hydrogen and oxygen. Such electrolyzers can also be operated without liquid water on the cathode, allowing hydrogen to be produced in the gas phase with non-zero vapor phase moisture content. Non-zero vapor phase moisture content can be defined as a gas containing more than one part per million of water vapor by volume.

[0007] The impact of carbon dioxide on global climate change is well documented. As society's efforts to address global climate change accelerate, the need for deep decarbonization of most or all human energy use has become clear and urgent. The use of hydrogen as a carbon-free energy carrier is necessary to reach certain areas of human industry that are difficult or impossible to decarbonize directly with electricity. Examples of such areas include steel production, fertilizer manufacturing, construction, and heavy transportation such as trucking, shipping, and aviation. Beyond these areas, hydrogen's energy density and stable storage properties have made it the most viable candidate for seasonal-scale energy storage using only renewable electricity and for building grid resilience, which will be required to fully convert energy use to carbon-free sources. These and other benefits have driven a high level of interest in the production of "green hydrogen."

[0008] If hydrogen is produced from renewable electricity (wind, solar, hydro, etc.) by electrolysis, it is given a "green" label. The other "colors" of hydrogen are conventionally assigned to other energy sources. The scale required to meet the potential demand for green hydrogen in the future global energy system is daunting. Over the next decade, the production capacity of electrolyzers will need to increase by many orders of magnitude and their cost reduced by ten times or more to meet such demand. Until now, the production of hydrogen electrolyzers has been a niche industry with small systems and limited configurations based on cells and stacks designed for research and development. Only little consideration has been given to the manufacturing speeds required to produce and assemble cells and stacks at a rate commensurate with society's ultimate needs.

[0009] Summary of the Invention

[0010] Recognizing the urgent need for innovative electrolytic cell technologies in addressing climate change, the present application relates to flow fields for scalable electrolytic cells and stacks, scalable electrolytic cells and stacks, scalable stack compression systems, and methods for high-speed manufacturing. Embodiments of the present application relate to the design and manufacture of a key component for these cells and stacks: a fluid flow field. A flow field is a component within a cell assembly that provides the open space necessary for reactants and products to flow continuously into and out of the operating cell and stack. Such a flow field can include other functions within the cell, such as uniform mechanical load distribution on the membrane and electrode layers, and electrical conduction through the cell. The present disclosure includes innovative arrangements of flow field component geometry and dimensions that facilitate advantages associated with the assembly and compression of cells within an electrochemical stack. The present disclosure also includes improved geometries and dimensions for electrolytic cells having a reduced overall thickness relative to the prior art. The present disclosure also includes innovative arrangements of flow field component geometry and dimensions that facilitate advantages associated with the formation and removal of bubbles formed during reactions on the liquid flow side of the cell. The present disclosure also includes innovative methods for manufacturing flow field components at higher speeds relative to the prior art. For clarity, the following description will focus on water electrolysis to produce hydrogen, but those skilled in the art can apply it to other electrochemical processes.

[0011] 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 is produced at the anode, while hydrogen is produced at the cathode. The specific ions conducted between the anode and cathode depend on the electrolyte used. In acid batteries, the positively charged hydronium ion (H3O + ) is conducted from the anode to the cathode. In alkaline batteries, negatively charged hydroxide ions (OH - ) is conducted from the cathode to the anode. In both systems, the overall reaction is the same: (2) H2O(l) → (2) H2(g) + O2(g). Electricity must be supplied to drive the reaction. The open circuit or thermoneutral voltage for the basic reaction of hydrogen to liquid water is 1.481, so a voltage higher than 1.481 must be applied to a hydrogen electrolysis cell fed with liquid water to cause the reaction to proceed (as described below, an overpotential is generally required to allow the reaction to proceed at an acceptable rate). The size of the cell (i.e., active area) determines the rate at which hydrogen / oxygen can be produced from one cell at a given applied voltage. The total current required for a particular applied voltage can be proportional to the active area of ​​the cell. In practical systems, multiple cells can be "stacked" on top of each other to increase production capacity. Such cell stacking results in the need to apply a higher voltage (an integer multiple of the cell count) to drive the reaction. For example, a 1000 cm 2 A single cell with an active area of ​​500 cm 2 The two stacked cells have the same hydrogen flow, but 500 cm 2A stack would require an input of twice the voltage and half the current. Flexibility in selecting the desired voltage and current can be an important consideration in the design and cost of the overall electrolysis system. For example, power supplies for higher currents and lower voltages can be more expensive than power supplies for higher voltages and lower currents due to the size of the required electrical conductors and the additional materials required for their construction. Therefore, easily scalable cell active area is a significant advantage in terms of cost and configuration flexibility.

[0012] The elements of a hydrogen electrolyzer stack may include repeating assemblies (a stack of repeating "cells") and a system of non-repeating assemblies to hold the cells together in a stacked configuration. As the name indicates, repeating assemblies are those whose number is proportional to the stack height and typically include membrane / electrolyte, anode and cathode electrodes, anode and anode electrode reinforcement layers, water and hydrogen flow fields, water and hydrogen seals, and bipolar cell separators. Non-repeating assemblies typically include end units and a mechanical system for maintaining compression of the stack of repeating assemblies ("core"), as well as power terminals, electrical insulators, fluid distributors, and / or drain / cleaning 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 in the core. This compression of the core may be necessary to ensure electrical contact and fluid sealing between individual cells and with the end units. In a typical electrolyzer stack, the compliant elements may be located outside the core because the core itself may be relatively mechanically "rigid." In this case, a relatively "soft" or compliant compression system external to the core may be required to ensure that a continuous compressive load is maintained as the stack height changes over time or with temperature or pressure. These external elements can be large and / or expensive and / or inconvenient to manufacture. Alternatively, repeating components with built-in compliance can enable the designer to minimize or eliminate the need for a large number of external springs, rods, bolts, etc., which results in advantages in cost, size and speed of stack assembly. In this case, compliance can be defined as the inverse of the effective elastic spring constant along the z-axis, which is the axis aligned with the axis of the stacked cells (i.e., change in "z" [mm] per unit of applied force [kgf]).

[0013] The present disclosure relates to a novel structure of a fluid flow field for scalable electrolytic cells and stacks. The flow field is an element of a battery that provides an open space for transporting battery reactants (such as water) to the battery active area and for collecting battery products (such as hydrogen, oxygen) from the battery active area. In a conventional electrolytic cell, the flow field may include a series of channels formed in a bipolar plate. Due to the lack of scalability and the need for a relatively large thickness to maintain a reasonable water pressure loss through the small channels formed, channel-like flow fields present significant challenges in electrolysis. In the present disclosure, the flow field includes a three-dimensional continuous open space ("open flow field" or "OFF") formed using a porous material to maintain the separation of the electrode from the adjacent battery under the compressive load applied to the battery. The OFF can also conduct electricity through the open space between the electrode and the adjacent battery.

[0014] Previous constructions of OFFs for electrolytic cells consist of various configurations of metal foams, sintered metal frits, flat wire meshes, expanded metal meshes, and perforated sheets. These OFFs are flat structures with low porosity and, like channels, require cells of large thickness to provide reasonable water pressure losses. These cells are relatively rigid (non-compliant) along the z-axis and may require large, expensive, and inconvenient compression systems to maintain cell-to-cell contact and sealing throughout the life of a stack of such cells. Previous methods of OFF in fuel cells have included forming porous sheets, such as corrugations and indentations of thin flat sheets, to provide larger volumes and lower pressure drops for airflow in these devices. However, fuel cells do not have the bubble management issues present in electrolytic cells, and therefore these prior art flow fields are no longer suitable for two-phase flow and bubble evacuation. Existing OFF methods have significant limitations in size, cost, flow resistance, cell performance, and manufacturability, which the present disclosure aims to overcome.

[0015] In some embodiments, the present disclosure includes a scalable flow field that can be used as an anode flow field and combined with a bipolar plate assembly that includes a scalable cathode flow field that further includes an embedded hydrogen seal. In this configuration, the porous cathode flow field provides both mechanical reinforcement for the hydrogen seal and open space for collecting and directing the hydrogen flow away from the active area of ​​the cell. The hydrogen seal can be completely embedded within the porous structure of the porous cathode flow field, forming an airtight seal for the hydrogen in the cathode while physically adhering the components of the bipolar plate assembly together. In this configuration, the cathode flow field can be made very thin by virtue of the hydrogen seal coinciding with the porous flow field along the z-axis. Minimizing the thickness of each repeating cell in the core can be important for achieving a small stack with high output (i.e., high power density). Achieving built-in compliance for very thin repeating components can be challenging because, fundamentally, thin components (i.e., short "springs") are more rigid than thick components. The material and geometry of the anode flow field can be important to developing a core with sufficient compliance because this component can be relatively thick compared to the other layers in each cell, including the cathode flow field.

[0016] In some embodiments, the present disclosure may include a scalable flow field configured to enable improved compressive load distribution to the membrane and electrodes in combination with selected electrode reinforcement materials. Applying a uniform compressive load to the electrodes and membrane may be important for battery performance and service life. One or more corrugated layers may have a size selected to minimize the bending of the electrode reinforcement under load, resulting in a more uniform transfer of mechanical loads to the electrodes and membrane through the reinforcement. The peak-to-peak (i.e., "corrugation spacing") size of the layer adjacent to the electrode reinforcement can be selected based on the elastic properties and thickness of the reinforcement to achieve this function.

[0017] In some embodiments, the present disclosure may 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 function.

[0018] For convenience, we can define a Cartesian coordinate system with perpendicular xyz axes, where "x" is parallel to the general direction of water flow through the stack, "y" is perpendicular to x, but in the same plane defined by the individual cells, and "z" is generally parallel to the direction of the stacking of the cells. In this case, the compression system generally acts to apply a compressive load along the z-axis, keeping the cells and their various repeating assemblies in contact with each other. The compliance of the core can then be measured along this defined z-axis.

[0019] When an electrolytic cell operates, water is consumed and hydrogen and oxygen are produced, so water must be continuously supplied to the cell to fuel the reaction. Stoichiometry is a term referring to the "balance" of a chemical reaction. In electrochemical cells, the term "stoichiometry" or "stoich" refers to the ratio of reactants fed to the cell relative to the amount required to precisely balance the overall reaction. For example, an electrolytic cell operating at a water stoichiometry of 2 will have twice the amount of water required to produce the hydrogen and oxygen leaving the cell as its input. The conservation of mass in a system with a stoichiometry of 1 indicates that 1 kg of hydrogen production per hour is associated with approximately 8 kg of oxygen production per hour and approximately 9 kg of water consumption per hour. Typically, electrolytic cells can be operated with a minimum water stoichiometry greater than 1 to ensure sufficient reactants throughout the cell. For example, at a water flow stoichiometry of 1, all water supplied to the cell is converted to oxygen at the anode, resulting in an oxygen fraction of 100% at the cell outlet (i.e., no water leaves the cell). This situation can be unstable and can lead to damage due to anode starvation of the cell near the outlet. Since all that leaves the cell is vapor, this can also lead to high fluid velocities and pressure losses at the outlet. Therefore, process conditions can be selected to keep the oxygen vapor fraction at the cell outlet below a given threshold. For example, an outlet oxygen fraction of <40% can result in a flow field velocity increase of less than 2X from the water inlet to the outlet. In order to maintain an oxygen fraction of <40%, a water stoichiometry of up to or greater than 100 may be required. The selection of materials and geometry for the anode flow field, which transports water and removes oxygen from the cell, can also be important for maintaining high performance and low pressure drop. Geometries and dimensions that minimize velocity while promoting convection of oxygen bubbles away from the anode electrode can provide such advantages.

[0020] The electrolysis process is not 100% efficient, and therefore, some of the input electricity is converted into heat within the cell rather than chemical energy stored as hydrogen. This results in the actual hydrogen output flow requiring a voltage greater than the thermal neutral voltage (1.481). The conservation of energy of the system shows that the portion of the electrical power delivered to the cell that becomes heat (voltage times current) can be equal to [1-(1.481 / V 电池)]. A practical electrolytic cell may be operated at 1.8V, which results in [1-(1.481 / 1.8)] = ~18% of the power sent to the cell being converted into heat rather than hydrogen. Therefore, practical electrolytic cells require cooling during operation, and an effective way to achieve this cooling may be by utilizing 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 remains below an acceptable threshold and that the temperature gradient within the cell is acceptable. This flow rate may also represent a water stoichiometry that is much greater than 1. For example, for a cell operating at 1.8V, releasing 18% of the input energy as heat and 2 An operating cell may require a water stoichiometry greater than 100 to maintain a temperature rise of <10° C. across the cell. From the design considerations described above, the water flow rate into the cell may be determined by the need for sufficient reactants or by the need for adequate temperature control, whichever is higher.

[0021] Therefore, managing the water supplied to the hydrogen electrolysis cell / stack can be a major consideration for the overall hydrogen generation system. All flows, pressures, temperatures, and compositions must 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 to recirculate water at the required flow rate. As the system produces hydrogen and oxygen, a "stoichiometric" amount of water is consumed. This consumed water (i.e., "make-up water") can be added to the system by injecting a stoichiometric amount of new water into the system loop from a source of acceptable quality (e.g., demineralized, desalinated, "buffered," or city water). When considering the scale of the electrolysis equipment, the required water flow consumed by the cell / stack can be proportional to the equipment capacity. It can be desirable to keep other process parameters (pressure, temperature, composition) consistent regardless of scale, as this can greatly simplify system component selection, overall system control, and engineering, procurement, and construction (EPC) costs at the deployment site. For example, water pumps are generally commercially available in a wide range of sizes at flow rates for a given pressure capability. Therefore, it may be advantageous to have a basic cell / stack whose resistance to water flow is minimized and is independent of the cell or stack size. Larger systems can then be constructed in a modular manner from more cells and / or more stacks without having to change the water pump technology and the basic pressure ratings for the system and equipment. In view of the high water flow rates required for these considerations, the material and geometry of the anode flow field represent an important consideration for minimizing pressure losses, which enables the active area to be varied without changing the pressure losses and thereby reduces the cost of the water pumps for the electrolysis system.

[0022] In some embodiments, the present disclosure may include a scalable flow field configured to have substantially equal water flow resistance, equal temperature rise, and equal outlet oxygen fraction at a given operating voltage, regardless of the selected active area. In some embodiments, the flow field may be substantially rectangular, characterized by a dimension along the x-axis selected based on the roll width (w) of the flow field material used in its production. In some embodiments, the desired roll width (w) may be selected based on maintaining process parameters for operating the cell within target thresholds. For example, it may be desirable to maintain the water pressure drop across the cell below the pumping pressure limit of the system in which the cell may be installed. Alternatively, it may be desirable to maintain the water flow temperature rise along the x-axis below the stack temperature gradient limit to ensure acceptable performance and service life. Alternatively, it may be desirable to maintain the temperature gradient within the cell along the z-axis below the cell temperature gradient limit, which may require making the cell as thin as possible to promote efficient internal heat transfer. Alternatively, it may be desirable to maintain the cell outlet oxygen volume fraction below a limit to ensure stable performance and service life of the cell. Alternatively, the desired roll width (w) can be selected based on the available source materials used to construct the flow field. For example, it may be desirable to select a roll width that minimizes waste when converting the roll into flow field parts during assembly. In this case, the desired roll widths for the membrane, electrode, and flow field may be the same or different. If they are different, the selected roll width may be selected based on the most expensive membrane, electrode, or flow field, and other material rolls may be selected with a roll width (w) that is consistent with the others, where consistency means a roll width (w) that improves manufacturing speed and / or overall cost. Batteries of various active areas can then be constructed by varying the dimensions only along the y-axis, which greatly simplifies the material sourcing and manufacturing process for rolls of fixed width.

[0023] In some embodiments, the present disclosure may include a variable cell implemented using a scalable flow field by adjusting the length of the cell along the y-axis. Water distribution windows may be arranged parallel to the y-axis along the leading edge of the anode flow field, and each window may be associated with a unit length (abbreviated as "ULAFF") along the y-axis of the anode flow field. The leading edge of the anode flow field may be defined as the edge through which water enters the anode flow field. The area or effective diameter (the diameter of a circle whose area is equal to the area of ​​the window) of each water distribution window may be selected to maintain the water velocity along the z-axis through the window below a predetermined threshold at a water flow stoichiometry selected to maintain one or more of the cell temperature increase or the oxygen outlet volume fraction 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. The number of water distribution windows may then be selected to achieve the overall target hydrogen production rate for the cell while keeping the water flow pressure loss, water temperature increase, and oxygen outlet volume fraction below the target threshold.

[0024] In some embodiments, the present disclosure may include a scalable flow field comprising one or more metal meshes, expanded metal sheets, or perforated sheets, wherein at least one of the sheets is corrugated into a wave-like pattern that effectively increases its thickness along the z-axis. This geometry can provide a larger volume for a given amount of flow field material, effectively increasing the porosity and thickness of the flow field relative to a non-corrugated sheet, which will result in reduced water flow velocity and lower pressure loss. Multiple corrugated layers can be combined to adjust the pressure drop, bubble evacuation, compressive load application, and mechanical compliance along the z-axis within the cell. Further configuration of both the material and geometry of the flow field layers can allow the electrolytic cell to have high compliance and a smaller thickness while providing lower pressure loss than the prior art.

[0025] Meeting the requirements for flow restriction, bubble evacuation, mechanical load distribution, and elastic compliance simultaneously can be particularly challenging for electrolytic cells utilizing an open flow field, and solutions are not readily apparent to those skilled in the art.

[0026] It should be understood that both the foregoing general description and the following detailed description are exemplary and illustrative only and are not restrictive of the present disclosure as claimed. Further objects, features and advantages of the present application will become apparent from the detailed description of the preferred embodiments set forth below when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are incorporated into and constitute a part of this specification. The accompanying drawings illustrate only certain embodiments of the present disclosure and, together with the preceding and following descriptions, explain the principles of the present disclosure. Wherever possible, the same reference numerals have been used to indicate common or similar components across different figures.

[0029] Figure 1 A cross-sectional view showing one preferred embodiment of the layers of the scalable electrolytic cell of the present disclosure is shown.

[0030] Figure 2 An isometric view of a preferred embodiment of a scalable electrolysis cell including the scalable flow field of the present disclosure is shown.

[0031] Figure 3 shows several prior art flow fields used in electrolyzers and fuel cells.

[0032] Figure 4 An isometric view of a scalable bipolar plate assembly ("BPA") including an embedded hydrogen seal is shown.

[0033] Figure 5 show Figure 4Cross-sectional view of a BPA showing how the embedded hydrogen seal penetrates completely into the cathode flow field to form a gas-tight, reinforced seal with minimal thickness along the z-axis.

[0034] Figure 6 Mathematical model output is shown for oxygen volume fraction at the outlet relative to water stoichiometry for exemplary cell operating pressures and illustrative oxygen volume fraction thresholds.

[0035] Figure 7 The mathematical model output of water temperature rise relative to water stoichiometry is shown for two exemplary battery operating voltage values ​​and illustrative water temperature rise thresholds.

[0036] Figure 8 Published scientific results showing the structure of a fluid flowing over a channel, illustrating the effect of channel size on vortices within the channel.

[0037] Figure 9 An isometric view of a preferred embodiment of a scalable flow field and associated electrode stiffener is shown, illustrating the orientation of the water flow and associated fluid dynamics of the flow field elements to simultaneously minimize water flow pressure losses and promote evacuation of gas bubbles from the anode electrode.

[0038] Figure 10 A cross-sectional view showing a preferred embodiment of a scalable flow field and associated electrode reinforcement, as shown. Figure 8 , showing the relative geometric dimensions of the various elements that promote uniform distribution of the compressive load to the electrodes and membrane, and which promotes fluid dynamics to effectively evacuate air bubbles from the anode electrode.

[0039] Figure 11 A cross-section of a preferred embodiment of a scalable flow field is shown, illustrating the elastic deformation of the flow field when exposed to a compressive load along the z-axis.

[0040] Figure 12 A preferred embodiment of a scalable flow field is shown, illustrating the integration of multiple layers by means of spot welding.

[0041] Figure 13 A preferred, high-speed, continuous manufacturing method showing scalable flow fields.

[0042] Figure 14 Shown is a comparison of a prior art stack compression system ("A") and a high efficiency stack compression system ("B") that can be achieved with various embodiments of a compliant flow field.

[0043] Figure 15 Shown are load uniformity test results comparing a preferred embodiment of the present invention with the prior art.

[0044] Detailed Description of the Figures

[0045] A detailed description of several preferred embodiments will now be 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 features, components, and methods described are applicable and adaptable to other electrochemical technologies, 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 aqueous lithium brine solutions, hydrogen compressors, hydrogen purifiers, and fuel cells.

[0046] Figure 1 A schematic representation of a cross-section of a typical electrolytic cell (102) according to the present disclosure is shown. The layers are shown relative to each other, generally lying in the xy plane and stacked along the z-axis (101). Each layer along the z-axis may be thicker or thinner than shown relative to the other layers in the cell. Layer (111) represents the anode flow field, which may include more than one layer (a), (b), etc. (only 2 layers, a and b, are shown). Layer (112) represents an optional anode electrode reinforcement layer. Layer (113) represents an anode electrode layer. Layer (114) represents an electrolyte membrane layer or liquid electrolyte. Layer (115) represents a cathode electrode layer. Layer (116) represents an optional cathode electrode reinforcement layer. Layer (117) represents a cathode flow field layer. Layer (118) represents a bipolar separator layer.

[0047] Figure 2 show Figure 13D isometric view of the cell layers depicted in (202) with several components added. Component (217) represents a hydrogen seal. Component (221) represents a cell frame. Component (222) represents a water seal. Component (214) represents an internal seal. The anode flow field (111) is represented in this embodiment as a two-layer corrugated laminate (111a, 111b) as shown in detail view (203). During operation, the anode flow field (111) can be used to transport and distribute water as a reactant to the cell active area, transport and distribute water as a coolant to the cell active area, and collect and remove oxygen as a product from the active area. During operation, hydrogen can be formed on the active area and collected and removed by the cathode flow field (117). The fluid within the cathode flow field can be primarily in the gas phase, having a non-zero water vapor content due to evaporation of water transported from the anode through the membrane. Since the flow rate of the fluid in the cathode flow field is relatively low relative to the anode flow field, the cathode flow field can be designed to have a relatively thin dimension along the z-axis. For example, the cathode flow field (117) may have a thickness along the z-axis of less than 2 mm, less than 1 mm, less than 0.5 mm, or less than 0.25 mm. The relatively thin z-axis dimension of the cathode flow field may advantageously contribute to the thinness of the overall battery; however, it may also result in it being mechanically stiff (non-compliant) along the z-axis. This inherent non-compliance in thin cathode flow fields may place an additional burden on designing an anode flow field with sufficient compliance, as described below in conjunction with Figure 11 Further discussion. The width "w" (231) of the anode flow field (111) is aligned with the x-axis (201), while the length "l" (232) is aligned with the y-axis (201). Scaling of the anode flow field and other repeating components can be achieved by increasing their dimensions (233) along the y-axis.

[0048] FIG3 shows several examples of prior art flow fields used in electrolytic cells and fuel cells. In addition to flow fields that are directly formed into the form of channels (not shown) of bipolar separator plates in some prior art, different separator assemblies have included flat wire mesh, expanded and perforated metal sheets, and 3-dimensionally formed versions of these. It is an object of the present disclosure to overcome the limitations of prior art configurations for electrolytic applications by providing a relatively thin electrolytic cell that simultaneously provides high mechanical compliance along the z-axis, uniform compressive load distribution to the electrodes and membrane, and a favorable geometry for evacuating air bubbles from the electrodes. Thus, the disclosed cell can enable the associated stack compression system to be simplified by providing the required mechanical compliance along the z-axis within the core stack of the cell, thereby eliminating the need for springs and other compliant components in the external compression system.

[0049] Thin electrolytic cells can enable more cells to be stacked in a single stack and result in a greater power density (kW / L) of such a stack. Thin electrolytic cells can have a dimension along the z-axis of less than 5 mm, less than 3 mm, less than 2 mm, or less than 1.75 mm. Thus, thinner cells can result from thinner flow fields, indicating better flow field design and a greater "figure of merit" (FoM) of the design.

[0050] High mechanical compliance along the z-axis can be defined by a "compliance ratio", which is defined as the ratio of the compression modulus "E0" of the non-corrugated porous sheet along the z-axis to the compression modulus "E1" of the corrugated porous sheet made of the same material along the z-axis (compliance ratio - E0 / E1). Values ​​of the compliance ratio greater than 2:1, greater than 5:1, greater than 10:1, greater than 25:1 or greater than 100:1 can provide favorable compressive load distribution and advantageously simplify the requirements for external battery and stack mechanical compression systems. Therefore, a larger compliance ratio can lead to better flow field design and a larger "FoM" of the design. The compression modulus "E" can be defined by traditional engineering conventions as the ratio of the stress measured in a material exposed to a compressive load to the strain measured. When exposed to up to 5 kgf / cm 2 、10kgf / cm 2 、15kgf / cm 2 、30kgf / cm 2 、45kgf / cm 2 or 100kgf / cm 2 The high compliance ratio may result in a thickness change of the corrugated sheet of greater than 0.05%, greater than 0.25%, greater than 1%, or greater than 3% when subjected to a mechanical load.

[0051] The uniformity of load distribution over the battery area can be determined by comparing the mechanical pressure [kgf / cm 2 ] is defined as the mechanical pressure within 10 mm centered on the point 2 The loads are averaged over a circular area (“point average load measurement”). The uniformity of the load distribution can then be expressed using the “uniformity coefficient” (see Equation 3-1).

[0052] Equation 3-1:

[0053] Here, U L is the uniformity coefficient, f max is the maximum point average load measurement at any location in the battery, and f avg is the average load on the entire battery. L The possible range is 0-1, where the ideal value is 1. Therefore, a larger uniformity coefficient can lead to a better flow field design and a larger "FoM" of the design.

[0054] The bubble evacuation measurement can be defined as the period of time during which no liquid reactant is present in a given volume within the flow field. A suitable volume for this measurement can be 1 mm 3 , 5mm 3 , or 10mm 3 The advantageous time to evacuate the bubbles from the volume may be less than 60 minutes, less than 1 minute, less than 10 seconds, or less than 1 second. The evacuation measurement may alternatively be characterized as the inverse of the evacuation time, yielding the evacuation frequency B f (Hz), where a larger frequency is required for operational stability. Therefore, a larger pumping frequency can lead to a better flow field design and a larger "FoM" of the design.

[0055] It may be desirable to minimize the resistance to water flow through the cell to maximize the efficiency of the system in pumping water through the cell or stack. The flow resistance can be characterized as the pressure loss experienced by the water flow per unit length of the anode flow field ("characteristic flow resistance" - millibars per centimeter, mb / cm). The material and geometry selected for the anode flow field, including corrugation spacing and height, material porosity, and thickness, can all affect the characteristic flow resistance. Therefore, a smaller characteristic flow resistance can lead to a better flow field design and a larger "FoM" of the design.

[0056] The coefficients previously described with reference to FIG. 3 may be formulated into an overall Figure-of-Merit “FoM” equation as shown in Equation 3-2.

[0057] Equation 3-2:

[0058] Here, (E0 / E1) is the compliance ratio, U L is the uniformity coefficient, B f is the bubble evacuation frequency [Hz], h is the total thickness of the anode flow field [cm], and ΔP is the characteristic flow resistance of the flow field [mb / cm]. The resulting engineering units of FoM are Hz per millibar [Hz / mb], which can be interpreted as the bubble removal rate for a given input energy. This bubble removal efficiency is then weighted by the important mechanical properties of compliance, load uniformity, and thickness to produce the overall FoM of the design. A favorable FoM can be one greater than 1, greater than 5, greater than 10, or greater than 25.

[0059] Figure 4An isometric view of a preferred embodiment bipolar plate assembly is shown, comprising a porous sheet (117) into which a hydrogen seal (217) may be embedded using screen printing, liquid dispensing, injection or compression molding, or other suitable processes. 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 hydrogen flow from the active area of ​​the cell. The porous sheet (117) can be relatively thin while also providing precise thickness control for the bipolar plate assembly during pressing and curing of the hydrogen seal (217) and frame (221). Because it is relatively thin, the porous sheet (117) may not significantly contribute to the compliance function required in the overall cell and thereby place an additional burden on other cell components (including the anode flow field) to provide such function.

[0060] Figure 5 Shown Figure 4 A cross-sectional view (502) of a cathode electrode reinforcement (116), a cathode electrode (115), a membrane (114), an anode electrode (113), an anode electrode reinforcement (112), an anode flow field (111), an internal seal (214), and a water seal (222) are added. After assembly and curing, the hydrogen seal (217) can be completely embedded in the porous structure of the porous sheet (117), forming an airtight seal for hydrogen in the cathode flow field, while also physically adhering the bipolar plate (118) to the porous sheet (117) and the frame (221). The porous sheet (117) can serve as a reinforcement for the hydrogen seal, increasing its strength to enable sealing high hydrogen pressures. The sheet (117) can be selected from one or more of foam, felt, woven screen, expanded metal, perforated metal, or sintered metal frit. The sheet (117) may comprise an alloy of iron, steel, stainless steel, titanium, nickel, nickel-chromium, Inconel, Fecralloy, or a combination of these, and may also be covered with a suitable coating, such as platinum, gold, tin, nickel, carbon, or a combination of these. The porous sheet (117) may be relatively thin, which contributes to a thin overall cell thickness "tc" (503).

[0061] Figure 6 Results of a mathematical model showing the oxygen volume fraction (621) at the anode flow field outlet as a function of the delivered water stoichiometry (622). The process of electrolysis decomposes water into hydrogen on the cathode side and oxygen on the anode side. When oxygen is formed at the anode, it can mix with the delivered liquid water as a gas to produce a two-phase flow in the anode flow field. The oxygen volume fraction at the anode outlet can be indicative of the operational stability, performance and / or durability of the electrolytic cell, and a target threshold for this parameter can be set by the designer. The conservation of mass of the cell can lead to a formula for the oxygen outlet volume fraction (631) as specified in Equation 6-1. Here, ρ O2 is the density of oxygen at the anode outlet, ρ H 2 O is the density of liquid water at the anode outlet, and St is the water stoichiometry delivered to the cell. The graph (602) shows the results of the model over a range of anode pressures (611) of the electrolysis cell and an illustrative oxygen volume fraction threshold (612) beyond which the cell may not operate stably or durably, or beyond which the electrolysis system may not operate efficiently. The oxygen volume fraction threshold may be used to specify a lower threshold (613) for the water stoichiometry. It may be advantageous to select the water stoichiometry to maintain the oxygen volume fraction below 80%, below 60%, below 50%, below 40%, or below 30 to maintain stable and durably operation of the electrolysis cell. This stoichiometric value may be greater than 50, or greater than 75, or greater than 100, and therefore requires careful consideration of the anode flow field geometry to ensure that acceptable flow restriction can be achieved during operation. Further, as oxygen is generated, the volume fraction may be a function of the operating pressure (611a to e), and the bubble size formed may be a function of the volume fraction. Therefore, careful consideration of the flow dynamics in the anode flow field can be important to ensure effective removal of bubbles from the electrode and reinforcement layer, and may also directly impact the operational performance and / or durability of the cell.

[0062] Equation 6-1:

[0063] Figure 7 Mathematical model results showing water temperature rise [°C] as a function of the stoichiometric value of the water delivered. The heat released during electrolytic cell operation can be a function of efficiency, which in turn can be a function of the operating cell voltage. The cell's energy conservation can lead to the water temperature rise formula specified by Equation 7-1 (below). Here V is the operating cell voltage, V0 is the thermoneutralized cell voltage [1.481 V], HHV is the higher hydrogen heating value [141.79 MJ / kg], and c pis the specific heat capacity of water [4.182 kJ / kg°C], and St is the water stoichiometry delivered to the cell. Graphs (711a) and (711b) show the results of the model at two possible operating voltages, representing exemplary values ​​for the beginning of life [BoL] and end of life [EoL] of the electrolysis cell. Also shown is an illustrative water temperature rise target threshold (712) above which the electrolysis cell may not operate stably or durably, or above which the electrolysis system may not operate efficiently. The temperature rise threshold can be used in conjunction with the EoL voltage limit to define a lower threshold for water stoichiometry (713). It may be advantageous to select a water stoichiometry to maintain a water temperature rise below 100°C, below 50°C, below 25°C, below 15°C, or below 10°C at end of life to maintain stable and durably operating electrolysis cells. This stoichiometric value may be greater than 50, or greater than 75, or greater than 100, and therefore requires careful consideration of the anode flow field geometry to ensure that acceptable flow restriction can be achieved during operation.

[0064] Equation 7-1:

[0065] Figure 8 Published illustration showing flow dynamics, and the formation of instabilities and flow vortices as the fluid flows through the cavity. During operation of an electrolytic cell, liquid water may be provided at the anode and oxygen gas may be formed. During this process it is important to remove the oxygen gas quickly and efficiently from the electrodes and reinforcements so that additional reactants (i.e. water) can access the active sites and the reaction can proceed with minimal resistance. Therefore, poor oxygen bubble removal can lead to poor cell performance and higher voltages or lower currents than required for operation. The anode flow field can play an important role in removing bubbles. The geometry of the anode flow field can define the fluid streamlines near the anode electrode reinforcement and create dynamic structures, such as instabilities, vortices, and shear layers, which can promote efficient convection of bubbles away from the electrode. As Figure 8As shown in (802), fluid flow through a cavity is one way to create such a dynamic structure. Here, a cavity can be defined by depth "D" (811) and length "L" (812). The ratio L / D (816) can be an important parameter for establishing the desired flow pattern within the cavity. As shown, an L / D of less than 10 can produce a vortex pattern within the cavity, which will promote fluid vortex flow from the bottom of the cavity to the top (813, 814). In contrast, an L / D greater than 10 can establish smaller vortices (815) on either side of the cavity, which never reach the top of the cavity. In an electrolytic cell, the bottom of the cavity can represent the anode electrode reinforcement surface, and the top of the cavity can represent the main water flow through the anode. One or more cavities can be formed by the appropriate geometry of the corrugated porous sheet, specifically configured to provide the cavity by orienting the corrugation peaks and valleys along the y-axis, perpendicular to the flow direction along the x-axis (801). Therefore, it may be advantageous to arrange the geometry of the corrugated porous sheet to mimic the geometry of the cavity shown (802).

[0066] Figure 9 A preferred flow arrangement (902) is shown that provides low water flow resistance in the anode flow field (111a, 111b) while generating instabilities and eddies (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 located closest to the anode electrode reinforcement and is oriented with its peaks and valleys along the y-axis (901) and substantially perpendicular to the water flow through the cell (911). The first layer may have a peak-to-peak spacing "p1" (915) and be formed from a porous sheet having a thickness "t1" (925). The second layer (111a) is located farthest from the anode electrode reinforcement and is oriented with its peaks and valleys along the x-axis (901) and substantially parallel to the water flow through the cell (911). The second layer may have a peak-to-peak spacing "p2" (914) and be formed of a porous sheet having a thickness "t2" (924). Since both sheets are porous, liquids and gases can move freely along any of the three axes within the space defined by the two layers. Most of the flow may follow relatively straight streamlines above (911) or below (912) the second layer (111a). The streamlines below the second layer (111a) may behave similarly Figure 8 In this case, the cavity may be generally defined by a corrugated pattern of the first layer (111b), which may induce flow instabilities (913) and convective vortices (916), which may promote efficient transport of bubbles from the electrode reinforcement layer (112) into the main flow (912). Figure 8As described, it may be advantageous to configure layer 1 (111b) to have a cavity ratio L / D (816) of less than 10, or less than 5, or less than 2.5 to maximize the effectiveness of removing bubbles. The one or more porous layers of the anode flow field (111) may be selected from one or more of foam, felt, woven screen, expanded metal, perforated metal, or sintered metal frit. The porous material for (111) may include an alloy of iron, steel, stainless steel, titanium, nickel, nickel-chromium, Inconel, Fecralloy, or a combination of these, and may also be covered with a suitable coating, such as platinum, gold, tin, nickel, carbon, or a combination of these. The porous layer may be processed (e.g., by rolling between rollers) before corrugation to achieve the desired thickness ("t1", "t2") and / or to achieve the desired mechanical properties, such as yield strength, hardness, or elasticity.

[0067] Figure 10 show Figure 9 A cross-sectional view (1002) of (902) further illustrates the potential fluid dynamics that can be generated by the present invention. In this illustration, bubbles (1031) emerging from the electrode reinforcement layer (112) are removed by convection (1016) of the vortex along the z-axis (1001). The bubbles (1032) can then move through layer 1 (111b) and be further removed by convection (916) of the vortex along the z-axis. The bubbles (1033) can eventually enter the main water flow (912) for removal from the battery. The corrugated structure of layer 1 (111b), which has peaks and valleys perpendicular to the main water flow (112), can promote the generation of oscillating streamlines (913) that flow through the porous structure of layer 1 (111b). This configuration of layer 1 (111b) can further promote the generation of oscillating streamlines (1012) adjacent to the porous structure. The net result of the combination of oscillating streamlines can be the creation of instabilities that dislodge bubbles that adhere to the electrode stiffener (112) or the layer itself (111b, 111a) so they can be transported by convection into the main water flow (912) via the aforementioned dynamic structure. It can be advantageous to configure layer 1 (111b) to have a ratio of height "h1" (1022) to spacing "p1" (915) that simulates a ratio of less than 10, or less than 5, or less than 2.5, which can facilitate as Figure 8 The preferred kinetic mode (816) described in . Layer 1 (111b), by virtue of its corrugations being aligned along the y-axis, perpendicular to the flow streamlines (912), can present a greater resistance to fluid flow than layer 2 (111a), which has corrugations aligned along the x-axis, parallel to the streamlines. Thus, it may be advantageous to minimize the overall flow resistance through the anode flow field by configuring layer 2 (111a) to have a height "h2" (1023) greater than or equal to the height of layer 1 ("h1", 1022), thereby yielding a preferred ratio h2 / h1 ≥ 1.

[0068] Figure 11 Graph showing 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 11 a shows the dimensions before load application; Figure 11 b shows the dimensions during load application; Figure 11c shows the dimensions after the load is applied. The elastic response can be defined as the anode flow field recovering to within 0.5% of its initial height ("h1" + "h2") when the exposed load is removed. The elastic response can be further defined as a corrugated porous sheet that can withstand an applied compressive load of at least 20 kilograms per square centimeter when applied along the z-axis without permanent deformation. The compliance can be defined as the inverse of the effective elastic spring constant along the z-axis (i.e., the change in "z" [mm] per unit applied force [kgf]). The greater the compliance, the greater the elastic change in thickness for a given applied load, and the more spring-like the component will behave. The preferred compliance of the anode flow field can be defined so that its height ("h1" + "h2") decreases by between 3% and 15% when exposed to a load between 10 and 100 kilograms-force per square centimeter. The height "h0" (1021) of the electrode reinforcement layer (112) is relatively thin and can be rigid (i.e., non-compliant) relative to the other layers shown. Thus, the height "h0" may not change significantly with the addition of a load (1111). Due to the geometry and material properties of the corrugated layers 1 (111b) and 2 (111a), their respective heights "h1a" (1022) and "h2a" (1023) may change significantly with the application of a load (1111) ("h1b", 1122 and "h2b", 1123). Furthermore, the material properties (including yield strength, hardness, or elasticity) and geometry (including thicknesses "t1" (925) and "t2" (924)) of the corrugated structures (111b, 111a) may be configured so that they respond elastically to the application of a load such that when the load is removed, the respective heights of each layer substantially recover to within ±5% of their initial value ("h1c", 1132 and "h2c", 1133). Even distribution of the compressive load (1111) over the active area of ​​the battery may be important for efficient operation of the battery. Thus, uniform distribution of the applied load through layer 2 (111a), layer 1 (111b), and electrode reinforcement (112) can be benefited by selecting the geometry of these layers (e.g., thickness "t", height "h", and spacing "p"). To achieve this goal, it can be important to minimize the bending of each layer in the xy plane. Since bending in such structures can be significantly affected by the unsupported length of the layer relative to the height of the layer, it can be advantageous to limit the ratio of the unsupported length to the height of each layer in the battery. For example, the spacing "p1" of layer 1 (111b) defines the unsupported length of the electrode reinforcement layer (112), which has a height "h0" (1021). It can be advantageous to limit the ratio p1 / h0≤10, p1 / h0≤5, or p1 / h0≤2.5. Similarly, the spacing "p2" (914, Figure 9 ) defines the unsupported length of layer 1 (111b), which has a height "h1" (1022, Figure 10 ). It may be advantageous to have a limiting ratio of p2 / h1≤10, p2 / h1≤5 or p2 / h1≤2.5. Since the compliance within layer 1 (111b) and layer 2 (111a) is desirable, deflection of the corrugation peaks and valleys is required. This deflection may be significantly controlled by the geometry and material properties of the layers. In particular, the thickness ("t", 925, 924) of the porous layer relative to the corrugation dimensions ("h" and "p") may significantly affect the overall compliance after being formed into the corrugated structure. It may be advantageous to have a limiting ratio of p1 / t1≤15, p1 / t1≤10 or p1 / t1≤5. It may be advantageous to have a limiting ratio of p2 / t2≤15, p2 / t2≤10 or p2 / t2≤5. It may be advantageous to have a limiting ratio of h1 / t1≤10, h1 / t1≤5 or h1 / t1≤2.5. A limitation ratio of h2 / t2≤10, h2 / t2≤5 or h2 / t2≤2.5 may be advantageous.

[0069] Figure 12 A flow field (1202) is shown in which two layers (111a, 111b) can be bonded at several points (1211a to 1211f) to facilitate alignment and handling as a single component having multiple layers. More than two layers can be bonded in this manner. The bonding points can be distributed over the surface of the layer in the xy plane (1201), with spacing along the x-axis (1212) and spacing along the y-axis (1213). The spacing along different axes can be the same or different. The number of bonding points (1211a-1211f) along different axes can be different. Bonding can be achieved by welding, brazing, diffusion bonding, adhesive bonding, or any other known method.

[0070] Figure 13 Display for continuous, high-speed manufacturing Figure 12A preferred embodiment of a system (1302) for an anode flow field. Two rolls (1311a, 1311b) of porous material may be installed at the beginning of the process with the roll axis aligned with the x-axis. The two materials may be the same or different and may be pre-treated to achieve the desired thickness "t" (1332a, 1332b). The roll width "w" (1331a) of roll (1311a) and the roll width "w" (1331b) of roll (1311b) may be equal within ±5%. The web from roll (1311a) may be guided through a forming roller (1312a) which may have forming teeth oriented parallel to the roller axis to emboss a corrugation pattern into the web material, thereby increasing its dimension along the z-axis. The corrugation pattern of roll (1311a) may be oriented with peaks and valleys substantially aligned with the x-axis. The web from roll (1311b) may be directed through a forming roller (1312b) which may have forming teeth oriented substantially circumferentially around the roller to emboss a corrugation pattern into the web material, thereby increasing its dimension along the z-axis. The corrugation pattern of roll (1311b) may be oriented with peaks and valleys substantially aligned with the y-axis. The corrugation pattern of each roll may be substantially the same or different. The corrugated web (1311a) may then pass over roller (1313) to direct it toward the corrugated web (1311b) wherein both webs may be positioned adjacent to each other by roller (1314). The two layers of web (1321) may then pass between welding rollers (1315) located on either side of the two layers of web. The welding rollers (1315) may be connected to an AC or DC power source configured to weld the two layers into a single, integrated web, such as Figure 12 Welding can be continuous or periodic, producing discrete spot welds, such as 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 the period of the welding pulse delivered to the welding roller (in seconds) divided by the speed of the web moving along the y-axis (in cm / second). The number of welding wheels on the roller and the period of the welding pulse can be determined to ensure sufficient bonding between the layers. More than two layers can also be processed in this manner. After welding, the integrated web can be cut into discrete parts (1202) using known cutting methods capable of cutting multiple layers of porous materials. Such methods can include laser cutting, die stamping, roller die cutting, water jet cutting, shearing, cutting, or any other known method.

[0071] Figure 14A prior art stack (1402a) and a stack (1402b) including elements of a preferred embodiment of the present disclosure are shown. The prior art stack (1402a) requires many large springs (1411) to maintain the compressive load on the core cells (1412) in the stack. These springs can take up considerable volume, are made up of many parts, and can be inefficient or inconvenient to assemble during stack production. Alternatively, the stack (1402b) does not require large external springs and can use a simple thin sheet wrapper (1421) to implement the compression. The wrapper (1421) can provide minimal spring function for compressing the stack. Therefore, the compressive load can be maintained by virtue of the inherent compliance in the core cells (1422) in the stack. The compliance can be provided to the cells by the flow fields disclosed in various embodiments of the present disclosure. In particular, the anode flow field (111) can be configured to have significant compliance along the z-axis and can therefore be combined with a stack compression wrap (1421) having minimal compliance to facilitate maintaining compression over time and during changes in temperature, pressure, or other process conditions to which the stack may be exposed. When combined with a relatively thin cathode flow field (117) having minimal compliance, the anode flow field can further provide the required compliance within the stack core cell (1422) and thus enable mechanical functionality of a relatively thin cell. Cells having a total thickness of tc ≤ 5.0 mm, or tc ≤ 3.0 mm, or tc ≤ 2.5 mm can be achieved by preferred embodiments of the present disclosure.

[0072] Figure 15 Results of pressure paper tests showing quantification of compressive load uniformity across the active area of ​​an electrolytic cell compared to prior art anode flow fields ( Figure 15 a) and a preferred embodiment of the present disclosure ( Figure 15 b). Figure 15 The assembly of a includes an anode flow field comprising three layers of flat stainless steel wire mesh. Figure 15 The assembly of b included an anode flow field comprising a layer of flat stainless steel wire mesh combined with a layer of stainless steel wire mesh corrugated with a geometry consistent with the present disclosure. Although the overall flow field and cell thickness were the same in both tests, the lack of compliance in the prior art assembly was evident from the highly non-uniform pressure (1511) exposed to the active area relative to the boundary region (1512) of the cell. In contrast, the inherent compliance in the preferred embodiment assembly enabled substantially equal loading in both the active (1521) and boundary (1522) regions of the cell. This result demonstrates the advantage of a compliant flow field structure in achieving more uniform load distribution in thin electrolytic cells.

[0073] Figure 16Results of finite element simulations calculated for a range of exemplary corrugated porous sheet geometries are shown (1602). The compression modulus "E" can be defined by conventional engineering practice as the ratio of the measured stress to the measured strain in a material exposed to a compressive load. Typical compression moduli "E0" (1613) for two different thicknesses of non-corrugated stainless steel woven wire mesh were used: namely, 150 μm (1621) and 250 μm (1622). 30 kgf / cm 2 The external load is applied to the model with different corrugation spacing to height ratios (1612). The calculated deformation (deflection) is converted into the compression modulus "E1" (1614). The ratio, i.e., the compliance ratio E0 / E1 (1611) is then plotted against the spacing to height ratio (1612) to obtain data for two thicknesses (1621, 1622). The least squares curve fit of the two data sets (1631, 1632) shows that the compliance ratio can be significantly affected by the selection of the spacing to height ratio, and compliance ratio values ​​greater than 2, 5, 10, 25 or 100 can be achieved. These values ​​of compliance ratio can provide a favorable compressive load distribution over the battery area (such as Figure 15 ), and can further provide advantageous simplification requirements for the design of external battery and stack mechanical compression systems. 2 、10kgf / cm 2 、15kgf / cm 2 、30kgf / cm 2 、45kgf / cm 2 or 100kgf / cm 2 The high compliance ratio may result in a thickness change of the corrugated sheet of greater than 0.05%, greater than 0.25%, greater than 1%, or greater than 3% when subjected to a mechanical load.

[0074] Figure 17 (1702) shows measured characteristic flow resistance [millibars per centimeter, mb / cm] (1711) versus water flow velocity [centimeters per second, cm / s] (1712) for various exemplary flow fields (1721). Also shown are mathematical model results for the exemplary flow fields (1731). Anode flow fields exhibiting characteristic flow resistance versus flow velocity curves of these values ​​can be advantageous for minimizing the pumping energy consumed by a system employing a stack of cells containing flow fields having these characteristics.

[0075] Exemplary embodiments

[0076] A. An electrolytic cell comprising: a membrane, an anode, a cathode, an anode reinforcement layer, a cathode reinforcement layer, an anode flow field, a cathode flow field, and a bipolar plate assembly, wherein the anode flow field comprises one or more porous sheets having at least one straight edge, and wherein at least one of the porous sheets has the form of a corrugated pattern having a plurality of peaks and valleys whose axes are generally aligned with one straight edge of the sheet and whose protrusion height "h" along the z-axis is generally aligned with the thickness dimension of the sheet.

[0077] The electrolytic cell of BA, wherein the anode flow field is configured such that its thickness decreases by between 3% and 15% when exposed to a load between 10 and 100 kilogram-force per square centimeter, and wherein the anode flow field recovers to within 0.5% of its original thickness when the exposed load is removed.

[0078] The electrolytic cell of CA, wherein the at least one corrugated porous sheet can withstand an applied compressive load of at least 20 kilograms-force per square centimeter when applied along a z-axis generally aligned with the thickness of the sheet without permanent deformation.

[0079] The electrolytic cell of DA, wherein the one or more porous sheets are calendered to a thickness selected to achieve a target yield strength, hardness, or elastic modulus.

[0080] The electrolytic cell of claim EA, wherein the anode flow field comprises two or more porous sheets, and wherein the two or more porous sheets are spot welded to form a single flow field structure.

[0081] The electrolytic cell of FA, wherein the anode flow field comprises a corrugated porous sheet adjacent to the anode reinforcement layer, and wherein the ratio of the corrugation 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.

[0082] The electrolytic cell of GA, wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the ratio of the corrugation pitch "p2" of the sheet farthest 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.

[0083] The electrolytic cell of HA, wherein the anode flow field comprises at least one corrugated porous sheet, and wherein the ratio of the corrugation pitch to the sheet thickness is p / t≤15 or p / t≤10 or p / t≤5.

[0084] The electrolytic cell of IA, wherein the anode flow field comprises at least one corrugated porous sheet, and wherein the ratio of the corrugation height to the sheet thickness is h / t≤10 or h / t≤5 or h / t≤2.5.

[0085] The electrolytic cell of JA, wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the corrugation pitch "p1" of the sheet closest to the anode electrode is between 0.4 mm and 2.0 mm, and wherein the corrugation pitch "p2" of the sheet farthest from the anode electrode is between 0.5 mm and 2.5 mm.

[0086] The electrolytic cell of KA, wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the height "h1" of the sheet closest to the anode electrode is between 0.1 mm and 1.0 mm, and wherein the height "h2" of the sheet farthest from the anode electrode is between 0.2 mm and 2.0 mm.

[0087] The electrolytic cell of LA, wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the corrugation pitch "p1" of the sheet closest to the anode electrode is less than or equal to the corrugation pitch "p2" of the sheet farthest from the anode electrode.

[0088] The electrolytic cell of MA, wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the height "h1" of the sheet closest to the anode electrode is less than or equal to the height "h2" of the sheet farthest from the anode electrode.

[0089] The electrolytic cell of NA wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the sheet located farthest from the anode electrode is oriented with its peak and valley axes generally parallel to the direction of flow of the anode reactants.

[0090] The electrolytic cell of OA wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the sheet located closest to the anode electrode is oriented with its peak and valley axes substantially perpendicular to the direction of flow of the anode reactants.

[0091] The electrolytic cell of PA, wherein the one or more porous sheets are all corrugated, and

[0092] wherein the corrugation peaks of adjacent sheets are oriented generally perpendicular to each other.

[0093] The electrolytic cell described in QA, wherein the one or more porous sheets are selected from one or more of stainless steel, titanium, nickel or nickel-chromium materials.

[0094] The electrolytic cell of claim RA, wherein the one or more porous sheets are selected from one or more of a wire mesh, an expanded foil, or a perforated sheet.

[0095] The electrolytic cell of SA, wherein the cathode flow field comprises a porous sheet containing an embedded hydrogen seal, such that the porous sheet provides both mechanical reinforcement for the embedded hydrogen seal and open space for hydrogen to flow from the active area of ​​the electrolytic cell to the outlet of the cell.

[0096] T. An electrolytic cell stack comprising one or more electrolytic cells, each of the electrolytic cells comprising: a membrane, an anode, a cathode, an anode reinforcement layer, a cathode reinforcement layer, an anode flow field, a cathode flow field, and a bipolar plate assembly, wherein the anode flow field comprises one or more porous sheets having at least one straight edge, and wherein at least one of the porous sheets has the form of a corrugated pattern having a plurality of peaks and valleys whose axes are generally aligned with one straight edge of the sheet and which protrude a height "h" along a z-axis generally aligned with the thickness dimension of the sheet, and

[0097] The stack includes a compression system comprising: a structural wrapper comprising one or more wrap layers circumferentially surrounding at least a portion of an electrolytic cell stack comprising a plurality of cells.

[0098] The electrolytic stack of UT, wherein the anode flow field is configured such that when exposed to a load between 10 and 100 kilogram-force per square centimeter, its thickness decreases by between 3% and 15%, and wherein when the exposed load is removed, the anode flow field recovers to within 0.5% of its original thickness.

[0099] The electrolytic stack of VT, wherein the at least one corrugated porous sheet can withstand an applied compressive load of at least 20 kilograms-force per square centimeter when applied along a z-axis generally aligned with the thickness of the sheet without permanent deformation.

[0100] The electrolytic stack described in WT, wherein the anode flow field comprises a corrugated porous sheet adjacent to the anode reinforcement layer, and wherein the ratio of the corrugation 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.

[0101] The electrolysis stack of XT, wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the ratio of the corrugation pitch "p2" of the sheet farthest 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.

[0102] The electrolytic stack of YT, wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the average thickness of the cells in the core is less than 5 mm, less than 3 mm, or less than 2.5 mm.

[0103] The electrolysis stack of ZT, wherein the structural wrap serves as a tensile element of the compression system, and wherein the one or more wrap layers are substantially flat sheets of material having a substantially uniform thickness.

[0104] The electrolytic cell stack of AA.T, wherein the total thickness of the one or more wrapping layers is determined by the x-axis dimension of the cell stack and the maximum allowable operating pressure of the electrolytic cell stack.

[0105] BB. A method of operating and an electrolytic cell,

[0106] wherein the reactants entering the anode flow field comprise liquid water containing no more than 1% by weight of elements other than hydrogen and oxygen, and

[0107] wherein the product exiting the cathode flow field has a non-zero vapor phase moisture content, and wherein the anode flow field comprises one or more porous sheets having at least one straight edge, and wherein at least one of the porous sheets is in the form of a corrugated pattern having a plurality of peaks and valleys whose axes are generally aligned with one of the straight edges of the sheet and having a z-axis protrusion height "h" generally aligned with the thickness dimension of the sheet.

[0108] CC. A method of manufacturing an anode flow field for an electrolytic cell, wherein a continuous process of corrugation and lamination is performed, wherein a web ("Web 1") from one roll of flat porous material is directed through a pair of rollers configured to corrugate the web to have a plurality of peaks and valleys at a corrugation pitch of "p1", and wherein the axis of the corrugations of "Web 1" is generally aligned with the axis of the roll, and wherein the height "h1" of the corrugations of "Web 1" extends along a z-axis that is generally aligned with the thickness dimension of "Web 1", and wherein a web ("Web 2") from a second roll of flat porous material is directed through a pair of rollers configured to corrugate the web to have a plurality of peaks and valleys at a corrugation pitch of "p2", and wherein the axis of the corrugations of "Web 2" is generally aligned with the unwinding direction of "Web 2", and

[0109] wherein the height "h2" of the corrugations of "Web 2" extends along a z-axis that is substantially aligned with the thickness dimension of "Web 2", and wherein after passing through the corrugating rollers, "Web 1" is

[0110] and "web 2" are adjacent to each other, and the two layers span the width of the web and the length in the unwinding direction.

[0111] periodically spot welded to each other, and wherein discrete anode flow field components are cut by laser, roller

[0112] Die cutting or punching cuts from the laminated web.

Claims

1. An electrolytic cell comprising: membrane, anode, cathode, Anode reinforcement layer, cathode reinforcement layer, Anode flow field, cathode flow field, and bipolar plate assembly, wherein the anode flow field comprises one or more porous sheets having at least one straight edge, and wherein at least one of the porous sheets has the form of a corrugated pattern having a plurality of peaks and valleys whose axes are generally aligned with one straight edge of the sheet and which projects a height "h" along a z-axis generally aligned with the thickness dimension of the sheet.

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

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

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

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

6. The electrolytic cell according to claim 1, wherein the anode flow field comprises a corrugated porous sheet adjacent to the anode reinforcement layer, and The ratio of the corrugation 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 electrolytic cell according to claim 1, wherein the anode flow field comprises exactly two corrugated porous sheets, and The ratio of the corrugation pitch "p2" of the sheet farthest 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 electrolytic cell according to claim 1, wherein the anode flow field comprises at least one corrugated porous sheet, and wherein the ratio of the corrugation pitch to the sheet thickness is less than 15, less than 10, or less than 5.

9. The electrolytic cell according to claim 1, wherein the anode flow field comprises at least one corrugated porous sheet, and wherein the ratio of the corrugation height to the sheet thickness is less than 10, less than 5, or less than 2.

5.

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

11. The electrolytic cell according to claim 1, wherein the anode flow field comprises exactly two corrugated porous sheets, and wherein the height "h1" of the sheet closest to the anode electrode is between 0.1 mm and 1.0 mm, and The height "h2" of the sheet farthest from the anode electrode is between 0.2 mm and 2.0 mm.

12. The electrolytic cell according to claim 1, wherein the anode flow field comprises exactly two corrugated porous sheets, and The height "p1" of the sheet closest to the anode electrode is less than or equal to the height "p2" of the sheet farthest from the anode electrode.

13. The electrolytic cell according to claim 1, wherein the anode flow field comprises exactly two corrugated porous sheets, and The height "h1" of the sheet closest to the anode electrode is less than or equal to the height "h2" of the sheet farthest from the anode electrode.

14. The electrolytic cell according to claim 1, wherein the anode flow field comprises exactly two corrugated porous sheets, and The sheets located farthest from the anode electrode are oriented with their peak and valley axes generally parallel to the direction of flow of the anode reactants.

15. The electrolytic cell according to claim 1, wherein the anode flow field comprises exactly two corrugated porous sheets, and The sheets located closest to the anode electrode are oriented with their peak and valley axes generally perpendicular to the direction of flow of the anode reactants.

16. The electrolytic cell according to claim 1, wherein the one or more porous sheets are all corrugated, and wherein the corrugation peaks of adjacent sheets are oriented generally perpendicular to each other.

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

18. The electrolytic cell according to claim 1, The one or more porous sheets are selected from one or more of a wire mesh, an expanded foil or a perforated sheet.

19. The electrolytic cell according to claim 1, Wherein the cathode flow field comprises a porous sheet containing an embedded hydrogen seal, such that the porous sheet provides both mechanical reinforcement for the embedded hydrogen seal and open space for hydrogen to flow from the active area of ​​the electrolytic cell to the outlet of the cell.

20. An electrolytic cell stack comprising one or more electrolytic cells, each of the electrolytic cells comprising: membrane, anode, cathode, Anode reinforcement layer, cathode reinforcement layer, Anode flow field, cathode flow field, and bipolar plate assembly, wherein the anode flow field comprises one or more porous sheets having at least one straight edge, and wherein at least one of the porous sheets has the form of a corrugated pattern having a plurality of peaks and valleys whose axes are generally aligned with one straight edge of the sheet and which project a height "h" along a z-axis generally aligned with the thickness dimension of the sheet, and wherein the stack includes a compression system comprising: A structural wrap comprising one or more wrap layers circumferentially surrounds at least a portion of an electrolytic cell stack comprising a plurality of cells.

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

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

23. The electrolytic stack according to claim 20, wherein the anode flow field comprises a corrugated porous sheet adjacent to the anode reinforcement layer, and The ratio of the corrugation 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 electrolysis stack of claim 20, wherein the anode flow field comprises exactly two corrugated porous sheets, and The ratio of the corrugation pitch "p2" of the sheet farthest 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 electrolytic stack according to claim 20, wherein the anode flow field comprises exactly two corrugated porous sheets, and The average thickness of the cells in the core is less than 5 mm, less than 3 mm or less than 2.5 mm.

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

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

28. A method of operating and an electrolytic cell, wherein the reactants entering the anode flow field comprise liquid water containing no more than 1% by weight of elements other than hydrogen and oxygen, and wherein the product exiting the cathode flow field has a non-zero vapor phase moisture content, and wherein the anode flow field comprises one or more porous sheets having at least one straight edge, and wherein at least one of the porous sheets has the form of a corrugated pattern having a plurality of peaks and valleys whose axes are generally aligned with one straight edge of the sheet and which projects a height "h" along a z-axis generally aligned with the thickness dimension of the sheet.

29. A method of manufacturing an anode flow field for an electrolytic cell, In which a continuous process of corrugation and lamination is carried out, wherein a web ("Web 1") from a roll of flat porous material is directed through a pair of rollers configured to corrugate the web into a plurality of peaks and valleys at a corrugation pitch of "p1," and wherein the axis of the corrugations of "Web 1" is substantially aligned with the axis of the roll, and wherein the height "h1" of the corrugations of "Web 1" extends along a z-axis that is generally aligned with the thickness dimension of "Web 1", and wherein a web ("Web 2") from a second roll of flat porous material is directed through a pair of rollers configured to corrugate the web into a plurality of peaks and valleys at a corrugation pitch of "p2", and wherein the axes of the corrugations of "web 2" are substantially aligned with the unwinding direction of "web 2", and wherein the height "h2" of the corrugations of "Web 2" extends along a z-axis that is generally aligned with the thickness dimension of "Web 2," and wherein "Web 1" and "Web 2" are brought adjacent to each other after passing through the corrugating rollers, and wherein the two layers are spot welded to each other periodically across the width of the web and along its length in the unwinding direction, and Discrete anode flow field components are cut from the laminated web by laser cutting, roll die cutting or punching.

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