Bipolar plates with integrated cooling circuits, electrolytic cells, and electrolytic cell stacks.

Abstract

A bipolar plate (14) for an electrolytic cell is disclosed, comprising at least one electrolyte supply duct, a first duct for discharging a first electrolytic product and a second duct for discharging a second electrolytic product, and two plates (14.10, 14.20) joined together to define at least one hollow volume (20) between them, each having a thicker annular edge forming an outer peripheral zone (22) of the bipolar plate (14), a duct for supplying cooling fluid to the hollow volume (20), and a duct (19) for discharging cooling fluid from the hollow volume (20). An electrolytic cell and an electrolytic cell stack comprising such a bipolar plate are also disclosed.

Description

Technical Field

[0001] The present invention relates to the field of electrolysis, and more particularly to the production of hydrogen.

Background Art

[0002] The overall architecture of what is generally called an electrolyzer stack typically consists of a block of electrolytic cells connected in series from an electrical perspective and in parallel from a fluid perspective, in addition to a sealing gasket.

[0003] Each electrolytic cell is designed to facilitate the electrolysis of an electrolytic solution (alkaline water, pure water, untreated water, salts, aqueous chloride solution, aqueous bromide solution, aqueous hydrochloric acid solution, etc.). For example, the function of the electrolyzer stack is to promote the reaction that generates hydrogen gas (H2) and oxygen gas (O2) resulting from the dissociation of water after the injection of a direct current into an alkaline solution, typically potassium hydroxide (KOH) or sodium hydroxide (NaOH). Each electrolytic cell is considered to be mainly composed of metals and conductive members (although some may be non-metallic), and generally consists of two bipolar plates enclosing two spacers (more generally known as flow field materials), and further those spacers enclose two electrodes, which are typically in the form of plates, meshes, or metallic fabrics. In the case of an alkaline electrolyzer stack, the electrodes are generally made of nickel. The two electrodes (cathode and anode) are separated by a membrane (also called a diaphragm or porous separator in the case of an alkaline electrolyzer stack), thereby ensuring electrical insulation between the two electrodes, gas separation, and ion conduction within the electrolytic cell.

[0004] The flow field material has two functions. That is, i) to provide a low-resistance metal path between each bipolar plate and the associated electrode, and ii) to enable the electrolytic solution to be properly circulated to cool the electrolyzer stack and transport the generated gas.

[0005] The term "bipolar plate" refers to a bipolar plate N where all electrolytic cells are placed directly adjacent to each other. - It will have a higher potential than the downstream bipolar plate N+1, and as a result, bipolar plate N will play the role of an anode in the electrolytic cell defined by bipolar plates N and N+1. - This is due to the fact that bipolar plate N has a lower potential compared to the upstream bipolar plate N-1, and as a result, bipolar plate N acts as a cathode in the electrolytic cell defined by bipolar plates N-1 and N.

[0006] In addition to the bipolar plate, other metal components include a distribution plate (which supplies and distributes power within the electrolytic cell) and end plates (which separate the entire set of electrolytic cells, securely clamping and sealing them together). Specifically, the electrolytic cell stack ends with two end plates positioned immediately before the first stacked electrolytic cell and immediately after the last stacked electrolytic cell. In other words, one end plate is located upstream of the cell block and the other is located downstream of the cell block, thereby physically defining the two ends of the electrolytic cell block.

[0007] The electrolyte plays the following three roles in the electrolytic cell: - To ensure ion conduction within the electrolytic cell. For this purpose, the solution must have high ionic conductivity. - Removing gas bubbles that make up the electrolytic product. - To remove heat generated by overvoltage within each electrolytic cell (in this case, "overvoltage" refers to a voltage exceeding the thermal neutral voltage, which is dissipated as heat and leads to a temperature rise within the electrolytic cell). The electrolyte circuit is connected to a heat exchanger, which can lower the temperature of the electrolyte when the electrolytic cell stack is discharged, thereby enabling this cooling function to be performed effectively.

[0008] It is necessary to limit the leakage currents resulting from the relatively high ionic conductivity of the electrolyte. These leakage currents must be compensated for by either increasing the length of the electrolyte circuit or by using electrically insulating materials in the piping of the electrolyte supply network and the two-phase mixture discharge network. However, the first solution is disadvantageous in terms of the size and cost of the electrolytic cell stack, and the materials used to implement the second solution are generally polymers, whose properties impose limitations on the pressure and temperature of the fluid circulating in the pipes. Therefore, neither of these two solutions is optimal. [Overview of the Initiative]

[0009] One of the objectives of the present invention is to provide an electrolytic cell stack with improved efficiency. [Means for solving the problem]

[0010] To this end, the present invention provides a bipolar plate for an electrolytic cell, comprising at least one electrolyte supply conduit, a first discharge conduit for a first electrolytic product, and a second discharge conduit for a second electrolytic product. The bipolar plate comprises at least one hollow volume, a cooling fluid supply conduit into the hollow volume, and a cooling fluid discharge conduit from the hollow volume.

[0011] Therefore, the cooling function is ensured by a heat transfer fluid circuit separate from the electrolyte supply circuit and the electrolytic product discharge circuit. Thus, these circuits can be optimally sized and managed according to their respective functions. Furthermore, since the cooling water is injected directly into the stack of the electrolytic cell, it is possible to simplify installation by eliminating the electrolyte / cooling water heat exchanger (i.e., "lye cooler"). In addition, by using an appropriate heat transfer fluid, it becomes possible to remove the generated heat more effectively than when using the electrolyte alone, especially when operating at high current densities. In fact, the specific heat capacity of the KOH electrolyte is approximately 2.93 kJ / kg·K, while the specific heat of water used as a heat transfer fluid is approximately 4.18 kJ / kg·K, meaning that for a given flow rate and temperature difference, the heat capacity of water is 42% higher compared to KOH.

[0012] Preferably, the bipolar plate can then function as a heat exchanger.

[0013] The electrolytic cell stack according to the present invention may, in some cases, include one or more of the following optional features. - The supply and discharge conduits are formed on the outer circumference of the bipolar plate. - The supply conduit opens onto the main surface of the bipolar plate, and the discharge conduit opens onto the main surface of the bipolar plate. - The protrusions extend between the walls of the hollow volume, preventing the walls from coming close to each other and / or increasing the exchange surface area between the cooling fluid and the bipolar plate and / or ensuring electrical contact between the two walls. - Two plates joined together define a hollow volume between them.

[0014] The present invention also relates to electrolytic cells and electrolytic cell stacks that include this type of bipolar plate.

[0015] Other features and advantages of the present invention will become apparent from reading the following description of specific, non-limiting embodiments of the present invention. [Brief explanation of the drawing]

[0016] Refer to the attached drawings.

[0017] [Figure 1] FIG. 1 is a schematic exploded view of an electrolytic cell of an electrolytic cell stack according to a specific embodiment of the present invention. [Figure 2] FIG. 2 is a schematic perspective view of the bipolar plate of the electrolytic cell shown in FIG. 1. [Figure 3] FIG. 3 is a schematic view of an electrolytic cell stack including an electrolytic cell as shown in FIG. 1. [Figure 4] FIG. 4 is a schematic front view of a bipolar plate according to the present invention. [Figure 5] FIG. 5 is a cross-sectional view taken along line V-V of the intermediate plate shown in FIG. 4.

Mode for Carrying Out the Invention

[0018] In connection with various figures, the present invention relates to an electrolytic cell stack including a stack of elements extending longitudinally along an overall direction A.

[0019] The various elements are mainly formed by the electrolytic cell 10 described below.

[0020] The electrolytic cell 1 includes a stack or block 2 of electrolytic cells 10 arranged in direct contact with each other along the overall direction A. Within the block 2, the electrolytic cells 10 are connected in parallel from a fluid perspective and in series from an electrical perspective.

[0021] At both ends of the block 2 of the electrolytic cell 1 (in the overall direction A), two end plates or terminal plates 3 and 4 are positioned.

[0022] These end plates 3 and 4 act as supports between which the electrolytic cell 10 is compressed, thereby sealing the electrolytic cell stack 1 and establishing high-quality electrical contact within the electrolytic cell 10.

[0023] Furthermore, the end plates 3 and 4 are designed to withstand not only the forces generated by the internal pressure within block 2, but also the external forces applied to block 2 necessary to ensure its compression.

[0024] The end plates 3 and 4 can function as conductors and current distributors.

[0025] Preferably, the electrolytic cell stack 1 includes a first distribution plate 5 associated with a first end plate 3 and a second distribution plate 6 associated with a second end plate 4. In this example, the distribution plates 5 and 6 will function as conductors and current distributors.

[0026] The first distribution plate 5 (connected to the positive terminal) is located upstream of block 2, and the second distribution plate 6 (connected to the negative terminal) is located downstream of block 2.

[0027] The terms "upstream" and "downstream" are understood in their traditional sense, referring to the current flowing through Block 2.

[0028] The first of the two distribution plates, distribution plate 5, is connected to the positive terminal of the electrolytic cell stack 1. In this example, a portion of the inner main surface of the first end plate 3 (the main surface facing the direction of block 2, and particularly the direction of distribution plate 5) is covered with an insert made of an electrically insulating material. This portion is, for example, located at the center of the inner main surface.

[0029] The second of the two distribution plates, the 6th distribution plate, is connected to the negative terminal of the electrolytic cell stack 1. The second end plate 4 is at the same potential and also serves as a conduit for supplying the electrolyte containing the gas generated during electrolysis in block 2 and for discharging the same electrolyte.

[0030] Accordingly, holes are formed in the second end plate 4. The holes often have different cross-sections between the two main surfaces of the second end plate 4. For example, the outer main surface (the surface facing the outside of block 2) includes at least one or two holes (e.g., cylindrical) for supplying the electrolyte and two holes for discharging the electrolytic reaction products along with the heated electrolyte. On the inner main surface of the second end plate 4 (opposite the outer main surface), at least three or four holes are formed for the same purpose, and can be rectangular, for example, to improve fluid distribution or collection. The holes on the outer main surface are fitted with flanges suitable for connecting, for example, an electrolyte inlet pipe and a return pipe.

[0031] Furthermore, in this example, the electrolytic cell stack 1 is powered by a direct current.

[0032] For example, the first distribution plate 5 has a potential of several hundred volts, while the second distribution plate 6 has a potential of 0 volts (the electrolytic cell stack 1 typically contains 10 to 400, preferably 100 to 350, electrolytic cells 10, with each cell voltage being approximately 2 volts, preferably less than 1.85 volts, at the nominal point at the start of its service life). The supply (or delivery) and discharge of electrolyte occurs at the levels of the second distribution plate 6 and the second end plate 4, with the potential of the second distribution plate 6 being 0 volts, thereby preventing current leakage (the potential of the second distribution plate 6 is at ground potential).

[0033] Within the electrolytic cell stack 1, the current passes through the electrolyte and through the membrane 11 from end to end. This membrane is described below. Block 2 also contains sealing gaskets (described below). These sealing gaskets are made of a material having a much higher electrical resistance than the electrolyte. The electrolytic cell stack 1 includes an end sealing gasket (not shown) positioned between the first distribution plate 5 and the first end plate 3. However, because the first end plate 3 is at ground potential, the potential difference across the end sealing gasket reaches the same value as the voltage applied between the positive and negative terminals of the electrolytic cell stack 1, for example, approximately 700 volts.

[0034] This means that the first end plate 3 is electrically insulated from block 2.

[0035] For example, the electrolytic cell stack 1 includes a layer (not shown) made of an electrical insulating material, positioned between the first end plate 3 and the first distribution plate 5.

[0036] This layer is, for example, a disk attached to the first end plate 3 and / or the first distribution plate 5, or an applied coating.

[0037] The electrolytic cell stack 1 includes means for securing various electrolytic cells 10 to each other by common clamps.

[0038] For example, the fixing means includes a plurality of tie rods 7. Each tie rod 7 extends linearly through the electrolytic cell stack 1. Thus, each tie rod 7 extends longitudinally through the electrolytic cell stack 1 parallel to the overall direction A. Each tie rod 7 is formed in a rod shape.

[0039] Therefore, all tie rods 7 extend parallel to each other. The tie rods 7 are positioned around the periphery of various electrolytic cells 10. Preferably, the tie rods 7 are arranged around block 2, preferably at regular intervals.

[0040] The tie rod 7 penetrates the end plates 3 and 4 of the electrolytic cell stack 1 and extends through specific holes formed in the end plates 3 and 4, and thus has two ends, each located outside the block 2.

[0041] Preferably, the tie rod 7 is partially covered with a sleeve made of an electrically insulating material. This makes it possible to avoid a short circuit between the electrolytic cells 10 in the event of contact or splashing. For example, the sleeve extends along the entire length of the tie rod 7, which is positioned between the two end plates 3 and 4.

[0042] Preferably, the ends of the tie rod 7 are threaded. For example, the threads at the ends are rolled threads. Rolled threads have the advantage of simplifying the machining of the tie rod 7, especially when the tie rod 7 is of considerable length, for example, several meters.

[0043] The fastening means also includes nuts 8 screwed onto both ends of the tie rod 7.

[0044] These nuts 8 compress the two end plates 3 and 4 so that they press against each other, and thus the various electrolytic cells 10 are also compressed, thereby ensuring good sealing of the electrolytic cell stack consisting of the electrolytic cells 10.

[0045] Preferably, the fixing means also includes preloading means for preloading the two end plates 3 and 4 so as to press them against each other, thereby preloading the various electrolytic cells 10 to come into contact with each other. The preloading means also serves to absorb the deformation and / or changes in thickness of the members forming the electrolytic cell stack 1 due to thermal expansion of the electrolytic cell stack 1 or changes in external and internal mechanical stresses (e.g., internal pressure of the electrolytic cell stack).

[0046] Since the preload application means is attached to both ends of the tie rod 7, for a given end, the preload application means is positioned between the nearest end plate (3 or 4) and the nut 8 located at the same end.

[0047] For example, the fastening means includes a spring washer 9, such as a Belleville washer. The spring washer 9 is attached to both ends of the tie rod 7.

[0048] More specifically, in this example, the spring washer 9 is positioned on each tie rod 7, on the outer portion after the tie rod 7 has passed through the nearest end plate (3 or 4).

[0049] The aforementioned fixing means enable the electrolytic cell stack 1 to cope with changes in thermal expansion and / or mechanical load both externally and internally (e.g., internal pressure of the electrolytic cell stack 1).

[0050] In this example, since all the electrolytic cells 10 in the electrolytic cell stack 1 are identical to each other, the following description of the electrolytic cells 10 can also be applied to the descriptions of the other electrolytic cells 10.

[0051] This type of electrolytic cell 10 includes a central membrane 11 sandwiched between two electrodes 12a and 12b (anode and cathode, respectively), the electrodes themselves being sandwiched between two spacers 16 (or flow-field material), and further sealed by two bipolar plates 14. In this example, the spacers 16 are identical, but may differ on the anode and cathode sides. In addition, the electrolytic cell 10 also includes a sealing gasket 13 (whose presence has already been described above), which is compressed between the two bipolar plates 14 of the electrolytic cell 10.

[0052] The film 11, spacer 16, and electrodes 12a and 12b are known in the prior art and will not be described in detail here.

[0053] The fact that the two bipolar plates 14 of the electrolytic cell 10 are identical to one another means that the following description of one bipolar plate 14 also applies to the other bipolar plate 14 of the same electrolytic cell 10. The bipolar plates 14 are made of a material that can withstand the corrosive environment that is common inside the electrolytic cell 10. The bipolar plates 14 are, for example, nickel-based and may be made of nickel or nickel-plated carbon steel.

[0054] Next, the external and internal structures of the bipolar plate 14 will be described.

[0055] The shape of the bipolar plate 14 is further constructed to have two main surfaces, namely, a first main surface facing inwards towards the interior of each electrolytic cell 10 and a second main surface facing outwards towards the exterior of each electrolytic cell 10.

[0056] The bipolar plates 14 will later be found to be asymmetrical (with respect to a plane of symmetry that penetrates the center of each bipolar plate). As a result, within a single electrolytic cell 10, the first face of the bipolar plate 14 being described faces the second face of the other bipolar plate 14 which is identical to the one being described. Within block 2, all bipolar plates 14 are oriented in the same way.

[0057] The following defines the X and Y axes that form a plane extending from one of the main surfaces of the bipolar plate 14, as well as the Z axis perpendicular to the XY plane.

[0058] When the bipolar plate 14 is in a predetermined position within the electrolytic cell 10, and the electrolytic cell 10 itself is in the correct position within the electrolytic cell stack 1, the Z-axis is aligned with the overall direction A.

[0059] The thickness of bipolar plate 14 (along the Z-axis) is smaller than the other dimensions.

[0060] The bipolar plate 14 is formed to have a cross-section (in the XY plane) of any geometric shape (e.g., square, rectangle, circle, etc.). In this example, the bipolar plate 14 has a circular cross-section.

[0061] The outer periphery of the bipolar plate 14 is defined by a first zone 21, a second zone 22, and a third zone 23.

[0062] The first zone 21 extends around the entire circumference of at least one of the main surfaces of the bipolar plate 14. Thus, the first zone 21 forms a ring that defines the outer edge of the main surface.

[0063] The first zone 21 enhances the resistance of the bipolar plate 14 to the internal pressures that are common within the electrolytic cell stack 1, thereby improving the sealing of the electrolytic cell 10 to the outside of the electrolytic cell stack 1. In particular, the first zone 21 enhances the resistance of the bipolar plate 14 to radial pressure loads applied to it (when assembling the electrolytic cell 10 in the electrolytic cell stack 1). For example, the first zone 21 can be sized to conform to standards applicable to pressure vessels, such as the PED2014 / 68 / EU standard.

[0064] The first zone 21 is preferably textured. For example, the first zone 21 includes grooves, stripes, protrusions, or a roughened surface texture, etc., on at least one of the main surfaces of the bipolar plate 14, preferably on both of the main surfaces of the bipolar plate 14.

[0065] In contrast, the circular edges of the bipolar plate 14 (i.e., the surfaces that join the two main surfaces of the bipolar plate 14 to each other) are smooth, i.e., untextured.

[0066] The second zone 22 also extends circumferentially, and its outer boundary is defined by the first zone 21. The second zone 22 is coaxial with the first zone 21.

[0067] In this example, the second zone 22 extends around the entire circumference of at least one of the main surfaces of the bipolar plate 14. Therefore, the second zone 22 is a ring.

[0068] The second zone, 22, is smooth, i.e., untextured.

[0069] This second zone 22 is located around the electrolyte supply channel and the gas exhaust channel resulting from electrolysis.

[0070] This second zone 22 is thinner than the first zone 21 (thickness is considered along the Z-axis) (the difference in thickness is not visible in the very schematic Figures 4 and 5). For example, the shape of the bipolar plate 14 is made to have at least one shoulder between the first zone 21 and the second zone 22. Preferably, the shape of the bipolar plate 14 is made to have two shoulders between the first zone 21 and the second zone 22. These two shoulders are identical in this example and are formed on the two main surfaces of the bipolar plate 14.

[0071] Therefore, the bipolar plate 14 is symmetrical at the levels of its first zone 21 and its second zone 22, according to a symmetrical central plane parallel to the X and Y axes.

[0072] The reduction in thickness between the first zone 21 and the second zone 22 makes it possible to achieve different sealing configurations between the two zones.

[0073] The third zone 23 also extends circumferentially, and its outer boundary is defined by the second zone 22. The third zone 23 is coaxial with the second zone 22.

[0074] The third zone 23 extends around the entire circumference of the bipolar plate 14 in this case. The third zone 23 is a ring.

[0075] This third zone 23 is thinner than the second zone 22 (in terms of thickness along the Z-axis). For example, the shape of the bipolar plate 14 is designed to have at least one shoulder between the second zone 22 and the third zone 23.

[0076] Preferably, the shape of the bipolar plate 14 is made to exhibit a single shoulder between the second zone 22 and the third zone 23. This shoulder is formed on the first main surface of the bipolar plate 14, i.e., the surface facing inward towards the electrolytic cell 10. This shoulder provides a seat for the membrane 11.

[0077] Preferably, the second zone 22 and the third zone 23 extend continuously from each other on the second main surface of the bipolar plate 14. Therefore, there is no shoulder between the second zone 22 and the third zone 23 on the second main surface.

[0078] Therefore, the second surface of the bipolar plate 14 does not have this type of shoulder, and consequently, the second surface of the other bipolar plate 14 of each electrolytic cell 10 also does not have this type of shoulder. Thus, the membrane 11 is positioned between the two bipolar plates 14 so as to fit only to the shoulder of one of the two bipolar plates 14.

[0079] Therefore, the bipolar plate 14 is asymmetric with respect to the symmetrical central plane parallel to the X and Y axes, considering the three zones mentioned above (which are not visible in the very schematic Figure 5).

[0080] The third zone 23 is entirely smooth (i.e., untextured), partially smooth, or entirely textured. Preferably, the third zone 23 is textured on the first main surface of the bipolar plate 14.

[0081] This allows the film 11 to be held in place. For example, on the first main surface, the third zone 23 includes grooves, stripes, surface roughness, protrusions, and so on.

[0082] Preferably, the third zone 23 is smooth on the second main surface of the bipolar plate 14.

[0083] Therefore, the thickness of the bipolar plate 14 (along the Z-axis) gradually decreases at the shoulder, at the junction between the first zone 21 and the second zone 22, and again at the junction between the second zone 22 and the third zone 23 (these differences in thickness are not visible in the very schematic Figures 4 and 5). Thus, the bipolar plate 14 is thicker in the first zone 21 than in the second zone 22, and the second zone 22 is thicker than in the third zone 23.

[0084] The central portion 24 of the bipolar plate 14 also extends outward, bounded by the third zone 23. The central portion 24 is coaxial with the third zone 23. The central portion 24 is solid. The central portion 24 forms a circular flat area. This central portion 24 is thinner than the third zone 23 (in terms of thickness considered along the Z-axis).

[0085] For example, the shape of the bipolar plate 14 is made to exhibit at least one shoulder between the third zone 23 and the central portion 24. Preferably, the shape of the bipolar plate 14 is made to exhibit two shoulders between the third zone 23 and the central portion 24. These two shoulders are identical in this example and are located on the two main surfaces of the bipolar plate 14. The central portion 24 itself may optionally exhibit at least one shoulder, thereby further decreasing its thickness (considered along the Z-axis) toward the center of the bipolar plate 14. Thus, the central portion 24 is the thinnest part of the bipolar plate 14 (in terms of thickness considered along the Z-axis). The central portion 24 may be smooth or it may be textured.

[0086] The central portion 24 acts as a current collector, transmitting current to the spacer 16 positioned on either side of the central portion 24. In fact, unlike the outer annular portion of the bipolar plate 14, the function of the central portion 24 is not to withstand high-voltage loads. Therefore, the central portion 24 primarily functions as a support for the components stacked within the electrolytic cell 10, namely the spacer 16, electrodes 12a and 12b, and the film 11. Thus, the mechanical forces are equal on both sides of the central portion 24.

[0087] Therefore, the bipolar plate 14 exhibits a specific geometric shape. The thickness of each of the aforementioned zones varies from zone to zone, ranging from a few tenths of a millimeter to several millimeters. The thickness of a given zone also changes due to the thermal expansion of the bipolar plate 14 (and therefore, the change in the thickness of each zone due to thermal expansion also differs from zone to zone).

[0088] In addition, the bipolar plate 14 includes conduits 15 that extend through it from one side to the other. These conduits 15 are dedicated to supplying the electrolyte and discharging the electrolytic products.

[0089] For example, the bipolar plate 14 includes 3 to 6 conduits 15. For example, the conduits 15 are arranged in pairs, and pairs of two conduits 15 are evenly distributed along the circumference of the bipolar plate 14. In this example, the bipolar plate 14 includes a pair of conduits 15 for electrolyte delivery, a first discharge conduit 15 for a first electrolytic product (a two-phase mixture of electrolyte and oxygen gas), and a second discharge conduit 15 for a second electrolytic product (a two-phase mixture of electrolyte and hydrogen gas).

[0090] For example, at least one of the conduits 15 is located in the second zone 22. In this example, all of the conduits 15 are formed in the second zone 22. The conduits 15 can have a circular, rectangular, or other cross-sectional shape. For example, at least one of the conduits 15 has a rectangular cross-section. The conduits 15 are connected to the inner volume of the electrolytic cell 10 by radial grooves / counterbores that extend from the conduits 15 in zone 22 to the central portion 24.

[0091] The bipolar plate 14 further includes a cooling water supply conduit 18 and a cooling water discharge conduit 19. The cooling water can be replaced with any heat transfer fluid capable of carrying thermal energy. These two conduits 18 and 19 extend laterally (parallel to direction A) through zone 22, each having an end that opens onto one of the main surfaces of the bipolar plate 14 (the supply conduit 18 and the discharge conduit 19 open onto the opposite surface). The conduits 18 and 19 communicate with a hollow volume 20 located inside the bipolar plate 14 via a lateral branch, and are connected to each other through this hollow volume 20.

[0092] More precisely, the bipolar plate 14 in this example is formed by an assembly consisting of two plates 14.1 and 14.2. Each plate 14.1, 14.2 is disc-shaped with a thickened annular edge intended to form zones 21 and 22, where conduits 18 and 19 are formed. The central region of each plate 14.1, 14.2 on the surface facing the other plate 14.2, 14.1 includes raised shapes 14.10, 14.20 (pins, protrusions, ribs, etc.) that allow each plate to abut against the other plate 14.2, 14.1 without obstructing the flow of cooling water from the supply conduit 18 to the discharge conduit 19 through the hollow volume 20. These raised shapes prevent deformation of the central part of the bipolar plate 14. The raised shapes also ensure that electrical contact between the two bipolar half plates 14.1 and 14.2 is as reliable and optimal as possible. Plates 14.1 and 14.2 are joined to each other by welding, bonding, bolting, or any other fastening method, with or without the insertion of a sealing gasket depending on the type of fastening. In one variant, only the first plate of plate 14.1 or 14.2 has a disc shape with a thickened annular rim intended to form zones 21 and 22, with conduits 18 and 19 formed in this annular rim, and the second plate of plate 14.1, 14.2 has a disc shape that is inserted into the thickened annular rim of the first plate.

[0093] As mentioned above, within the electrolytic cell 10, the two bipolar plates 14 compress the sealing gasket 13 between them.

[0094] Note that within the electrolytic cell stack 1, all bipolar plates 14 are separated in pairs by sealing gaskets 13 (each bipolar plate 14 acts as the cathode of one electrolytic cell 10 and as the anode of another electrolytic cell 10 immediately adjacent to it).

[0095] An advantage is that the two bipolar plates 14 compress a single sealing gasket 13 between them.

[0096] Advantageously, since all sealing gaskets 13 used in the electrolytic cell 10 are identical within block 2, the following description of one of the sealing gaskets 13 is equally applicable to the other sealing gaskets 13 in the other electrolytic cells 10.

[0097] The main functions of the sealing gasket 13 are as follows: i) to securely seal each electrolytic cell 10 to the outside of the electrolytic cell stack 1; ii) to securely seal the channel carrying one gas generated in block 2 from the channel carrying another gas generated in block 2; iii) to securely seal the chambers where the electrolytic reactions that generate the two aforementioned gases take place, isolating them from each other, and also ensuring that the channels mentioned above are securely sealed; iv) to act as an electrical insulating layer between two adjacent bipolar plates 14; and v) to define the compression thickness of the electrolytic cell 10 along the Z direction.

[0098] Preferably, the sealing gasket 13 is made to have a square or rectangular cross-section (in its transverse form).

[0099] Therefore, the sealing gasket 13 is called a flat gasket.

[0100] Preferably, the shape of the sealing gasket 13 is made to match the shape of the annular portion 25 of the associated bipolar plate 14.

[0101] In this example, the sealing gasket 13 is generally ring-shaped, and the associated bipolar plate 14 is disc-shaped.

[0102] Note that the sealing gasket 13 contains multiple holes.

[0103] This ensures that electrolytes are reliably supplied to block 2 and that electrolytic products are discharged from block 2, as well as that coolant is supplied and discharged. For example, the holes formed in the sealing gasket 13 correspond to the holes formed in zone 22 of the bipolar plate 14.

[0104] The shape of the sealing gasket 13 is made such that the diameter (of the cross-section) is as constant as possible along both its inner and outer circumference, and / or the thickness (along the Z-axis) is as uniform as possible across its entire cross-section (and from one sealing gasket 13 to another).

[0105] This helps to increase the efficiency of the electrolytic cell 10 in the electrolytic cell stack 1.

[0106] In particular, the surfaces of the sealing gasket 13 can be made as parallel as possible to each other and to the opposing main surfaces of the bipolar plate 14. This further enhances the overall sealing performance.

[0107] The dimensional tolerances of the sealing gasket 13 are determined by the intended application (for example, a tolerance of ±0.1 mm for thickness).

[0108] As mentioned above, and as can be seen more clearly in Figure 3c, the sealing gasket 13 is compressed between two adjacent bipolar plates 14, and more specifically between two outer circumferences of opposing main surfaces of the bipolar plates 14, and more specifically between two opposing annular portions of the bipolar plates 14.

[0109] Due to the specific geometric shape of the outer circumference of the bipolar plate 14, and especially the annular portion, the bipolar plate 14 deforms in such a way that when the sealing gasket 13 is compressed, it defines and shapes the sealing gasket 13 into three distinct parts.

[0110] In contrast, the sealing gasket 13 is not compressed between the central portions 24 of the two bipolar plates 14.

[0111] The diameter (by cross-section) of the sealing gasket 13 is such that the sealing gasket 13 extends from the side edge of the bipolar plate 14 to the joint between the third zone 23 and the central portion 24 (preferably extending beyond the third zone 23).

[0112] Therefore, each part of the sealing gasket 13 performs a separate sealing function, and the specific level of compression varies from part to part. As a physical and mechanical result, the thickness of the sealing gasket 13 decreases variably depending on the part.

[0113] Therefore, when the sealing gasket 13 is in an uncompressed state, it has a conventional annular shape and a substantially uniform initial thickness.

[0114] When the sealing gasket 13 is compressed between the two bipolar plates 14, - Between the first zones 21 of the two bipolar plates 14, the sealing gasket 13 exhibits a corresponding textured first portion to conform to the geometric shape of the first zone 21. - Between the second zone 22 of the two bipolar plates 14, the sealing gasket 13 exhibits a smooth, corresponding second portion, in which case the thickness of the sealing gasket 13 is also greater than that of the first portion. - Between the third zone 23 of the two bipolar plates 14 and the film 11, the sealing gasket 13 has a corresponding third portion that is smooth and / or grooved.

[0115] In the first part, the sealing gasket 13 is compressed directly between the two first zones 21 (without an intermediate member).

[0116] In the second part, the sealing gasket 13 is compressed directly between the two second zones 22 (without an intermediate member).

[0117] In contrast, in the third section, the sealing gasket 13 is not directly compressed between the two third zones 23. This is because a membrane 11 is also interposed between the two third zones 23. As a result, the sealing gasket 13 is directly compressed on one side by one of the third zones 23, and on the other side by the membrane 11, which itself is compressed by the opposing third zones 23 of the bipolar plate 14.

[0118] Therefore, in the third section, the thickness of the sealing gasket 13 is significantly thinner than that of the second section, and the film 11 fills the remaining space between the two third zones 23. This arrangement ensures that the film 11 is securely sealed.

[0119] The sealing gasket 13 is thus distributed across its entire height (along the X-axis) between its three parts, and therefore between the three zones of the annular portion.

[0120] As a result, the portion of the electrolytic cell 10 located in the first zone 21 of the first part of the two bipolar plates 14 and the sealing gasket 13 serves to prevent the leakage of electrolyte or gas from the electrolytic cell stack 1, in other words, it is dedicated to reliably sealing the electrolytic cell 10 from the external environment. When the degree of sealing was measured using helium gas, for example, 10 meters per second -3 A degree of airtightness of milligrams - mg / (m·s) or higher, preferably 10 -4 A degree of airtightness of mg / (m·s) or higher is ensured.

[0121] This first part is characterized by the presence of texture on the bipolar plate 14 through which the sealing gasket 13 deforms. In particular, as the sealing gasket 13 deforms, it fills in the recesses of the first part of the bipolar plate 14, thereby enhancing the sealing performance of the electrolytic cell 10. In fact, these textures act as an additional barrier to the gas and other substances present, making it more difficult for them to find a path out of the electrolytic cell stack 1. The presence of texture also contributes to increased friction between the electrolytic cells 10, thus helping to maintain the self-supporting structure of the multiple electrolytic cells 10 stacked to form block 2. This advantage is enhanced when block 2 is positioned horizontally during operation.

[0122] For example, the compression of the sealing gasket 13 in the first portion is such that the sealing gasket 13 reaches a maximum thickness (along the Z axis) equal to 94%, preferably 78%, more preferably 75%, of its original thickness (i.e., the thickness when it is relaxed and laid flat on a surface without external load). The original thickness is, for example, 3.0 mm or more. Preferably, this original thickness does not exceed 3.5 mm. Alternatively, a thinner sealing gasket may be used. The second portion of the electrolytic cell 10, located in the second zone 22 of the two bipolar plates 14 and the second portion of the sealing gasket 13, serves to prevent crossflow between channels that transport hydrogen and oxygen gases within the electrolytic cell 10, or crossflow from the electrolytic cell 10 itself (originating from the third zone 23 and central portion 24) toward the channels.

[0123] For example, the compression of the sealing gasket 13 in the second portion is such that the sealing gasket 13 reaches a thickness (along the Z-axis) between 92% and 97% of its original thickness (i.e., its thickness when laid flat on a surface without external load), preferably equal to 92% of its original thickness. In all cases, the sealing gasket 13 is not compressed as much in the second portion as in the first portion, and is therefore thicker than in the first portion.

[0124] The wider sealing gasket 13 between the first zone 21 and the second zone 22 makes it possible to achieve different sealing behaviors between the first zone 21 and the second zone 22. In any case, the sealing between the first zone 21 and the second zone 22 is of high quality.

[0125] The third portion of the electrolytic cell 10, located in the third zone 23 of the two bipolar plates 14 and the third section of the sealing gasket 13, serves to house the membrane 11, as described above.

[0126] Therefore, this third part ensures that the space between the anode chamber and the cathode chamber of the electrolytic cell 10 is securely sealed.

[0127] Therefore, both the film 11 and the sealing gasket 13 are then compressed between the two bipolar plates 14 in this third portion, and the sealing gasket 13 thus overlaps with the film 11 in this region of the electrolytic cell 10.

[0128] This ensures excellent sealing around the membrane 11 toward the fluid supply conduit and the fluid discharge conduit.

[0129] The third portion of the sealing gasket 13 thereby defines a third compression zone intended to hold the film 11 in place and ensure a secure seal around it. For example, the compression of the sealing gasket 13 in the third portion causes the sealing gasket 13 to reach a thickness (along the Z-axis) between 86% and 92% of its original thickness (i.e., its thickness when laid flat on a surface without external load), preferably between 88% and 92% of its original thickness, and more preferably 90% of its original thickness.

[0130] In another embodiment, the sealing gasket 13 is made of a homopolymer or copolymer material, for example, a thermoplastic material.

[0131] For example, the sealing gasket 13 is made of a material such as polytetrafluoroethylene or polytetrafluoroethene (commonly abbreviated as PTFE, or more widely known by the trade name Teflon (registered trademark)), or FKM (commonly known by the trade name Viton (registered trademark)).

[0132] Preferably, the material is made of polytetrafluoroethylene or polytetrafluoroethene reinforced with at least one filler, or is based on them, or of the same type. For example, the filler is glass fiber.

[0133] For example, the material is reinforced polytetrafluoroethylene. For example, the reinforced polytetrafluoroethylene is polytetrafluoroethylene reinforced with glass fibers, or the reinforced polytetrafluoroethene is polytetrafluoroethene reinforced with carbon fibers.

[0134] The characteristics of the sealing gasket 13 described are defined as follows: - Despite high temperatures (typically around 90 to 95 degrees Celsius), the electrolytic cell 10 maintains excellent performance and favorable mechanical properties at its operating temperature, and this performance persists over a long period of time. - It has resistance to the corrosive environment inside the electrolytic cell 10, and this resistance lasts for a long period of time. - Excellent sealing properties. - It exhibits excellent electrical insulation properties (due to high electrical resistance) even at operating temperatures and in contact with the electrolyte. - Low creep allows for a long service life of the electrolytic cell stack 1, which consists of 10 electrolytic cells. - There is still a slight creep behavior in order to best fit the geometric shape characteristics of the sealing zone 21 of the sealing gasket 13. - The thickness (along the Z-axis) is uniform.

[0135] In one selective configuration, the end sealing gasket positioned between the first distribution plate 5 and the first end plate 3 is made from the same material as the sealing gasket 13 of the electrolytic cell 10. The end sealing gasket is, for example, identical to the sealing gasket 13. The end sealing gasket is optionally made from a homopolymer or copolymer material, for example, a thermoplastic material.

[0136] In one selective embodiment, the layer of electrical insulating material between the first end plate 3 and the first distribution plate 5 is made of the same material as the end sealing gasket placed between the first distribution plate 5 and the first base plate 3. In a further selective embodiment, the layer of electrical insulating material between the first base plate 3 and the first distribution plate 5 is made of the same material as the sealing gasket 13. The layer is optionally made of a homopolymer or copolymer material, for example, a thermoplastic material.

[0137] In one selective embodiment, the end sealing gasket positioned between the second distribution plate 6 and the second base plate 4 is made of the same material as the sealing gasket 13 of the electrolytic cell 10. The end sealing gasket is, for example, identical to the sealing gasket 13. The end sealing gasket is optionally made of a homopolymer or copolymer material, for example, a thermoplastic material.

[0138] In one selective embodiment, the pads positioned on the inner surface of the first distribution plate 5 are either a layer of material directly coated onto the first distribution plate 5, or formed by a powder deposition of a fluoropolymer, particularly ethylene chlorotrifluoroethylene, which is commercially available from SOLVAY under the trademark name Halar.

[0139] The electrolytic cell 10 described above has excellent sealing characteristics due to the specific compression of the sealing gasket 13 between the bipolar plates 14. It should also be noted that the electrolytic cell 10 is sealed using a single sealing gasket 13, which provides three separate sealing and compression zones.

[0140] By using a single sealing gasket 13 made of plastic (no longer an elastomer as in the prior art), it is also possible to enhance the sealing of the electrolytic cell stack.

[0141] In fact, the sealing gasket 13 has high resistance to the corrosive environment that is common inside the electrolytic cell stack 1, even over long periods of time.

[0142] Therefore, the sealing gasket 13 is made of a rigid material that can withstand the high mechanical compression that the electrolytic cell stack 1 is subjected to.

[0143] Next, we will explain how to assemble electrolytic cell stack 1.

[0144] In the first step, the subassemblies are constructed individually, with each subassembly consisting of two spacers 16 and two electrodes 12a and 12b assembled on either side of the bipolar plate 14. Each subassembly, strictly speaking, forms two adjacent semi-electrolytic cells 10.

[0145] In the second step, the subassemblies, separated from each other by the film 11 and sealing gasket 13, are stacked in sequence to form the electrically series-connected electrolytic cells 10. The last electrolytic cell 10 at one end of the stack 2 is covered by a second distribution plate 6, which itself is covered by a second end plate 4, and the last electrolytic cell 10 at the other end of the stack 2 is covered by a first distribution plate 5, which itself is covered by a first end plate 3, thereby defining the electrolytic cell stack 1. Care is taken to ensure that the conduits 15, 18, and 19 of each bipolar plate 14 are aligned with the conduits 15, 18, and 19 of the adjacent bipolar plate 14. The negative base plate is also equipped with additional holes and flanges specifically for the incorporated cooling circuit.

[0146] In the third step, the newly assembled electrolytic cell stack 1 is compressed using tie rods 7, nuts 8, and spring washers 9.

[0147] This type of assembly, having thick distribution plates 5 and 6 and a flat bipolar plate 14, enables a uniform current in all electrolytic cells 10 of the electrolytic cell stack 1, even if the voltages across the terminals of each electrolytic cell 10 are different, and even if the current is connected at only one or more points around the periphery of each distribution plate 5 and 6.

[0148] Furthermore, the bipolar plates 14 are properly parallel to each other within block 2 due to their special shape and the proper tightening of each sealing gasket 13. This further improves the uniformity of the current across all electrolytic cells 10.

[0149] In the assembly process, ideally, each sealing gasket 13 is particularly, - To be able to deform according to the geometric shape imposed by the bipolar plate 14 that encloses the gasket 13, - To cover the textures of the first zone 21, make it possible to embed them into those textures, - To allow the material forming the gasket 13 to be intentionally and prematurely aged, - To eliminate the plastic behavior of the material as much as possible, - The material of the gasket 13 is made to be within the range of elastic behavior (centered on the operating point of the electrolytic cell stack 1), - It is necessary to achieve the desired clamping value that ensures both the intended sealing performance and electrical contact between various components, thereby enabling the intended energy performance to be achieved.

[0150] The nominal operating point of electrolytic cell stack 1 is, for example, 85 degrees Celsius under 3 megapascals.

[0151] Naturally, the present invention is not limited to the embodiments described, but includes any modifications that fall within the scope of the invention as defined by the claims.

[0152] One or more end sealing gaskets may differ from sealing gasket 13.

[0153] Electrolytic cell stack 1 can be assembled in a manner different from that described.

[0154] The electrolytic cell stack 1 can be used horizontally, vertically, or in any other position. The electrolytic cell stack can be assembled horizontally, vertically, or in any other position. Preferably, the electrolytic cell stack 1 is assembled vertically and used horizontally.

[0155] There may be only one conduit 15 associated with the supply of electrolyte and only one conduit 15 associated with the discharge of each electrolytic product. However, for redundancy in case one of the conduits 15 becomes clogged, it is preferable to have two conduits 15 associated with the supply of electrolyte and / or two conduits 15 associated with the discharge of each electrolytic product. Generally speaking, the distribution plates 5 and 6 may have only one conduit 15 at each of their ends, opening onto one of the main surfaces of each distribution plate 5 and 6.

[0156] Similarly, it is preferable to have two grooves associated with each end of each conduit 15 for redundancy.

[0157] The number of supply conduits 18 and discharge conduits 19 may differ.

[0158] Bipolar plates can have circular, elliptical, polygonal, or other contours.

[0159] The bipolar plate 14 may include any type of relief extending between the walls of the hollow volume 20, preventing the walls from coming into close proximity to each other and / or increasing the exchange surface between the cooling fluid and the bipolar plate 14.

[0160] Various conduits 18 and 19 may not be identical to one another.

[0161] Different grooves may not be identical to each other.

[0162] The two distribution plates 5 and 6, each associated with one end of block 2, may be different from and not identical to each other, as described above. The distribution plates 5 and 6 may have only one reinforcing member instead of two, as described above. At least one of the ends of the distribution plates 5 and 6 may include at least one conduit 15 that does not open onto the outer periphery of the associated main surface (for example, opening into the central zone of the main surface, and possibly into a recess present on the main surface).

[0163] For example, the distribution plates 5 and 6 may include at least one conduit 15 that opens into a recess in the distribution plates 5 and 6 at at least one of its ends. Optionally, the conduit 15 may open at at least one of its ends close enough to the outer circumference of one of its main surfaces to allow for complete or near-complete drainage of the space (of liquid and / or gas) between each distribution plate 5 and 6 and the opposing end plates 3 and 4. Optionally, the conduit 15 may be configured to open into a recess in the first main surface of the distribution plates 5 and 6 at a first end, and to open into a recess in the second main surface of the distribution plates 5 and 6 at a second end, thereby connecting the two recesses.

[0164] The electrolytic cell stack 1 may include three electrodes, namely two end cathodes and one central anode. The spring washers 9 may be placed at both ends of the tie rod, or at only one of these ends, and / or can be replaced with any elastic compression member.

Claims

1. A bipolar plate (14) for an electrolytic cell (10), comprising at least one electrolyte supply conduit, a first discharge conduit for a first electrolytic product, and a second discharge conduit (15) for a second electrolytic product, wherein the bipolar plate (14) comprises two plates (14.1, 14.2) joined together to define at least one hollow volume (20) between them, each having a thicker annular rim forming an outer zone (22) around the bipolar plate (14); and a supply conduit (18) for supplying cooling fluid to the hollow volume (20) and a discharge conduit (19) for removing the cooling fluid from the hollow volume (20), located in the outer zone (22) around the periphery.

2. A bipolar plate (14) according to claim 1, characterized in that the supply conduit (18) opens onto the main surface of the bipolar plate (14), and the discharge conduit (19) opens onto the main surface of the bipolar plate (14).

3. A bipolar plate (14) according to claim 1 or 2, comprising a raised portion extending between the walls of the hollow volume (20), thereby preventing the walls from approaching each other and / or increasing the exchange surface between the cooling fluid and the bipolar plate (14) and / or providing electrical contact between the two walls.

4. An electrolytic cell (10) characterized by comprising at least one bipolar plate (14) according to any one of claims 1 to 3.

5. An electrolytic cell stack (1) comprising an electrolytic cell (10) according to any one of claims 1 to 4, wherein the electrolyte supply conduit (15) of each bipolar plate (14.1 and 14.2), the first discharge conduit for the first electrolytic product, and the second discharge conduit (15) for the second electrolytic product are all incorporated into an electrolyte supply network, a first discharge network for the first electrolytic product, and a second discharge network for the second electrolytic product, respectively, which extend along the electrolytic cell stack (1), and the supply conduit (18) for the cooling fluid and the discharge conduit (19) for the cooling fluid are incorporated into a cooling fluid supply network and a cooling fluid discharge network, respectively, which extend along the electrolytic cell stack (1).

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