Electrolyzer stack with low leakage currents

Abstract

Disclosed is an electrolyzer stack comprising two base plates between which a stack of elements comprising electrolytic cells is clamped, and at least one intermediate plate (30) clamped in the stack of elements. The intermediate plate (30) has a thickness within which at least one electrolyte supply duct, a first duct for discharging the first electrolysis product and a second duct for discharging the second electrolysis product (33) are arranged which are integrated to a supply network, a first discharge network and a second discharge network, respectively. Each of said ducts (33) in the intermediate plate (30) has a length that is greater than the thickness of the intermediate plate (30) and includes a bent section (34) connecting the inlet and outlet ports to each other.

Description

[0001] ELECTROLYSER CELL WITH LOW LEAKAGE CURRENTS

[0002] The invention relates to the field of electrolysis and more particularly the production of hydrogen.

[0003] BACKGROUND OF THE INVENTION

[0004] The overall architecture of an electrolyzer cell (generally referred to as an "electrolyzer stack") usually consists of a block of electrolytic cells, which are stacked in series from an electrical point of view and in parallel from a fluidic point of view, and seals.

[0005] Each electrolytic cell has the purpose of promoting the electrolysis of an electrolytic solution (alkaline water, pure water, unpurified water, salt, aqueous chloride solution, aqueous bromide solution, aqueous hydrochloric acid solution, etc.). For example, the functionality of an electrolyzer cell is to promote the reaction of production of dihydrogen (H2) and dioxygen (02) gas resulting from the dissociation of water after injecting a direct electric current into an alkaline solution, generally potassium hydroxide (KOH) or sodium hydroxide (NaOH).

[0006] Each electrolytic cell, considered as a mainly metallic and conductive part (but some parts of which may be non-metallic), is generally composed of two bipolar plates, framing two interlayers (better known under the English term "flow field material"), themselves framing two electrodes generally in the form of plates or grids or metallic fabrics. In the case of an alkaline electrolyzer cell, said electrodes are generally made of nickel. The two electrodes (a cathode and an anode) are separated by a membrane (also called a diaphragm or porous separator in the case of the alkaline electrolyzer cell), which ensures electrical insulation between the two electrodes, the separation of gases as well as ionic conduction within the electrolytic cell.

[0007] The interlayer has two functions: i) to provide a low resistivity metallic path between each bipolar plate and the associated electrode and ii) to allow proper circulation of the electrolytic solution for cooling the electrolyzer stack and transporting the generated gases.

[0008] The name bipolar plate comes from the fact that since the electrolytic cells are all placed next to each other, an N bipolar plate will have a potential: higher compared to the downstream N+l bipolar plate, so that the N bipolar plate will act as anode within an electrolytic cell defined by the N and N+l bipolar plates; lower compared to the upstream Nl bipolar plate, so that the N bipolar plate will act as cathode within an electrolytic cell defined by the Nl and N bipolar plates.

[0009] Among the other metal parts, in addition to the bipolar plates, are listed the distribution plates (which allow the power supply and electrical distribution of the electrolytic cells) as well as the base plates (allowing the demarcation of all the electrolytic cells and ensuring the clamping of said electrolytic cells between them and their sealing).

[0010] In fact, the electrolyser stack ends with two bottom plates located just before the first electrolytic cell and just after the last stacked electrolytic cell, in other words one bottom plate is located upstream of the block of electrolytic cells and the other bottom plate is placed downstream of the latter in order to physically delimit the two ends of said block of electrolytic cells.

[0011] To ensure ionic conduction within the electrolytic cell, the electrolytic solution has a high ionic conductivity. However, there is a risk that, due to this high ionic conductivity, leakage currents will propagate, via the electrolyte, in the electrolyte supply and discharge network of two-phase mixtures (i.e. electrolyte and oxygen on the one hand and electrolyte and hydrogen on the other). These leakage currents penalize the overall efficiency of the electrolysis process.

[0012] These leakage currents can be compensated either by reducing the passage section of the pipes, or by using pipes made of electrically insulating materials in the electrolyte supply and two-phase mixture evacuation networks.

[0013] The first solution causes pressure losses which risk leading to poor distribution of the electrolyte between the electrolytic cells and to difficulties in evacuating the gases produced by electrolysis. The materials used to implement the second solution are generally polymer materials whose properties impose limitations on the pressure and temperature of the fluid circulating in the pipes.

[0014] These two solutions are therefore not optimal.

[0015] SUBJECT OF THE INVENTION

[0016] An aim of the invention is to propose an electrolyzer cell having improved efficiency.

[0017] SUMMARY OF THE INVENTION

[0018] To this end, according to the invention, an electrolyser stack is provided comprising two base plates enclosing a stack of elements comprising electrolytic cells, and at least one intermediate plate clamped in the stack of elements. The intermediate plate has a thickness in which are arranged at least one electrolyte supply conduit, a first conduit for discharging the first electrolysis product and a second conduit for discharging the second electrolysis product which are respectively integrated into a supply network, a first discharge network and a second discharge network. Each of these conduits arranged in the intermediate plate has a length greater than the thickness of the intermediate plate and has at least one bent section to form a U with two branches extending next to each other in the direction of the thickness of the intermediate plate.

[0019] Thus, the conduits provided in the intermediate plate increase the electrical resistance of the supply network and the evacuation networks by increasing their lengths without causing an equivalent increase in the axial size of the electrolyser stack or affecting the flow rate of the fluids circulating in said networks for a given pumping capacity. This solution therefore presents a compromise between the increase in the electrical resistance of the networks and the axial size of the electrolyser stack, influencing the overall efficiency of the electrolyser stack.

[0020] The electrolyzer cell according to the invention may optionally comprise one or more of the following optional features:

[0021] - at least two intermediate plates are arranged on either side of a plurality of electrolytic cells;

[0022] - the plurality of electrolytic cells comprises between ten and four hundred and preferably between twenty and fifty electrolytic cells;

[0023] - the intermediate plate is a bipolar plate of one of the electrolytic cells;

[0024] - the intermediate plate is a current distribution plate extending between an end plate and the adjacent electrolytic cell;

[0025] - the stack of elements is arranged vertically or horizontally.

[0026] Other characteristics and advantages of the invention will emerge on reading the following description of a particular and non-limiting embodiment of the invention.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Reference will be made to the attached drawings, among which: Figure 1 is an exploded schematic view of an electrolytic cell of an electrolyzer stack according to a particular embodiment of the invention,

[0029] Figure 2 is a perspective view of a bipolar plate of the electrolytic cell shown in Figure 1,

[0030] Figure 3a is a sectional view of a portion of the bipolar plate shown in Figure 2,

[0031] Figure 3b is a sectional view of a portion of the bipolar plate illustrated in Figure 2, a membrane of said electrolytic cell also being present,

[0032] Figure 3c is a sectional view of a portion of the electrolytic cell shown in Figure 1, [Fig. 4] Figure 4 is a view of an electrolyzer stack comprising electrolytic cells as shown in Figure 1, Figure 5 is a front view of an intermediate plate according to the invention,

[0033] Figure 6 is a sectional view along line VI-VI of the intermediate plate of Figure 5.

[0034] DETAILED DESCRIPTION OF THE INVENTION

[0035] With reference to the various figures, the invention relates to an electrolyser stack comprising a stack of elements extending longitudinally in a general direction A. The various elements are mainly formed by electrolytic cells 10 which will be described below.

[0036] The electrolyzer stack 1 comprises a block 2 of electrolytic cells 10 which comprises at least two electrolytic cells 10 which are mounted adjacent to each other in the general direction A. Within the block 2, the electrolytic cells 10 are mounted in parallel from a fluidic point of view and in series from an electrical point of view.

[0037] At both ends (in the general direction A) of the block 2 of the electrolyser stack 1 are arranged two end or bottom plates 3 and 4.

[0038] These bottom plates 3 and 4 form supports between which the electrolytic cells 10 are compressed so that the electrolyser stack 1 is sealed and so that a good quality electrical contact is created inside the electrolytic cells 10.

[0039] In addition, the base plates 3 and 4 make it possible to support the forces generated by the internal pressure in block 2 as well as the external forces in block 2 necessary to ensure the compression of block 2.

[0040] The bottom plates 3 and 4 can play the role of electrical conductor and current distributor.

[0041] Preferably, the electrolyser cell 1 comprises a first distribution plate 5 associated with the first bottom plate 3 and a second distribution plate 6 associated with the second bottom plate 4. It is then the distribution plates 5 and 6 which will here play the role of electrical conductor and current distributor.

[0042] The first distribution plate 5 (associated with the positive terminal) is arranged upstream of the block 2 and the second distribution plate 6 (associated with the negative terminal) is arranged downstream of said block 2.

[0043] The concepts "upstream" and "downstream" are understood according to the conventional sense of current flow through block 2.

[0044] A first of the two distribution plates, 5, is connected to the positive terminal of the electrolyser cell 1. Then, a portion of the main internal face of the first bottom plate 3 (main face facing the block 2 and in particular the distribution plate 5) is covered with a pellet made of electrically insulating material. Said portion is for example arranged in the centre of said main internal face.

[0045] The second of the two distribution plates, 6, is connected to the negative terminal of the electrolyser stack 1. The second bottom plate 4 will be at the same potential and also serves as a gateway for the supply of an electrolytic solution and the exhaust of this same solution charged with the gases formed during electrolysis in block 2.

[0046] Thus, holes are provided in said second bottom plate 4. Said holes often have a different section between the two main faces of the second bottom plate 4. For example, the external main face (the one facing the outside of the block 2) has at least one or two holes (for example cylindrical in shape) for supplying electrolytic solution and two holes for discharging electrolytic reaction products in addition to the heated electrolytic solution. At least three or four holes are drilled on the internal main face (opposite the external main face) of said second bottom plate 4 for the same purpose, and for example oblong holes to improve the distribution or collection of fluids. For example, the holes in the external main face are equipped with suitable flanges for connecting the inlet and return pipes for the electrolytic solution.

[0047] Furthermore, the electrolyser stack 1 is supplied with direct current here.

[0048] For example, the first distribution plate 5 has, for example, a potential of several hundred volts while the second distribution plate 6 has a potential of 0 volts (the electrolyzer stack 1 typically comprises between 10 and 400, preferably between 100 and 350, electrolytic cells 10 having a cell voltage of the order of 2 volts and preferably less than 1.85 volts at the nominal point at the start of life). The supply and evacuations of electrolytic solution are carried out at the level of the second distribution plate 6 and the second bottom plate 4, the second distribution plate 6 having a potential of 0 volts which avoids any current leakage (the potential of the second distribution plate 6 being that of the earth).

[0049] Inside the electrolyser cell 1, the current passes through the electrolytic solution through a membrane 11 which will be introduced below. Within the block 2 there are seals (which will be described below): these seals are chosen from a material having a much greater electrical resistance than that of the electrolytic solution.

[0050] The electrolyser stack 1 comprises an end seal (not visible in the figures) arranged between the first distribution plate 5 and the first bottom plate 3. However, the first bottom plate 3 is grounded so that the potential difference at the level of said end seal reaches the same value as the voltage applied between the positive and negative terminals of the electrolyser stack 1, for example, substantially 700 volts.

[0051] As a result, the first bottom plate 3 is electrically insulated from the block 2.

[0052] For example, the electrolyser stack 1 comprises a layer (not visible in the figures) of electrically insulating material, a layer arranged between the first bottom plate 3 and the first distribution plate 5.

[0053] The layer is for example an added disc or a deposit made on the first base plate 3 and / or the first distribution plate 5.

[0054] The electrolyzer stack 1 comprises means for fixing the different electrolytic cells 10 together by common clamping.

[0055] For example, the fixing means comprise a plurality of tie rods 7. Each tie rod 7 extends rectilinearly in the stack of the electrolyzer stack 1. Each tie rod 7 thus extends longitudinally in the electrolyzer stack 1 parallel to the general direction A. Each tie rod 7 is shaped as a rod.

[0056] The tie rods 7 therefore all extend parallel to each other. The tie rods 7 are positioned around the perimeter of the different electrolytic cells 10. Preferably, the tie rods 7 are distributed all around the block 2 and preferably at a regular interval.

[0057] The tie rods 7 extend through the bottom plates 3 and 4 of the electrolyser stack 1, through specific holes in said bottom plates 3 and 4, and thus each have two ends external to the block 2.

[0058] Preferably, the tie rods 7 are partially covered with a sleeve made of electrically insulating material. This makes it possible to avoid short circuits between the electrolytic cells 10 in the event of contact or projection. For example, the sleeve extends over the entire section of the tie rod 7 arranged between the two base plates 3 and 4.

[0059] Preferably, the ends of the tie rods 7 are threaded.

[0060] For example, the end threads are rolled threads. Rolled threads will have the advantage of making the machining of the tie rods 7 easier, especially if the tie rods 7 are of a significant length, for example several meters long.

[0061] The fixing means also comprise nuts 8 screwed onto the ends of the tie rods 7.

[0062] The nuts 8 make it possible to constrain the two bottom plates 3 and 4 together, and therefore the different electrolytic cells 10 together, which ensures good sealing of the electrolyser stack 1 of electrolytic cells 10.

[0063] Preferably, the fixing means also comprise means for prestressing the two bottom plates 3 and 4 between them and therefore the different electrolytic cells 10 between them. Said prestressing means also make it possible to absorb the deformations and / or the variations in thickness of the elements constituting the electrolyzer stack 1, due to thermal expansion or to variations in the external and internal mechanical stresses of the electrolyzer stack 1 (such as for example the internal pressure of the electrolyzer stack 1).

[0064] The prestressing means are received on the ends of the tie rods 7 so as to be arranged, for a given end, between the nearest base plate (3 or 4) and the nuts 8 arranged on the same end.

[0065] For example, the fixing means comprise spring washers 9 such as Belleville washers. The spring washers 9 are received on the ends of the tie rods 7.

[0066] The spring washers 9 are more precisely arranged here on each tie rod 7, at the level of the external part of said tie rod 7, when the latter has passed through the nearest base plate (3 or 4).

[0067] The fixing means thus described allow the electrolyser stack 1 to cope in particular with thermal expansions and / or variations in mechanical stresses external and internal to the electrolyser stack 1 (such as for example the internal pressure in the electrolyser stack 1). In the present case, all the electrolytic cells 10 of the electrolyser stack 1 are identical to each other so that the following description of an electrolytic cell 10 is also applicable to the description of the other electrolytic cells 10.

[0068] Such an electrolytic cell 10 comprises a central membrane 11 which is framed by two electrodes 12a and 12b (an anode and a cathode, respectively) which are themselves framed by two spacers 16 (or "flow field material" in English) which are themselves framed by two bipolar plates 14. Furthermore, the electrolytic cell 10 also comprises a seal 13 (the existence of which has already been mentioned above) which is compressed between the two bipolar plates 14 of the electrolytic cell 10. The membrane 11, the spacers 16 and the electrodes 12a and 12b being known from the prior art, they will not be detailed here.

[0069] The two bipolar plates 14 of an electrolytic cell 10 being identical to each other, the following description of one of the bipolar plates 14 is also applicable to the other of the bipolar plates 14 of the same electrolytic cell 10. The bipolar plate 14 is made of a material capable of withstanding the corrosive environment prevailing inside the electrolytic cell 10.

[0070] The bipolar plate 14 is for example nickel-based and is for example made of nickel or nickel-plated carbon steel.

[0071] The bipolar plate 14 is further shaped so as to have two main faces: a first main face facing the inside of the electrolytic cell 10 in question and a second main face facing the outside of the electrolytic cell 10 in question.

[0072] It will be seen later that the bipolar plates 14 are asymmetrical (along a plane of symmetry passing through the center of the bipolar plate considered). Consequently, within the same electrolytic cell 10, the first face of the bipolar plate 14 which is being described is opposite a second face of another bipolar plate 14 identical to that which is being described. Within block 2, all the bipolar plates 14 are oriented in the same way.

[0073] Subsequently, the X and Y axes are defined, which form a plane in which one of the main faces of the bipolar plate 14 extends, and the Z axis, which is normal to said XY plane.

[0074] When the bipolar plate 14 is in place in the electrolytic cell 10 which is itself in place in the electrolyzer stack 1, the Z axis here coincides with the general direction A.

[0075] The thickness of the bipolar plate 14 (along the Z axis) is less important than its other dimensions. The bipolar plate 14 is shaped so as to have a cross-section (in an XY plane) in any geometric shape (square, rectangular, disc, etc.). The bipolar plate 14 here has a disc-shaped cross-section.

[0076] The external periphery of the bipolar plate 14 is defined by a first zone 21, a second zone 22 and a third zone 23.

[0077] The first zone 21 here extends over the entire circumference of at least one of the main faces of the bipolar plate 14. The first zone 21 is therefore a ring forming the external periphery of the main face.

[0078] The first zone 21 makes it possible to improve the resistance to the internal pressure prevailing within the electrolytic cell 1 of the bipolar plate 14 and makes it possible to improve the sealing of the electrolytic cell 10 with respect to the exterior of the electrolytic cell 1. In particular, said first zone 21 makes it possible to reinforce the resistance of the bipolar plate 14, in particular to the radial pressure loads exerted on the bipolar plate 14 (when the electrolytic cell 10 is arranged in the electrolytic cell 1). For example, the first zone 21 is dimensioned to meet the standard applicable to pressure tanks and, for example, the PED 2014 / 68 / EU standard.

[0079] The first zone 21 is preferably textured. For example, the first zone 21 has grooves, ridges, roughness, a rough appearance, etc. on at least one of the main faces of the bipolar plate 14 and preferably on both main faces of the bipolar plate 14.

[0080] On the other hand, the circular edge of the bipolar plate 14 (i.e. the surface connecting the two main faces of the bipolar plate 14 to each other) is very smooth, i.e. not textured. The second zone 22 also extends circumferentially so as to be bordered externally by the first zone 21. The second zone 22 is coaxial with the first zone 21.

[0081] The second zone 22 here extends over the entire circumference of at least one of the main faces of the bipolar plate 14. The second zone 22 is therefore a ring.

[0082] The second zone 22 is smooth i.e. not textured.

[0083] This second zone 22 is located around the electrolyte supply channels and the channels for discharging the gaseous products resulting from electrolysis.

[0084] This second zone 22 is less thick (the thickness being considered along the Z axis) than the first zone 21. For example, the bipolar plate 14 is shaped to have at least one shoulder between the first zone 21 and the second zone 22. Preferably, the bipolar plate 14 is shaped to have two shoulders between the first zone 21 and the second zone 22. These two shoulders are here identical (as visible in FIG. 3a) and arranged at the level of the two main faces of the bipolar plate 14. The bipolar plate 14 is thus symmetrical along a central plane of symmetry parallel to the X and Y axes at the level of its first zone 21 and its second zone 22.

[0085] The narrowing between the first zone 21 and the second zone 22 makes it possible to achieve a different seal between the two zones.

[0086] The third zone 23 further extends circumferentially so as to be bordered externally by the second zone 22. The third zone 23 is coaxial with the second zone 22.

[0087] The third zone 23 here extends over the entire circumference of the bipolar plate 14. The third zone 23 is a ring.

[0088] This third zone 23 is less thick (the thickness being considered along the Z axis) than the second zone 22. For example, the bipolar plate 14 is shaped to have at least one shoulder between the second zone 22 and the third zone 23.

[0089] Preferably, the bipolar plate 14 is shaped to have a single shoulder between the second zone 22 and the third zone 23. This shoulder is provided at the level of the first main face of the bipolar plate 14, that is, the one facing the inside of the electrolytic cell 10. This shoulder makes it possible to house the membrane 11.

[0090] Preferably, the second zone 22 and the third zone 23 extend in line with one another at the level of the second main face of the bipolar plate 14.

[0091] There is therefore no shoulder between the second zone 22 and the third zone 23 at the level of the second main face.

[0092] It is therefore understood that the second face of the bipolar plate 14 is devoid of such a shoulder so that the second face of the other bipolar plate 14 of the electrolytic cell 10 considered is devoid of such a shoulder. The membrane 11 is thus arranged between the two bipolar plates 14 so as to be housed only in the shoulder of one of the two bipolar plates 14.

[0093] The bipolar plate 14 is thus asymmetrical according to a central plane of symmetry parallel to the X and Y axes if we consider the three aforementioned zones (as more visible in figures 3a and 3b and 3c).

[0094] The third zone 23 is entirely smooth (i.e. not textured) or partially smooth or entirely textured. Preferably, the third zone 23 is textured at the first main face of the bipolar plate 14. This makes it easier to hold the membrane 11 in place. For example, at the level of said first main face, the third zone 23 has grooves, ridges, roughness, a rough appearance, etc.

[0095] Preferably, the third zone 23 is smooth at the level of the second main face of the bipolar plate 14. The thickness of the bipolar plate 14 (along the Z axis) therefore decreases as the shoulders progress, at the level of the junction between the first and second zones 21 and 22 but also between the second zone 22 and the third zone 23. The bipolar plate 14 is thus thicker at the level of its first zone 21 than of its second zone 22 than of its third zone 23.

[0096] The first zone 21, the second zone 22 and the third zone 23 together form a crown 25. The crown 25 thus forms the circumferential periphery of the bipolar plate 14.

[0097] A central portion 24 of the bipolar plate 14 further extends so as to be bordered externally by the third zone 23. The central portion 24 is coaxial with the third zone 23.

[0098] The central portion 24 is solid. The central portion 24 thus forms a circular plate.

[0099] This central portion 24 is less thick (the thickness being considered along the Z axis) than the third zone 23. For example, the bipolar plate 14 is shaped to have at least one shoulder between the third zone 23 and the central portion 24. Preferably, the bipolar plate 14 is shaped to have two shoulders between the third zone 23 and the central portion 24. These two shoulders are here identical and formed at the level of the two main faces of the bipolar plate 14.

[0100] The central portion 24 may optionally itself have at least one shoulder so that its thickness (the thickness being considered along the Z axis) narrows towards the center of the bipolar plate 14.

[0101] The central portion 24 is therefore the thinnest part (the thickness being considered along the Z axis) of the bipolar plate 14.

[0102] The central portion 24 may be smooth or textured. The central portion 24 acts as a current collector and will transmit it to the spacers 16 which are on either side of the central portion 24.

[0103] Furthermore, the bipolar plate 14 comprises conduits 15 passing right through it. These conduits 15 are dedicated to the supply of electrolytic solution and the exhaust of the electrolysis products.

[0104] For example, the bipolar plate 14 comprises between three and six conduits. The conduits are for example associated two by two, the pairs of two conduits being distributed homogeneously over the circumference of the bipolar plate 14. In this case, the bipolar plate 14 comprises a pair of conduits 15 for the supply of electrolyte, a first conduit 15 for discharging a first electrolysis product (a two-phase mixture of electrolyte and dioxygen gas), a second conduit 15 for discharging a second electrolysis product (a two-phase mixture of electrolyte and dihydrogen gas).

[0105] For example, at least one of the conduits 15 is arranged in the second zone 22. In the present case, all of the conduits 15 are arranged in the second zone 22.

[0106] The conduits 15 may have a circular, oblong, ... or other cross-section. For example, at least one of the conduits 15 has an oblong cross-section. The conduits 15 are connected to the internal volume of the electrolytic cell 10 by radial grooves / countersinks extending from the conduits 15 of the zone 22 to the central portion 24.

[0107] In reality, the role of said central portion 24 is not really to withstand high pressure forces unlike the crown 25. The central portion 24 thus has the main role of serving as a support for the components stacked within the electrolytic cell 10, namely the interlayers 16, the electrodes 12a and 12b and the membrane 11. The forces are therefore equal on the two faces of the central portion 24. The bipolar plates 14 consequently have a particular geometry. The thickness of each aforementioned zone varies between one and the other from a few tenths of a millimeter to several millimeters. The thickness of a aforementioned zone also has a variable value under the effect of the thermal expansion of the bipolar plate 14 (the variability of the thickness of each zone due to the thermal expansion thus also varying from one zone to another).As already indicated within the electrolytic cell 10, the two bipolar plates 14 compress a seal 13 between them.

[0108] It should be noted that within the electrolyzer stack 1, all the bipolar plates 14 are separated two by two by a seal 13 (since each bipolar plate 14 acts as a cathode for one electrolytic cell 10 and as an anode for another electrolytic cell 10 immediately adjacent).

[0109] Advantageously, the two bipolar plates 14 compress a single seal 13 between them.

[0110] Advantageously, all the seals 13 of the electrolytic cells 10 are identical within the block 2 so that the following description of one of the seals 13 is also applicable to the other seals 13 of the other electrolytic cells 10.

[0111] The main functionalities of the seal 13 are as follows: i) ensuring the sealing of each electrolytic cell 10 with respect to the outside of the electrolyzer stack 1, ii) ensuring the sealing of the channels carrying a gas which is generated within the block 2 with respect to those carrying another gas generated within the block 2, iii) ensuring the sealing of the chambers which are the seats of the electrolysis reactions where the two aforementioned gases are generated to isolate them from each other but also ensuring the sealing towards the channels mentioned just before, iv) acting as an electrical insulation layer between two adjacent bipolar plates 14 and v) defining the thickness to which the electrolytic cells 10 are compressed in the Z direction.

[0112] Preferably, the seal 13 is shaped so as to have a square or rectangular cross-section (along a transverse section plane).

[0113] The sealing gasket 13 is therefore called a "flat gasket".

[0114] Preferably the seal 13 is shaped correspondingly to the shape of the crown 25 of the associated bipolar plate 14.

[0115] In the present case, the seal 13 is generally shaped as a ring, the associated bipolar plate 14 being in the form of a disc.

[0116] It is noted that the sealing gasket 13 is pierced with a plurality of holes.

[0117] This ensures the supply of block 2 and the evacuation of fluids from block 2. For example, the holes made in the sealing gasket 13 correspond to those made in the zone 22 of the bipolar plate 14.

[0118] The seal 13 is shaped to have a diameter (of its cross-section) that is as constant as possible over all its internal and external circumferences and / or a thickness (along the Z axis) that is as constant as possible over its entire section (but also from one seal 13 to another).

[0119] This makes it possible to improve the efficiency of the electrolytic cells 10 of the electrolyzer stack 1.

[0120] In particular, this makes it possible to have the faces of the sealing joint 13 as parallel as possible to each other and to the main faces of the facing bipolar plates 14. This makes it possible to further improve the sealing of the assembly.

[0121] The tolerance on the dimensions of the seal 13 will depend on the application for which it is intended (for example the tolerance is + / -0.1 millimeter in thickness). As we have said, and as more visible in Figure 3c, the seal 13 is compressed between two adjacent bipolar plates 14 and more precisely between the two external peripheries of the main faces opposite said bipolar plates 14 and more precisely between the two crowns 25 opposite said bipolar plates 14.

[0122] Due to the particular geometry of the bipolar plates 14 at their external periphery, and in particular their crown 25, the bipolar plates 14, by compressing the seal 13, deform it in turn so as to delimit and characterize said seal 13 into three distinct portions.

[0123] On the other hand, the sealing gasket 13 is not compressed between the central portions 24 of said two bipolar plates 14.

[0124] The diameter of the seal 13 (along a cross-section) is such that the seal 13 extends from the lateral edge of the bipolar plates 14 to the connection between the third zones 23 and the central portions 24 (preferably protruding from the third zones 23).

[0125] Thus, each portion of the present seal 13 fulfills a distinct sealing function and is characterized by a specific compression level, the latter varying from one portion to another. The physical and mechanical consequence is the variable reduction in thickness of said seal 13 depending on the portion considered.

[0126] Thus, when the seal 13 is in the rest state, it has a conventional annular shape and a substantially single initial thickness.

[0127] When the seal 13 is compressed between two bipolar plates 14:

[0128] - between the first zones 21 of the two bipolar plates 14, the seal 13 has a first corresponding textured portion because it matches the geometry of said first zones 21;

[0129] - between the second zones 22 of the two bipolar plates 14, the seal 13 has a second corresponding smooth portion, the seal 13 then also having a greater thickness than at its first portion;

[0130] - between the third zones 23 of the two bipolar plates 14 and the membrane 11, the sealing joint 13 has a third corresponding smooth and / or grooved portion.

[0131] At its first portion, the seal 13 is directly compressed between the first two zones 21 (without intermediate component).

[0132] At its second portion, the seal 13 is directly compressed between the two second zones 22 (without intermediate component).

[0133] On the other hand, at its third portion, the seal 13 is not directly compressed between the two third zones 23. Indeed, the membrane 11 is also present between these two third zones 23. Consequently, the seal 13 is compressed on one of its faces directly by one of the third zones 23 and on the other of its faces directly by the membrane 11 which is itself directly compressed by the third zone 23 of the opposite bipolar plate 14.

[0134] At its third portion, the seal 13 then has a thickness substantially less than that of its second portion, the membrane 11 filling the remainder of the space between the two third zones 23. The sealing of the membrane 11 is thus obtained.

[0135] The seal 13 is thus distributed over its entire height (along the X axis) between its three portions and therefore between the three zones of the crowns 25.

[0136] Consequently, the part of the electrolytic cell 10 located at the level of the first zones 21 of the two bipolar plates 14 and the first portion of the seal 13 makes it possible to prevent the electrolyte solution or the gases from escaping from the electrolyser stack 1, in other words it is dedicated to ensuring the sealing of the electrolytic cell 10 with respect to the external environment. For example, it ensures a seal greater than or equal to 10~ 3 milligrams per meter per second - mg / (m*s) when the tightness is measured using helium gas - and preferably a tightness greater than or equal to 10~ 4 mg / (m*s) .

[0137] This first part is characterized by the presence of textures on the bipolar plates 14 in which the seal 13 deforms. In particular, the seal 13 can, by deforming, fill the hollows of the first portions of the bipolar plates 14 and thus reinforce the sealing of the electrolytic cell 10. Indeed, these textures constitute an additional obstacle to the gases and other substances present, to find the path to the outside of the electrolyzer stack 1. This presence of textures also plays a role which promotes the friction between the electrolytic cells 10 and therefore the self-maintenance of the plurality of electrolytic cells 10 stacked to form the block 2. This advantage is reinforced when the block 2 is horizontal in operation.

[0138] For example, the compression of the seal 13 is such that the seal 13 reaches, at the first part, a maximum thickness (along the Z axis) of 94% and preferably 78% and, more preferably, 75% of its starting thickness (when it is in its resting state flat on a flat surface without external stress). The starting thickness is for example equal to or greater than 3.0 millimeters. Preferably, this starting thickness does not exceed 3.5 millimeters. Alternatively, a thinner seal can be used.

[0139] The second part of the electrolytic cell 10 located at the level of the second zones 22 of the two bipolar plates 14 and of the second portion of the seal 13 makes it possible to avoid an exchange between the channels carrying the dihydrogen and the dioxygen in the electrolytic cell 10 or from the electrolytic cell 10 itself (from the third zone 23 and the central portion 24) towards said channels.

[0140] For example, the compression of the seal 13 is such that the seal 13 reaches, at the second part, a thickness (along the Z axis) of between 92 and 97% of its starting thickness (when it is in its resting state flat on a flat surface without external stress) and, preferably, a thickness of 92% of its starting thickness. In all cases, the seal

[0141] 13 is less compressed than at the level of the first part and therefore has a greater thickness than at the level of the first part.

[0142] The widening of the seal 13 between the first zones 21 and the second zones 22 makes it possible to achieve a different seal between the first zones 21 and the second zones 22. The seal between the first zones 21 and the second zones 22 is in any case of good quality.

[0143] The third part of the electrolytic cell 10 located at the level of the third zones 23 of the two bipolar plates

[0144] 14 and the third portion of the seal 13 allows the membrane 11 to be accommodated as already indicated. This third part therefore ensures the seal between the anode and cathode compartments of the electrolytic cell 10.

[0145] It is therefore noted that the membrane 11 and the seal 13 are then compressed between the two bipolar plates 14 at the level of this third part: the seal 13 is thus superimposed on the membrane 11 on this part of the electrolytic cell 10.

[0146] This ensures a very good seal around the membrane

[0147] 11 on its perimeter and in the direction of the fluid supply and discharge conduits. The third portion of the seal 13 thus defines a third compression zone intended to maintain the membrane 11 and to ensure its sealing on its perimeter. For example, the compression of the seal 13 is such that the seal 13 reaches, at the level of the third part, a thickness (along the Z axis) of between 86 and 92% of its starting thickness (when it is in its resting state flat on a flat surface without external stress) and, preferably, a thickness of between 88 and 92% of its starting thickness and, more preferably, a thickness of 90% of its starting thickness.

[0148] According to another aspect, the seal 13 is made of homopolymer material or copolymer material and for example of thermoplastic material.

[0149] For example, the sealing gasket 13 is made of a material of the polytetrafluoroethylene or polytetrafluoroethylene type (commonly abbreviated PTFE or better known under the trade name Teflon - registered trademark) or FKM (better known under the trade name Viton - registered trademark).

[0150] Preferably, the material is made of, or based on, or of the type of, polytetrafluoroethylene or polytetrafluoroethylene with at least one filler added. For example, the filler is fiberglass.

[0151] For example, the said material is reinforced polytetrafluoroethylene. For example, reinforced polytetrafluoroethylene is glass fiber reinforced polytetrafluoroethylene or reinforced polytetrafluoroethylene is carbon fiber reinforced polytetrafluoroethylene.

[0152] The properties of the seal 13 described are defined below: good behavior of the material and preservation of its good mechanical properties at the operating temperature of the electrolytic cell 10 which is nevertheless high (typically of the order of 90 to 95 degrees Celsius) and this over the long term; resistance to the corrosive environment inside the electrolytic cell 10 and this over the long term; good sealing properties; good electrical insulation properties (given by good electrical resistance) and this even at the operating temperature and in contact with the electrolyte solution; little creep allows a good longevity of the electrolyzer stack 1 of electrolytic cells 10; slight creep behavior all the same in order to best match the geometrical particularities of the seating zone 21 of the seal 13; uniformity of the thickness (along the Z axis).

[0153] According to one option, the end seal arranged between the first distribution plate 5 and the first bottom plate 3 is made of the same material as that of the seal 13 of an electrolytic cell 10 which has just been described. The end seal is for example identical to said seal 13. Said end seal is optionally made of homopolymer material or copolymer material and for example of thermoplastic material.

[0154] According to one option, the layer of electrically insulating material between the first base plate 3 and the first distribution plate 5 is made of the same material as that of the end seal arranged between the first distribution plate 5 and the first base plate 3. According to one option, the layer of electrically insulating material between the first base plate 3 and the first distribution plate 5 is made of the same material as that of said seal 13. Said layer is optionally made of homopolymer material or copolymer material and for example of thermoplastic material.

[0155] According to one option, the end seal arranged between the second distribution plate 6 and the second bottom plate 4 is made of the same material as that of said seal 13 of an electrolytic cell 10 which has just been described. Said end seal is for example identical to said seal 13. Said end seal is optionally made of homopolymer material or copolymer material and for example of thermoplastic material.

[0156] According to one option, the pellet arranged on the internal face of the first distribution plate 5 is a layer of material directly applied to the first distribution plate 5 or is formed by deposition of powder, such as a fluoropolymer and in particular ethylene-chlorotrifluoroethylene such as that produced under the Halar brand by the company SOLVAY.

[0157] The electrolytic cell 10 thus described has very good sealing due to the specific compression of the sealing gasket 13 between the bipolar plates 14.

[0158] It is also noted that the electrolytic cell 10 is made watertight thanks to a single seal 13 and this with three different sealing and compression zones. The use of a single seal 13 made of plastic material (and no longer of elastomer as in the prior art) also makes it possible to improve the watertightness of the electrolyzer cell.

[0159] In fact, the sealing gasket 13 is more resistant, even over a long period, to the corrosive environment prevailing inside the electrolyser stack 1.

[0160] The sealing gasket 13 is thus made of a hard material resistant to the strong mechanical compressions to which the electrolyser stack 1 is subjected.

[0161] The electrolyser stack 1 also comprises intermediate plates, generally designated 30, which are clamped in the stack of elements forming the block 2. Each intermediate plate 30 comprises an external peripheral part 31 of annular shape and a central part 32 of discoidal shape. The intermediate plate 30 has a thickness in which are provided here at least two electrolyte supply conduits, a first conduit for discharging the first electrolysis product and a second conduit for discharging the second electrolysis product, all designated by the reference numeral 33, which are integrated respectively into the supply network, the first discharge network and the second discharge network of the electrolyser stack 1. The thickness of the intermediate plate 30 here has a measurement of between a few millimetres and a few tens of millimetres and, preferably, between 50 and 70 mm.Each of the conduits 33 formed in the intermediate plate 30 opens in the vicinity of the opposite main faces of the external peripheral part 31 respectively by an inlet orifice and an outlet orifice and has between these two orifices a length greater than the measurement of the thickness of the intermediate plate 30. Each conduit 33 comprises a bent section 34 connecting the inlet and outlet orifices to each other by extending into the central part 32 of the intermediate plate 30 and, preferably, to the vicinity of the center of the central part 32. The bent section 34 thus has a U shape with two branches which extend parallel to the main faces of the intermediate plate 30 and which have first ends connected to each other by an elbow and on the opposite side each one end forming one of the orifices on the main faces of the intermediate plate 30.The intermediate plates 30 are made of electrically conductive material by additive manufacturing, molding (using, for example, drawer molds), forging and then machining.

[0162] The intermediate plates 30 are distributed in the block 2 so that two intermediate plates 30 are arranged on either side of a plurality of the electrolytic cells 10. The plurality of electrolytic cells 10 preferably comprises between twenty and fifty electrolytic cells 10. The sealing between each intermediate plate 30 and the electrolytic cells 10 which surround it is for example ensured by two seals identical to the seals 13.

[0163] A method of assembling the electrolyzer stack 1 will now be described.

[0164] According to a first step, subassemblies are individually constructed, each subassembly being composed by assembling two spacers 16 and two electrodes 12a, 12b on either side of a bipolar plate 14. Each subassembly constitutes, strictly speaking, two electrolytic half-cells 10 joined together.

[0165] In a second step, said subassemblies are stacked successively, separated from each other by a membrane 11 and a seal 13, forming said electrolytic cells 10 electrically connected in series. The last electrolytic cell 10 at one end of the block 2 is covered by the second distribution plate 6, itself covered by the second bottom plate 4 and the last electrolytic cell 10 at the other end of the block 2 is covered by the first distribution plate 5, itself covered by the first bottom plate 3, thus delimiting the electrolyser stack 1. An intermediate plate 30 is periodically interposed between two consecutive electrolytic cells 10. During this operation, care is of course taken to ensure that the conduits 33, 15 are in communication with each other to form the supply network, the first evacuation network and the second evacuation network.

[0166] In a third step, the newly assembled electrolyser stack 1 is put into compression using the tie rods 7, nuts 8 and spring washers 9.

[0167] Such an assembly with thick distribution plates 5 and 6 and thin, flat bipolar plates 14 allows homogeneity of the current in all the electrolytic cells 10 of the electrolyser stack 1 while the voltage is different at the terminals of each electrolytic cell 10 and the current is only connected to one or more points at the periphery of each distribution plate 5 and 6.

[0168] Furthermore, the bipolar plates 14 are well parallel to each other within the block 2 thanks to their particular shape and the good tightening of each sealing joint 13. This further improves the homogeneity of the current in all the electrolytic cells 10.

[0169] The assembly process must ideally allow in particular each sealing joint 13: to deform according to the geometry imposed by the bipolar plates 14 enclosing it, to sink into the textures of the first zones 21 in order to fill them, to deliberately and prematurely age the material composing it, to eliminate as much as possible the plastic component of the component, to bring its material into a range of elastic behavior (centered on an operating point of the electrolyzer stack 1). to reach the desired tightening value combining both the desired seals and the electrical contacts between the different components making it possible to achieve the envisaged energy performances.

[0170] The nominal operating point of the electrolyser cell 1 is for example 85 degrees Celsius under 3 Megapascals. Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0171] The end seal(s) may be different from the seals 13.

[0172] The electrolyzer stack 1 may be assembled differently from what has been described. The electrolyzer stack 1 may be used horizontally, vertically or in any other position. The electrolyzer stack 1 may be assembled horizontally, vertically or in any other position. Preferably, the electrolyzer stack 1 will be assembled vertically and used horizontally.

[0173] It will be possible to have only one conduit 33 associated with the supply of the electrolytic solution and one conduit 33 associated with the evacuation of each electrolysis product. However, it will be preferable to have two conduits 33 associated with the supply of the electrolytic solution and / or two conduits 33 associated with the evacuation of each electrolysis product for reasons of redundancy in the event that one of the conduits 33 becomes blocked. In general, the distribution plate 5, 6 may have only one conduit 33 opening at each of its ends onto a respective one of the main faces of the distribution plate 5, 6.

[0174] Similarly, it is preferable to have two grooves associated with each end of each conduit 33 for redundancy reasons.

[0175] The different conduits 33 may not be identical to each other.

[0176] The different grooves may not be identical to each other.

[0177] The two distribution plates 5, 6 each associated with one end of the block 2 may be different and not identical to each other as mentioned above.

[0178] The distribution plate 5, 6 may have only one reinforcement and not two as indicated.

[0179] The distribution plate 5, 6 may comprise at least one conduit 33 not opening at at least one of its ends onto the external periphery of the associated main face (and for example opening into the central zone of said main face and for example into the recess possibly present on said main face).

[0180] For example, the distribution plate 5, 6 may comprise at least one conduit 33 opening at least at one of its ends into a recess of said distribution plate 5, 6. Optionally, the conduit 33 will open at least at one of its ends at a position sufficiently close to the external periphery of one of the main faces to allow complete or almost complete emptying (emptying of a liquid and / or a gas) present in the space between the distribution plate 5, 6 in question and the facing bottom plate 3, 4. Optionally, this conduit 33 may be arranged so as to open at a first end into the recess of the first main face of the distribution plate 5, 6 and to open at a second end into the recess of the second main face of said distribution plate 5, 6 so as to put the two recesses in communication.

[0181] The electrolyzer stack 1 may comprise three electrodes, namely two end cathodes and a central anode. One or more of the bipolar plate(s) 14 may be arranged with conduits 15 having a bent section to make this or these bipolar plate(s) 14 one or more intermediate plate(s) 30. In this case, all or part of the conduits 15 provided in the intermediate plate 30 has a length greater than the thickness of the bipolar plate 14.

[0182] Alternatively also, one or two of the intermediate plate(s) 30 may be formed by one of the distribution plate(s) 5, 6 extending between an end plate 3, 4 and the adjacent electrolytic cell 10. In this case, the conduits 15 provided in the distribution plate 5, 6 have a length greater than the thickness of the distribution plate 5, 6. The spring washers 9 may be placed at both ends of the tie rod or at only one of these ends and / or be replaced by any elastic compression member.

[0183] The U-shaped sections may not extend to the center of the intermediate plate.

Claims

CLAIMS 1. Electrolyzer stack (1) comprising two bottom plates (3, 4) enclosing a stack of elements (2) comprising electrolytic cells (10), each electrolytic cell (10) comprising at least one electrolyte supply conduit, a first conduit for discharging a first electrolysis product and a second conduit for discharging a second electrolysis product (15) communicating from one electrolytic cell (10) to the other to form in the electrolyzer stack (1) along the latter an electrolyte supply network, a first network for discharging the first electrolysis product and a second network for discharging the second electrolysis product, characterized in that the electrolyzer stack (1) comprises at least one intermediate plate (30) clamped in the stack of elements (2), the intermediate plate (30) having a thickness in which are provided at least one electrolyte supply line,a first evacuation conduit for the first electrolysis product and a second evacuation conduit for the second electrolysis product (33) which are integrated respectively into the supply network, the first evacuation network and the second evacuation network, and in that each of these conduits (33) arranged in the intermediate plate (30) has a length greater than the thickness of the intermediate plate (30) and comprises an elbow section (34) connecting an inlet orifice on a first main face of the intermediate plate and an outlet orifice on a second main face of the intermediate plate, the elbow section having a U shape with two branches which extend parallel to the main faces of the intermediate plate (30) and which have first ends connected to each other by an elbow and on the opposite side each one end forming one of the orifices on the main faces of the intermediate plate (30)., 2. Electrolyzer cell (1) according to one of the preceding claims, comprising at least two intermediate plates (30) arranged on either side of a plurality of electrolytic cells (10).

3. Electrolyzer cell (1) according to claim 2, wherein the plurality of electrolytic cells (10) comprises between twenty and fifty electrolytic cells (10).

4. Electrolyzer cell (1) according to one of the preceding claims, in which the intermediate plate (30) is a bipolar plate (14) of one of the electrolytic cells (10).

5. Electrolyzer cell (1) according to one of claims 1 to 4, wherein the intermediate plate (30) is a current distribution plate (5, 6) extending between an end plate (3, 4) and the adjacent electrolytic cell (10).

6. Electrolyzer cell (1) according to one of the preceding claims, in which the cell stack (2) is arranged vertically or horizontally.

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