Bipolar plate, electrolytic cell, electrolyser stack, water electrolysis plant and alkaline water electrolysis method

Abstract

Bipolar plate, electrolytic cell, electrolyser stack, water electrolysis plant and alkaline water electrolysis method The present invention relates to a bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1). According to the invention, the bipolar plate (100, 100') has at least one flow-disrupting element which is a lye-permeable element (50) and is arranged against the internal circumference of the peripheral ring (43) where a supply passage (40) or extraction passage (41) emerges. Further, the flow-disrupting element covers a portion of the surface of the disc (42) lower than the total surface of the disc (42). Other aspects of the invention relate to an electrolytic cell equipped with such a bipolar plate, to an electrolyser stack comprising a stack of such electrolytic cells, to an electrolysis plant comprising such an electrolyser stack, and to an alkaline water electrolysis method implemented in such a plant.

Description

Bipolar plate, electrolytic cell, electrolyser stack, water electrolysis plant and alkaline water electrolysis method

[0001] Description

[0002] The present invention relates to the alkaline electrolysis of water and more particularly to a bipolar plate, to an electrolysis cell comprising such a plate, to an electrolyser stack comprising a cell, to an alkaline water electrolysis plant comprising such a stack and to an alkaline water electrolysis method implemented in such a plant.

[0003] Description of the prior art

[0004] The need to reduce the production of greenhouse gases and to use renewable energy is now well known. Molecular hydrogen is an alternative to hydrocarbons because this is an energy carrier that is easy to store, unlike electricity, and its oxidation releases a very large amount of energy (285 kJ / mole).

[0005] There are a number of known ways of producing gaseous molecular hydrogen, the most advantageous being to electrolyse the water molecule because this is a high-yield reaction that does not directly produce CO2, unlike the very widely-employed methods of methane, coal and hydrocarbon reforming.

[0006] There are three known broad types of electrolyser for electrolysing water:- alkaline electrolysers (AWA, which stands for Alkaline Water Electrolysis), which are characterized by the use of a liquid electrolyte allowing hydroxide anions (OH ) to be transferred from the cathode to the anode;- high-temperature electrolysers (SOEC, which stands for Solid Oxide Electrolysis Cell), in which the electrolyte is a ceramic; and- proton exchange membrane (PEM) electrolysers, in which the electrolyte is a protonconducting ion exchange membrane.

[0007] The present invention is more particularly concerned with an alkaline electrolyser.

[0008] An alkaline electrolysis device generally comprises a stack of electrolytic cells within which the water electrolysis reaction is carried out. The electrolytic cells are assembled electrically in series and fluidical ly in parallel. With reference to Fig. 1, an electrolytic cell 10' may be described as being made up of, in this order, a first bipolar plate 100', a space delimited by an interleaf 101', a first electrode, for example a cathode 102', a membrane (also referred to as porous separator or diaphragm) 103', a second electrode, for example an anode 104', a second space delimited by an interleaf 105', and a second bipolar plate 100. The space (sometimes also referred to as an electrode chamber) delimited by the interleaf 101' is intended for the circulation of the electrolyte and of the electrolysis gases and, thanks to the circulation of the electrolytic fluid, allows the reagents (water and hydroxide ions) to reach the surface of the electrodes 102' and 104'. The electrolytic fluid or electrolyte of an alkaline electrolyser is made up of an alkaline solution of potassium hydroxide (KOH) and / or of sodiumhydroxide (NaOH), better known as "lye". The circulation of an electrical current through the electrolytic cell 10' allows the water to be split into gaseous molecular hydrogen (H2) and gaseous molecular oxygen (02) according to known reactions and mechanisms.

[0009] The circulation of the lye through the electrolytic cell 10' performs a number of functions: i) it ensures that a sufficient quantity of hydroxide anions (OH-) are supplied near the membrane 103' to close the electrical circuit as a result of the conduction of the hydroxide anions (OH ) through the membrane 103', ii) it removes the heat generated by the overvoltages within the electrolytic cell 10' (the excess voltage compared with the thermally neutral voltage is in fact dissipated in the form of heat which causes the temperature to rise), the lye therefore acting as a heat-transport fluid, and iii) it enables the removal of gas bubbles generated by the water electrolysis reaction. The electrodes 102' and 104' are electrically connected to one another through their being immersed in the electrolytic solution. In general, the electrodes 102' and 104' are made entirely from nickel or covered with nickel and are separated by a membrane 103' which performs the following functions: i) electrical insulation of the two electrodes 102' and 104', ii) separation of the gases, and iii) ion conduction within the electrolytic cell 10'.

[0010] Most of the metal components of the electrolyser stack which are intended to come into contact with the electrolytic fluid are protected by a layer of nickel in order to improve their resistance to corrosion from the alkaline electrolytic fluid. The presence of the very uniform nickel coating also smooths the surfaces of the constituent elements of the electrolyser stack and therefore also contributes to the sealing of the electrolyser stack.

[0011] An electrolyser stack 1 is made up of a stack of electrolytic cells 10, 10', 10", etc. as described above. Such a stack is generally arranged along a principal axis (the constituent components described hereinabove are therefore each arranged in planes perpendicular to this axis and parallel to one another). In use, the principal axis is generally horizontal. It will be noted that the bipolar plate 100 that terminates a first electrolytic cell 10' constitutes the start of the next electrolytic cell 10. Thus, the bipolar plate 100' of the first electrolytic cell 10' (upstream of the next) is at a higher potential than the bipolar plate 100 of the second electrolytic cell 10 (downstream of the previous one) and consequently its surface in contact with the space adjoining the cathode 102 acts as an anode. Conversely, the surface of the bipolar plate 100' in contact with the space adjoining the anode 102' acts as a cathode. At the ends of the electrolyser stack 1 there are also distribution plates 110 which supply and distribute the electricity of the electrolytic cells 10, 10', 10", etc., and the end-plates 112 bounding the collection of electrolytic cells 10, 10', 10", etc. and clamping and sealing the electrolytic cells with respect to one another, by virtue of gaskets 111 installed between the distribution plate 110 and the end-plate 112. The electrolyser stack 1 ends in two end-plates 112 situated just before the first electrolytic cell 10 and just after the last electrolytic cell (notdepicted in Fig. 1) that are stacked so as to physically delimit the two ends of the electrolyser stack 1.

[0012] The bipolar plates 100, 100', etc. also perform a number of functions in the electrolytic cell 10, 10', 10", etc.: i) that of delimiting the electrolytic cell 10, 10', 10", etc. and ii) that of supplying the electrolytic cell 10, 10', 10", etc. both with electrical current and with electrolytic fluid and of allowing the gases formed by the water electrolysis chemical reaction (gaseous molecular hydrogen (H2) and gaseous molecular oxygen (02)) to be extracted in the electrolytic fluid. The bipolar plates 100, 100', etc. are therefore provided with passages to allow fluid(s) to be supplied or extracted.

[0013] In general, from a structural standpoint, the design of the bipolar plate, referred to as a Lurgi plate, in alkaline electrolyser stacks is mandated. In this configuration, the bipolar plate is circular and comprises a disc-shaped surface, of diameter Dd, and a peripheral ring. The peripheral ring has an internal circumference of internal diameter Dai, and an external circumference of external diameter Dae. The disc and the peripheral ring define at least one internal cylindrical space.

[0014] The peripheral ring is provided with orifices (the term "manifold" is often used) connecting its external circumference to its internal circumference so as to create a continuous duct after the juxtaposition of the electrolytic cells. These orifices are arranged on opposing sectors of the peripheral ring and are configured to allow the supply or extraction of fluids to or from the at least one internal cylindrical space. The orifices generally, but not exclusively, consist of oblong holes. Other geometric configurations may define said orifices. The orifices also define an axis of flow of the electrolytic fluid between the supply orifices and the extraction orifices. The bipolar plate is configured so that the fluids flow in the internal cylindrical space at the surface of the disc from at least one supply orifice to at least one extraction orifice. Both at the inlet (supply) and at the outlet (extraction), these orifices are directly connected to at least one inlet duct and to at least one outlet duct, respectively. These supply and extraction ducts have any geometric configuration that does not affect the functionality of each of them in any way. For a better understanding of the present invention and throughout the remainder of its description, the connection between the orifice and the duct will be defined by the term passage. In other words, the peripheral ring is made up of at least one supply passage and at least one extraction passage.

[0015] The disc may adopt various configurations: i) planar; ii) bumpy, directly incorporating the interleaf, or iii) some other geometric arrangement ultimately offering the same features with regard to the water electrolysis process. The two elements, the disc and the peripheral ring, are connected to one another using known methods, for example, and nonlimitingly, by welding.

[0016] It is known that a poorly configured flow of the fluids or of electrical current will lead to nonuniformity in the other components of the electrolytic cel I, for example the electrodes. On this subject, reference is made to Wang T et al., Non-uniform liquid flow distribution in an alkaline water electrolyzer with concave-convex bipolar plate (CCBP): A numerical study, International Journal of Hydrogen Energy, https: / / doi.Org / 10.1016 / j.ijhydene.2022.12.203 which describes the paths followed by the flow of the electrolytic fluids from the supply passages to the extraction passages. This study reveals that the flows of the electrolytic fluids follow preferred pathways from the supply passages to the extraction passages. The preferred pathways are rectilinear and connect the supply passages to the extraction passages. In such a configuration, the speed at which the electrolytic fluids circulate along these preferred pathways is very high and, above all, more significant. By contrast, outside of these preferred pathways, the speed at which the fluids circulate is slow to the extent that the electrolytic fluids are not properly renewed and stagnation zones arise. These zones are situated on each side of the preferred pathways. The pathways preferably followed lead to reduced coverage of the surface of the bipolar plate. The consequence of the presence of the preferred pathways at the surface of the bipolar plate is a nonuniformity of the flows of the fluids over the surface of the electrolytic cells, leading to a reduction in the overall performance of the system because only a limited part of the surface of said electrolytic cells is operating under optimal operating conditions. Specifically, poorly distributed flows of the fluids or of electrical current over the surface of the bipolar plate lead to nonuniformity in the other components of the electrolytic cell, for example the electrodes. The problems generated are as follows:- Nonuniformity of the temperature at the surface of the electrolytic cells. Specifically, before entering the electrolyser stack, the lye is maintained at an optimal temperature for encouraging the water electrolysis reaction and for enjoying the best possible dynamic conditions. The fluids situated in the stagnant zones, which are poorly supplied, are not renewed, which means that the temperature in these zones drops as a result of a lack of heat transfer. As a result, temperature differences at the surface of the electrolytic cell are induced, or in other words the temperature of the fluids for performing the water electrolysis reaction is no longer optimal there. Under such conditions, the dynamics of the water electrolysis reaction drop, again resulting in a reduction in the production of gaseous molecular hydrogen;- Poor distribution of the reagents of the water electrolysis reaction at the surface of the components of the electrolytic cells. Thus, the reagents of the water electrolysis reaction, OH', present in the lye are progressively consumed over the entire surface of the electrodes. The lye situated in the stagnant zones is not renewed, which means that these zones receive an impoverished supply, or even no supply at all, of reagents. As a result, because of the lack of reagents, the dynamics of the water electrolysis reaction decrease, at the same time leading to a lower production of gaseous molecular hydrogen;- Poor removal of the products of the water electrolysis reaction at the surface of the electrolytic cells. As is well known from the prior art, the gaseous products of the water electrolysis reaction (O2, H2) are present at the surface of the electrodes. In the stagnant zones, the lye is not renewed and does not carry the produced gas bubbles away with it to the extraction passages. The surface-area on which the gaseous products of the water electrolysis reaction are collected is limited solely to the surface-area of the bipolar plate that corresponds to the preferred paths taken by the fluid flows. As a result, the detachment of the gas bubbles originating from the water electrolysis reaction is limited on the sides of the axis between the supply and extraction passages of the bipolar plate. This slow detachment of the products of the water electrolysis chemical reaction leads to a drop in the dynamics of the water electrolysis reaction.

[0017] Furthermore, the collection of problems outlined hereinabove leads to resistive phenomena which contribute to generating overvoltages at the electrodes and therefore to a drop in the performance of the electrolytic system. The overvoltages are due to a number of different resistive phenomena within the electrolytic cells: i) increased contact resistance between various components of the electrolytic cell (by way of example, mention may be made of the poor physical contact between the electrode and the interleaf and the greater difficulty that the electrical current has in passing between the components; ii) electrolyte resistance which is dependent on the conductivity of this electrolyte, which is manifested by the fact that if the temperature of the electrolyte is high, its conductivity is better and its resistivity lower.

[0018] Temperature has a direct effect on resistive phenomena. In general, the higher the temperature, the lower the electrical / ionic resistance. The conductivity of the electrolyte also depends on its reactive-species (OH ) concentration. Specifically, the more reactive species the electrolyte contains, the more its conductivity increases and its resistivity decreases (although there is a limit on maximum concentration). Following the same logic, if the products of the water electrolysis reaction (bubbles of molecular hydrogen gas and of molecular oxygen gas) are removed with the flow of the fluids so that the surfaces of the electrodes are accessible to the electrolytic fluids. Failing that, the gas bubbles adsorbed at the surface of the electrodes constitute electrical resistances.

[0019] In other words, the overvoltages correspond to the difference in potential between the theoretical thermodynamic potential of the water electrolysis chemical reaction and the actual potential that has to be applied according to the various additional resistive phenomena present in the electrolytic cell.

[0020] It would therefore be desirable to provide a solution that enables these overvoltages to be reduced and, more particularly, to provide an electrolytic cell that enables the fluid flows to be made uniform.

[0021] Summary of the invention

[0022] The invention that forms the subject matter of the present patent application seeks to overcome these technical problems. In order to achieve this, according to the present invention, use is made of a bipolar plate like that described in Claim 1. This bipolar plate is circular. The technical advantages stemming from the present invention remain similar whatever the geometric shape of the bipolar plate. When considering a circular configuration, the bipolar plate comprises a disc-shaped surface, of diameter Dd, and a peripheral ring. The peripheral ring has an internal circumference of internal diameter Dai, and an external circumference of external diameter Dae. The disc and the peripheral ring define at least one internal cylindrical space. This is the volume comprised between the disc and the circumferences of the peripheral ring. If the disc is attached to one end of the peripheral ring, an internal cylindrical space the volume of which corresponds to the height of the ring multiplied by the internal circumference of the peripheral ring is formed. In that case, the circumference of the disc may be equal to the internal circumference of the peripheral ring. If the disc is attached to the peripheral ring in a position comprised between the two ends of the peripheral ring, two internal cylindrical spaces are defined in this configuration.

[0023] The peripheral ring is provided with orifices each arranged along an axis parallel to the axis of symmetry of the internal cylindrical space and orifices connect the orifices to the internal circumference of the peripheral ring. The assembly of duct and orifice thus formed defines a passage, both for the inlet reserved for the supply of the fluid, and referred to as the supply passage, and the outlet reserved for the extraction of the fluid, and referred to as the extraction passage. These supply and extraction passages are arranged on opposing sectors of the peripheral ring and are configured to allow the supply or extraction of fluids to or from the at least one internal cylindrical space, respectively. The orifices generally, but not exclusively, consist of oblong holes. Other geometric configurations may define said orifices. The ducts also define an axis of flow of the electrolytic fluid between the supply ducts and the extraction ducts. The bipolar plate is configured so that the fluids flow in the internal cylindrical space at the surface of the disc from at least one supply duct to at least one extraction duct.

[0024] According to the invention, at least one of the surfaces of the disc contains at least one flow-disrupting element. In the case of there being just a single internal cylindrical space, the flow-disrupting element is comprised in this internal cylindrical space. In cases where the bipolar plate comprises two internal cylindrical spaces, the flow-disrupting element is comprised in one of the internal cylindrical spaces or in both of the internal cylindrical spaces.

[0025] A configuration in which flow-disrupting elements are provided at the surface of the disc of the bipolar plate is already known from the prior art. Reference is made for example to utility model CN-U-21 699 8609. That document, of which the bipolar plate has been illustrated in Figures 2a and 2b, proposes an electrode structure having wedge-shaped disrupting elements for improving the effectiveness of the distribution of the electrolytic fluids over the surface of the electrodes, so as to reduce the retention of gas bubbles and increase the turbulence of the flow. The inventors of the present invention have found that this configuration, while improving the situation, was still not yet optimal in as much as significant over-voltages are still needed to electrolyse the water effectively. The inventors reached the conclusion that the situation could be improved still further by changing the arrangement and the type of the flow-disrupting elements.

[0026] According to the present invention, the flow-disrupting element is a lye-permeable element and is arranged against the internal circumference of the peripheral ring where a passage emerges. A lye-permeable element is understood to mean an element which allows the lye to flow while still splitting the stream of the flow into a plurality of streams taking different flow orientations. Further, the flow-disrupting element covers a portion of the surface of the disc that is lower than the total surface of the disc. Thus, the flow reaches all the zones, including the stagnant zones described for the bipolar plates of the prior art. Ideally, the lye- permeable element does not significantly reduce the flow rate. Examples of suitable lye- permeable elements are sponges, for example synthetic sponges, foams, for example metal or polymer foams, or three-dimensionally printed parts provided with ducts or micro-ducts.

[0027] Preferably, the flow-disrupting element covers a portion of the surface of the disc lower than 30%, more preferably, lower than 20% of the surface of the disc.

[0028] According to one embodiment, the lye-permeable element is a porous element with an open porosity. Advantageously in this case, the porous element has an open porosity of 30% to 90% by volume, preferably 40% to 60% by volume. Also advantageously, the mean diameter of the pores is comprised between 0.1 mm and 20.0 mm and preferably between 0.1 mm and 10.0 mm.

[0029] According to one embodiment, all of the supply passages are provided with a lye- permeable element arranged against the internal circumference of the peripheral ring wherever a supply passage emerges. According to a variant, all of the extraction passages are provided with a lye-permeable element arranged against the internal circumference of the peripheral ring wherever an extraction passage emerges. Lastly, according to another variant of the invention, both all of the supply passages and all of the extraction passages are provided with a lye-permeable element arranged against the internal circumference of the peripheral ring wherever a supply passage emerges and wherever an extraction passage emerges.

[0030] According to one embodiment, it is possible for one and the same lye-permeable element to cover multiple points where a supply passage or an extraction passage emerges. This embodiment allows a configuration in which such points are very close together.

[0031] According to one embodiment, at least one lye-permeable element has a thickness along an axis perpendicular to the surface of the disc that is identical to the height of the peripheral ring. Thus, the lye-permeable element can come into contact with the surface of the disc and, on its opposite face, reach the opposite surface of the peripheral ring.

[0032] According to one embodiment, at least one lye-permeable element is a non-polyhedral solid (i.e. a solid of which at least one face is not planar) of which one of the faces, referred to as contact face, has the same curvature as the internal surface of the peripheral ring, the contact face being arranged against the internal circumference of the peripheral ring. In this way, the lye-permeable element can easily be placed against the internal surface of the peripheral ring. Advantageously, the non-polyhedral solid is an annular sector which can be industrially produced easily and inexpensively.

[0033] According to one embodiment, the non-polyhedral solid has six faces, the faces connecting the contact face and the opposite face being planar. This configuration makes it easier to machine.

[0034] According to an advantageous embodiment, the faces of the non-polyhedral solid that are parallel to the plane of the disc are mutually parallel and the two faces perpendicular to the plane of the disc get further away from or closer to one another in the direction away from the internal surface of the peripheral ring. Advantageously, the two faces perpendicular to the plane of the disc get further away from one another in the direction away from the internal surface of the peripheral ring. This configuration allows a clear improvement in the flow distribution. As an alternative and in order to make the machining easier, all the faces except for the contact face and the face opposite the contact face are parallel in pairs.

[0035] According to another of its aspects, the invention relates to an electrolytic cell for an electrolyser stack of an alkaline water electrolysis plant comprising, in this order, a first bipolar plate as defined hereinabove, a first interleaf, a first electrode, a membrane, a second electrode, a second interleaf and a second bipolar plate. The second bipolar plate may be conventional (without a lye-permeable element) or a bipolar plate as defined hereinabove.

[0036] Another aspect of the invention relates to an electrolyser stack comprising a stack of electrolytic cells as defined hereinabove, the terminal bipolar plate of one electrolytic cell constituting the initial bipolar plate of the adjacent electrolytic cell. Yet another aspect of the invention relates to an electrolysis plant containing an electrolyser stack as defined hereinabove.

[0037] Finally, the invention also relates to an alkaline water electrolysis method comprising the following steps:- supplying the electrolyser stack with lye via at least one of the supply passages of the bipolar plate;- applying a voltage to the electrodes; and- extracting the electrolysis fluid containing gaseous molecular hydrogen or gaseous molecular oxygen via at least one of the extraction passages of the bipolar plate.

[0038] Brief description of the figures

[0039] The invention will now be described by means of the figures, the sole purpose of which is to illustrate the present invention. These figures schematically depict:

[0040] Fig. 1: a stack of electrolytic cells constituting a partial electrolyser stack;

[0041] Fig. 2a: a bipolar plate of the prior art, viewed in three-dimensions;

[0042] Fig. 2b: a bipolar plate of the prior art, viewed in section on a plane corresponding to the diameter along the flow axis of the bipolar plate;

[0043] Fig. 3: one embodiment of a bipolar plate according to the invention, viewed face-on;

[0044] Figs 4a to 4c: various embodiments of a bipolar plate according to the invention, viewed in section on a plane perpendicular to the plane of the disc along the flow axis of the bipolar plate;

[0045] Fig. 5: one embodiment of a bipolar plate according to the invention, viewed face-on;

[0046] Fig. 6: one embodiment of a bipolar plate according to the invention, viewed face-on;

[0047] Fig. 7: a non-polyhedral solid representing a lye-permeable element.

[0048] Detail of one embodiment

[0049] A stack of electrolytic cells has been depicted schematically in Fig. 1. Each electrolytic cell 10' is made up of, in this order, a bipolar plate 100', a space delimited by an interleaf 101', a first electrode, for example a cathode 102', a membrane 103', a second electrode, for example an anode 104', a second space delimited by an interleaf 105', and a second bipolar plate 100. The space (sometimes also referred to as an electrode chamber) delimited by the interleaf 101' is intended for the circulation of the electrolyte and of the electrolysis gases and, thanks to the circulation of the electrolytic fluid, allows the reagents (water and hydroxide ions) to reach the surface of the electrodes 102' and 104'. A succession of electrolytic cells 10, 10', 10" etc. form an electrolyser stack 1. It will be noted that the second bipolar plate 100 of the electrolytic cell 10' constitutes the first bipolar plate 100 of the adjacent electrolytic cell 10. Aside from the electrolytic cells 10, 10', 10", etc., the electrolyser stack 1 further comprises two distribution plates 110 (which replace the second bipolar plate of the last cell and the first bipolar plate of the first electrolytic cell), two end-plates 112 bounding the collection of the electrolytic cells 10, 10', 10", etc. and clamping and sealing the electrolytic cells 10, 10', 10", etc. with respect to one another, by virtue of gaskets 111 installed between the distribution plate 110 and the end-plate 112.

[0050] According to the invention, the bipolar plates 100, 100', etc. comprise a surface in the form of a disc 42 of diameter Dd and a peripheral ring 43. The technical advantages stemming from the present invention remain similar whatever the geometric shape of the bipolar plates 100, 100', etc. The peripheral ring 43 has an internal circumference of internal diameter Dai and an external circumference of external diameter Dae. The disc 42 and the peripheral ring 43 define at least one internal cylindrical space 44, 45. The peripheral ring 43 is provided with supply passages 40 and extraction passages 41 (visible in Fig. 3) each arranged along an axis parallel to the axis of symmetry of the internal cylindrical space 44, 45. These supply passages40 and extraction passages 41 group together a supply orifice and a supply duct, on the one hand, and an extraction orifice and an extraction duct (neither depicted), the respective geometric configurations of which may be circular, rectangular, etc. or any, given that these have absolutely no influence on the way in which the fluid is supplied to and extracted from the electrolytic cell. The supply passages 40 and extraction passages 41 are arranged on opposing sectors of the peripheral ring 43 and configured to allow the supply or extraction of fluids to or from the at least one internal cylindrical space 44, 45, specifically lye supplied via the supply passages 40 and lye / gaseous molecular hydrogen or gaseous molecular oxygen extracted via the extraction passages 41. The supply passages 40 and extraction passages 41 define a flow axis 46. The bipolar plate 100 is configured so that the fluids flow in the at least one internal cylindrical space 44, 45 at the surface of the disc 42 from at least one supply passage 40 to at least one extraction passage 41. At least one of the surfaces of the disc 42 contains at least one flow-disrupting element.

[0051] According to the invention, and as illustrated more particularly in Fig. 3, the flowdisrupting element is a lye-permeable element 50 and is arranged against the internal circumference of the peripheral ring 43 where a supply passage 40 or extraction passage 41 emerges. Fig. 3 shows four lye-permeable elements 50 arranged against the internal circumference of the peripheral ring 43 where all the supply passages 40 or extraction passages41 emerge into the internal cylindrical space 44. As can be seen on Fig. 3, the flow-disrupting element covers a portion of the surface of the disc 42 that lower than the total surface of the disc 42. Particularly, the covered surface of the disc 42 is lower than 20%, of the total surface of the disc.

[0052] Figs 4a and 4b show a bipolar plate 100 with a disc 42 that has a diameter identical to the internal diameter of the peripheral ring 43. Thus, the disc 42 is inserted into the peripheral ring 43 and attached thereto, for example by welding. The disc 42 divides the internal volume of the peripheral ring 43 into two internal cylindrical spaces 44 and 45, one on each side of the disc 42. The bipolar plate 100 may then be fitted with lye-permeable elements 50 on a single side of the disc 42, as depicted in Fig. 4a, or one on each side of the disc 42, as shown in Fig. 4b. Fig. 4c depicts a bipolar plate 100 of which the disc 42 has a diameter identical to theexternal diameter of the peripheral ring 43. The disc 42 may then be fixed to the surface of the peripheral ring 43 for example by welding. The disc 42 and the peripheral ring 43 here define a single internal cylindrical space 44 in which the lye-permeable elements 50 are situated. As may be seen in Fig. 4c, the lye-permeable elements 50 have a thickness along an axis perpendicular to the surface of the disc 42 that is identical to the height of the peripheral ring 43. Figs 4a and 4b show embodiments in which the thickness of the lye-permeable elements 50 is less than the height of the peripheral ring 43.

[0053] Fig. 6 illustrates a bipolar plate 100 in which one and the same lye-permeable element 50 covers multiple points where a supply duct 40 or an extraction duct 41 emerges.

[0054] A preferred shape for a lye-permeable element 50 is that of a non-polyhedral solid as depicted in Fig. 7. Such a solid contains a curved first surface, referred to as contact face 502, the curvature of which corresponds to the curvature of the internal surface of the peripheral ring 43, thus making it possible to attach the lye-permeable element 50 to this surface as illustrated in Figs 3 to 6. The opposite surface 501 to the contact face 502 can be parallel (and thus also be a curved surface). In this case, the non-polyhedral solid is an annular sector. For example, one with a rectangular cross section. The opposite faces 503 and 504 correspond to the cross section of the ring of which the non-polyhedral solid represents an annular sector. Advantageously, the opposite faces 505 and 506 comprised between the faces 501, 502, 503 and 504 have a surface parallel to the disc 42. This configuration makes it even easier to place the at least one lye-permeable element 50.

[0055] As can be seen in Fig. 3, the two faces 503, 504 perpendicular to the plane of the disc 42 roughly converge towards the centre of the disc 42 in the direction away from the internal surface of the peripheral ring 43. This configuration is economical and makes it possible to use all the sectors of a ring intended to form the various lye-permeable elements 50. However, this configuration is not particularly favourable to a distribution of the flow and preference is given to the configurations in Figs 5 and 6 in which the two faces 503, 504 perpendicular to the plane of the disc 42 get further away from one another (diverge) in the direction away from the internal surface of the peripheral ring 43. This configuration allows a very favourable distribution of the flows in the internal cylindrical space.

[0056] References in the figures1 electrolyser stack10, 10', 10", etc. electrolytic cells40 supply ducts41 extraction ducts42 disc43 peripheral ring44 internal cylindrical space45 internal cylindrical space46 flow axis50 lye-permeable element501 face of the lye-permeable element 502 contact face of the lye-permeable element503, 504, 505, 506 faces of the lye-permeable element100, 100' bipolar plates 101' first interleaf 102' first electrode 103' membrane104' second electrode105' second interleaf110 distribution plate111 gasket 112 end-plate

Claims

Claims1. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) comprising a surface in the form of a disc (42) of diameter (Dd), and a peripheral ring (43), the peripheral ring (43) having an internal circumference of internal diameter (Dai), and an external circumference of external diameter (Dae), the disc (42) and the peripheral ring (43) defining at least one internal cylindrical space (44, 45), the peripheral ring (43) being provided with supply passages (40) and extraction passages (41) each arranged along an axis parallel to the axis of symmetry of the internal cylindrical space (44, 45), supply ducts (40) and extraction ducts (41) respectively connecting the supply orifices and the supply ducts and the extraction orifices and the extraction ducts to the internal circumference of the peripheral ring (43), the supply passages (40) and extraction passages (41) being arranged on opposing sectors of the peripheral ring (43) and configured to allow the supply or extraction of fluids to or from the at least one internal cylindrical space (44, 45), and defining a flow axis (46), the bipolar plate (100, 100') being configured so that the fluids flow in the internal cylindrical space (44, 45) at the surface of the disc (42) from at least one supply passage (40) to at least one extraction passage (41), at least one of the surfaces of the disc (42) containing at least one flow-disrupting element, characterized in that the at least one flowdisrupting element is a lye-permeable element (50) and is arranged against the internal circumference of the peripheral ring (43) where a supply passage (40) or an extraction passage (41) emerges.

2. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to Claim 1, wherein at least one supply passage (40) is provided with at least one lye- permeable element (50) arranged against or near the internal circumference of the peripheral ring (43) where at least one supply passage (40) emerges.

3. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to Claim 1, wherein at least one extraction passage (41) is provided with at least one lye- permeable element (50) arranged against or near the internal circumference of the peripheral ring (43) where at least one extraction passage (41) emerges.

4. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to Claims 2 and 3, wherein at least one supply passage (40) and extraction passage (41) is provided with at least one lye-permeable element (50) arranged against the internal circumference of the peripheral ring (43) where at least one supply passage (40) emerges and where an extraction passage (41) emerges.

5. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to any one of Claims 1 to 4, wherein at least one same lye-permeable element (50) covers multiple points where a supply passage (40) or an extraction passage (41) emerges.

6. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to any one of Claims 1 to 5, wherein at least one lye-permeable element (50) is a porous element with an open porosity.

7. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to Claim 6, wherein the at least one porous element has an open porosity of 30% to 90% by volume, preferably 40% to 60% by volume.

8. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to either one of Claims 6 and 7, wherein the diameter of the pores is comprised between 0.1 mm and 20.0 mm and preferably between 0.1 mm and 10.0 mm.

9. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to any one of Claims 1 to 8, wherein at least one lye-permeable element (50) has a thickness along an axis perpendicular to the surface of the disc (42) that is identical to the height of the peripheral ring (43).

10. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to any one of Claims 1 to 9, wherein the at least one lye-permeable element (50) is a non-polyhedral solid of which one of the faces, referred to as contact face (502), has the same curvature as that of the internal surface of the peripheral ring (43), the contact face (502) being disposed against the internal circumference of the peripheral ring (43).

11. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to Claim 10, wherein the non-polyhedral solid is an annular sector.

12. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to Claim 10 or 11, wherein the non-polyhedral solid has six faces (501, 502, 503, 504, 505, 506), the faces (503, 504, 505, 506) connecting the contact face (502) and the opposite face (501) being planar.

13. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to Claim 12, wherein the faces (505, 506) parallel to the plane of the disc (42) are mutually parallel and the two faces (503, 504) perpendicular to the plane of the disc (42)get further away from one another in the direction away from the internal surface of the peripheral ring (43).

14. Bipolar plate (100, 100') for an electrolytic cell (10) of an electrolyser stack (1) according to Claim 12, wherein the faces (503, 504, 505, 506) connecting the contact face (502) and the opposite face (501) are parallel in pairs (503 and 504, 505 and 506).

15. Electrolytic cell (10, 10') for an electrolyser stack (1) of an alkaline water electrolysis plant comprising, in this order:- a first bipolar plate (100, 100') according to any one of Claims 1 to 14,- a first interleaf (101'),- a first electrode (102'),- a membrane (103'),- a second electrode (104'),- a second interleaf (105'), and- a second bipolar plate (100).

16. Electrolytic cell (10') according to Claim 15, wherein the first and the second bipolar plate (100', 100) are as defined in any one of Claims 1 to 14.

17. Electrolyser stack for an alkaline water electrolysis plant comprising an electrolytic cell as defined in one of Claims 15 and 16, the terminal bipolar plate of one electrolytic cell constituting the initial plate of the adjacent electrolytic cell.

18. Alkaline water electrolysis plant containing an electrolyser stack as defined in Claim 17.

19. Alkaline water electrolysis method implemented in an electrolysis plant as defined in Claim 18 and comprising the following steps:- supplying the electrolyser stack with lye via at least one of the supply passages of the bipolar plate;- extracting the electrolysis fluid containing lye together with gaseous molecular hydrogen or gaseous molecular oxygen via at least one of the extraction passages of the bipolar plate.

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