Bipolar plate for electrochemical cells, enabling a reduction of short-circuit flows at the edge of the reaction zone.

Abstract

The invention relates to a bipolar plate comprising upper and lower plates (10, 20), having, along the active zone, an intermediate longitudinal zone (Zint) where there is a longitudinal alternation between at least a first short-circuit protection region (Rsup) and at least a second short-circuit protection region (Rinf). In the first short-circuit protection region (Rsup), the lower plate (20) has: a plurality of lower studs (25), projecting, in a direction opposite to the upper plate (10), opposite a lower intermediate recess (24) in which they are located, and having substantially equal dimensions along any two orthogonal axes in a plane parallel to the bipolar plate; and an absence of transverse ribs extending into the intermediate longitudinal zone (Zint) by joining internal (22i) and external (22e) lower longitudinal ribs. Figure for the summary: Fig. 3B

Description

Title of the invention: Bipolar plate for an electrochemical cell enabling a reduction of short-circuit flows at the edge of the reaction zone technical field

[0001] The field of the invention is that of electrochemical reactors comprising a stack of electrochemical cells, such as fuel cells and electrolyzers, and relates more particularly to bipolar plates with conductive foils. PRIOR TECHNOLOGY

[0002] An electrochemical reactor, such as a fuel cell or an electrolyzer, usually comprises a stack of electrochemical cells, each of which includes an anode and a cathode electrically separated from each other by an electrolyte. The cells are the site of an electrochemical reaction between two reactant fluids introduced continuously.

[0003] Generally, in the case of a fuel cell, the fuel fluid (for example, hydrogen) is supplied to the anode, while the oxidizing fluid (for example, air) is supplied to the cathode. The electrochemical reaction is subdivided into two half-reactions, an oxidation reaction and a reduction reaction, which take place respectively at the anode / electrolyte interface and the cathode / electrolyte interface. For the electrochemical reaction to occur, the presence of an ionic conductor between the two electrodes, namely the electrolyte, for example, contained in a polymer membrane, and an electronic conductor formed by the external electrical circuit. The stack of cells is thus the site of the electrochemical reaction: the reactive fluids must be supplied to it, the products and non-reactive species must be removed, as well as the heat produced during the reaction.

[0004] Electrochemical cells are usually separated from each other by bipolar plates that provide electrical interconnection between them and allow the flow of reactant fluids. The bipolar plates have an anodic face on which a fuel fluid distribution circuit is formed, and an opposite cathodic face on which an oxidant fluid distribution circuit is formed. Each distribution circuit takes the form of a network of channels arranged to deliver the reactant fluid to the corresponding electrode. The bipolar plates may also include a cooling circuit consisting of a network of internal channels that allow the flow of a heat transfer fluid to dissipate the heat produced locally during the electrochemical reaction by the cell.

[0005] Figure [1A] is a schematic and partial view of an example of a bipolar plate 1, of the conductive lamination type, in top view and from the cathode side. Figure [1B] is a cross-sectional view of the bipolar plate 1 of Figure [1A] along section line AA.

[0006] The bipolar plate 1 comprises two plates, upper 10 and lower 20, made of an electrically conductive material, and superimposed one on top of the other. Each plate 10 and 20 has a distribution circuit 7 adapted to convey a reactive fluid to the corresponding electrode. The anodic and cathodic distribution circuits 7 are superimposed on each other and define, in the XY plane, the reaction zone of the electrochemical cell. An air collector 2 and a hydrogen collector 3 are located opposite each other on the same side of the distribution circuit 7 and are separated from each other by a heat transfer fluid collector 4. The air collector 2 is adapted to supply the distribution circuit 7 with air, via an injection zone 8 and then a homogenization zone 9.

[0007] The plates 10, 20 have an external sealing line, formed of superimposed upper longitudinal ribs 12e and lower longitudinal ribs 22e, each associated with an external sealing gasket 5 (upper and lower). The external sealing line extends continuously around the periphery of the bipolar plate 1 and surrounds, in the XY plane, the collectors 2 and 3 (and here also the collector 4) and the reaction zone 7. It prevents reactive fluids from flowing outside the bipolar plate. Furthermore, the plates 10, 20 have upper internal longitudinal ribs 12i and lower internal longitudinal ribs 21i, which extend longitudinally along the edges of the distribution circuits and help to define a distribution channel.The external longitudinal ribs 12e, 22e (also called joint ribs) and the internal longitudinal ribs 12i, 22i (also called channel ribs) longitudinally delimit an intermediate longitudinal zone Z int located at the edge of the distribution circuit.

[0008] Thus, during operation, air is supplied by the inlet manifold 2, flows through the injection zone 8 and then the homogenization zone 9, and comes into contact with the cathode 32 by means of the distribution circuit 7. Unconsumed air then flows through an outlet homogenization zone and then an outlet injection zone, finally reaching the air outlet manifold 2 (see solid arrows in [Fig. 1A]). The same applies to hydrogen on the anodic side.

[0009] However, it appears that air can bypass the reaction zone by flowing into intermediate longitudinal zones Zint located between the distribution circuit 7 and the external sealing line. Indeed, as shown by the dashed arrows in [Fig. 1A], air can escape from the injection zone 8 to reach The intermediate longitudinal zones of the Zint and flow along the longitudinal edges of the reaction zone. These flows are short-circuit flows insofar as they do not participate in the electrochemical reaction, thus degrading the fuel cell's performance. This is the case for air on the cathodic side, but also for hydrogen on the anodic side.

[0010] There is therefore a need to have bipolar plates whose structural configuration of the conductive sheets makes it possible to reduce these flows in these intermediate longitudinal zones, both for reactive fluids and for the heat transfer fluid.

[0011] In this respect, document EP3171439 A1 describes a structural configuration of the conductive sheets in the intermediate longitudinal zones, where the conductive sheets have upper and lower intermediate transverse ribs superimposed on one another, each directly connecting the inner longitudinal rib to the outer longitudinal rib. The intermediate transverse ribs are deformable, so that when deformed, they extend vertically towards the sealing film (see film 34 in [Fig. 1B]), between the AME and the outer joint, and conform as closely as possible to the shape of the AME. Thus, the cross-sectional flow area of ​​the reactive fluids in this intermediate longitudinal zone is reduced, which limits the short-circuit flow of the reactive fluids.However, the cross-sectional area of ​​the heat transfer fluid flow is increased, which reduces cooling efficiency and degrades the performance of the electrochemical cell. Description of the invention

[0012] The invention aims to remedy at least in part the disadvantages of the prior art, and more particularly to propose a bipolar electrochemical cell plate whose structural configuration of the conductive sheets, in at least one of the intermediate longitudinal zones, makes it possible to reduce both the short-circuit flow of the reactive fluids and that of the heat transfer fluid, while also limiting the risks of mechanical deformation of the conductive sheets and / or the membrane / electrode assemblies in the intermediate longitudinal zone.

[0013] To this end, the object of the invention is a bipolar electrochemical cell plate, comprising: upper and lower plates, superimposed one on top of the other, comprising: • upper and lower distribution circuits, superimposed on each other, adapted to bring reactive fluids respectively to upper and lower electrodes; • upper and lower internal longitudinal ribs, superimposed on one another, forming respectively a longitudinal border of the circuits upper and lower distribution; • upper and lower external longitudinal ribs, superimposed on each other, extending along the internal longitudinal ribs, laterally delimiting, with the latter, an intermediate longitudinal zone.

[0014] Furthermore, in the intermediate longitudinal zone there is a longitudinal alternation between at least one first anti-short-circuit region and at least one second anti-short-circuit region, where: • in the first anti-short-circuit region, known as the upper contact plane region, the upper sheet metal has an intermediate upper longitudinal rib extending throughout the first anti-short-circuit region; and the lower sheet metal has an intermediate lower recess superimposed on and in contact with the intermediate upper longitudinal rib; • in the second anti-short-circuit region, known as the lower contact plane region, the lower sheet metal has a lower intermediate longitudinal rib extending throughout the second anti-short-circuit region; and the upper sheet metal has an upper intermediate recess, superimposed on and in contact with the lower intermediate longitudinal rib.

[0015] According to the invention, in the first anti-short-circuit region, the lower sheet metal has: • a plurality of lower studs, projecting outwards in a direction opposite to the upper plate, opposite the lower intermediate recess in which they are located, and having substantially equal dimensions along any two orthogonal axes in a plane parallel to the bipolar plate; • an absence of transverse ribs extending into the intermediate longitudinal zone by joining the lower internal and external longitudinal ribs.

[0016] Furthermore, in the second anti-short-circuit region, the upper sheet metal has: • a plurality of upper studs, projecting outwards in a direction opposite to the lower plate, opposite the upper intermediate recess in which they are located, and having substantially equal dimensions along any two orthogonal axes in a plane parallel to the bipolar plate; • an absence of transverse ribs extending into the intermediate longitudinal zone by joining the upper internal and external longitudinal ribs.

[0017] Some preferred but not limiting aspects of this bipolar plate are the following.

[0018] The bipolar plate may comprise several first anti-short-circuit regions arranged alternately longitudinally with several second anti-short-circuit regions.

[0019] The upper studs can be arranged longitudinally in a periodic manner, and the lower studs can be arranged longitudinally in a periodic manner.

[0020] The upper and lower studs can be distributed over at least two lines parallel to a longitudinal axis of the intermediate longitudinal zone.

[0021] The upper and lower studs may have a height substantially equal, respectively, to that of the upper and lower internal longitudinal ribs.

[0022] The upper and lower pads may have a circular or square base.

[0023] The upper and lower studs can be distinct from the ribs respectively upper and lower internal longitudinal ribs, and, respectively, upper and lower external longitudinal ribs.

[0024] The upper and lower external longitudinal ribs can each be in contact with a sealing gasket.

[0025] The invention also relates to an electrochemical cell, comprising at least the bipolar plate according to any one of the preceding characteristics, and membrane / electrode assemblies, one in contact with the upper sheet and the other in contact with the lower sheet.

[0026] An upper membrane / electrode assembly can be in contact with the upper pads, and a lower membrane / electrode assembly can be in contact with the lower pads.

[0027] The invention also relates to an electrochemical reactor, comprising at least one electrochemical cell according to the preceding characteristics. Brief description of the drawings

[0028] Other aspects, objects, advantages and features of the invention will become more apparent upon reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0029] [Fig.1A], already described, is a schematic and partial top view of a bipolar plate according to an example from the prior art;

[0030] [Fig.1B], already described, is a schematic and partial view, in cross-section, of the bipolar plate of [Fig.1A], along the section line AA;

[0031] [Fig.2] is a schematic and partial top view of a bipolar plate according to one embodiment, illustrating the first and second short-circuit protection regions located in the intermediate longitudinal zones;

[0032] [Fig.3A] is a schematic and partial perspective view of a portion of a bipolar plate according to one embodiment, illustrating a longitudinal alternation of first and second anti-short-circuit regions in an intermediate longitudinal zone (the reaction zone is not shown);

[0033] [Fig.3B] is a schematic and partial view, in longitudinal section in the intermediate longitudinal zone, of the bipolar plate of [Fig.3A];

[0034] [Fig.4A] is a schematic and partial view, in perspective and in cross-section in an anti-short-circuit region with lower contact plane, of the bipolar plate of [Fig.3A];

[0035] [Fig.4B] is a schematic and partial cross-sectional view in an anti-short-circuit region with lower contact plane, of the bipolar plate of [Fig.4A], where the upper and lower membrane / electrode assemblies are also illustrated;

[0036] [Fig.5A] is a schematic and partial view, in perspective and in cross-section in an anti-short-circuit region with upper contact plane, of the bipolar plate of [Fig.3A];

[0037] [Fig.5B] is a schematic and partial cross-sectional view in an anti-short-circuit region with an upper contact plane, of the bipolar plate of [Fig.5A], where the upper and lower membrane / electrode assemblies are also illustrated.

[0038] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0039] In the figures and in the following description, the same reference numerals represent identical or similar elements. Furthermore, the various elements are not drawn to scale in order to enhance the clarity of the figures. Moreover, the different embodiments and variants are not mutually exclusive and may be combined. Unless otherwise indicated, the terms "Approximately," "around," and "in the order of" mean within 10%, and preferably within 5%. Furthermore, the terms "between ... and ..." and equivalents mean that the limits are inclusive, unless otherwise stated.

[0040] The invention relates to a bipolar plate for an electrochemical cell in electrochemical reactors such as fuel cells and electrolyzers. The bipolar plate is of the conductive sheet type, which includes ribs and indentations. More specifically, the invention relates to a particular structural configuration of the bipolar plate in at least one of the intermediate longitudinal zones extending longitudinally between the external sealing line and the distribution circuit. This structural configuration of the conductive sheets reduces the short-circuit flow of reactive fluids as well as that of the heat transfer fluid, while also limiting the risks of leakage. formation of the AME or conductive sheets in the intermediate longitudinal zone.

[0041] Various embodiments and variants will be described with reference to a fuel cell, and in particular to a PEM (Proton Exchange Membrane) type fuel cell in which the cathode is supplied with oxygen and the anode with hydrogen. However, the invention applies to any type of fuel cell, particularly those operating at low temperatures, i.e., below 200°C, as well as to electrochemical electrolyzers.

[0042] Figure 2 is a schematic, partial top view of a portion of the bipolar plate 1 according to one embodiment. Certain elements are described with reference to Figure 1B. Figure 3A is a perspective view of a portion of a bipolar plate similar to that of Figure 2 (where the reaction zone is not shown), and Figure 3B is a perspective and longitudinal sectional view of the bipolar plate 1 of Figure 3A.

[0043] Here and for the rest of the description we define a direct orthogonal frame XYZ, where the Z axis is oriented along the thickness of the bipolar plate 1 (from the lower sheet 20 to the upper sheet 10), and where the X and Y axes define a principal plane along which the bipolar plate extends.

[0044] The electrochemical cells here belong to a stack of cells in a fuel cell. Each electrochemical cell comprises a membrane / electrode assembly 30 (MEA, see [Fig. 1B]) consisting of a cathode 32 and an anode 33 separated from each other by an electrolyte 31, which here includes a polymer membrane. The MEAs 30 of the electrochemical cells are arranged between bipolar plates 1 adapted to deliver reactive species to the electrodes and to dissipate the heat produced during the electrochemical reaction. The MEA extends partially into the intermediate longitudinal zone along the X-axis. A sealing film 34 (a material distinct from the membrane 31 or a film corresponding to the membrane itself) can extend from the MEA 30 to the edge of the bipolar plates 1 and be in contact with the external sealing gaskets 5.

[0045] Each bipolar plate 1 is formed of two overlapping and joined upper and lower sheets 10 and 20. They are made of an electrically conductive material. These conductive sheets 10, 20 are locally deformed to form channels for the flow of reactive fluids, and in particular an injection zone 8, a homogenization zone 9, and a distribution circuit 7, as well as a cooling circuit located between the conductive sheets 10, 20. Thus, the lower sheet 20, for example the anodic sheet, is intended to be in contact with the anode of the membrane / electrode assembly 30 of an adjacent electrochemical cell, while the upper sheet 10, here the cathodic sheet, is intended to be in contact with the cathode 32. of the AME of the electrochemical cell.

[0046] Each conductive plate 10, 20 has an external face and an opposite internal face, the conductive plates 10, 20 facing each other at their internal faces. An external face is called anodic when it is intended to be in contact with the anode 33, or is called cathodic when it is intended to be in contact with the cathode 32. The anodic face of one conductive plate has the distribution circuit for a combustible reactive fluid, for example hydrogen here, and the cathodic face of the other conductive plate has the distribution circuit for the oxidizing reactive fluid, for example air here.

[0047] The conductive sheets 10, 20 are in the form of thin sheets or elementary plates made of an electrically conductive material, for example a metal or even a composite material, for example, one loaded with graphite. The thickness can be on the order of a few tens of microns to a few hundred microns, for example, from approximately 50 µm to 200 µm in the case of metal sheets.

[0048] Each conductive sheet 10, 20 has ribs and indentations, obtained for example by deep drawing, stamping, or any other forming technique, the shape of which on one face is the complement of the shape on the opposite face. The ribs notably allow for defining the distribution circuit of a reactive fluid on the outer face, as well as the cooling circuit of the heat transfer fluid on the inner face.

[0049] Manifolds 2, 3, 4 are openings that pass through each of the bipolar plates 1. The reactive fluid manifolds 2, 3 are located on either side of the reaction zone, along a principal axis of reactive fluid flow, here along the Y axis. In this example, a heat transfer fluid manifold 4 is located between the reactive fluid manifolds 2, 3. Alternatively, they can be located along an X axis orthogonal to the longitudinal Y axis.

[0050] The reactant fluid manifolds 2, 3 are adjacent to each other (separated or not by the heat transfer fluid manifold 4), and are arranged opposite the same opening (inlet or outlet) of the reaction zone. In this example, an air inlet manifold 2 and a hydrogen manifold 3 (inlet or outlet) are located opposite the inlet of the cathodic distribution circuit 7.

[0051] The conductive sheets 10, 20 have injection zones 8 to allow fluid circulation to and from the manifolds. Thus, an air injection zone 8 provides the fluid connection between the air manifold 2 and the homogenization zone 9. It is formed of conduits that cross the sealing line of the air manifold and open onto the external face of the upper sheet 10, to allow air to flow towards the homogenization zone 9. The same applies to the lower sheet 20, whose injection zone communicates with the hydrogen manifold 3 and the homogenization zone. The heat transfer fluid injection zone is formed of conduits which open between the two cathodic 10 and anodic 20 conductive sheets. Similar injection zones are described in particular in document EP3136492A1.

[0052] Each conductive sheet 10, 20 here includes a homogenization zone 9 which communicates with the injection zone 8 on one side, and with the distribution circuit 7 on the other. Such a homogenization zone 9 makes it possible to homogenize the airflow at the inlet of the distribution circuit 7. It can be formed by homogenization channels made in the conductive sheet 10. Document EP3136492A1 also describes an example of such a homogenization zone.

[0053] Each conductive plate 10, 20 comprises a distribution circuit 7, formed of channels extending between an inlet and an outlet aligned along a principal direction (here the Y-axis). These channels are separated in pairs by a separating rib that is in contact with the corresponding FAME. The cathodic and anodic distribution circuits define the reaction zone of the electrochemical cell in the XY plane.

[0054] Furthermore, a reference plane Pref of the bipolar plate 1 is defined as the contact plane of the conductive sheets 10, 20 at their outer edges 11 and 21e (see [Fig. 1B]). This is the reference plane Pref with respect to which the ribs and recesses are defined, when considered from the outer face of each conductive sheet 10, 20.

[0055] Thus, a rib is obtained by local deformation of the conductive sheet 10, 20, from its inner face to its outer face. It is therefore a relief or boss on the conductive sheet 10, 20, viewed from the outer face, which deviates from the reference plane Pref along the Z-axis (and therefore deviates from the other conductive sheet). In other words, a rib is a surface that protrudes from the reference plane Pref. Thus, an upper rib is a rib on the upper sheet 10 that deviates from the reference plane Pref along the +Z direction. And a lower rib is a rib on the lower sheet 20 that deviates from the reference plane Pref along the -Z direction. Furthermore, a rib has an elongated shape in the XY plane: a dimension (length) along a longitudinal axis is greater than its dimension (width) along a transverse axis.

[0056] Furthermore, an intermediate longitudinal rib is defined as a rib located in the intermediate longitudinal zone Zint (i.e., situated between the internal and external longitudinal ribs) and extending longitudinally along the same longitudinal axis Y as that of the intermediate longitudinal zone. Moreover, an intermediate transverse rib is defined as a rib located in the intermediate longitudinal zone Zint and extending longitudinally along an inclined axis (in the XY plane), or even— thogonal, to the longitudinal axis Y of the intermediate longitudinal zone Zint.

[0057] Conversely, a recess is obtained by local deformation of the conductive sheet 10, 20, from its outer face to its inner face. It is therefore a depression or hollow in the conductive sheet 10, 20, viewed from its outer face, which extends below the reference plane Pref along the Z-axis (and thus moves closer to the other conductive sheet). Thus, an upper recess is a recess in the upper sheet 10 that extends beyond the reference plane Pref along the -Z direction. And a lower recess is a recess in the lower sheet 20 that extends beyond the reference plane Pref along the +Z direction.

[0058] As illustrated in [Fig. 1B], the bipolar plate 1 has superimposed external longitudinal ribs, upper 12e and lower 22e, which completely surround the collectors 2 and 3 and the reaction zone 7 in the XY plane. They extend longitudinally along the edge of the bipolar plate 1. External sealing gaskets 5 are arranged in contact with the upper external longitudinal rib 12e and the lower external rib 22e, respectively. They are also in contact with the sealing film 34. This configuration, which forms an external sealing line, prevents fluids, particularly reactive gases, from flowing outside the bipolar plate 1.

[0059] Furthermore, the bipolar plate 1 has internal longitudinal ribs, upper 12i and lower 22i, superimposed on one another, which extend longitudinally along the edge of the reaction zone. They form the edge ribs of the distribution circuits 7. They are in contact with the diffusion layer of the FAME electrode 30. Thus, the intermediate longitudinal zone Zint corresponds to the area delimited laterally (here along the X-axis) by the external sealing line and by the reaction zone, and more precisely by the external longitudinal ribs 12e, 22e on the one hand, and by the internal longitudinal ribs 12i, 22i on the other. Its longitudinal axis is here the Y-axis (this longitudinal axis may be straight or not).

[0060] It should also be noted that the conductive sheets 10, 20 comprise upper and lower flat portions, superimposed on one another and in contact with each other at the level of the reference plane Pref. Thus, external longitudinal portions 11e, 21e extend in the XY plane between the external longitudinal ribs 12e, 22e and the edge of the bipolar plate 1, over its entire periphery. In addition, upper internal longitudinal portions 11i and lower internal longitudinal portions 21i extend between the internal longitudinal ribs 12i, 22i and the distribution ribs.

[0061] The bipolar plate 1 comprises, in an intermediate longitudinal region Zint, a longitudinal alternation between at least one first short-circuit protection region Rsup (called the upper contact plane region Pcsup) and at least one second short-circuit protection region R inf (called the lower contact plane region Pcinf). By longitudinal alternation, it is understood that these The first and second short-circuit protection regions Rsup and Rinf alternate along the longitudinal axis Y of the intermediate longitudinal zone Zint. This longitudinal alternation of first short-circuit protection regions Rsup with second short-circuit protection regions Rinf may be periodic or asynchronous.

[0062] In the first anti-short-circuit region Rsup, the contact plane between the two conductive plates 10, 20 is a superior contact plane Pcsup, in the sense that it is located above the reference plane Pref along the +Z direction.

[0063] The upper plate 10 has an intermediate upper longitudinal rib 16 extending throughout the entire first short-circuit protection region Rsup, i.e., over its entire surface. It therefore extends along the entire length (along the Y-axis) of the first short-circuit protection region Rsup, and over its entire width (along the Y-axis). It thus directly connects the external upper longitudinal rib 12e with the internal upper longitudinal rib 12i, without any intermediate recess. The intermediate upper longitudinal rib 16 may be in contact with FAME over at least part of its width (as illustrated in [Fig. 5B]). This intermediate upper longitudinal rib 16 extends along the longitudinal axis of the intermediate longitudinal zone Zint. Preferably, it extends in a continuously planar manner.It may or may not be coplanar with the external upper longitudinal rib 12e and / or with the internal upper longitudinal rib 12i.

[0064] Furthermore, the lower plate 20 has a lower intermediate recess 24, superimposed on and in contact with the upper intermediate longitudinal rib 16. The contact plane between the upper intermediate longitudinal rib 16 and the lower intermediate recess 24 corresponds to the upper contact plane Pcsup. It is located above the reference plane Pref in the +Z direction.

[0065] The contact between the lower intermediate recess 24 and the upper intermediate longitudinal rib 16 can be continuous, meaning that the recess 24 is in contact with the rib 16 over its entire surface. Alternatively, the contact can be localized, meaning that there are one or more points of contact between the recess 24 and the rib 16. Apart from these points of contact, the recess 24 and the rib 16 are separated along the Z-axis by a small distance, for example on the order of a few tens of microns, for example at most 50 µm or even less (sufficiently small to prevent the flow of the heat transfer fluid). Note that bipolar plates can exhibit such localized contact before applying the clamping force to the stack, and then continuous contact after the application of this force.

[0066] According to the invention, the lower plate 20, in the anti-short-circuit region Rsup, comprises a plurality of lower studs 25, projecting, in a direction -Z opposite to the upper plate 10, opposite the lower intermediate recess 24 in which they are located. They have approximately equal dimensions along any two orthogonal axes in a plane parallel to the bipolar plate 1.

[0067] Generally speaking, a stud differs from a rib in that it has substantially equal dimensions along any two orthogonal axes in the XY plane. Studs can thus have a substantially circular (as shown here) or square base, which is therefore not elongated or oblong. They have a base located at the level of the recess and a crest. The crest can be curved or flattened. They have a height (distance between the base and the crest along the Z-axis) which preferably corresponds to the depth of the recess. Thus, the crest is preferably substantially coplanar with the internal and / or external longitudinal ribs of the conductive sheet. However, the height of the studs can be equal to at least 50%, and preferably to at least 75%, of the depth of the recess.

[0068] The lower studs 25 extend from the lower intermediate recess 24 and are preferably not connected to the inner lower longitudinal rib 22i or the outer lower longitudinal rib 22e. They can be arranged along the longitudinal axis Y periodically or not, for example in the form of several parallel lines. Along the axis X, the lower studs 25 can be aligned, staggered, or even randomly arranged.

[0069] The lower studs 25 here ensure good mechanical strength of the conductive sheets 10, 20, and here in particular of the lower sheet 20, to prevent them from deforming in the intermediate longitudinal zone Zint, or to prevent the lower FAME from deforming in the direction of the lower intermediate recess 24. They also ensure good mechanical contact between the bipolar plate and the lower and upper AME.

[0070] Furthermore, the lower plate 20, in the short-circuit protection region Rsup, does not have a transverse rib extending into the intermediate longitudinal zone Zint by joining the lower internal longitudinal ribs 22i and external ribs 22e. This transverse axis can be the X-axis itself or an axis inclined with respect to the X-axis. Indeed, such transverse ribs can allow short-circuit flow of the heat transfer fluid, which would reach the external sealing line and thus bypass the reaction zone. Therefore, it is understood that the lower intermediate recess 24 is a single recess that extends continuously over the entire width and length of the short-circuit protection region Rsup, surrounding each of the lower studs 25 in the XY plane.

[0071] Thus, in the anti-short-circuit region Rsup with upper contact plane Pcsup, the cross-sectional area of ​​airflow, at the level of the upper (cathodic) sheet 10, is greatly reduced by the presence of the upper intermediate longitudinal rib 16, which limits the short-circuit flow of air (increasing the linear pressure drop). Furthermore, the conductive sheets 10, 20 exhibit good mechanical strength thanks to the lower studs 25, which prevent their deformation as well as that of the lower AME. Finally, the short-circuit flow of the heat transfer fluid is limited or absent, since there are no lower transverse ribs connecting the inner longitudinal rib 22i to the outer longitudinal rib 22e. Thus, the heat transfer fluid cannot flow through them and therefore cannot reach the reaction zone.

[0072] Furthermore, in the second anti-short-circuit region Rinf, the contact plane between the two conductive plates 10, 20 is a lower contact plane Pcinf, in the sense that it is located below the reference plane Pref along the direction -Z.

[0073] The lower plate 20 has a lower intermediate longitudinal rib 26 extending throughout the entire short-circuit protection region Rinf, i.e., over its entire surface. It therefore extends along the entire length (along the Y-axis) of the short-circuit protection region Rinf, and over its entire width (along the Y-axis). It thus directly connects the outer lower longitudinal rib 22e with the inner lower longitudinal rib 22i, without any intermediate recess. The lower intermediate longitudinal rib 26 may be in contact with the AME over at least part of its width (as illustrated in [Fig. 4B]). This lower intermediate longitudinal rib 26 extends along the longitudinal axis of the intermediate longitudinal zone Zint. Preferably, it extends in a continuously planar manner.It may or may not be coplanar with the outer lower longitudinal rib 22e and / or with the inner lower longitudinal rib 22i.

[0074] Furthermore, the upper plate 10 has an upper intermediate recess 14, superimposed on and in contact with the lower intermediate longitudinal rib 26. The contact plane between the lower intermediate longitudinal rib 26 and the upper intermediate recess 14 corresponds to the lower contact plane Pcinf. It is located below the reference plane Pref in the -Z direction. As previously stated for the recess 24 and the rib 16, the contact between the upper intermediate recess 14 and the lower intermediate longitudinal rib 26 can be continuous, i.e., the recess 14 is in contact with the rib 26 over its entire surface. Alternatively, the contact can be localized, i.e., there is one or more points of contact between the recess 14 and the rib 26.Apart from these contact points, the recess 14 and the rib 26 are spaced along the Z axis by a small distance, for example on the order of a few tens of microns, for example at most 50pm or even less (sufficiently small to prevent the flow of the heat transfer fluid).

[0075] According to the invention, the upper sheet metal 10, in the anti-short-circuit region Rinf, comprises a plurality of upper studs 15, projecting in a +Z direction opposite the lower plate 20, with respect to the upper intermediate recess 14 in which they are located. They have substantially equal dimensions along any two orthogonal axes in a plane parallel to the bipolar plate 1.

[0076] The upper studs 15 extend from the upper intermediate recess 14 and are preferably not connected to the inner upper longitudinal rib 12i or the outer upper longitudinal rib 12e. They may be arranged along the longitudinal axis Y periodically or not, for example in the form of several parallel lines. Along the axis X, the upper studs 15 may be aligned, staggered, or even randomly arranged.

[0077] The upper studs 15 here ensure good mechanical strength of the conductive sheets 10, 20, and here in particular of the upper sheet 10, to prevent them from deforming in the intermediate longitudinal zone Zint, or to prevent the upper FAME from deforming in the direction of the upper intermediate recess 14. They also ensure good mechanical contact between the bipolar plate and the lower and upper AME.

[0078] Furthermore, the upper plate 10, in the short-circuit protection region Rinf, does not have a transverse rib extending into the intermediate longitudinal zone Zint by joining the inner upper longitudinal ribs 12i and outer upper longitudinal ribs 12e. This transverse axis can be the X axis itself or an axis inclined with respect to the X axis. It is also understood that the upper intermediate recess 14 is a single recess that extends continuously over the entire width and length of the short-circuit protection region Rinf, surrounding each of the upper studs 15 in the XY plane.

[0079] Also, in the anti-short-circuit region Rinf with lower contact plane Pcinf, the cross-sectional area for hydrogen flow at the lower plate 20 is significantly reduced by the lower intermediate longitudinal rib 26, which limits the short-circuit flow of hydrogen (increasing the linear pressure drop). Furthermore, the conductive plates 10, 20 exhibit good mechanical strength thanks to the upper studs 15, which prevent their deformation as well as that of the upper AME. Finally, the short-circuit flow of the heat transfer fluid is limited or absent, since there are no upper transverse ribs connecting the inner longitudinal rib 12i to the outer longitudinal rib 12e. Thus, the heat transfer fluid cannot flow through them, nor can it partially bypass the reaction zone.

[0080] Furthermore, it should be noted here, as illustrated in [Fig. 3B], that the upper plate 10 may include an upper curved portion 17 which provides the longitudinal connection (along the Y-axis) between the upper intermediate recess 14 and the upper intermediate rib 16. Similarly, the lower plate 20 includes a curved portion lower 27 which ensures the longitudinal junction between the lower intermediate rib 26 and the lower intermediate recess 24. These upper curved portions 17 and lower 27 are here offset along the longitudinal axis Y so as not to be in contact with each other, thus avoiding a transmission of mechanical stresses likely to weaken the bipolar plate 1.

[0081] Fig. 4A is a partial, perspective and cross-sectional view of the bipolar plate of Fig. 3A in the Rinf short-circuit protection region with lower contact plane, and Fig. 4B is a schematic and partial cross-sectional view of the bipolar plate of Fig. 4A.

[0082] The lower plate 20 has a lower intermediate longitudinal rib 26, which extends continuously along the transverse axis X between the lower internal longitudinal ribs 22i and external longitudinal ribs 22e, and which extends along the longitudinal axis Y to the anti-short-circuit region Rsup. It therefore extends throughout the entire anti-short-circuit region Rinf. It comes into contact with the anodic side of the lower AME, which reduces the short-circuit flow of hydrogen.

[0083] The upper plate 10 has an upper longitudinal recess 14, which extends along the transverse axis X between the inner upper longitudinal ribs 12i and outer upper longitudinal ribs 12e, and along the longitudinal axis Y from the short-circuit protection region Rinf. The upper longitudinal recess 14 and the lower longitudinal rib 26 are in contact with each other (continuous or localized contact) at a lower contact plane Pcinf along the Z axis (below the reference plane Pref).

[0084] The upper plate 10 has upper studs 15, located in the intermediate longitudinal zone Zint, and projecting from the upper intermediate recess 14 in which they are situated. They extend from this recess in the +Z direction, towards the cathode of the upper core with which they come into contact. These are studs and not ribs, and therefore have substantially equal dimensions along any two orthogonal axes in the XY plane. Here, they have a circular base, but a square base is also possible. Their apex is rounded (see [Fig. 4A]), but a flat surface is also possible (as illustrated in [Fig. 4B]). Thus, the upper studs 15 prevent deformation along the Z-axis of the conductive plates, as well as deformation along the -Z direction of the upper core.They ensure good contact between the conductive sheets 10, 20 and the upper and lower AME.

[0085] Thus, the upper sheet 10 does not have transverse ribs extending along the transverse axis X (or inclined to the axis X) joining the upper internal longitudinal ribs 12i and external ribs 12e. This avoids the risk of the heat transfer fluid at least partially bypassing the reaction zone by passing through the intermediate longitudinal zone Zint to reach the sealing line. external.

[0086] Fig. 5A is a partial, perspective and cross-sectional view of the bipolar plate of Fig. 3A in the anti-short-circuit region Rsup with upper contact plane, and Fig. 5B is a schematic and partial, cross-sectional view of the bipolar plate of Fig. 5A.

[0087] The upper plate 10 has an intermediate upper longitudinal rib 16, which extends continuously along the transverse axis X between the inner upper longitudinal ribs 12i and outer upper longitudinal ribs 12e, and which extends along the longitudinal axis Y from or to the anti-short-circuit region Rinf. It therefore extends throughout the entire anti-short-circuit region Rsup. It comes into contact with the cathodic side of the upper FAME (not shown), which reduces the air short-circuit flow.

[0088] The lower plate 20 has a lower longitudinal recess 24, which extends along the transverse axis X between the lower internal longitudinal ribs 22i and external ribs 22e, and along the longitudinal axis Y from the short-circuit protection region Rinf. The lower longitudinal recess 24 and the upper intermediate longitudinal rib 16 are in contact with each other (continuous or localized contact) at an upper contact plane Pcsup along the Z axis (above the reference plane Pref).

[0089] The lower plate 20 has lower studs 25, located in the intermediate longitudinal zone Zint, and projecting from the lower intermediate recess 24 in which they are situated. They extend from this recess in the -Z direction, towards the lower FAME anode with which they come into contact. These studs are not ribs, and therefore have substantially equal dimensions along any two orthogonal axes in the XY plane. Here, they also have a circular base, but a square base is also possible. Their apex is rounded (see [Fig. 5A]), but a flat surface is also possible (see [Fig. 5B]). Thus, the lower studs 25 prevent deformation along the -Z direction of the conducting plates, as well as deformation along the +Z direction of the upper FAME.They ensure good contact between the conductive sheets 10, 20 and the upper and lower AME.

[0090] Thus, the lower sheet 20 does not have transverse ribs extending along the transverse axis X (or inclined to the X axis) joining the lower internal and external longitudinal ribs. This avoids the risk of the heat transfer fluid at least partially bypassing the reaction zone by passing through the intermediate longitudinal zone Zint to reach the external sealing line.

[0091] Finally, the fact that there is a longitudinal succession of at least one anti-short-circuit region Rsup and at least one anti-short-circuit region Rinf makes it possible to limit both the risks of short-circuit flow of air on the cathodic side and of hydrogen on the anodic side.

[0092] Specific embodiments have just been described. Various variants and modifications will be apparent to those skilled in the art.

Claims

Demands

1. Bipolar plate (1) of an electrochemical cell, comprising: • upper (10) and lower (20) sheets, superimposed one on top of the other, comprising: • upper and lower distribution circuits, superimposed on each other, adapted to bring reactive fluids respectively to upper and lower electrodes; • upper (12i) and lower (22i) internal longitudinal ribs, superimposed on each other, forming respectively a longitudinal border of the upper and lower distribution circuits; • upper (12e) and lower (22e) external longitudinal ribs, superimposed on each other, extending along the internal longitudinal ribs (12i, 22i), laterally delimiting, with the latter, an intermediate longitudinal zone (Zint); • in the intermediate longitudinal zone (Zint) there is a longitudinal alternation between at least one first anti-short-circuit region (Rsup) and at least one second anti-short-circuit region (Rinf), where: • in the first anti-short-circuit region (Rsup) called the upper contact plane (Pcsup), the upper sheet (10) has an upper intermediate longitudinal rib (16) extending throughout the first anti-short-circuit region (Rsup); and the lower sheet (20) has a lower intermediate recess (24) superimposed on and in contact with the upper intermediate longitudinal rib (16); • in the second anti-short-circuit region (Rinf) called the lower contact plane region (Pcinf), the lower sheet (20) having a lower intermediate longitudinal rib (26), extending throughout the second anti-short-circuit region (Rinf); and the upper sheet (10) has an upper intermediate recess (14), superimposed on and in contact with the lower intermediate longitudinal rib (26); • characterized in that: • in the first anti-short-circuit region (Rsup), the lower plate (20) has: • a plurality of lower studs (25), projecting, in a direction opposite to the upper plate (10), opposite the lower intermediate recess (24) in which they are located, and having substantially equal dimensions along any two orthogonal axes in a plane parallel to the bipolar plate; • an absence of transverse ribs extending into the intermediate longitudinal zone (Zint) by joining the lower internal (22i) and external (22e) longitudinal ribs;and • in the second anti-short-circuit region (Rinf), the upper plate (10) has: • a plurality of upper studs (15), projecting, in a direction opposite to the lower plate (20), opposite the upper intermediate recess (14) in which they are located, and having substantially equal dimensions along any two orthogonal axes in a plane parallel to the bipolar plate; and • an absence of transverse ribs extending into the intermediate longitudinal zone (Zint) joining the inner (12i) and outer (12e) upper longitudinal ribs.

2. Bipolar plate (1) according to claim 1, comprising several first anti-short-circuit regions (Rsup) arranged alternately longitudinally with several second anti-short-circuit regions (Rinf).

3. Bipolar plate (1) according to claim 1 or 2, wherein the upper studs (15) are arranged longitudinally in a periodic manner, and the lower studs (25) are arranged longitudinally in a periodic manner.

4. Bipolar plate (1) according to any one of claims 1 to 3, wherein the upper (15) and lower (25) studs are distributed over at least two lines parallel to a longitudinal axis of the intermediate longitudinal zone (Zint).

5. Bipolar plate (1) according to any one of claims 1 to 4, wherein the upper (15) and lower (25) studs have a height substantially equal, respectively, to that of the upper (12i) and lower (22i) internal longitudinal ribs.

6. Bipolar plate (1) according to any one of claims 1 to 5, wherein the upper (15) and lower (25) studs have a circular or square base.

7. Bipolar plate (1) according to any one of claims 1 to 5, wherein the upper (15) and lower (25) studs are distinct respectively from the upper (12i) and lower (22i) internal longitudinal ribs, and, respectively, from the upper (12e) and lower (22e) external longitudinal ribs.

8. Bipolar plate (1) according to any one of claims 1 to 8, wherein the upper (12e) and lower (22e) external longitudinal ribs are each in contact with a sealing gasket (5).

9. Electrochemical cell, comprising at least the bipolar plate (1) according to any one of the preceding claims, and membrane / electrode assemblies (30), one in contact with the upper plate (10) and the other in contact with the lower plate (20).

10. Electrochemical cell according to claim 9, wherein an upper membrane / electrode assembly is in contact with the upper pads (15), and a lower membrane / electrode assembly is in contact with the lower pads (25).

11. Electrochemical reactor, comprising at least one electrochemical cell according to claim 9 or 10.

Images