Bipolar plate for a fuel cell, as well as a fuel cell comprising such bipolar plates and a method for manufacturing such a fuel cell

Abstract

Bipolar plate for a fuel cell, as well as a fuel cell comprising such bipolar plates and a method for manufacturing such a fuel cell. This bipolar plate comprises two plates, anodic and cathodic, provided with channels for the circulation of a reactive fluid. Figure for the abstract: Figure 4.

Description

Title of the invention: Bipolar plate for a fuel cell, as well as a fuel cell comprising such bipolar plates and a method for manufacturing such a fuel cell

[0001] The present invention relates to a bipolar plate of a fuel cell. It also relates to a fuel cell comprising such bipolar plates, as well as a method for manufacturing such a fuel cell.

[0002] A fuel cell is a device that generates electricity through an electrochemical reaction between a fuel, typically hydrogen, and an oxidant, typically oxygen from the air. This discussion focuses on fuel cells comprising several cells, each constituting an electrochemical generator, stacked one against the other along a specific stacking direction. Schematically, each cell comprises an anodic plate and a cathodic plate, extending perpendicularly to the stacking axis, with an electrolyte interposed between them. The invention is particularly applicable when the electrolyte is in the form of a proton exchange membrane (PEM).In such a case, the membrane is coated or in contact, on its side facing the anodic plate, with an anodic catalytic layer and, on its side facing the cathodic plate, with a cathodic catalytic layer. The assembly of the membrane and the anodic and cathodic catalytic layers, generally with gas diffusion layers arranged on each side of the membrane, forms a membrane-electrode assembly, usually designated by its acronym "MEA". Generally, the catalytic layer, cathodic and / or anodic, is deposited, for example by coating, printing, etc., either on the corresponding face of the membrane or on the face of the corresponding gas diffusion layer that faces the membrane.For each pair of two immediately adjacent cells, the anodic plate of one of the two cells in the pair and the cathodic plate of the other cell in the pair are directly applied to each other along the stacking axis and form a bipolar plate in its operational state. In some embodiments, in the operational state of the bipolar plate, the anodic and cathodic plates are fixed to each other, for example by welding, brazing, or bonding. In other embodiments, in the operational state of the bipolar plate, the anodic and cathodic plates are clamped together, notably by compression clamping imposed on the stack of cells in the battery. Each of the two plates, respectively anodic and cathodic, of . Each bipolar plate, on its face opposite the other plate, defines channels for the circulation of a reactive fluid, typically hydrogen and oxygen respectively. These channels are covered by the membrane-electrode assemblies belonging to the two cells sharing the bipolar plate. Between the two plates of each bipolar plate in its operational state, there are free passages for the circulation of a cooling fluid, such as glycol water.

[0003] The invention is more specifically concerned with bipolar plates in which the channels in which the reactive fluids, typically hydrogen and oxygen, circulate do not extend in length in a straight line but in a wavy manner, the channel undulations of each of the two plates of each bipolar plate being in opposite phase with the channel undulations of the other plate of the bipolar plate, as for example in US 7 781 122.The respective bottom walls of the channels in each of the two plates of each bipolar plate are designed to be generally flat so that, at the assembly interface between the two plates, they rest in substantially flat contact against the bottom walls of the other plate in the operational state of the bipolar plate. Due to the undulation of the channels and their phase opposition, the contact between the two plates of each bipolar plate is achieved through a multitude of contact zones, each of which is small and distributed across the assembly interface between the two plates. In principle, the overall pattern formed by these contact zones at the interface between the two plates of each bipolar plate is predictable since it depends on the geometric characteristics of the undulating bottom walls of the channels in each of the two plates and the relative positioning of these two plates in the operational state of the bipolar plate.This overall design allows for control of both the mechanical stability of the assembly of the two plates and the electrical connection between them: the aim is therefore generally to maximize the cumulative extent of the contact areas while ensuring their distribution at the contact interface. However, in practice, the relative positioning of the two plates in the operational state of the bipolar plate very often suffers from a tolerance much greater than the manufacturing tolerance of the corrugated channels of each plate, particularly because the stacking of the plates introduces a positioning uncertainty that is intrinsic to the fuel cell assembly operations.It follows that, in the operational state of each bipolar plate, the overall pattern actually formed by the contact areas at the interface between the two plates of the bipolar plate does not ultimately correspond to the overall pattern that was desired but, on the contrary, risks inducing degraded performance for the mechanical stability of the assembly of the two plates and / or for the electrical connection between them.

[0004] The object of the present invention is to propose a bipolar plate with corrugated channels in opposite phase, whose mechanical and electrical performance of the contact interface between the two plates of the bipolar plate is controlled despite the uncertainty of the assembly positioning between the two plates.

[0005] To this end, the invention relates to a bipolar plate for a fuel cell, comprising two plates, respectively anodic and cathodic, which, in the operational state of the bipolar plate, are applied against each other along a stacking axis. Each of the two plates delimits, on its face opposite the other plate, channels for the circulation of a reactive fluid, each of which has a bottom wall in contact with a bottom wall of a single channel of the other of the two plates.The bottom walls of the channels of each of the two plates form, in orthogonal projection onto the same geometric plane perpendicular to the stacking axis, respective undulations which, for each of the two plates (i) are identical and parallel to each other, being distributed regularly along a distribution axis and separated in pairs by a step, denoted p, the step of the undulations associated with the anodic plate being equal to the step of the undulations associated with the cathodic plate, and (ii), in the operational state of the bipolar plate, are in opposite phase with the undulations associated with the other of the two plates.Each of the undulations associated with each of the two plates defines a mean axis (i) which is perpendicular to the distribution axis, (ii) along which the undulation extends lengthwise while alternating on either side of the mean axis, and (iii) which, in a nominal configuration of the bipolar plate's operating state, coincides with one of the mean axes of the undulations associated with the other of the two plates.Each of the undulations associated with each of the two plates is delimited by two longitudinal edges which (i) are opposite each other along the distribution axis, (ii) are parallel to each other, separated from each other by a undulation width, the undulation width of the undulations associated with the anodic plate being denoted 11 while the undulation width associated with the cathodic plate is denoted 12, and (iii) define a neutral fiber of the undulation, which extends both parallel to and midway between the two longitudinal edges.Each of the undulations associated with each of the two plates includes, as longitudinal parts furthest from the mean axis along the distribution axis, first and second apex parts. The first apex parts are both arranged on the same first side of the mean axis of the undulation and aligned with each other in a direction parallel to the mean axis, while the second apex parts are both arranged on the same second side, opposite the first side, of the mean axis of the undulation and aligned with each other in a direction parallel to the mean axis. The undulations associated with the anodic plate and the undulations associated with the... cathode plates have the same offset, noted D, which corresponds to the spacing, along the distribution axis and measured at the level of the neutral fiber between the first summit parts and the second summit parts of each undulation, the offset being such that D = p + x with min(ll, 12) / 2 < x < (11 +12) / 2.

[0006] The operational state of the bipolar plate is that which is found when the battery is assembled and operational.

[0007] One of the ideas underlying the invention is to maximize the mechanical and electrical performance of the contact interface between the two plates of the bipolar plate, while taking into account a typical positioning tolerance between the two plates in the bipolar plate's operating state. To this end, the invention provides that the identical and parallel corrugations of the anodic plate and the identical and parallel corrugations of the cathodic plate are in opposite phase and have the same pitch, while being able to have a corrugation width that is either identical or different between the two plates.According to the invention, the offset of the anodic plate undulations and that of the cathodic plate undulations, which are the same, are provided to be equal to the sum between the aforementioned pitch and a predetermined value which is between, inclusive, half of the smaller of the two undulation widths and, inclusive, half of the sum of the two undulation widths.In a nominal configuration of the bipolar plate's operating state, in which the mean axes of the anodic plate's corrugations are respectively aligned, along the stacking direction of the two plates, with the mean axes of the cathodic plate's corrugations, the contact areas between the two plates at their assembly interface form an overall pattern that exhibits good mechanical and electrical performance: in particular, as described in more detail later, each crest of each corrugation of one of the two plates is applied against one of the crests of the corrugations of the other of the two plates, forming a double rhombus contact area whose two rhombuses are connected by a band whose minimum width is between zero and half of the larger of two corrugation widths.One of the advantages of the invention is to maintain these double-rhombus contact areas when the two plates of the bipolar plate are not, in the operating state, exactly in their nominal configuration but in a non-nominal configuration where the mean axes of the corrugations of the anodic plate are offset relative to the mean axes of the corrugations of the cathode plate. This offset is due to the usual positioning tolerance of the two plates during their assembly and is typically of the same order of magnitude as half the sum of the two corrugation widths. Thanks to the invention, regardless of the actual positioning difference between the two plates in the operating state of the bipolar plate, Within the limits of standard positioning tolerances, the offset prescribed by the invention ensures contact areas between the two plates that are both sufficiently large cumulatively to guarantee a good electrical connection between them, and sufficiently distributed at the interface between the two plates to ensure good mechanical stability of the plate assembly, and, consequently, good performance for a fuel cell comprising a stack of bipolar plates according to the invention. Furthermore, the control of the mechanical and electrical performance of the bipolar plate according to the invention is advantageously optimized by manipulating the geometric characteristics of the corrugations of the two plates, as described in more detail below.

[0008] Thus, by following additional advantageous characteristics of the bipolar plate according to the invention, taken individually or according to all technically possible combinations:

[0009] - The undulation width 11 of the undulations associated with the anodic plate is equal to the wave width 12 of the waves associated with the cathode plate.

[0010] - The undulation width 11 of the undulations associated with the anodic plate is strictly greater than the ripple width 12 of the ripples associated with the cathode plate.

[0011] - The undulation width 11 of the undulations associated with the anodic plate is strictly less than the ripple width 12 of the ripples associated with the cathode plate.

[0012] - Each of the undulations associated with each of the two plates comprises a pattern of undulation which (i) is identical between the undulations of each of the two plates, (ii) includes only one of the first apex parts and only one of the second apex parts of the undulation, and (iii) is repeated several times successively along the mean axis of the undulation to constitute the undulation.

[0013] - The wave pattern of each of the waves associated with each of the two The plate consists of a first segment and a second segment, which follow each other along the mean axis of the corrugation and are positioned on either side of the mean axis, respectively including the first and second apex parts of the corrugation pattern. The first segment has an axis of symmetry, which extends perpendicularly to the mean axis of the corrugation and passes through the first apex part of the corrugation pattern. The second segment is symmetrical to the first segment with respect to a point formed at the intersection between the mean axis and the neutral fiber of the corrugation.

[0014] - The first and second summit parts of each of the associated undulations Each of the two plates is curved.

[0015] - Each of the first and second apex parts of each of the undulations associated with each of the two plates follows a circular profile.

[0016] The invention also relates to a fuel cell, comprising bipolar plates, each of which is as defined above and which is stacked against each other in the stacking direction, with interposition of a membrane-electrode assembly between two successive bipolar plates.

[0017] The invention also relates to a method of manufacturing a fuel cell as defined above, in which before assembling the anodic and cathodic plates of each of the bipolar plates together, each of the membrane-electrode assemblies is assembled with one of the anodic plates and one of the cathodic plates, brought together on either side, along the stacking axis, of the membrane-electrode assembly concerned.

[0018] The manufacturing process according to the invention takes advantage of the fact that the mechanical and electrical performance of the fuel cell is guaranteed regardless of the actual positioning gap between the two plates of each bipolar plate during the assembly of the latter, within the limits of the usual positioning tolerance.

[0019] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the drawings in which: - [Fig.1] [Fig.1] is an exploded perspective view of a fuel cell according to the invention; - [Fig.2] [Fig.2] is a schematic partial section along plane II of the [Fig.l] ; - [Fig.3] [Fig.3] is a diagram illustrating channel undulations of one of the two plates of a bipolar plate, according to the invention, belonging to the fuel cell of figures 1 and 2; - [Fig.4] [Fig.4] is a view similar to [Fig.3], illustrating the superimposition the respective undulations of the two plates of the bipolar plate; - [Fig. 5] [Fig. 5] is a diagram of the contact zones between the two plates of the bipolar plate, resulting from the superposition of the undulations illustrated in [Fig.4]; - [Fig.6] [Fig.6] is a view similar to [Fig.4], illustrating a variant of dimensioning for the respective undulations of the two plates of the bipolar plate according to the invention; - [Fig.7] [Fig.7] is a view similar to [Fig.5] but applied to the super position of the undulations illustrated in [Fig.6]; - [Fig.8] [Fig.8] is a view similar to [Fig.4], illustrating another variant sizing for the respective undulations of the two plates of the bipolar plate according to the invention; and - [Fig.9] [Fig.9] is a view similar to [Fig.5] but applied to the super position of the undulations illustrated in [Fig.8].

[0020] Figure 1 shows a fuel cell 1. The fuel cell 1 is, for example, intended to be installed in a vehicle and to produce, from reactive fluids such as hydrogen and oxygen, electricity to power an electric motor providing propulsion for the vehicle.

[0021] The fuel cell 1 comprises a stack of cells 2, in which the cells 2 are arranged against each other along a stacking axis Z. The stack of cells 2 is held between two end plates, which are not shown in [Fig.1] and which in particular allow the stack of cells 2 to be kept compressed, i.e. tight, along the stacking axis Z, and to be supplied with both a reactive fuel fluid and a reactive oxidant fluid.According to a preferred example that will be used subsequently, the reactive fuel fluid consists of hydrogen in gaseous form and the reactive oxidant fluid consists of oxygen in gaseous form. It should be noted that, in practice, the fuel cell 1 may not be supplied with pure oxygen, but with air, or even with a gaseous mixture containing oxygen, for example, a mixture of oxygen and nitrogen, a mixture which may be in an oxygen-to-nitrogen ratio similar to that of air or in a different ratio. Here, the terms "oxygen" and "dioxygen" are used interchangeably; likewise, the terms "hydrogen" and "dihydrogen" are used interchangeably. For the sake of simplicity, the terms "oxygen" and "dioxygen" will also cover air or any gaseous mixture containing oxygen in a non-negligible proportion.

[0022] As shown in Figures 1 and 2, each cell 2 comprises a membrane-electrode assembly 10, a detail of a section of which is integrated into [Fig. 1].

[0023] Each cell 2 also comprises two polar plates arranged on either side, along the stacking axis Z, of the membrane-electrode assembly 10, namely an anodic plate 20 and a cathodic plate 30. For each cell 2, the anodic plate 20 supplies the cell 2 with hydrogen, while the cathodic plate 30 supplies this cell with oxygen. To this end, and as clearly visible in [Fig. 2], the anodic plate 20, on its face facing the membrane-electrode assembly 10, delimits channels 21 for the flow of hydrogen, while the cathodic plate 30, on its face facing the membrane-electrode assembly 10, delimits channels 31 for the flow of oxygen.For each pair of two cells 2 immediately adjacent to each other, the anodic plate 20 of one of the two cells and the cathodic plate 30 of the other of the two cells are arranged directly against each other along the stacking axis Z and form, in the operational state of the fuel cell 1, a bipolar plate 3. Thus, in the state . In the operational state of the fuel cell 1, the two cells 2 of each pair of immediately adjacent cells share the same bipolar plate 3, which separates the membrane-electrode assembly 10 of one of these two cells 2 from the membrane-electrode assembly 10 of the other of these two cells 2. In the operational state of each bipolar plate 3, the channels 21 are delimited by the face of the anodic plate 20 of the bipolar plate 3, facing away from the cathodic plate 30 of the bipolar plate 3, while the channels 31 are delimited by the face of the cathodic plate 30 of the bipolar plate 3, facing away from the anodic plate 20 of this bipolar plate 3. Also in the operational state of each bipolar plate 3, the anodic plate 20 and cathodic plate 30 of the plate bipolar 3 form between them free passages 4 for the circulation of a cooling fluid, separated from channels 21 and 31.The cooling fluid does not play a direct role in the electrochemical reactions occurring in cells 2, but the circulation of this cooling fluid allows the temperature of cells 2 to be controlled, therefore the temperature of the electrochemical reaction, and therefore the operating conditions of the electrochemical reaction.

[0024] In practice, each of the plates 20 and 30 is a shaped sheet metal piece, in particular stamped, made of metal. However, the invention can also be implemented with other embodiments of the plate, the latter being able to be made of other materials, in particular for example of graphite, and / or the latter being able to be shaped by means other than stamping, for example by machining, by chemical etching, electro-erosion, or by additive manufacturing.

[0025] Before describing the channels 21 and 31 in more detail, the structural and functional characteristics of the membrane-electrode assembly 10 of each cell 2 are described below, it being emphasized that the specifics of these characteristics are not limiting. Thus, in the embodiment shown in the figures, the membrane-electrode assembly 10 of each cell 2 comprises two gas diffusion layers 11 and 12 which are arranged on either side, along the stacking axis Z, of a proton exchange membrane 13 whose two opposite faces are respectively covered by, or in contact with, an anodic catalytic layer 14 and a cathodic catalytic layer 15.In the assembled state of the fuel cell 1, each cell 2 thus comprises, successively along the stacking axis Z, the anodic plate 20, the gas diffusion layer 11, the anodic catalytic layer 14, the proton exchange membrane 13, the cathodic catalytic layer 15, the gas diffusion layer 12, and the cathodic plate 30. .

[0026] For each cell 2, the gas diffusion layer 11 covers the channels 21 and allows the transport of hydrogen from the channels 21 of the anodic plate 20 to the anodic catalytic layer 14. Similarly, the gas diffusion layer 12 covers the channels 31 and allows the transport of oxygen from the channels 31 of the cathode plate 30 to the cathode catalytic layer 15. In practice, the gas diffusion layers 11 and 12 are formed of a porous material such as a carbon fiber fabric or porous carbon paper.

[0027] For each cell 2, the proton exchange membrane 13 conducts hydrogen ions, or protons, from the anodic catalytic layer 14 to the cathodic catalytic layer 15, while preventing the flow of electrons. The proton exchange membrane 13 is, for example, made of a perfluorinated sulfide polymer material, such as the material known by the trade name "Nafion". The proton exchange membrane 13 also allows the flow of water in liquid form, for the purpose of removing the water produced at the cathodic catalytic layer 15 from cell 2.

[0028] Within each cell 2, when the fuel cell 1 is operating, an oxidation reaction occurs at the catalytic anodic layer 14, consisting of the catalytic splitting of the hydrogen supplied by the gas diffusion layer 11 into protons and electrons. The protons thus produced pass through the proton exchange membrane 13 until they reach the catalytic cathodic layer 15, while the electrons thus produced are captured by the anodic plate 20 and then conducted to the cathodic plate 30 of the bipolar plate 3 to which the anodic plate 20 of the cell 2 in question belongs.At the same time, a reduction reaction occurs at the cathodic catalytic layer 15 and consists of reacting the oxygen supplied by the gas diffusion layer 12 with the protons crossing the proton exchange membrane 13, as well as with electrons supplied by the cathodic plate 30 of the cell 2 considered, to form water molecules.

[0029] In practice, the anodic catalytic layers 14 and cathodic 15 are made up of porous structures, which allow the transport of reactive fluids, i.e. here hydrogen and oxygen, inside these catalytic layers, and which are made of three different materials, namely:

[0030] - a material for transporting protons, for example the same material as the proton exchange membrane 13, such as the "Nafion" material mentioned above,

[0031] - a material for transporting electrons, for example carbon, and

[0032] - a material for catalyzing electrochemical oxidation and reactions reduction described above, for example of platinum.

[0033] In practice, the membrane-electrode assembly 10 of each cell 2, which is interposed between the anodic plates 20 and cathodic plates 30 of the cell 2 under consideration, also includes a support frame 40. Advantageously, the support frame 40 is formed of two superimposed films 16 bonded to each other, for example, films made of PET or PEN themselves in the form of a frame for which to delimit an internal window whose contour is slightly smaller than the contour of the proton exchange membrane 13, the contour of the latter being trapped, along the contour of the internal window, between the two films of the support frame 40.

[0034] Also, before describing channels 21 and 31 in more detail, it should be noted that, as schematically illustrated in [Fig. 1], the fuel cell 1 comprises a hydrogen inlet 50 supplying hydrogen to the anodic plates 20 and a hydrogen outlet 51 removing the hydrogen from the anodic plates 20. The fuel cell 1 also comprises an oxygen inlet 52 supplying oxygen to the cathodic plates 30 and an oxygen outlet 53 removing the oxygen from the cathodic plates 30. The fuel cell 1 also comprises a coolant inlet 54 supplying coolant to the bipolar plates 3 and a coolant outlet 55 removing the coolant from the bipolar plates 3.In the embodiment illustrated in the figures, the inlets 50, 52 and 54, as well as the outlets 51, 53 and 55, are formed by openings in the anodic plates 20, the cathodic plates 30 and the support frames 40. In practice, these inlets and outlets are connected to corresponding openings in one of the two aforementioned terminal plates, which are themselves connected to circuits supplying hydrogen, oxygen and coolant. In an alternative, not shown, these inlets and outlets are formed by conduits around the stack of cells 2, in a dedicated housing of the fuel cell 1.

[0035] As schematically represented in [Fig. 1], each cathode plate 30 has three adjacent zones which successively connect the oxygen inlet 52 to the oxygen outlet 53, namely a homogenization zone 30A, an active zone 30B which is connected to the oxygen inlet 52 by the homogenization zone 30A, and a homogenization zone 30C connecting the active zone 30B to the oxygen outlet 53. The channels 31 of the cathode plate 30 extend lengthwise over the entire active zone 30B, each connecting the homogenization zone 30A to the homogenization zone 30C. The active zone 30B has substantially the same dimensions as the window delimited by the support frame 40 of the membrane-electrode assembly 10 of the cell 2 to which the cathode plate 30 in question belongs, and it is generally expected that the gas diffusion layer 12 will completely cover at least the active zone 30B.The homogenization zones 30A and 30C, which connect the oxygen inlet 52 and oxygen outlet 53 respectively to the active zone 30B, allow the oxygen to be distributed over the entire transverse extent of the active zone 30B, i.e. throughout all the channels 31.

[0036] Each anodic plate 20 has an active zone and two zones homogenization zones, which are respectively similar to the active zone 30B and the homogenization zones 30A and 30C of each cathode plate 30: the two homogenization zones of each anodic plate connect to the active zone of this anodic plate respectively the hydrogen inlet 50 and the hydrogen outlet 51 and allow the hydrogen to be distributed over the entire transverse extent of this active zone, that is to say in all the channels 21 extending lengthwise over the entire active zone, from one to the other of the two homogenization zones.

[0037] In the embodiment shown in the figures, the bipolar plates 3 and the support frames 40 have a rectangular peripheral contour. In addition, the hydrogen inlet 50 and the hydrogen outlet 51 are located diagonally to each other, while the oxygen inlet 53 and the oxygen outlet 53 are also located diagonally to each other, which makes it possible to obtain a more homogeneous distribution of the reactive fluids on the respective active areas of the anodic plates 20 and cathodic plates 30.

[0038] We will now look in more detail at the structural and dimensional characteristics of the channels 21 of the anodic plates 20 and the channels 31 of the cathodic plates 30, based on figures 2 to 9. It will be noted that these characteristics differ between the embodiment illustrated in figures 4 and 5, the embodiment illustrated in figures 6 and 7, and the embodiment in figures 8 and 9, as explained later.

[0039] As schematically represented in [Fig.2], the channels 21 of each anodic plate 20 are, along their entire length, separated in pairs by tooth walls 22 belonging to the anodic plate 20. In the assembled state of the fuel cell to which the anodic plate 20 belongs, these tooth walls 22 are in total applied, along the stacking axis Z, directly against the membrane-electrode assembly 10 of the cell 2 concerned, more precisely against the gas diffusion layer 11 of this membrane-electrode assembly 10.Similarly, the channels 31 of each cathode plate 30 are, along their entire length, separated in pairs by tooth walls 32 belonging to the cathode plate 30: in the assembled state of the cell 2 to which the cathode plate 30 belongs, the tooth walls 32 are fully applied, along the stacking axis Z, directly against the membrane-electrode assembly 10 belonging to the cell 2 concerned, more precisely to the gas diffusion layer 12 of this membrane-electrode assembly 10. In practice, the tooth walls 22 and 32 are each substantially flat, within manufacturing tolerances.

[0040] Also as schematically represented in [Fig. 2], each of the canals 21 is delimited, along its entire length, by both a bottom wall 23 and a lateral wall 24 which connects the bottom wall 23 to one of the two tooth walls 22 adjacent to the canal 21 considered, and a lateral wall 25 which connects the bottom wall 23 to the other of the two aforementioned tooth walls 22. The bottom wall 23 and the lateral walls 24 and 25 belong to the anodic plate 20. Similarly, each of the canals 31 is delimited, along its entire length, by a bottom wall 33, a lateral wall 34 and a lateral wall 35, all of which belong to the cathodic wall 30, the lateral wall 24 connecting the bottom wall 23 to one of the two tooth walls 32 adjacent to the canal 31 considered while the lateral wall 25 connects the bottom wall 23 to the other of these two tooth walls 32.In the operational state of each bipolar plate 3, the bottom walls 23 of the anodic plate 20 belonging to the bipolar plate 3 in question are in direct contact, along the stacking axis Z, against the bottom walls 33 of the cathodic plate 30 belonging to the bipolar plate 3 in question, forming contact zones C3 between the anodic plate 20 and the cathodic plate 30. In practice, for this purpose, the bottom walls 23 and 33 are substantially flat, so that, at the contact zones C3, these bottom walls 33 and 23 are in substantially planar contact. For each bipolar plate 3, the contact areas C3 are arranged in a geometric plane ir which is perpendicular to the stacking axis Z. The free passages 4, which are formed between the anodic plates 20 and cathodic plates 30 of each bipolar plate 3 for the circulation of the cooling fluid, extend in the extent of the geometric plane ji, outside the contact areas C3.

[0041] As illustrated very schematically for channels 31 in [Fig.1], the channels . 21 and 31 do not extend in a straight line lengthwise, but in a wavy fashion, at least over a major part of their length. Indeed, it can be predicted that the channels, particularly at their connection ends with the homogenization zones, include segments, especially end segments, whose geometry differs from the geometry they exhibit in a main segment, particularly a central segment extending between these possible end segments. The geometry of such main segments of the channels is considered below. More precisely, for each of the bipolar plates 3, the bottom walls 23 and the bottom walls 33 form, in orthogonal projection onto the geometric plane ji, respective undulations 26 and 36: on [Fig. 3], whose plane corresponds to the geometric plane ji, two of the undulations 26 are shown alone, while on [Fig. 3], the two undulations 26 are shown together.[4], whose plane also corresponds to the geometric plane ji, represent both several of the undulations 26 and several of the undulations 36 in the operational state of the corresponding bipolar plate 3. It is understood that, in [Fig. 4], the regions of the geometric plane ji, at which the undulations 26 of the anodic plate 20 and the undulations 36 of the cathodic plate 30 overlap, correspond to the contact zones C3. In [Fig. 5], whose plane also corresponds to the geometric plane ji, only the contact zones C3 and . They are greyed out for better visualization. As detailed below, we will distinguish, among the C3 contact zones, on the one hand, summit contact zones C3.1, and on the other hand, axial contact zones C3.X.

[0042] As clearly visible in Figures 3 and 4, for each bipolar plate 3, the undulations 26 of a given bipolar plate 3 are identical to each other and parallel to each other, being distributed in the geometric plane ir in a regular manner along a distribution axis Y26. These undulations 26 are thus separated in pairs by a constant pitch, which is denoted p in Figures 2, 3, 4, 6 and 8. Similarly, for each bipolar plate 3, the undulations 36 of a bipolar plate 3 are identical to each other and parallel to each other, being distributed in the geometric plane ir in a regular manner along a distribution axis Y36 which, in the operational state of the bipolar plate 3, is, within positioning tolerances, coincident with the distribution axis Y26. The undulations 36 are thus separated two by two by a constant step, which is equal to the step p of the undulations 26 and which is therefore also noted p on figures 2, 4, 6 and 8.

[0043] As can be clearly seen in Figures 4, 6 and 8, for each bipolar plate 3, the undulations 26 of the anodic plate 20 of a given bipolar plate 3 are, in the operational state of the bipolar plate 3, in opposite phase with the undulations 36 of the cathodic plate of said given bipolar plate 3.

[0044] As shown in Figures 3, 4, 6, and 8, for each bipolar plate 3, each of the undulations 26 of the anodic plate 20 defines a mean axis X26, which is perpendicular to the distribution axis Y26 and along which the corresponding undulation 26 extends lengthwise while alternating on either side of this mean axis X26. The respective mean axes X26 of the undulations 26 all lie in the geometric plane ir and are parallel to each other. Similarly, for each bipolar plate 3, each of the undulations 36 of the cathodic plate 30 defines a mean axis X36, which is perpendicular to the distribution axis Y36 and along which the corresponding undulation 36 extends lengthwise while alternating on either side of the mean axis X36. The respective mean axes X36 all belong to the geometric plane ir and are parallel to each other.In the operational state of each bipolar plate 3, the mean axes X26 and the mean axes X36 are parallel to each other: more precisely, in a nominal configuration of the operational state of the bipolar plate 3 concerned, the mean axes X26 are respectively coincident with the mean axes X36, as illustrated in figures 4, 6 and 8. Conversely, in a non-nominal configuration of this operational state, resulting from a usual relative positioning tolerance which is intrinsic to the manufacture of each bipolar plate 3 by stacking the anodic plates 20 and cathodic plates 30 of the latter, the mean axes X26 are not coincident with the mean axes X36, but are offset from the latter. along the distribution axes Y26 and Y36, the corresponding offset is referred to as ô in what follows. The value of this offset ô is in any case strictly less than half of the pitch p which is common to both the 26 undulations and the 36 undulations, preferably strictly less than a quarter of this pitch p.

[0045] In all cases, it will therefore be possible to define two undulations 26 and 36, one belonging to the anodic plate 20 and the other belonging to the cathode plate 30, as being two corresponding undulations of the bipolar plate 3, when the mean axis X26 of one is coincident with the mean axis X36 of the other, or when their mean axes X26, X36 are offset from each other by an offset less than half of the pitch p which is common on the one hand to the undulations 26 of the anodic plate 20 and on the other hand to the undulations 36 of the cathode plate 30, preferably strictly less than a quarter of this pitch p.

[0046] Since the undulations 26 of the anodic plate 20 of a given bipolar plate 3 are, in the operational state of the bipolar plate 3, in opposite phase with the undulations 36 of the cathodic plate 30 of said given bipolar plate 3, each undulation 26 of the anodic plate 20 and the corresponding undulation 36 of the cathodic plate 30 necessarily cross at their mean axis to form, among the contact zones 3, the axial contact zones C3.X.

[0047] As illustrated in figures 3 and 4, for each bipolar plate 3, each of the undulations 26 of the anodic plate 20 is delimited, along its entire length, by two longitudinal edges 26A and 26B, which are opposite each other along the distribution axis Y26 and which, here, undulate each on either side of the mean axis X26 of the undulation 26 concerned. These longitudinal edges 26A and 26B are parallel to each other, being separated from each other by a width of the corresponding undulation 26, denoted 11 in figures 2, 3, 4, 6 and 8. Insofar as the undulations 26 are identical to each other, the width 11 is the same for all the undulations 26 and, for each of these undulations 26, is constant over the entire length of the undulation.It is thus possible to define, for each of the undulations 26 of the anodic plate 20 of each bipolar plate 3, a neutral fiber 26C as being the undulating line which extends both parallel to and midway between the two longitudinal edges 26A and 26B of the undulation 26 concerned.

[0048] Similarly, and as illustrated in [Fig. 4], for each bipolar plate 3, each of the undulations 36 of each cathode plate 30 is delimited, along its entire length, by two longitudinal edges 36A and 36B, which are opposite each other along the distribution axis Y36 and which, here, undulate on either side of the mean axis X36 of the undulation 36 in question. These longitudinal edges 36A and 36B are parallel to each other, separated from each other by a width of the corresponding undulation 36, denoted 12 in Figures 2, 3, 4, 6 and 8. Insofar as the on The 36 undulations are identical to each other, the width 12 is the same for all the undulations 36 and, for each of these undulations 36, is constant over the entire length of the undulation. It is thus possible to define, for each of the undulations 36, the cathode plate 30 of each bipolar plate 3, a neutral fiber 36C as the undulating line that extends both parallel to and midway between the two longitudinal edges 36A and 36B of the undulation 36 in question.

[0049] It should be noted that the width 11 and the width 12 are equal to each other in both the embodiment illustrated in Figures 4 and 5 and in the embodiment illustrated in Figures 6 and 7. On the other hand, in the embodiment illustrated in Figures 8 and 9, the width 11 is different from the width 12: here, the width 11 is strictly greater than the width 12; however, in an alternative not shown, the width 11 can be provided to be strictly less than the width 12.

[0050] As illustrated in Figures 3, 4, 6, and 8, each of the corrugations 26 of each anodic plate 20 includes, as longitudinal portions furthest from the mean axis X26 of the corrugation 26 in question along the distribution axis Y26, both first apex portions 26.1, which are arranged on the same first side of the mean axis X26, and second apex portions 26.2, which are arranged on the same second side, opposite the aforementioned first side, of the mean axis X26. The apex portions 26.1 of each corrugation 26 are aligned with each other in a direction parallel to the mean axis X26 in question. Similarly, the apex portions 26.2 are aligned with each other in a direction parallel to the mean axis X26 in question.Similarly, and as illustrated in Figures 4, 6, and 8, each of the corrugations 36 of each cathode plate 30 includes, as longitudinal portions furthest from the mean axis X36 of the corrugation 36 in question along the distribution axis Y36, both first apex portions 36.1, which are arranged on the same first side of the mean axis X36, and second apex portions 36.2, which are arranged on the same second side, opposite the aforementioned first side, of the mean axis X36. The apex portions 36.1 of each corrugation 36 are aligned with each other in a direction parallel to the mean axis X36 in question. Likewise, the apex portions 36.2 are aligned with each other in a direction parallel to the mean axis X36 in question.

[0051] According to a preferred embodiment, which is implemented in the embodiments illustrated in the figures and which have, among other advantages, the simplification of the design and manufacture of the anodic plates 20 and cathodic plates 30 of each bipolar plate 3, each of the undulations 26, respectively 36, of each anodic plate 20, respectively cathodic plate 30, consists of the repetition of a undulation pattern M26, respectively M36. More precisely, the undulation pattern M26, which is identical here for the different undulations 26 of each anodic plate 20, includes only one of the first apex parts 26.1 and only one of the second apex parts 26.2, and is repeated several times successively along the mean axis X26 of each undulation 26 to constitute the entirety of the latter. Similarly, the undulation pattern M36, which is identical here for the different undulations 36 of each cathode plate, includes only one of the first apex parts 36.1 and only one of the second apex parts 36.2, and is repeated several times successively along the mean axis X36 of each undulation 36 to constitute, in some examples, the entirety of the latter.

[0052] In order to further simplify the design and manufacture of the anode 20 and cathode 30 plates of each bipolar plate 3, the wave pattern M26, respectively M36, is preferably made up of two sections which follow each other along the mean axis X26, respectively X36, and which are arranged on either side of this mean axis, namely a first section M26.1, respectively M36.1, which includes the first summit part 26.1, respectively 36.1, of the wave pattern M26, respectively M36, and a second section M26.2, respectively M36.2, which includes the second summit part 26.2, respectively 36.2, of the wave pattern M26, respectively M36. The first segment M26.1, respectively M36.1, thus includes, in addition to the first summit part 26.1, respectively 36.1, of the undulation pattern M26, respectively M36, two longitudinal parts 26.3 and 26.4 of the corresponding undulation 26, respectively 36.3 and 36.4 of the corresponding undulation 36, which each connect the first apex part 26.1, respectively 36.1, to the mean axis X26, respectively X36, of the corresponding undulation. Similarly, the second segment M26.2, respectively M36.2 includes, in addition to the second apex part 26.2, respectively 36.2, of the undulation pattern M26, respectively M36, two longitudinal parts 26.5 and 26.6 of the corresponding undulation 26, respectively 36.5 and 36.6 of the corresponding undulation 36, which each connect the second apex part 26.2, respectively 36.2, to the mean axis X26, respectively X36, of the corresponding undulation. The longitudinal parts 26.4 and 26.5, respectively 36.4 and 36.5, connect directly to each other, at the level of the mean axis X26, respectively X36. The first section M26.1, respectively M36.1, has an axis of symmetry YM26.1, respectively YM36.1, which extends perpendicularly to the mean axis X26 of the corresponding undulation 26, respectively X36 of the corresponding undulation 36, and which passes through the first apex part 26.1 of the undulation pattern M26, respectively 36.1 of the undulation pattern M36: this axis of symmetry YM26.1, respectively YM36.1, constitutes an axis of symmetry for the first apex part 26.1, respectively 36.1, and the longitudinal parts 26.3 and 26.4, respectively 36.3 and 36.4, are symmetrical to each other with respect to this axis of symmetry YM26.1, respectively YM36.1. Furthermore, . the second segment M26.2, respectively M36.2, is symmetrical to the first segment M26.1, respectively M36.1, with respect to a point OM26, respectively OM36, which is formed at the intersection between the corresponding mean axis X26, respectively X36, and the corresponding neutral fiber 26C, respectively 36C: thus, the longitudinal part 26.5, respectively 36.5, is symmetrical to the longitudinal part 26.4, respectively 36.4, with respect to this point of symmetry OM26, respectively OM36; the second summit part 26.2, respectively 36.2, is symmetrical to the summit part 26.1, respectively 36.1, with respect to this point of symmetry OM26, respectively OM36; and the longitudinal part 26.6, respectively 36.6, is symmetrical to the longitudinal part 26.3, respectively 36.3, with respect to this point of symmetry OM26, respectively OM36.

[0053] In all cases, each undulation 26 of each anodic plate 20 has an offset, noted D in figures 3, 4, 6 and 8, this offset D corresponding to the spacing, along the distribution axis Y26 and measured at the level of the neutral fiber 26C of the undulation 26 concerned, between the first summit parts 26.1 and the second summit parts 26.2 of the undulation 26 concerned. Since the undulations 26 of the anodic plate 20 are identical to each other, this offset D is the same for all the undulations 26. In the same way, each undulation 36 of each cathodic plate 20 has an offset corresponding to the spacing, along the distribution axis Y36 and measured at the level of the neutral fiber 36C of the undulation 36 concerned, between the first summit parts 36.1 and the second summit parts 36.2 of the ripple 36 concerned: this offset of the ripples 36 of the cathode plate 30, which is the same for all the ripples 36 since the latter are identical to each other, is the same as the offset D of the ripples 26 of the anode plate 20. and is therefore also noted D on figures 4, 6 and 8. .

[0054] This offset D of the undulations 26 and 36 of each bipolar plate 3 is dimensioned so as to respect the following relationship:

[0055] D = p + x with min(ll, 12) / 2 < x < (11 +12) / 2.

[0056] In other words, the offset D is equal to the sum of the pitch p and a predetermined value x which is between, inclusive, half of the smaller of the widths 11 and 12 and, inclusive, half of the sum of the widths 11 and 12.

[0057] In the embodiment shown in Figures 4 and 5, where the widths 11 and 12 are equal, the offset D is chosen to be equal to the sum of the pitch and half of the width 11 or 12. In other words, D = p + ll = p + 12.

[0058] In the embodiment shown in Figures 6 and 7, where the widths 11 and 12 are also equal to each other, the offset D is chosen to be equal to the sum of the pitch p and the width 11 or 12. In other words, D = p + 11 / 2 = p + 12 / 2.

[0059] In the embodiment shown in Figures 8 and 9, where one of the widths, here width 11, is strictly greater than the other width, here width 12, with the larger of the two widths, here therefore width 11, strictly greater than the smaller of the two widths, here width 12, the offset D is chosen equal to the sum between the pitch p and half of the smaller width 12. In other words, D = p + 12 / 2.

[0060] In all cases, the above relationship allows, in the nominal configuration of the operating state of each bipolar plate 3, and for all the undulations 26 of the anodic plate 20 with the exception of the end undulations 26 along the distribution axis Y26, to bring into contact the summit parts 26.1 of each undulation 26 of the anodic plate 20 with respectively the summit parts 36.2 of an adjacent undulation 36 of the cathodic plate 30, and to bring into contact the summit parts 26.2 of the same undulation 26 of the anodic plate 20 with respectively the summit parts 36.1 of another adjacent undulation 36 of the cathodic plate 30, forming between them summit contact zones C3.1 among the contact zones C3.For a given undulation 26 of the anodic plate 20, the two adjacent undulations 36 of the cathodic plate 30 are the two undulations that are immediately adjacent to the corresponding undulation 36 of the cathodic plate 30 as defined above, namely having the mean axis X36 coincide with the mean axis X26 of the given undulation 26 or exhibiting an offset strictly less than half the undulation pitch p.

[0061] Conversely, the above relationship allows, in the nominal configuration of the operating state of each bipolar plate 3, and for all the undulations 36 of the cathode plate 30 except for the end undulations 36 along the distribution axis Y36, to bring the summit parts 36.1 of each undulation 36 of the cathode plate 30 into contact with respectively the summit parts 26.2 of an adjacent undulation 26 of the anode plate 20, and to bring the summit parts 36.2 of the same undulation 36 of the cathode plate 30 into contact with respectively the summit parts 26.1 of another adjacent undulation 26 of the anode plate 20, forming between them summit contact zones C3.1 among the contact zones C3.For a given undulation 36 of the cathode plate 30, the two adjacent undulations 26 of the anode plate 20 are the two undulations 26 that are immediately adjacent to the corresponding undulation 26 of the anode plate 20 as defined above, namely having the mean axis X26 coincide with the mean axis X36 of the given undulation 36 or exhibiting an offset strictly less than half the undulation pitch p.

[0062] More specifically, it is noted that each given undulation 26 of the anodic plate 20, with the exception of the end undulations 26 along the distribution axis Y26, is thus in contact with exactly 3 distinct undulations 36 of the cathodic plate 30, namely: - with the corresponding undulation 36 of the cathode plate 30, to form the axial contact zones C3.X for this given undulation 26; - with a first convection 36 adjacent to the cathode plate 30, at the level of its summit parts 26.1, to form half of the summit contact zones C3.1 for this given convection 36; - and with a second convection 36 adjacent to the cathode plate 30, at the level of its summit parts 26.2, to form the other half of the summit contact zones C3.1 for this given convection 26.

[0063] Conversely, each given undulation 36 of the anodic plate 30, with the exception of the end undulations 36 along the distribution axis Y36, is thus in contact with exactly 3 distinct undulations 26 of the anodic plate 20, namely: - with the corresponding undulation 26 of the anodic plate 20, to form the axial contact zones C3.X for this given undulation 36; - with a first convection 26 adjacent to the anodic plate 30, at the level of its summit parts 36.1, to form half of the summit contact zones C3.1 for this given convection 36; - and with a second convection 36 adjacent to the cathode plate 30, distinct from the first, at the level of its summit parts 36.2, to form the other half of the summit contact zones C3.1 for this given convection 36.

[0064] Particularly advantageously, the above relationship ensures that, for each undulation 26 of the anodic plate 20 and each undulation 36 of the cathodic plate 30, there is necessarily a summit contact zone C3.1 between two immediately successive axial contact zones C3.X. Thus, with the exception of the end undulations 26, 36 along the distribution axis Y26, Y36, there is no summit zone that is not in contact with an undulation of the opposite plate.

[0065] As clearly visible in Figures 5, 7, and 9, each of the summit contact zones C3.1 has a double rhombus shape, comprising two rhombuses and a band connecting the two aforementioned rhombuses, the minimum width of which is between zero, as in the embodiment shown in Figures 4 and 5, and half the greater of the two widths 11 and 12, as in the embodiment shown in Figures 6 and 7, as well as in the embodiment shown in Figures 8 and 9. It should be noted that the term "rhombus" used here is not understood in its strict geometric sense, but rather as a shape descriptor. In the event that the operational state of one of the bipolar plates 3 is not in its nominal configuration, the offset mentioned above does not prevent the formation of the summit contact zones C3.1, even if the effective contour of each of these summit contact zones C3.1 differs somewhat from the double diamond shape described above for the nominal configuration, . since this offset ô is of the same order of magnitude as the widths 11 and 12, typically being worth the min (11,12) value of the smaller of the width 11 and the width 12. In this regard, by way of non-limiting example, the widths 11 and 12 are typically between 0.1mm and 1 mm, preferably between 0.1 and 0.5 mm, while the usual positioning tolerance between the anodic plates 20 and cathodic plates 30 of each bipolar plate 3 induces a value of about 0.15 mm for the offset ô.

[0066] Thus, and more generally, by applying the above relationship, we guarantee the obtaining of the contact zones C3, in particular the summit contact zones C3.1 and we control in this way the mechanical and electrical performance at the contact interface between the anodic plates 20 and cathodic plates 30 of each bipolar plate 3, regardless of the actual positioning of these two plates during their assembly within the limits of the usual positioning tolerance.

[0067] In practice, to control the value of the offset D, one can play on various geometric characteristics of the undulations 26 and 36 of each bipolar plate 3. According to a possibility which is both practical, efficient and economical, which is implemented here, the apex parts 26.1 and 26.2 of each undulation 26, respectively 36.1 and 36.2 of each undulation 36, are each curved, preferably following a circular profile: in this way, one can play on the radius of curvature of these apex parts 26.1 and 26.2, respectively 36.1 and 36.2, it being noted that the apex parts 26.1, respectively 36.1, have a concavity which is opposite to that of the apex parts 26.2, respectively 36.2. That being said, other possibilities are conceivable: as examples not shown, the summit parts 26.1 and 26.2, respectively 36.1 and 36.2, are each curved but following a sinusoidal profile, or these summit parts 26.1 and 26.2, respectively 36.1 and 36.2, are each straight, following a flat profile.

[0068] Taking into account the explanations given so far, it is understood that the fuel cell 1 is preferably manufactured by first bringing one of the anodic plates 20 and one of the cathodic plates 30 to either side, along the stacking axis Z, of each of the membrane-electrode assemblies 10, so as to form the different cells 2, and then assembling the anodic plates 20 and cathodic plates 30 of each bipolar plate 3 together. That being said, other possibilities are conceivable for manufacturing the fuel cell 1. In general, the anodic plates 20 and cathodic plates 30 of each bipolar plate 3 can be assembled to each other in different ways, including by brazing, welding, gluing, or by simple compression assembly of the stack of cells.

[0069] Finally, various modifications and variations to the bipolar plate 3 and the fuel cell 1 described so far are conceivable. For example, the different variants having been mentioned in different places in the description above can be combined with each other, at least partially.

Claims

Demands

1. Bipolar plate (3) for a fuel cell (1), comprising two plates, respectively anodic (20) and cathodic (30), which, in the operational state of the bipolar plate (3), are applied against each other along a stacking axis (Z), in which each of the two plates (20, 30) delimits, on its face opposite the other plate, channels (21, 31) for the circulation of a reactive fluid, which each have a bottom wall (23, 33) in contact with a bottom wall (33, 23) of a single channel (31, 21) of the other of the two plates, in which the bottom walls (23, 33) of the channels (21, 31) of each of the two plates (20, 30) form, in orthogonal projection onto the same geometric plane (jt) perpendicular to the stacking axis (Z), respective undulations (26, 36) which, for each of the two plates (20, 30): - are identical and parallel to each other, being regularly distributed along a distribution axis (Y26, Y36) and separated in pairs by a pitch, denoted p, the pitch of the undulations (26) associated with the anodic plate (20) being equal to the pitch of the undulations (36) associated with the cathode plate (30), and - in the operational state of the bipolar plate (3), are in opposite phase to the undulations associated with the other of the two plates, in which each of the undulations (26, 36) associated with each of the two plates (20, 30) defines a mean axis (X26, X36): - which is perpendicular to the distribution axis (Y26, Y36), - along which the undulation extends lengthwise while alternating on either side of the mean axis, and - which, in a nominal configuration of the operating state of the bipolar plate (3), coincides with one of the mean axes of the undulations associated with the other of the two plates, in which each of the undulations (26, 36) associated with each of the two plates (20, 30) is delimited by two longitudinal edges (26A, 26B, 36A, 36B) which: - are opposite each other along the distribution axis (Y26, Y36), - are parallel to each other, separated from each other by a wave width, the wave width of the waves (26) associated with the anodic plate (20) being denoted 11 while the width undulations (36) associated with the cathode plate (30) is noted 12, and - define a neutral fiber (26C, 36C) of the undulation (26, 36), which extends both parallel and midway between the two longitudinal edges, in which each of the undulations (26, 36) associated with each of the two plates (20, 30) includes, as longitudinal parts furthest from the mean axis (X26, X36) along the distribution axis (Y26, Y36), first and second apex parts, the first apex parts (26.1, 36.1) being both arranged on the same first side of the mean axis of the undulation and aligned with each other along a direction parallel to the mean axis, while the second apex parts (26.2, 36.2) are both arranged on the same second side, opposite to the first side, of the mean axis of the undulation and aligned with each other in a direction parallel to the mean axis, and in which the undulations (26) associated with the anodic plate (20) and the undulations (36) associated with the cathodic plate (30) have the same offset, noted D, which corresponds to the spacing, along the distribution axis (Y26, Y36) and measured at the level of the neutral fiber (26C, 36C), between the first summit parts (26.1, 36.1) and the second summit parts (26.2, 36.2) of each undulation, the offset being such that D = p + x with min(11, 12) / 2 < x < (11 + 12) / 2.

2. Bipolar plate according to claim 1, wherein the wave width 11 of the waves (26) associated with the anodic plate (20) is equal to the wave width 12 of the waves (36) associated with the cathodic plate (30).

3. Bipolar plate according to claim 1, wherein the wave width 11 of the waves (26) associated with the anodic plate (20) is strictly greater than the wave width 12 of the waves (36) associated with the cathodic plate (30).

4. Bipolar plate according to claim 1, wherein the wave width 11 of the waves (26) associated with the anodic plate (20) is strictly less than the wave width 12 of the waves (36) associated with the cathodic plate (30).

5. Bipolar plate according to any one of the preceding claims, wherein each of the corrugations (26, 36) associated with each of the two plates (20, 30) comprises a corrugation pattern (M26, M36) which: - is identical between the undulations of each of the two plates, - includes only one of the first summit parts (26.1, 36.1) and only one of the second summit parts (26.2, 36.2) of the undulation, and - is repeated several times successively along the mean axis (X26, Y26) of the undulation to constitute the undulation.

6. Bipolar plate according to claim 5, wherein the corrugation pattern (M26, M36) of each of the corrugations (26, 36) associated with each of the two plates (20, 30) consists of a first segment (M26.1, M36.1) and a second segment (M26.2, M36.2), which follow one another along the mean axis (X26, X36) of the corrugation and which are arranged on either side of the mean axis of the corrugation, respectively including the first apex portion and the second apex portion of the corrugation pattern, wherein the first segment (M26.1, M36.1) has an axis of symmetry (YM26.1), which extends perpendicularly to the mean axis (X26, X36) of the corrugation (26, 36) and which passes through the first summit part (26.1, 36.1) of the wave pattern (M26, M36), and in which the second segment (M26.2, M36.2) is symmetrical to the first segment (M26.1, M36.1) with respect to a point (OM26) formed at the intersection between the mean axis (X26, X36) and the neutral fiber (26C, 36C) of the undulation (26, 36).

7. Bipolar plate according to any one of the preceding claims, wherein the first and second summit parts (26.1, 26.2, 36.1, 36.2) of each of the undulations (26, 36) associated with each of the two plates (20, 30) are each curved.

8. Bipolar plate according to claim 7, wherein each of the first and second summit parts (26.1, 26.2, 36.1, 36.2) of each of the undulations (26, 36) associated with each of the two plates (20, 30) follows a circular profile.

9. Fuel cell (1), comprising bipolar plates (3), each of which conforms to any one of the preceding claims and which are stacked against each other along the stacking direction (Z), with interposition of a membrane-electrode assembly (10) between two successive bipolar plates.

10. A method for manufacturing a fuel cell (1) according to claim 9, wherein, before assembling the anodic (20) and cathodic (30) plates of each of the bipolar plates (3), each of the membrane-electrode assemblies (10) is assembled with one of the anodic plates (20) and one of the cathodic plates (30), brought together on either side, along the stacking axis (Z), of the membrane-electrode assembly concerned.

Images