Separator plate, electrochemical cell and electrochemical device

Abstract

The separator plate (15, 17) comprises: - an active zone (39); - a homogenization zone (43); - an intermediate zone (45) positioned longitudinally between the active zone (39) and the homogenization zone (43); the homogenization zone (43) of the separator plate (15, 17) having a homogenization end wall (51) at a first altitude (a1); the intermediate zone (45) of the separator plate (15, 17) having an intermediate end wall (55) at a second altitude (a2) greater than the first altitude (a1), the intermediate end wall (55) being separated from the homogenization end wall (51) by a step (59); a buffer volume (60) for equalizing the distribution of the reactive fluid arriving from the homogenization zone (43) in the active channels (41) being defined between the intermediate end wall (55), the step (59) and the end of the active teeth.

Description

[0001] TITLE: Separator plate, electrochemical cell and electrochemical device

[0002] The invention relates generally to an electrochemical device, in particular a fuel cell, more particularly an electrochemical cell, or a separator plate intended to be used in said electrochemical device.

[0003] This electrochemical device is of the type comprising a plurality of electrochemical cells stacked in a stacking direction.

[0004] Each electrochemical cell comprises:

[0005] - a membrane-electrode assembly (MEA) comprising a membrane, catalytic layers arranged on two large opposite faces of the membrane, and two gas diffusion layers arranged on the catalytic layers;

[0006] - a frame, internally delimiting a window in which the membrane-electrode assembly is fixed;

[0007] - two separating plates pressed against the two gas diffusion layers.

[0008] The separating plates have openings for the circulation of reactive fluids. Each plate also has an active zone opposite the window, comprising longitudinal channels for the circulation of one of the reactive fluids.

[0009] The separating plate has at its two opposite longitudinal ends homogenization zones putting the channels of the active zone into fluid communication with the circulation openings of said reactive fluid.

[0010] The homogenization zones allow the reactive fluid to be distributed in the channels of the active zone.

[0011] The fluid distribution must be as homogeneous as possible, to allow satisfactory use of the entire surface of the AME.

[0012] In this context, the invention aims to propose an electrochemical device with separator plates allowing a particularly uniform distribution of fluid.

[0013] To this end, the invention relates according to a first aspect to a separator plate, for forming an electrochemical cell of an electrochemical device such as a fuel cell, the separator plate comprising:

[0014] - an opening for the passage of a reactive fluid;

[0015] - an active zone comprising active teeth delimiting between them longitudinal active channels for circulation of the reactive fluid, the active teeth having vertices falling within a reference plane;

[0016] - a homogenization zone fluidly connecting said opening to the active channels of the active zone; - an intermediate zone interposed longitudinally between the active zone and the homogenization zone, fluidly connecting the homogenization zone to the active channels; the separating plate having in the homogenization zone a homogenization bottom located at a first altitude relative to the reference plane; the separating plate having in the intermediate zone an intermediate bottom located relative to the reference plane at a second altitude higher than the first altitude, the intermediate bottom being separated from the homogenization bottom by a step; at least a portion of the active teeth having proximal ends defining a separation line between the active zone and the intermediate zone;a buffer volume being delimited between the intermediate bottom, the step and the separation line, and making it possible to balance the distribution of the reactive fluid arriving from the homogenization zone in the active channels.;

[0017] Because there is a buffer volume between the tips of the active teeth and the step, the reactive gas arriving from the homogenization zone can easily distribute into the active channels.

[0018] In particular, it can disperse transversely in this buffer volume, which makes it possible to balance the distribution of the reactive fluid between the active channels.

[0019] The reactive gas flow then undergoes a significant pressure loss front, created by the gas diffusion layer, which also contributes to distributing the reactive gas transversely.

[0020] Furthermore, the presence of the buffer volume, and in particular its height, advantageously allows the extra thickness traditionally formed by the gas diffusion layer and the frame to be accommodated, thus avoiding problems of overcompression during stacking and compression of the cells.

[0021] The separating plate may also have one or more of the following characteristics, considered individually or in all technically possible combinations:

[0022] - the active zone presents longitudinally an active length, the separation line being separated longitudinally from the step by a longitudinal spacing of between 2% and 20% of the active length;

[0023] - the intermediate zone comprises intermediate channels and intermediate teeth projecting towards the reference plane relative to the intermediate base, the intermediate teeth delimiting the intermediate channels between them;

[0024] - the intermediate teeth extend longitudinally along the entire length of the intermediate zone, from the separation line to the step; - the intermediate teeth extend longitudinally at least part of the active teeth beyond the separation line;

[0025] - the active zone has a first number of active channels, the intermediate zone having a second number of intermediate channels different from the first number, preferably less than the first number, advantageously between 25 and 75% of the first number;

[0026] - the separating plate has in the active zone an active bottom located at the second altitude relative to the reference plane, the active teeth projecting towards the reference plane relative to the active bottom;

[0027] - the intermediate teeth protrude towards the reference plane relative to the intermediate base over a first height, the active teeth protruding towards the reference plane relative to the active base over a second height equal to the first height;

[0028] - a difference between the second altitude and the first altitude is between 10 pm and 300 pm, preferably between 50 pm and 200 pm, for example being substantially equal to 80 pm or 160 pm.

[0029] According to a second aspect, the invention relates to an electrochemical cell for an electrochemical device such as a fuel cell, the electrochemical cell comprising:

[0030] - a membrane-electrode assembly comprising a membrane, catalytic layers arranged on two large opposite faces of the membrane and two gas diffusion layers arranged on the catalytic layers;

[0031] - a frame, internally delimiting a window in which the membrane-electrode assembly is fixed;

[0032] - two separating plates pressed against the two gas diffusion layers, at least one of the separating plates being as defined above, the active zone of the or each separating plate being located opposite the window, the homogenization zone of the or each separating plate being located opposite the frame.

[0033] The electrochemical cell may also have one or more of the following characteristics, considered individually or in all technically possible combinations:

[0034] - the gas diffusion layer pressed against said at least one separating plate ends longitudinally towards the homogenization zone by an edge, the edge being separated longitudinally from the step by a longitudinal spacing of between 2% and 20% of the active length;

[0035] - the homogenization zone has, at the level of the step (59), a first passage section for the reactive fluid taken perpendicular to the longitudinal direction; the buffer volume having, between said edge and the step, a second passage section for the reactive fluid taken perpendicular to the longitudinal direction, between the first passage section + 20% and the first passage section + 80%, preferably substantially equal to the first passage section + 60%;

[0036] - intermediate teeth with peaks located at a distance from the frame

[0037] - the gas diffusion layer extends longitudinally beyond the window and covers an edge zone of the frame, the edge of the gas diffusion layer being located opposite the intermediate zone.

[0038] According to a third aspect, the invention relates to an electrochemical device, comprising a plurality of electrochemical cells stacked in a stacking direction, each electrochemical cell having the above characteristics.

[0039] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0040] - [Fig.1] Figure 1 is a perspective view of an electrochemical device;

[0041] - [Fig.2] Figure 2 is an exploded view of an electrochemical cell of the device of Figure 1, considered in perspective;

[0042] - [Fig 3] Figure 3 is a schematic longitudinal sectional view of the electrochemical cell of Figure 2, showing in particular the intermediate zones of the separator plates; and

[0043] - [Fig 4] Figure 4 is an enlarged perspective view of a detail of the intermediate zone of the cathode separator plate of Figures 2 and 3.

[0044] The electrochemical device 1 shown in Figure 1 is typically a fuel cell.

[0045] Alternatively, it is an electrolyzer or any other type of corresponding electrochemical device.

[0046] This electrochemical device comprises a stack 3 of electrochemical cells 5.

[0047] The electrochemical cells 5 are stacked in a stacking direction E, one on top of the other.

[0048] The electrochemical device 1 further comprises two end plates 7, arranged on either side of the stack 3.

[0049] The electrochemical cells 5 of the stack are pressed against each other between the two end plates 7.

[0050] Each electrochemical cell 5 comprises, as illustrated in Figures 2 and 3, a membrane-electrode assembly 8 (MEA). The MEA 8 comprises a membrane 9, catalytic layers 10 arranged on two large opposite faces of the membrane 9 and two gas diffusion layers 11 arranged on the catalytic layers 10.

[0051] Thus the membrane 8 is intercalated between two catalytic layers 10, themselves intercalated between two gas diffusion layers 11.

[0052] Each electrochemical cell 5 also comprises two separator plates 15, 17 pressed against the two gas diffusion layers 11.

[0053] More precisely, a first separator plate 15 is in contact with a first gas diffusion layer 11 and a second separator plate 17 is in contact with a second gas diffusion layer 11. In other words, the two separator plates 15, 17 sandwich the two gas diffusion layers 11 which themselves sandwich the membrane-electrode assembly.

[0054] The two separating plates 15, 17 are arranged on two opposite sides of the membrane-electrode assembly 8.

[0055] The two gas diffusion layers 11 (GDL, i.e. Gas Diffusion Layer in English) are each interposed between one of the separating plates 15, 17 and one of the catalytic layers 10.

[0056] One of the catalytic layers 10 constitutes an anode and is called the anodic catalytic layer. The separator plate located on the same side of the membrane 9, and separated from the anodic catalytic layer 10 by one of the GDLs, is called the anodic separator plate 15.

[0057] The other catalytic layer 10 constitutes a cathode and is called the cathodic catalytic layer. The separator plate located on the same side of the membrane 9, and separated from the cathodic catalytic layer by the other GDL, is called the cathodic separator plate 17.

[0058] When several cells 3 are stacked on top of each other, the anode separator plate 15 of a given cell is placed against the cathode separator plate 17 of the neighboring cell, with the interposition of a sealing device, for example a gasket or a weld. These two plates delimit between them a passage for the circulation of a heat transfer fluid, intended to cool the cells in the case of a fuel cell.

[0059] Membrane 9 is typically a proton exchange polymer membrane.

[0060] The proton exchange membrane is for example made of a sulfonated perfluorinated polymer material, such as the material known under the trade name “Nation”. The anodic and cathodic catalytic layers 10 are typically made of porous structures, which allow the transport of reactive fluids, i.e. hydrogen and oxygen inside the catalytic layers.

[0061] These layers are typically formed from three different materials, namely:

[0062] - a material for transporting protons, for example the same material as the proton exchange membrane, such as the “Nation” material mentioned above,

[0063] - a material to transport electrons, for example carbon, and

[0064] - a material for catalyzing electrochemical oxidation and reduction reactions, for example platinum.

[0065] The reactive fluids are an anodic fluid and a cathodic fluid.

[0066] The anode fluid is typically dihydrogen.

[0067] The cathode fluid is typically air or oxygen.

[0068] The gas diffusion layers 11 are formed of a porous material such as carbon fiber fabric or porous carbon paper. They are pressed against the large faces of the membrane, with the anodic and cathodic catalytic layers interposed.

[0069] When the fuel cell 1 is in operation, an oxidation reaction occurs at the anodic catalytic layer. This reaction consists of catalytically splitting the hydrogen supplied by the anodic fluid into protons and electrons. The protons thus produced pass through the proton exchange membrane until they reach the cathodic catalytic layer, while the electrons are conducted by the gas diffusion layer to the anodic separator plate and then conducted to the cathodic separator plate. At the same time, a reduction reaction occurs at the cathodic catalytic layer. This reaction consists of reacting the oxygen supplied by the anodic fluid with the protons passing through the proton exchange membrane, as well as with the electrons supplied by the cathodic separator plate of the cell in question, thus forming water molecules.

[0070] Each cell 5 also includes a frame 19, internally delimiting a window 20 in which the AME 8 is fixed.

[0071] The frame 19 has an edge zone 21 delimiting the window 20.

[0072] The edge area 21 is closed contour.

[0073] Window 20 is preferably rectangular.

[0074] The frame 19 is typically formed from two layers 22 of a polymer film, for example polyethylene naphthalate or terephthalate (PEN or PET). The frame 19 extends in a longitudinal and transverse plane, substantially perpendicular to the stacking direction E. The longitudinal direction L and transverse direction T are shown in FIGS. 1 and 2.

[0075] In the example shown, the frame 19 is generally rectangular in shape.

[0076] The AME 8 is substantially flat, and extends in the same plane as the frame 19.

[0077] The AME 8 has, at its two opposite longitudinal ends, two edges called overlap zones 23.

[0078] The overlap zones 23 extend transversely across the entire width of the AME 8.

[0079] In the example shown, the AME 8 is rectangular. The overlapping zones 23 are rectilinear and transverse strips.

[0080] As seen in Figure 3, in each overlap zone 23, the edge zone 21 is interposed between the membrane 9 and at least one of the gas diffusion layers 11.

[0081] This allows the membrane 9 to be held in place and ensures that the two sides of the membrane are sealed against each other.

[0082] In each overlap zone 23, the two layers of polymer film 22 constituting the edge zone 21 are arranged on either side of the membrane 9, between the membrane 9 and the gas diffusion layers 11. They cover the large faces of the membrane 9. Typically, they are plated on the anodic and cathodic catalytic layers 10.

[0083] According to a variant not shown, one of the two layers of polymer film 22 constituting the edge 21 is arranged on one side of the membrane 9, between the membrane 9 and one of the gas diffusion layers 11. The other layer of polymer film 22 does not extend between the membrane 9 and the gas diffusion layers 11. It stops before covering the membrane 9.

[0084] According to another variant not shown, the frame 19 is made up of a single layer of polymer film. The part of this layer constituting the edge 21 is arranged on one side of the membrane 9, between the membrane 9 and one of the gas diffusion layers 11

[0085] The overlapping areas 23 extend over a fraction of the longitudinal length of the MEA 8. For example, the edge area 21 covers the membrane 9 longitudinally over a length of between 0.5 and 8 mm in each overlapping area.

[0086] The gas diffusion layers 11 cover all the large faces of the membrane 9. In particular, the gas diffusion layers 11 cover the overlapping zones 23 of the MEA 8.

[0087] This ensures that there is no area of ​​the membrane not covered with the gas diffusion layer and possibly to fix the gas diffusion layer to the frame 19 by different bonding techniques.

[0088] The gas diffusion layers 11 terminate longitudinally with edges 25.

[0089] The edges 25 are transverse.

[0090] In the example illustrated in Figure 3, the edges 25 are located longitudinally immediately beyond the overlap zone 23.

[0091] Alternatively, the edges 25 are offset relative to the overlap zone 23, each GDL 11 covering a strip of the frame 19 adjoining this overlap zone 23.

[0092] According to yet another variant, the gas diffusion layers 11 are longitudinally shorter than the membrane 9, and only partially cover the overlapping zones 23 of the MEA 8. They only partially cover the edge zone 21.

[0093] The separating plates 15, 17 each extend substantially in a longitudinal and transverse plane, each being perpendicular to the stacking direction E. They are typically metallic.

[0094] The separating plates 15, 17 are generally rectangular in shape.

[0095] They are typically obtained by stamping, machining or any other manufacturing method.

[0096] The anode separator plate 15, as seen in FIG. 2, has at least a first anode opening 27a for the passage of the anode fluid and a second anode opening 29a for the passage of the cathode fluid.

[0097] The anode separator plate 15 further has third, fourth, fifth and sixth anode openings 31a, 33a, 35a, 37a.

[0098] The openings 31a and 33a are provided for the circulation of the anodic fluid and the cathodic fluid respectively.

[0099] For example, opening 27a allows the supply of the anode fluid and opening 31a is provided for the evacuation of the anode fluid.

[0100] Preferably, the openings 33a and 29a are provided respectively for the supply of the cathode fluid and for the evacuation of the cathode fluid.

[0101] The openings 35a and 37a are provided for the circulation of the heat transfer fluid. For example, the opening 35a is provided for the supply of the heat transfer fluid and the opening 37a for the discharge of the heat transfer fluid. The openings 27a and 31a are diagonally opposite in the anode separator plate 15. Similarly, the openings 29a and 33a are diagonally opposite.

[0102] The openings 27a, 35a and 29a are placed at one longitudinal end of the plate 15. They are aligned transversely, in this order.

[0103] The openings 31a, 37a and 33a are placed at the opposite longitudinal end of the plate 15. They are aligned transversely, in this order.

[0104] In the same way, the cathode separator plate 17 comprises at least a first cathode opening 27c for the passage of the anodic fluid and a second cathode opening 29c for the passage of the cathodic fluid.

[0105] The cathode separator plate 17 further has third, fourth, fifth and sixth cathode openings 31c, 33c, 35c, 37c.

[0106] Openings 31c and 33c are provided for the circulation of the anodic fluid and the cathodic fluid respectively.

[0107] For example, opening 27c allows the supply of the anode fluid and opening 31c is provided for the evacuation of the anode fluid.

[0108] Preferably, the openings 33c and 29c are provided respectively for the supply of the cathodic fluid and for the evacuation of the cathodic fluid.

[0109] Openings 35c and 37c are provided for the circulation of the heat transfer fluid. For example, opening 35c is provided for the supply of the heat transfer fluid and opening 37c for the discharge of the heat transfer fluid.

[0110] Openings 27c and 31c are diagonally opposite in the cathode separator plate 17. Similarly, openings 29c and 33c are diagonally opposite.

[0111] The openings 27c, 35c and 29c are placed at one longitudinal end of the plate 17. They are aligned transversely, in this order.

[0112] The openings 31c, 37c and 33c are placed at the opposite longitudinal end of the plate 17. They are aligned transversely, in this order.

[0113] The frame 19 comprises at least a first intermediate opening 27b for the passage of the anodic fluid and a second intermediate opening 29b for the passage of the cathodic fluid.

[0114] Frame 19 further has third, fourth, fifth and sixth intermediate openings 31b, 33b, 35b, 37b.

[0115] The openings 31b and 33b are provided for the circulation of the anodic fluid and the cathodic fluid respectively.

[0116] For example, opening 27b allows the supply of the anode fluid and opening 31b is provided for the evacuation of the anode fluid. Openings 33b and 29b are provided respectively for the supply of the cathode fluid and for the evacuation of the cathode fluid.

[0117] Openings 35b and 37b are provided for the circulation of the heat transfer fluid. For example, opening 35b is provided for the supply of the heat transfer fluid and opening 37b for the discharge of the heat transfer fluid.

[0118] Openings 27b and 31b are diagonally opposite in frame 19. Similarly, openings 29b and 33b are diagonally opposite.

[0119] The openings 27b, 35b and 29b are placed at one longitudinal end of the frame 19. They are aligned transversely, in this order.

[0120] The openings 31b, 37b and 33b are placed at the opposite longitudinal end of the frame 19. They are aligned transversely, in this order.

[0121] As seen in Figure 2, the openings 27a / 27b / 27c are coincident and together constitute a portion of the anode fluid supply manifold.

[0122] Similarly, the openings 29a / 29b / 29c are coincident and together constitute a portion of the cathode fluid discharge collector.

[0123] The openings 31a / 31b / 31c are coincident and together constitute a portion of the anode fluid discharge collector.

[0124] The openings 33a / 33b / 33c are coincident and together constitute a portion of the cathode fluid supply collector.

[0125] The openings 35a / 35b / 35c are coincident and together constitute a portion of the heat transfer fluid supply manifold.

[0126] The openings 37a / 37b / 37c are coincident and together constitute a portion of the heat transfer fluid evacuation collector.

[0127] Gaskets (broken lines not referenced in Figure 2) are placed around these openings and are interposed between the anode separator plate 15, the frame 19 and the cathode separator plate 17.

[0128] According to the invention, at least one of the separating plates of the cell 5 comprises:

[0129] - an active zone 39 comprising active teeth 71 delimiting between them longitudinal active channels 41 for circulation of a reactive fluid;

[0130] - a homogenization zone 43 fluidly connecting one of the openings of the separator plate to the active channels 41 of the active zone 39;

[0131] - an intermediate zone 45 interposed longitudinally between the active zone 39 and the homogenization zone 43, fluidly connecting the homogenization zone 43 to the active channels 41.

[0132] By "fluidically connecting" we preferably mean that the zones in question are connected to each other via a fluidic connection means, that is to say by any means capable of conveying a fluid, such as, for example, in a non-exhaustive and non-limiting manner, a channel, a groove, a slot, etc. It is then understood that the sealing of the fluidic connection is achieved by a part added to the separating plate, such as for example another separating plate.

[0133] If the separator plate is of the anodic type, the homogenization zone 43 fluidically connects the opening 27a for supplying the anodic fluid to the active channels 41.

[0134] If the separator plate is of the cathodic type, the homogenization zone 43 connects the cathodic fluid supply opening 29c to the active channels 41.

[0135] Active zone 39 is located opposite window 20.

[0136] The active zone 39, longitudinally, is located entirely opposite the membrane 9.

[0137] The homogenization zone 43 is located opposite the frame 19.

[0138] The homogenization zone 43 is located opposite a flat zone 49 of the frame.

[0139] The intermediate zone 45 is located opposite the edge zone 21 of the frame 19. It extends longitudinally beyond the edge zone 21, up to the homogenization zone 43. On the side opposite the homogenization zone 43, it stops at the level of the window 20, or extends slightly inside the window 20.

[0140] The active channels 41 are rectilinear and longitudinal. Alternatively, they extend in a general longitudinal direction, forming undulations on either side of this general longitudinal direction.

[0141] The active teeth 71 have respective proximal ends 72 defining a separation line LS between the active zone 41 and the intermediate zone 45.

[0142] This dividing line LS is for example transverse, as shown in Figure 4. Alternatively, it is oblique to the transverse direction. The dividing line LS is typically a straight line.

[0143] The active teeth 71 have vertices 73 falling within a reference plane P, as illustrated in figure 3.

[0144] The reference plane P is parallel to the plane in which the frame 19 extends.

[0145] As illustrated in Figure 3, the separating plate has in the homogenization zone 43 a homogenization bottom 51 located at a first altitude a1 relative to the reference plane P.

[0146] The homogenization bottom 51 is a region of the separating plate, extending along a plane preferably substantially perpendicular to the stacking direction E, that is to say parallel to the reference plane P. The altitude a1 is taken along the stacking direction E. It corresponds to the spacing between the homogenization bottom 51 and the plane P. The separating plate advantageously has in the homogenization zone 43 also reliefs 53 projecting towards the reference plane P relative to the homogenization bottom 51.

[0147] The reliefs 53 are provided to direct the flow of the reactive gas flow from the opening to the intermediate zone 45.

[0148] These reliefs 53 can have all sorts of shapes. For example, they are teeth spaced apart from each other and delimiting continuous or discontinuous channels between them. Alternatively, they are circular, triangular or any other shaped studs.

[0149] The separating plate has in the intermediate zone 45 an intermediate bottom 55 located relative to the reference plane P at a second altitude a2 greater than the first altitude a1.

[0150] The intermediate zone 45 preferably comprises intermediate channels 47 and intermediate teeth 57 projecting towards the reference plane P relative to the intermediate bottom 55. The intermediate teeth 57 delimit the intermediate channels 47 between them.

[0151] The intermediate bottom 55 is constituted by one or more regions of the separating plate. These regions are inscribed in the same plane perpendicular to the stacking direction E (i.e. parallel to the reference plane P). For example, these regions are substantially flat (see figure 4). This makes it possible in particular to simplify the manufacture of the separating plate.

[0152] The second altitude a2 corresponds to the distance between this plane and the reference plane P, taken perpendicular to the reference plane P, that is to say following the stacking direction E.

[0153] The intermediate bottom 55 defines the bottom of the intermediate channels 47.

[0154] As seen in Figure 3, the intermediate bottom 55 is separated from the homogenization bottom 51 by a step 59.

[0155] This step 59 results from the difference in altitude between the homogenization bottom 51 and the intermediate bottom 55, and can take any shape allowing the homogenization bottom 51 and the intermediate bottom 55 to be continuously connected. Preferably, as illustrated in FIG. 3, the step can have a step nose which is straight (i.e. rectilinear) oriented at an angle relative to the stacking direction, i.e. oriented in a direction intersecting the reference plane P. Alternatively, one could imagine, without departing from the scope of the invention, a step nose which is oriented perpendicular to the reference plane P. One could also imagine a non-rectilinear step nose, for example which would be rounded. This step, whatever its shape and orientation, thus makes it possible to constitute a boundary, an obstacle, a wall for the fluid.

[0156] The difference between the second altitude a2 and the first altitude a1 is between 10 pm and 300 pm, preferably between 50 pm and 200 pm, for example being substantially equal to 80 pm or 160 pm, advantageously respectively for a polar plate of the anode or cathode type.

[0157] Preferably, the intermediate bottom 55 is located at an altitude a2 of between 0.1 mm and 0.5 mm, advantageously between 0.2 and 0.3 mm, for example being substantially equal to one of these latter terminals, the latter preferably relating respectively to an anodic polar plate or a cathodic polar plate.

[0158] Preferably, the homogenization bottom 51 is located at an altitude a1 of between 0.05 mm and 0.3 mm, advantageously between 0.1 and 0.2 mm, for example being substantially equal to 0.12 mm and 0.14 mm, the latter preferably relating respectively to an anodic polar plate or a cathodic polar plate.

[0159] As visible in Figure 4, this step 59 is preferably substantially transverse, and extends over the entire transverse width of the homogenization zone 43. It is formed in the separating plate.

[0160] A buffer volume 60 is thus delimited between the intermediate bottom 55, the step 59 and the separation line LS, thus making it possible to balance the distribution of the reactive fluid arriving from the homogenization zone 43 in the active channels 41.

[0161] The active zone 41 has a determined active length LA longitudinally.

[0162] The separation line LS is separated longitudinally from the step 59 by a longitudinal spacing advantageously between 2% and 20% of the active length LA. Preferably, the longitudinal spacing is between 4 and 15%, and more preferably between 5 and 10% of the active length LA. This longitudinal spacing corresponds to the longitudinal length of the buffer volume 60.

[0163] The edge 25 of the GDL is separated longitudinally from the step 59 by a longitudinal spacing advantageously between 2% and 20% of the active length (LA). Preferably, the longitudinal spacing is between 4 and 15%, and more preferably between 5 and 10% of the active length LA.

[0164] Furthermore, the homogenization zone 43 has, at the level of the step 59, a first passage section P1 for the reactive gas. This passage section P1 is taken perpendicular to the longitudinal direction. The passage section is taken at the top of the step 59, that is to say at the limit between the homogenization bottom 51 and the step 59.

[0165] The first passage section P1 corresponds to the free section, offered to the reactive fluid which flows from the homogenization zone 43 into the intermediate zone 45. The first section corresponds to the section delimited between the homogenization bottom 51 and the frame 19, less the section possibly occupied by the reliefs formed at the level of the step 59. As described below, in the example shown, the intermediate teeth 57 extend to the step 59, the ends of the intermediate teeth reducing the first passage section P1.

[0166] The buffer volume 60 has, between the edge 25 and the step 59, a second passage section P2 for the reactive fluid, advantageously between the first passage section P1 plus 20% and the first passage section P1 plus 80%, preferably between the first passage section P1 plus 40% and the first passage section P1 plus 70%, typically substantially equal to the first passage section P1 plus 60%. The second passage section P2 is taken perpendicular to the longitudinal direction L.

[0167] The condition stated above is verified for all sections of the buffer volume 60 located between the step 59 and the edge 25. In other words, the passage section of the buffer volume 60 is preferably substantially constant from the step 59 to the edge 25 of the GDL.

[0168] The passage section corresponds to the free section offered to the reactive fluid to circulate longitudinally in the buffer volume 60. It thus corresponds to the section delimited between the intermediate bottom 55 and the frame 19, minus the section occupied by the intermediate teeth 57.

[0169] The intermediate teeth 57 have peaks 61 designed to be located at a distance from the frame 19.

[0170] This distance is taken along the stacking direction E.

[0171] Each intermediate tooth 57 has a first segment 63 intended to be pressed against the GDL 11, and a second free segment 65, extending the first segment 63 longitudinally. The first segment 63 adjoins the active zone 39. The second segment 65 is intended to be located longitudinally beyond the edge 25 of the GDL.

[0172] Preferably, each intermediate tooth 57 also has a third segment 67, formed on the step 59, and extending slightly inside the homogenization zone 43. In this case, the third segment 67 reduces the first passage section P1. In other words, the intermediate teeth 57 extend longitudinally over the entire length of the intermediate zone 45, up to the step 59, or even beyond the step 59.

[0173] The reactive fluid can therefore circulate transversely between the tops 61 of the intermediate teeth 57 and the frame 19 at the level of the second segments 65.

[0174] As can be seen in particular in Figures 3 and 4, the separating plate has, in the active zone 39, an active bottom 69 preferably located at the second altitude a2 relative to the reference plane P, the active teeth 71 projecting towards the reference plane P relative to the active bottom 69. The altitude of the active bottom 69 is taken according to the stacking direction E, that is to say perpendicular to the reference plane P.

[0175] The active bottom 69 is made up of regions of the separating plate lying in the same plane substantially perpendicular to the stacking direction E. This plane is preferably located at the same altitude a2 as the intermediate bottom 55. This makes it possible in particular to simplify the manufacture of the separating plate.

[0176] These regions are separated from each other by the active teeth 71 and delimit the bottom of the active canals 41.

[0177] In other words, the intermediate bottom 55 and the active bottom 69 are preferably inscribed in the same plane perpendicular to the stacking direction E, located at the altitude a2 relative to the reference plane P.

[0178] The apices 73 of the active teeth are located in contact with the GDL 11 when the cell is assembled.

[0179] The intermediate teeth 57 project towards the reference plane P relative to the intermediate base 57 over a first height h1. The active teeth 71 project towards the reference plane P relative to the active base 69 over a second height h2, preferably equal to the first height h1.

[0180] In other words, the intermediate teeth 57 and the active teeth 71 preferably have the same height.

[0181] The intermediate teeth 57, as seen in particular in FIG. 4, longitudinally extend at least part of the active teeth 71.

[0182] For example, the active zone 39 has a first number of active channels 41, the intermediate zone 45 having a second number of intermediate channels 47 between 25 and 75% of the first number.

[0183] In other words, the number of intermediate channels 47 is less than the number of active channels 41. Consequently, the number of intermediate teeth 57 is less than the number of active teeth 71. In the example shown in FIG. 4, the number of intermediate teeth 57 is approximately 50% of the number of active teeth 71. Every second active tooth 71 is extended by an intermediate tooth 57. Every second active tooth 71 is not extended by an intermediate tooth 57 and stops at the boundary separating the active zone 39 from the intermediate zone 45. Each active tooth 71 extended by an intermediate tooth 57 is framed by two active teeth 71 which are not extended by intermediate teeth 57.

[0184] This difference in the number of intermediate teeth 57 and active teeth 71 is advantageously studied in design in order to optimize the fluid distribution between the intermediate zone and the active zone while minimizing the loss of useful section for the passage of the fluid.

[0185] Thus, the intermediate channels 47 have a width much greater than the active channels 41. This width, for example, corresponds transversely to the cumulative width of two active channels and one active tooth.

[0186] Such an arrangement is used, for example, for anode and / or cathode type separator plates.

[0187] According to another variant not shown, the number of active channels 41 is equal to the number of intermediate channels 47.

[0188] Consequently, the number of active teeth 71 is substantially equal to the number of intermediate teeth 57. Each active tooth 71 is extended longitudinally by an intermediate tooth 57.

[0189] The separator plate, electrochemical cell and electrochemical device described above have multiple advantages.

[0190] The fact that the edge of the gas diffusion layer is also separated longitudinally from the step by a significant longitudinal gap helps to facilitate the distribution of the reactive gas leaving the homogenization zone in the active channels.

[0191] The passage section for the reactive gas between the homogenization zone and the edge of the gas diffusion layer is also particularly large, which also helps to facilitate the distribution of the reactive gas in the active channels.

[0192] Because the intermediate teeth have peaks located at a distance from the frame, the reactive fluid from the homogenization zone can easily circulate transversely in the intermediate zone and distribute itself in the different active channels.

[0193] The fact that the separator plate preferably has in the active zone an active bottom located at the second altitude relative to the reference plane, that is to say that the bottoms of the active zone and the intermediate zone are preferably located at the same altitude, makes it possible to create a significant volume in the intermediate zone to distribute the reactive fluid. This volume plays the role of collector or buffer zone.

[0194] The fact that the intermediate teeth and the active teeth have the same height simplifies the design and manufacture of the separator plate and allows uniform compression of the gas diffusion layer to be maintained.

[0195] The separator plate, electrochemical cell and electrochemical device described above have multiple variations.

[0196] The electrochemical device may not be a fuel cell, but may be an electrolyzer or any other corresponding type of electrochemical device.

[0197] Therefore, the catalytic layers are not necessarily anodic and cathodic catalytic layers of the type described above.

[0198] The homogenization zone has been described as fluidically connected to an anodic reactive fluid or cathodic reactive fluid supply opening, depending on the type of the separator plate. The homogenization zone can also be connected to the anodic reactive fluid discharge port or the cathodic reactive fluid discharge port.

[0199] It can also, depending on the type of electrochemical device, be connected to a supply or discharge opening for another type of fluid.

[0200] The two homogenizing zones and the two intermediate zones of the separating plate can be of the type described above.

[0201] Alternatively, only one of the homogenization zones and one of the intermediate zones, located on one longitudinal side of the plate, are as described above. The other intermediate zone and the other homogenization zone, located on the other side of the plate, are not as described above.

[0202] Preferably, the two separator plates of each electrochemical cell are as described above.

[0203] Alternatively, only one of the separator plates of the electrochemical cell is as described above, the other plate is of a different type.

[0204] Some cells may have one or two separator plates which are not of the type described above.

Claims

CLAIMS 1. Separator plate (15, 17) for forming an electrochemical cell of an electrochemical device such as a fuel cell, the separator plate comprising: - an opening for the passage of a reactive fluid; - an active zone (39) comprising active teeth (71) delimiting between them longitudinal active channels (41) for circulation of the reactive fluid, the active teeth (71) having peaks (73) falling within a reference plane (P); - a homogenization zone (43) fluidly connecting said opening to the active channels (41) of the active zone (39); - an intermediate zone (45) interposed longitudinally between the active zone (39) and the homogenization zone (43), fluidly connecting the homogenization zone (43) to the active channels (41); the separating plate (15, 17) having in the homogenization zone (43) a homogenization bottom (51) located at a first altitude (a1) relative to the reference plane (P); the separating plate (15, 17) having in the intermediate zone (45) an intermediate bottom (55) located relative to the reference plane (P) at a second altitude (a2) higher than the first altitude (a1), the intermediate bottom (55) being separated from the homogenization bottom (51) by a step (59); at least a portion of the active teeth (71) having proximal ends (72) defining a separation line (LS) between the active zone (41) and the intermediate zone (45);a buffer volume (60) being delimited between the intermediate bottom (55), the step (59) and the separation line (LS), and making it possible to balance the distribution of the reactive fluid arriving from the homogenization zone (43) in the active channels (41).; 2. Separator plate (15, 17) according to claim 1, in which the active zone (41) longitudinally has an active length (LA), the separation line (LS) being separated longitudinally from the step (59) by a longitudinal spacing of between 2% and 20% of the active length (LA).

3. Separator plate (15, 17) according to claim 1 or 2, in which the intermediate zone (45) comprises intermediate channels (47) and intermediate teeth (57) projecting towards the reference plane (P) relative to the intermediate bottom (55), the intermediate teeth (57) delimiting between them the intermediate channels (47).

4. Separator plate (15, 17) according to claim 3, wherein the intermediate teeth (57) extend longitudinally over the entire length of the intermediate zone (45), from the separation line (LS) to the step (59).

5. Separator plate (15, 17) according to claim 3 or 4, wherein the intermediate teeth (57) longitudinally extend at least a portion of the active teeth (71) beyond the separation line (LS).

6. Separator plate (15, 17) according to any one of claims 3 to 5, in which the active zone (39) has a first number of active channels (41), the intermediate zone (45) having a second number of intermediate channels (47) different from the first number, preferably less than the first number, advantageously between 25 and 75% of the first number.

7. Separator plate (15, 17) according to any one of claims 1 to 6, in which the separator plate (15, 17) has in the active zone (39) an active bottom (69) located at the second altitude (a2) relative to the reference plane (P), the active teeth (71) projecting towards the reference plane (P) relative to the active bottom (69).

8. Separator plate (15, 17) according to any one of claims 3 to 6 in combination with claim 7, in which the intermediate teeth (57) project towards the reference plane (P) relative to the intermediate bottom (55) over a first height (h 1 ), the active teeth (71) projecting towards the reference plane (P) relative to the active bottom (69) over a second height (h2) equal to the first height (h1).

9. Separator plate (15, 17) according to any one of claims 1 to 8, in which a difference between the second altitude and the first altitude is between 10 pm and 300 pm, preferably between 50 pm and 200 pm, for example being substantially equal to 80 pm or 160 pm.

10. Electrochemical cell (5) for an electrochemical device such as a fuel cell, the electrochemical cell comprising: - a membrane-electrode assembly (8) comprising a membrane (9), catalytic layers (10) arranged on two large opposite faces of the membrane (9) and two gas diffusion layers (11) arranged on the catalytic layers (10); - a frame (19), internally delimiting a window (20) in which the membrane-electrode assembly (8) is fixed; - two separator plates (15, 17) pressed against the two gas diffusion layers (11), at least one of the separator plates being according to any one of claims 1 to 9, the active zone (39) of the or each separator plate (15, 17) being located opposite the window (20), the homogenization zone (43) of the or each separating plate (15, 17) being located opposite the frame (19).

11. Electrochemical cell (5) according to claim 10, in which the gas diffusion layer (11) pressed against said at least one separator plate (15, 17) ends longitudinally towards the homogenization zone (43) by an edge (25), the edge (25) being separated longitudinally from the step (59) by a longitudinal spacing of between 2% and 20% of the active length (LA).

12. Electrochemical cell (5) according to claim 11, in which the homogenization zone (43) has, at the level of the step (59), a first passage section (S1) for the reactive fluid taken perpendicular to the longitudinal direction; the buffer volume (60) having, between said edge (25) and the step (59), a second passage section (S2) for the reactive fluid taken perpendicular to the longitudinal direction, between the first passage section (S1) + 20% and the first passage section (S1) + 80%, preferably substantially equal to the first passage section (S1) + 60%.

13. Electrochemical cell (5) according to any one of claims 10 to 12, in which the at least one separator plate (15, 17) is according to any one of claims 3 to 6, the intermediate teeth (57) having peaks (61) located at a distance from the frame (19).

14. Electrochemical cell (5) according to any one of claims 9 to 12, wherein the gas diffusion layer (11) extends longitudinally beyond the window (20) and covers an edge zone (21) of the frame (20), the edge (25) of the gas diffusion layer (11) being located opposite the intermediate zone (45).

15. Electrochemical device, comprising a plurality of electrochemical cells (5) stacked in a stacking direction, each electrochemical cell (5) being defined according to any one of claims 10 to 14.

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