Polar plate, electrochemical cell of a fuel cell comprising such a plate, and fuel cell comprising such a cell

Abstract

Pole plate, electrochemical cell of a fuel cell comprising such a plate and fuel cell comprising such a cell. Pole plate (40, 60) comprising a base plate (41, 61), made of a first electrically conductive material, and a plurality of channels (43, 63, 73) extending along a longitudinal axis (Y), each channel comprising a channel bottom (47, 67, 77), and two channel teeth (45, 65, 75), arranged on either side of the channel bottom, each channel tooth being made of at least a second material, and comprising a front face (46, 66, 76) and two lateral faces (48, 68, 78).The polar plate comprises a coating (50, 70) including a first zone covering and in electrical contact with the first material of the base plate, including a second zone covering the lateral faces, and including a third zone covering at least part of the frontal faces; the first, second, and third zones of the coating form a continuous material. (See Figure 1 for abbreviations.)

Description

Title of the invention: Polar plate, electrochemical cell of a fuel cell comprising such a plate and fuel cell comprising such a cell

[0001] The present invention relates to a polar plate, an electrochemical cell of a fuel cell, and a fuel cell.

[0002] In the field of fuel cells, it is known to use bipolar plates, formed by stamped polar plates, in order to form channels in which functional fluids circulate. The polar plates are also used to conduct the electrons formed during an electrochemical reaction in the fuel cell, from one electrochemical cell to another. For this, it is known to use electrically conductive materials to form the polar plates. This technique is generally satisfactory. However, stamping, which makes it possible to form the channels, has manufacturing limitations in terms of reducing the width of the teeth and channels and manufacturing time.

[0003] DE102017118318A1, EP1919015A1, DE102015015876A1, WO2020212128A1 describe polar plates produced in an alternative way, by additive manufacturing. Generally speaking, additive manufacturing uses an electrically conductive material, to allow the plate to perform its electrical conduction function. However, it should be noted that materials suitable for additive manufacturing, generally polymer materials, but which are also electrically conductive, are often more expensive and / or less easy to implement than common additive manufacturing materials which are poorly or not electrically conductive.

[0004] FR3117275A1 describes the formation of distribution channels on three electrical sheets electrically conductive, by making ribs, which are for example printed on the sheets. The sheets are then stacked, thus forming a bipolar plate. The ribs can be conductive or non-conductive, but this document provides for the creation of a peripheral electrical connection between the sheets to ensure the circulation of electrons from one face to the other of the bipolar plate. In the case of non-conductive ribs, the electrical performance of the bipolar plate is necessarily degraded.

[0005] The aim of the invention is to resolve the drawbacks described above.

[0006] To this end, the invention relates to a polar plate of an electrochemical cell, the polar plate comprising a base plate, made of a first material, the first material being electrically conductive, the base plate extending parallel to a main plane of the polar plate and a plurality of channels, the channels extending along a longitudinal axis, each channel comprising a channel bottom extending parallel to the longitudinal axis, and two channel teeth, extending parallel to the longitudinal axis, the channel teeth being arranged on either side of the channel bottom along a transverse axis, each channel tooth being made of at least one second material, different from the first material, and comprising a front face and two side faces. According to the invention, the polar plate comprises a coating, made of at least one third material, the third material being electrically conductive, the coating comprising a first zone which is arranged against at least a portion of the channel bottom of each channel, covering and being in electrical contact with the first material of the base plate, the coating comprising a second zone which is arranged against at least a portion of the sides of each channel, covering the side faces of the two channel teeth.Also according to the invention, the coating comprises a third zone which covers at least a part of the end faces of the canal teeth, this third zone of the coating forming an outer layer of the canal teeth or being covered exclusively with one or more layers of electrically conductive materials, the first zone, the second zone and the third zone of the coating form a continuity of material of the third material such that the coating ensures electrical conduction between the end faces of the canal teeth and the base plate.

[0007] By means of the invention, it is possible to improve the electrical conductivity of the plate, in particular at the channel teeth, by means of the coating, while forming the channel teeth of a material distinct from the substrate of the polar plate, which can be chosen primarily for its processing properties by additive manufacturing, without necessarily requiring a compromise. The coating facilitates electrical conduction in the polar plate, in particular so that the electrons collected in the electrochemical reaction, and transported to the plate in particular by the gas diffusion layer, circulate to the base plate, with good electrical conduction performance towards the polar plate. Since the coating covering the channel teeth offers a preferred conduction path, it is not necessary to provide a peripheral connection between the polar plates to facilitate the conduction of the electrons.

[0008] According to other advantageous aspects of the invention, the polar plate comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0009] - The second material is electrically insulating or the second material is intermediate conductivity.

[0010] - The channels extend on a first face of the base plate and on a second face of the base plate, opposite the first face, in which the first coating zone is arranged against at least a part of the canal bottom) of different channels, the second coating zone is arranged against at least a part of the sides of different channels, the third coating zone covers at least a part of the end faces of the canal teeth of the different channels.

[0011] - The channel teeth extending on the first face of the base plate are made of a second material and the canal teeth extending on the second face are made of a fourth material, distinct from the second material.

[0012] - The fourth material is electrically insulating or the fourth material is intermediate electrical conductivity.

[0013] - The base plate is coated with a protective coating, made in a fifth electrically conductive material.

[0014] - The coating comprises several layers, each layer being made in a material different from the other layers, each layer being electrically conductive, one of the layers being made of the third material, a first insulating layer is interposed between the second and / or the third zone and the lateral faces and / or the front faces of the canal teeth and / or a second insulating layer covers the first zone and / or the second zone.

[0015] - The coating comprises a plurality of electrically conductive fibers.

[0016] The invention also relates to an electrochemical cell of a fuel cell comprising: - a membrane-electrode assembly, extending parallel to a main plane of the electrochemical cell, comprising a membrane and two gas diffusion layers, the membrane being interposed between the two gas diffusion layers along a stacking axis; and

[0017] two polar plates as described previously, the main plane of each polar plate being parallel to the main plane of the electrochemical cell, each polar plate bearing against one of the two gas diffusion layers along the stacking axis, the coating forming an interface between the channel teeth and the gas diffusion layer against which the polar plate bears.

[0018] According to other advantageous aspects of the invention, the electrochemical cell comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0019] - The channels of one of the two polar plates extend exclusively over one same face of the base plate, and the channels of the other polar plate extend over a first face of the base plate and a second face of the base plate, opposite the first face.;

[0020] The invention also relates to a fuel cell comprising a stack of electrochemical cells, the electrochemical cells being as described above: previously, the electrochemical cells being stacked along the stacking axis.

[0021] 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: - [Fig.l] [Fig.l] is a partial section of an electrochemical cell comprising polar plates according to a first embodiment; - [Fig.2] [Fig.2] is a partial section, corresponding to detail II in [Fig.l], of a polar plate according to a second embodiment; - [Fig.3] [Fig.3] is a partial section, similar to [Fig.2], of a plate polar according to a third embodiment; and - [Fig.4] [Fig.4] is a partial section similar to [Fig.2], of a plate polar according to a fourth embodiment.

[0022] In [Fig.l] is partially shown an electrochemical cell 10, forming part of a fuel cell, not shown. Several electrochemical cells 10 are advantageously stacked along a stacking axis X, forming a stack which belongs to the fuel cell. The fuel cell can be used to power a vehicle, for example a car or a truck. When in operation, functional fluids circulate in the fuel cell, and in particular in each electrochemical cell 10 of the fuel cell. The functional fluids comprise a cooling fluid and two reactive gases, which are hydrogen and air, or possibly oxygen.

[0023] The electrochemical cell 10 extends along a main plane P10 of the electrochemical cell, perpendicular to the stacking axis X and comprises a membrane electrode assembly 20, an anode polar plate 40 and a cathode polar plate 60. A longitudinal axis Y and a transverse axis Z are defined, in addition to the stacking axis X. These three axes X, Y and Z are perpendicular to each other and define in space an orthogonal reference frame fixed relative to the cell 10.

[0024] The membrane electrode assembly 20 comprises a membrane 21 and two gas diffusion layers 22 and 23. The membrane 21 is advantageously a proton exchange polymer membrane. The membrane 21 extends parallel to the main plane P10 which is parallel to the Y and Z axes. The membrane 21 is substantially planar. The membrane 21 may be covered with a catalyst layer 25 on one of its faces or on its two faces parallel to the main plane P10, as is the case in [Fig.l],

[0025] The gas diffusion layers 22 and 23 extend parallel to the main plane P10 and are arranged on either side of the membrane 21 along the stacking axis X, resting on the catalyst layer 25 along the stacking axis X.

[0026] Each gas diffusion layer 22 and 23 is made of porous material, thus, each gas diffusion layer 22 and 23 is adapted for gas, in particular reactive gases, to diffuse therethrough.

[0027] The anode polar plate 40 extends along a main plane P40 of the anode polar plate 40, parallel to the main plane P10. The anode polar plate 40 comprises a base plate 41, a circulation field 42 and a coating 50.

[0028] The base plate 41 is flat and extends parallel to the main planes P10 and P40. The base plate 41 is made of a first material, which is electrically conductive, for example metal or graphite, or any material with electrical conductivity greater than 100 S / cm along the longitudinal axis Y.

[0029] Advantageously, a surface treatment is applied to the base plate 41, in order to optimize the surface conduction of the base plate 41, for example by physical vapor deposition. A surface contact resistance, ensured by the surface treatment applied to the base plate 41 is for example less than 10 mΩ.cm2.

[0030] The electrical conductivity of a material is determined, for example, using a technique consisting of connecting a 4-wire impedance meter to two current collectors between which the material to be tested is compressed to a pressure of 1 MPa, interposed between two gas diffusion layers. The electrical conductivity is then obtained by calculating the ratio between the thickness of the material to be tested and its resistance multiplied by its surface area.

[0031] The circulation field 42 comprises channels 43 extending mainly along the longitudinal axis Y on a first face 41A of the base plate 41, parallel to the main plane P40. The channels 43 are parallel to each other and aligned along the transverse axis Z. Each channel 43 comprises two channel teeth 45 and a channel bottom 47. Two successive channels 43 along the transverse axis Z comprise a common channel tooth 45.

[0032] The channel teeth 45 are arranged on the first face 41A parallel to the longitudinal axis Y, and are made of a second material, different from the first material of the base plate 4L. The second material is advantageously an electrically insulating material, i.e. with an electrical conductivity of less than 50 S / cm, for example between 0.1 and 50 S / cm. Alternatively, the second material is a material of intermediate electrical conductivity, i.e. with an electrical conductivity of between 50 and 100 S / cm. The second material is for example a material containing charged or uncharged polymers.

[0033] The channel teeth 45 have a thickness e45, measured along the stacking axis X, of between 100 and 300 μm, preferably between 150 and 200 μm, and a width 145, measured on the base plate 41 along the transverse axis Z, of between 50 and 150 μm. 400 pm, preferably 250 pm

[0034] The channel teeth 45 are produced by additive manufacturing techniques on the base plate 41. The channel teeth 45 are, for example, produced by injecting polymer onto the base plate 41, but are preferably produced by nozzle printing, for example by Polyjet 3D printing technology, or by screen printing, where a paste is applied to a mask, and then polymerized in order to obtain a desired pattern, here the channel teeth 45. In the case of manufacturing by screen printing, the channel teeth 45 are preferably obtained by a single screen printing operation, but can also be obtained following several successive screen printing operations.

[0035] The channel teeth 45 comprise a front face 46, parallel to the main plane P40 of the anode pole plate 40 and two side faces 48, which connect the front face 46 to the base plate 4L

[0036] The channel bottom 47 extends parallel to the main plane P40 of the anode polar plate 40. The channel teeth 46 are located on either side of the channel bottom 47 along the transverse axis Z.

[0037] The coating 50 covers the first face 41A at locations where the channel teeth 45 do not extend onto the first face 41A. The coating 50 includes a first area that is arranged against at least a portion of the channel bottom 47 of each channel 43.

[0038] The coating 50 also covers the channel teeth 45, more precisely the front face 46 and the side faces 48 of each channel tooth 45. More precisely, the coating 50 comprises a second zone which is arranged against at least a portion of the sides 49 of each channel 43, the second zone thus covering the side faces 48 of both channel teeth 45. The coating 50 also comprises a third zone which covers at least a portion of the front faces 46 of the channel teeth 45. This third zone of the coating 50 forms an outer layer of the channel teeth 45. Alternatively, the third zone of the coating 50 is covered exclusively with one or more layers of electrically conductive materials.

[0039] The coating 50 is made of a third material, electrically conductive, that is to say, as mentioned previously, of electrical conductivity greater than 100 S / cm. The electrical conductivity of the coating 50 is for example between 100 S / cm and 140,000 S / cm. The third material comprises for example carbon particles, in the form of graphite, but may also comprise particles formed from other materials, for example metals and / or comprise conductive polymers.

[0040] The coating 50 is preferably deposited on the anode polar plate 40 by physical vapor deposition, for example by cathodic sputtering, or by eva vacuum poration. Advantageously, the coating 50 has a thickness e50, measured along the stacking axis X at the level of the front faces 46 and the channel bottoms 47, and along the transverse axis Z at the level of the lateral faces 48, between 10 nm and 5 pm, preferably between 20 nm and 2 pm.

[0041] The anodic polar plate 40 bears, along the stacking axis X, against the gas diffusion layer 23. More precisely, the coating 50 covering the front faces 46 of the channel teeth 45 bears, along the stacking axis X, against the gas diffusion layer 23. It thus forms an interface between the channel teeth 45 and the gas diffusion layer 23. Thus, the coating 50 ensures electrical conduction between the gas diffusion layer 23 and the base plate 41.

[0042] In the case where the second material, constituting the channel teeth 45, has an intermediate electrical conductivity, the channel teeth 45 can ensure, in concert with the coating 50, a part of the electrical conduction between the gas diffusion layer 23 and the base plate 41. This makes it possible to reduce the thickness of the coating 50, in particular by allowing a compromise between an electrical conduction adapted to the electrochemical cell 10 and a thickness of the coating 50 which must be kept low, ideally less than 5 μm, to limit a thickness of the electrochemical cell 10 along the stacking axis X and to limit costs linked to the use of the coating 50, in particular the material costs.

[0043] Reactive gas, more precisely hydrogen, circulates in the channels 43 of the anode polar plate 40. The channels 43 thus supply the membrane electrode assembly 10 with hydrogen, which diffuses through the gas diffusion layer 23 to the membrane 21 covered with catalyst 25.

[0044] The cathode polar plate 60 extends along a main plane P60 of the cathode polar plate 60, parallel to the main plane P10. The cathode polar plate 60 comprises a base plate 61, two circulation fields 62, 64 and a coating 70. The base plate 61 is similar to the base plate 41 and, as such, is substantially planar and extends parallel to the main plane P10. The base plate 61 is made of the first material.

[0045] The circulation field 62 comprises channels 63 extending mainly along the longitudinal axis Y on a first face 61A of the base plate 61, parallel to the main plane of the plate P60. The channels 63 are parallel to each other and aligned along the transverse axis Z. Each channel 63 comprises two channel teeth 65 and a channel bottom 67. Two successive channels 63 along the transverse axis Z comprise a common channel tooth 65.

[0046] The channel teeth 65 are arranged on the first face 61A parallel to the longitudinal axis Y, and are made of a second material.

[0047] The channel teeth 65 have a thickness e65, measured along the stacking axis X, between 150 and 350 pm, preferably between 200 pm and 250 pm, and a width 165, measured on the base plate 41 along the transverse axis Z, between 50 and 400 pm, preferably 250 pm, similarly to the canal teeth 45.

[0048] The channel teeth 65 are made by additive manufacturing techniques, like the channel teeth 45. The channel teeth 65 are preferably made identically to the channel teeth 45.

[0049] The channel teeth 65 comprise a front face 66, parallel to the main plane of the plate P60 and two side faces 68, which connect the front face 66 to the base plate 61.

[0050] The channel bottom 67 extends parallel to the longitudinal axis Y, the channel teeth 65 being located on either side of the channel bottom 67 along the transverse axis Z.

[0051] The circulation field 64 comprises channels 73 extending mainly along the longitudinal axis Y on a second face 61B of the base plate 61, opposite the first face 60A. The channels 73 are parallel to each other and aligned along the transverse axis Z. Each channel 73 comprises two channel teeth 75 and a channel bottom 77. Two successive channels 73 along the transverse axis Z comprise a common channel tooth 75.

[0052] The channel teeth 75 are arranged on the second face 61B parallel to the longitudinal axis Y, and are made of a second material.

[0053] Alternatively, the channel teeth 75 are made of a fourth material, distinct from the first, second and third materials. The fourth material has, for example, an electrical conductivity similar to the second material and a thermal conductivity greater than the second material. Indeed, it may be particularly advantageous to have the channel teeth 75 with a high thermal conductivity, to facilitate cooling of the cell 10.

[0054] The channel teeth 75 have a thickness e75, measured along the stacking axis X, of between 150 and 300 pm, ideally between 200 pm and 250 pm, and a width 175, measured on the base plate 41 along the transverse axis Z, of between 50 and 400 pm, preferably 250 pm, similarly to the channel teeth 65.

[0055] The channel teeth 75 are produced by additive manufacturing techniques, preferably identical to those used for the channel teeth 65.

[0056] The channel teeth 75 comprise a front face 76, parallel to the main plane of the plate P60 and two side faces 78, which connect the front face 76 to the base plate 61.

[0057] The channel bottom 77 extends parallel to the longitudinal axis Y, the channel teeth 75 being located on either side of the channel bottom 77 along the transverse axis Z.

[0058] The coating 70 covers the faces 61A and 61B at the locations where the channel teeth 65 and 75 do not extend onto the base plate 61. The coating 70 comprises a first zone which is arranged against at least a portion of the channel bottom 67 of each channel 63 and against at least a portion of the channel bottom 77 of each channel 73. The coating 70 also covers the channel teeth 65 and 75, more precisely the front faces 66 and the side faces 68 of each channel tooth 65 and the front faces 76 and side faces 78 of each channel tooth 75. Thus, the coating 70 comprises a second zone which is arranged against at least a portion of the sides 69 of each channel 63 and the sides 79 of each channel 73. The coating 70 also comprises a third zone which covers at least a portion of the front faces 76 of the channel teeth 75. This third zone of the coating 70 forms an outer layer of the channel teeth 75. Alternatively, the third zone of the coating 70 is covered exclusively with one or more layers of electrically conductive materials.

[0059] Advantageously, the coating 70 has a thickness e70, measured along the stacking axis X at the level of the front faces 66 or 76 and the channel bottoms 67 or 77, and along the transverse axis Z at the level of the lateral faces 68 or 78, between 1 pm and 20 pm, preferably equal to 10 pm.

[0060] The coating 70 is preferably identical to the coating 50. In particular, the thicknesses e70 and e50 are identical, and the coating 70 is made of a third material.

[0061] The cathode polar plate 60 bears along the stacking axis X against the gas diffusion layer 22. More precisely, the coating 70 covering the front faces 66 of the channel teeth 65 bears along the stacking axis X against the gas diffusion layer 22, and thus forms an interface between the channel teeth 63 and the gas diffusion layer 22.

[0062] Reactive gas, more precisely air, circulates in the channels 63 of the cathode polar plate 60. The channels 63 thus supply the membrane electrode assembly 10 with air, which diffuses through the gas diffusion layer 22 to the membrane 21 covered with catalyst 25.

[0063] Cooling fluid circulates in the channels 73 of the cathode pole plate 60, making it possible to cool the electrochemical cell 10 when it is in operation. When several electrochemical cells 10 are stacked along the stacking axis X to form the fuel cell, a face opposite the first face 41A of the anode pole plate 40 of an electrochemical cell 10 bears against the cathode pole plate 60 of the adjacent electrochemical cell 10 in the stack. More precisely, the face opposite the first face 41A of the base plate 41 bears against the coating 70 covering the front faces 76 of the channels 73 of a cathode pole plate 60 of the adjacent electrochemical cell 10. The coating 70 thus forms an interface between the teeth of channel 73 of the cathode pole plate 60 of the adjacent electrochemical cell 10 and the anodic pole plate 40, allowing the conduction of electrons from the membrane 21 of one electrochemical cell 10 to the adjacent electrochemical cell 10 in the stack. The electrons flow from the membrane 21, through the gas diffusion layer 23, the coating 50, to the base plate 41 of the electrochemical cell 10, then flow through the coating 70 located on the side of the face 61 B, the base plate 61, the coating 70 located on the side of the face 61 A, the gas diffusion layer 22 to the membrane 21 of the adjacent electrochemical cell 10 in the stack. The anodic polar plate 40 of an electrochemical cell 10 and the cathodic polar plate 60 of the adjacent electrochemical cell 10 in the stack are advantageously glued, or welded together and then form a bipolar plate.

[0064] In a particularly advantageous manner, the channel teeth 45, 65 and 75, on the one hand, and the channels 43, 63 and 73 on the other hand, are aligned along the stacking direction X. This ensures good compression of the electrochemical cells 10 when they are stacked and makes it possible to limit deformations of the cells due to compression.

[0065] In the second and third embodiments shown in Figures 2 and 3, elements similar to those of the first embodiment bear the same references. If a reference is given in one of these figures without being mentioned in the description, or mentioned in the description without being given in a figure, it designates the same element as that bearing the same reference in the first embodiment. In the following, we mainly describe what distinguishes the second and third embodiments from the first.

[0066] [Fig.2] shows a detail of an anode pole plate 140 as an alternative embodiment to the anode pole plate 40.

[0067] The anode polar plate 140 differs from the anode polar plate 40 by its coating 150, which replaces the coating 50.

[0068] The coating 150 comprises two superimposed layers, a first layer 151 and a second layer 152, made of different materials, the materials of the first and second layers 151 and 152 being electrically conductive. The first layer 151 comprises, for example, metal particles, in particular titanium, or, according to another example, chromium. The second layer 152 is made of the same third material as in the first embodiment. Each layer 151 and 152 of the coating 150 is deposited by vapor deposition.

[0069] Preferably, thicknesses e151 and e152 of the layer 151, respectively of the layer 152, measured along the stacking axis X are between 1 μm and 19 μm. Furthermore, a total thickness e150 of the coating 150 does not exceed 20 μm and is preferably equal to 10 μm. The thicknesses e151 and e152 may be different.

[0070] The coating 150 covers the first face 41A at the locations where the channel teeth 45 do not extend over the first face 41A. The coating 150 thus constitutes the channel bottom 47 of each channel 43. The coating 150 also covers the channel teeth 45, more precisely the front faces 46 and the side faces 48 of each channel tooth 45. Thus, the coating 150 constitutes the sides 49 of each channel 43.

[0071] [Fig. 3] shows a detail of an anode pole plate 240 as an alternative embodiment to the anode pole plate 40.

[0072] The anode polar plate 240 differs from the anode polar plate 40 by its coating 250, which replaces the coating 50.

[0073] The coating 250 comprises electrically conductive fillers, here fibers 251, arranged in a matrix 252. In this case, the assembly comprising the fibers 251 and the matrix 252 constitutes the third material. The fibers 251 are electrically conductive and are for example carbon or graphite fibers. The fibers 251 are shown here with the same diameter d251, but may have a different diameter and length. The diameter d251 of the fibers 251 is ideally less than 10 m.

[0074] As seen in [Fig. 3], the fibers 251 are arranged parallel to each other. This arrangement is optional, and the fibers 251 can also be arranged in any manner relative to each other, including being entangled.

[0075] Alternatively, the fibers 251 are woven, then coated with the matrix 252 and arranged on the channel teeth 45 and the base plate 4L. They can also be arranged on the channel teeth 45 and the base plate 41 and then covered by the matrix 252, by vapor deposition for example. The matrix 252 can be electrically conductive or insulating. In the case where the matrix 252 is electrically insulating, the electrical conductivity of the third material is ensured by the fibers 251, the third material thus being generally electrically conductive.

[0076] According to an alternative not shown, the fillers are particles or spheres, rather than fibers.

[0077] The coating 250 covers the first face 41A at the locations where the channel teeth 45 do not extend over the first face 41A. The coating 250 thus constitutes the channel bottom 47 of each channel 43. The coating 250 also covers the channel teeth 45, more precisely the front faces 46 and the side faces 48 of each channel tooth 45. Thus, the coating 250 constitutes the sides 49 of each channel 43.

[0078] [Fig.4] shows a detail of an anode pole plate 340 as a form of alternative embodiment to the anode pole plate 240. The anode pole plate 340 differs from the anode pole plate 240 in that the base plate 41 is coated with a protective coating 389 made of a fifth material, and in that that the anode polar plate 340 comprises a first insulating layer 391 and a second insulating layer 392.

[0079] The fifth material is electrically conductive and has, for example, anti-corrosive properties. The protective coating 389 serves, for example, to protect the base plate 41 from corrosion, while maintaining electrical contact between the coating 150 and the base plate 4L. In this case, the coating 150 is in electrical contact with the base plate 41 via the protective coating 389. In this embodiment, the channel teeth 45 are in particular arranged on the protective coating 389.

[0080] In [Fig. 4], the first insulating layer 391 is interposed between, on the one hand, the front surface 46 and the lateral surfaces 48 of the channel teeth 45, and on the other hand the coating 150, more precisely the layer 152. The first insulating layer 391 therefore covers the front surface 46 and the lateral surfaces 48 of the channel teeth 45. Alternatively, the first insulating layer 391 covers only the front face 46, or only the lateral surfaces 48.

[0081] The first insulating layer 391 is made of electrically insulating material, and serves for example to facilitate the retention of the coating 150 on the canal teeth 45, or to protect the teeth 45 from the coating 150.

[0082] The second insulating layer 392 covers the second and third zones of the coating 150. Alternatively, the second insulating layer 392 covers only the second zone, or only the third zone. The second insulating layer 392 is made of electrically insulating material, and serves for example to protect the coating 150 against oxidation.

[0083] The first and second insulating layers 391 and 392 do not modify the flow of electrons from the gas diffusion layer 22 to the base plate 41, since the coating 150 remains in contact with the gas diffusion layer 22 and in electrical contact with the base plate 41 via the protective coating 389.

[0084] Figures 2, 3 and 4 depict the anode pole plates 140, 240 and 340 respectively. The described coatings 150 and 250 can of course be used for cathode pole plates. For example, a cathode pole plate may comprise a two-layer coating, or one comprising fibers, as described for the anode pole plates 140 and 240. This coating preferably covers the channel teeth located on both sides of the base plate of the cathode pole plate. Similarly, the protective coating 392 may cover the base plate of a cathode pole plate, and the first and second insulating layers 391 and 392 may be applied to a cathode pole plate.

[0085] According to a variant not shown, the anode polar plate comprises two circulation fields, one for hydrogen and one for the cooling fluid, and the cathode polar plate only comprises one for air. In this case, the coating made of a third electrically conductive material advantageously covers the teeth and constitutes the channel bottoms located on the two faces of the anode polar plate.

[0086] According to another variant not shown, the coating has at least one first discontinuity, located at at least one channel bottom. The channel bottom is then formed by the coating and a free surface of the face of the base plate, which is not covered by the coating. The coating may optionally have at least one second discontinuity, located on at least one front surface of a channel tooth. Any characteristic described for an embodiment or a variant in the above can be implemented for the other embodiments and variants described previously, as long as technically feasible.

Claims

Claims

1. A polar plate (40, 60; 140; 240; 340) of an electrochemical cell (10), the polar plate (40, 60; 140; 240; 340) comprising: - a base plate (41, 61), made of a first material, the first material being electrically conductive, the base plate (41, 61) extending parallel to a main plane (P40, P60) of the polar plate (40, 60; 140; 240); and - a plurality of channels (43, 63, 73), the channels (43, 63, 73) extending along a longitudinal axis (Y), each channel (43, 63, 73) comprising: • a channel bottom (47, 67, 77), extending parallel to the longitudinal axis (Y), and • two channel teeth (45, 65, 75), extending parallel to the longitudinal axis (Y), the channel teeth (45, 65, 75) being arranged on either side of the channel bottom (47, 67, 77) along a transverse axis (Z), each channel tooth (45, 65, 75) being made of at least one second material, different from the first material, and comprising a front face (46, 66, 76) and two side faces (48, 68, 78), characterized in that: - the polar plate (40, 60; 140; 240; 340) comprises a coating (50, 70; 150; 250), made of at least a third material, the third material being electrically conductive, - the coating (50, 70; 150; 250) comprises a first area which is arranged against at least a part of the channel bottom (47, 67, 77) of each channel (43, 63, 73), covering and being in electrical contact with the first material of the base plate (41, 61), - the coating (50, 70; 150; 250) comprises a second zone which is arranged against at least part of the sides (49, 69, 79) of each channel (43, 63, 73), covering the lateral faces (48, 68, 78) of the two channel teeth (45, 65, 75), and in that - the coating (50, 70; 150; 250) comprises a third zone which covers at least a part of the end faces (46, 66, 76) of the channel teeth (45, 65, 75), this third zone of the coating (50, 70; 150; 250) forming an outer layer of the channel teeth (45, 65, 75) or being covered exclusively with one or more layers of electrically conductive materials, - the first zone, the second zone and the third zone of the coating (50, 70; 150; 250) form a material continuity of the third material such that the coating (50, 70; 150; 250) ensures electrical conduction between the end faces (46, 66, 76) of the channel teeth (45, 65, 75) and the base plate (41, 61).

2. The polar plate (40, 60; 140; 240; 340) of claim 1, wherein the second material is electrically insulating or the second material is of intermediate conductivity.

3. Polar plate (60) according to claim 1 or 2, wherein the channels (63, 73) extend on a first face (61A) of the base plate (61) and on a second face (61B) of the base plate (61), opposite the first face (61A), wherein the first area of the coating is arranged against at least a part of the channel bottom (67, 77) of different channels (63, 73), the second coating area (70) is arranged against at least a part of the sides (69, 79) of different channels (63, 73), in that the third coating area (70) covers at least a part of the end faces (66, 76) of the channel teeth (65, 75) of the different channels (63, 73).

4. A polar plate (60) according to claim 3, wherein the channel teeth (65) extending on the first face (61A) of the base plate (61) are made of a second material and the channel teeth (75) extending on the second face (61B) are made of a fourth material, distinct from the second material.

5. The polar plate (60) of claim 4 wherein the fourth material is electrically insulating or the fourth material is of intermediate electrical conductivity.

6. A polar plate (340) according to any preceding claim, wherein the base plate (41) is coated with a re- protective clothing (389), made of a fifth electrically conductive material.

7. Polar plate (340) according to any one of the preceding claims, wherein the coating (150) comprises several layers (151, 152), each layer (151, 152) being made of a material different from the other layers, each layer (151, 152) being electrically conductive, one of the layers (151, 152) being made of the third material, a first insulating layer (391) is interposed between the second and / or the third zone and the lateral faces and / or the front faces (48, 46) of the channel teeth (45) and / or a second insulating layer (392) covers the first zone and / or the second zone.

8. A polar plate (240) according to any one of claims 1 to 6, wherein the coating (250) comprises a plurality of electrically conductive fibers (251).

9. Electrochemical cell (10) of a fuel cell comprising: - a membrane-electrode assembly (20), extending parallel to a main plane (P 10) of the electrochemical cell (10), comprising a membrane (21) and two gas diffusion layers (22, 23), the membrane (21) being interposed between the two gas diffusion layers (22, 23) along a stacking axis (X); and - two polar plates (40, 60; 140; 240) according to any one of claims 1 to 8, the main plane (P40, P60) of each polar plate (40, 60; 140; 240) being parallel to the main plane (P 10) of the electrochemical cell (10), each polar plate (40, 60; 140; 240) bearing against one of the two gas diffusion layers (22, 23) along the stacking axis (X), the coating (50, 70; 150; 250) forming an interface between the channel teeth (45, 65, 75) and the gas diffusion layer (22, 23) against which the polar plate (40, 60; 140;240) is supported.;

10. Electrochemical cell (10) of a fuel cell according to claim 9, in which the channels (43; 143; 243) of one of the two polar plates (40; 140; 240) extend exclusively on the same face (41A) of the base plate (41), and the channels (63, 73) of the other polar plate (60) extend on a first face (61A) of the base plate and a second face (61B) of the base plate (61), opposite the first face (61A).

11. A fuel cell comprising a stack of electrochemical cells (10), the electrochemical cells (10) being according to any one of claims 9 and 10, the electrochemical cells (10) being stacked along the stacking axis (X).

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