FR3110777A1 - System and method for joining bipolar plates made of composite material of an electrochemical device - Google Patents

Abstract

A system for securing (S) a first bipolar plate (1A) and a second bipolar plate (1B), each bipolar plate comprising an electrically conductive central portion (2A, 2B) and a peripheral portion (3A, 3B) electrically non-conductive, the securing system (S) comprising a first assembly device (4) configured to be in contact with the first bipolar plate and a second assembly device (5) configured to be in contact with the second plate bipolar, the first assembly device (4) comprises a heating member having a peripheral shape and configured to perform heating according to a peripheral heating zone on the peripheral portion (3A) of the first bipolar plate (1A). Figure of the abstract: Figure 11

Description

System and method for joining bipolar plates made of composite material to an electrochemical device

The present invention relates to the field of electrochemical devices and is aimed in particular at a system and a method for joining bipolar plates made of composite material to an electrochemical device.

Electrochemical device means any device making it possible to implement an electrochemical reaction, such as a fuel cell or a proton exchange membrane electrolyser, making it possible to respectively generate electrical energy or hydrogen from an oxidation-reduction reaction. The term "electrochemical device" also refers to an oxidation-reduction flow battery for generating electrical energy from potential energy stored in the battery.

In known manner, an electrochemical device comprises a stack of a plurality of cells extending along a stack axis and two end plates, placed at the ends of the stack. The end plates are connected by compression members which allow the cells to be compressed and to seal the electrochemical device.

Referring to Figure 1, each cell 110 includes a membrane-electrode assembly 120 and two bipolar plates 130, also called separator plates, which sandwich the membrane-electrode assembly 120 and allow the distribution of fluids into the cell 110. To form the electrochemical reaction in the electrochemical device, each cell 110 is, in known manner, supplied with an oxidizing fluid and a reducing fluid, for example dihydrogen and dioxygen, which react when they are brought into contact in a reaction of oxidation-reduction. Each cell 110 is also supplied with heat transfer fluid, used for thermal regulation of the electrochemical device.

In practice, two adjacent bipolar plates 130A, 130B of two adjacent cells 110A 110B are fastened together so as to form a bipolar module M defining several internal channels 140 which allow the heat transfer fluid to pass between the cells 110.

The present invention relates to bipolar plates formed from composite material and not bipolar plates formed from graphite, which are heavy and have a large bulk in the electrochemical device.

In known manner, a bipolar plate made of composite material comprises electrically conductive particles, generally carbon particles, dispersed in a polymer resin.

Referring to Figures 2 and 3, such a bipolar plate 130 comprises in a known manner a plurality of openings 131, which allow the entry and exit of the oxidizing and reducing fluids, and two entry and exit openings 132 of the fluid coolant. Each bipolar plate 130 further comprises an active central portion 133, in contact with the membrane-electrode assembly 120 and on which the oxidation-reduction reaction takes place, thanks to the conductive particles. The central portion 133 comprises concave portions 135 and convex portions 136 (shown in FIG. 3) allowing the circulation of fluids between the various inlet/outlet openings 131, 132. In known manner, the concave portions 135 of bipolar plates 130 are fastened together so that the convex portions 136 form the internal channels 140 of a bipolar module M. Each bipolar plate 130 also comprises a peripheral portion 134 (shown in FIG. 2) allowing the fastening of the two bipolar plates 130 to form the bipolar module M.

In a known manner, the connection of two composite bipolar plates is achieved by adding an elastomer seal applied to the peripheral zone of the bipolar plates, which is long and complex to implement. Production rates are then low.

A process for assembling composite panels by resistive welding is also known. Such welding is achieved by means of a welding tool which gradually melts the material as it travels along the edges of the panels to form a weld bead. However, such a method is not applicable to a composite bipolar plate as described above, in particular because of its composition. Indeed, a bipolar plate comprising conductive particles dispersed in a polymer resin cannot be melted without the conductive particles being entrained by the molten resin, which can affect its conductivity. In addition, such a welding process takes a long time to implement because it requires the regular movement of a welding tool all around the composite panel.

In the prior art, a bipolar plate made of composite material comprising conductive particles dispersed in a resin is known. To ensure high conductivity, it is necessary to integrate a large number of conductive particles. During the formation of such a bipolar plate, the resin in a viscous state is mixed with a very large number of conductive particles, which makes the mixture thick and does not allow the formation of thin bipolar plates. Also, a bipolar plate formed of conductive particles has a significant thickness, generally between 3 and 5 mm, which increases the size and mass of the electrochemical device. This is penalizing for an electrochemical device intended to be integrated for example in an aircraft or in any other vehicle.

Also, a bipolar plate made of composite material is known comprising reinforcing fibers (for example carbon fibers) impregnated with thermoplastic or thermosetting polymer resin forming a matrix. Such a bipolar plate has the advantage of being thinner, with a thickness of less than one millimeter, which makes it possible to limit its bulk and its mass.

However, to date there is no solution allowing the industrial assembly of bipolar plates made of composite material comprising reinforcing fibers impregnated in a polymer resin.

The invention thus aims to eliminate at least some of these drawbacks by proposing a system and a method for joining two bipolar plates that is simple and without adding material, allowing the rapid joining of two bipolar plates without impacting their mechanical properties and their permeability to fluids.

PRESENTATION OF THE INVENTION

• une portion centrale, électriquement conductrice, destinée à réaliser des échanges dans le dispositif électrochimique, et
• une portion périphérique, électriquement non conductrice, s’étendant extérieurement à la portion centrale.

The invention relates to a system for securing a first bipolar plate and a second bipolar plate so as to form a bipolar module of an electrochemical device, the electrochemical device being configured to implement an electrochemical reaction, each bipolar plate being made of a composite material comprising conductive reinforcing fibers impregnated in a polymer resin, each bipolar plate comprising:

• a central portion, electrically conductive, intended to carry out exchanges in the electrochemical device, and
• a peripheral portion, electrically non-conductive, extending externally to the central portion.

• un premier dispositif d’assemblage configuré pour être en contact avec la première plaque bipolaire, et
• un deuxième dispositif d’assemblage configuré pour être en contact avec la deuxième plaque bipolaire.

The connection system includes:

• a first assembly device configured to contact the first bipolar plate, and
• a second assembly device configured to be in contact with the second bipolar plate.

The first assembly device comprises a heating member having a peripheral shape and configured to perform heating according to a peripheral heating zone on the peripheral portion of the first bipolar plate so as to melt the matrix in order to secure the first bipolar plate with the second bipolar plate and form a peripheral weld bead extending outside the central portion and being strictly included in the peripheral portion of the first bipolar plate.

The joining system according to the invention advantageously makes it possible to join together two bipolar plates made of composite material and allows local heating only in the peripheral portion of each bipolar plate, allowing a partial overhaul of the residual layer of polymer resin present on each peripheral portion of each bipolar plate, without damaging the central portion of each.

A peripheral heating zone makes it possible to instantly weld the entire periphery of the bipolar plates without requiring the movement of a tool, which represents a significant time saving. Thanks to the system according to the invention, the joining of two bipolar plates is faster and more reliable.

Such a securing system also makes it possible to dispense with the addition of additional material during the formation of the bipolar module, which represents a significant saving in time and limits the number of steps necessary for the formation of the bipolar module.

Preferably, each bipolar plate comprises carbon fibers impregnated in a thermoplastic resin.

Preferably again, each bipolar plate has a thickness of less than 1 mm. The system according to the invention allows the joining together of two bipolar plates of very thin thickness for which there does not exist to date a reliable assembly process which makes it possible to preserve the mechanical characteristics of such bipolar plates.

In a preferred embodiment, the first assembly device comprises a pressure member configured to apply a pressure force according to a pressure zone at least on a part of the peripheral portion of the first bipolar plate so as to compress the first bipolar plate and the second bipolar plate between the first assembly device and the second assembly device, the heating member being mounted on the pressure member, the heating zone being in the vicinity of the pressure zone. The securing system thus advantageously makes it possible to keep the two bipolar plates immobile over their entire periphery, while providing local heating. In addition, pressure on the entire periphery of the bipolar plates makes it possible to limit the risks of the plates moving during the heating operation, which could cause an irregular weld bead.

In one embodiment, the pressure member having a parallelepipedal shape, the pressure zone extends both over the central portion and over part of the peripheral portion of the first bipolar plate, and the peripheral heating zone extends over the peripheral portion of the first bipolar plate outside the pressure zone.

In an alternative embodiment, the pressure member having a peripheral shape, the pressure zone extends peripherally only on the peripheral portion of the first bipolar plate. A peripheral pressure zone makes it possible to limit the damage to the central portion of each bipolar plate.

In one embodiment, the heating zone extends over the peripheral portion of the first bipolar plate outside the peripheral pressure zone.

Alternatively, the heating zone extends over the peripheral portion of the first bipolar plate inside the pressure zone.

In one embodiment, the pressure member having a peripheral shape, the pressure zone extends peripherally only over the peripheral portion of the first bipolar plate, and the peripheral heating zone is strictly included in the zone of peripheral pressure. Such an embodiment advantageously allows the pressure member to be applied to the peripheral portion of the first bipolar plate on either side of the heating member, which makes it possible to ensure that the two bipolar plates relative to each other. The pressure member including the heating member makes it possible to distribute pressure on either side of the weld bead. Thus, the mechanical characteristics of the peripheral portion of each bipolar plate are preserved as close as possible to the central portion and on the outer edges of the bipolar plate.

According to a preferred embodiment, the pressure member of the first assembly device comprising an interior cavity, the heating member of the first assembly device is slidably mounted in the interior cavity of the pressure member. Such mounting of the heating member makes it possible to ensure that the heating zone is included in the pressure zone, making it possible to ensure the positioning of the weld bead.

Preferably, the heating member being configured to come into contact with the first bipolar plate, the heating member comprises a positioning device configured to come into abutment against the pressure member so as to precisely define the position of the heater. Such a positioning device advantageously makes it possible to control the position of the heating member relative to the first bipolar plate.

Preferably, the heating member comprising a welding head, the welding head has a section less than or equal to 10 mm, allowing a sufficient quantity of polymer matrix to be melted, so as to ensure a welding surface sufficient to secure the two bipolar plates, while limiting the dimensions of the weld bead.

Preferably, the section of the welding member is less than or equal to 5mm.

According to one embodiment, the polymer resin of the composite material having a melting temperature, the heating member is configured to heat to a temperature between the melting temperature of the polymer resin and the melting temperature increased by 40°C . Such a temperature advantageously makes it possible to locally melt the residual layer of polymer resin of the first bipolar plate.

Preferably, the pressure member, having an operating temperature, is configured to maintain the operating temperature below or equal to the melting temperature of the polymer resin reduced by 20° C., so as to limit the transfer of heat between the heating member and the pressure member. Thus the polymer matrix does not melt on contact with the pressure member.

Preferably, the pressure member is configured to maintain the operating temperature at ambient temperature.

In a first embodiment, the pressure member is made of a thermally non-conductive material, making it possible to limit heat transfers while avoiding the addition of an additional device.

In a second embodiment, the pressure member includes a cooling device configured to maintain the operating temperature below a predetermined threshold. Such a cooling device makes it possible to manufacture the pressure member in any material while ensuring that the operating temperature of the pressure member is limited.

Preferably, the heating member being configured to apply a pressure force according to the peripheral heating zone, the pressure force applied by the heating member is between 0.1 and 1.5 MPa. Such a pressure force makes it possible to guarantee the maintenance of the two bipolar plates, without risking deforming the joined bipolar plates and without risking the polymer resin moving into a zone outside the welding portion. Thus the securing system makes it possible to guarantee the positioning of the heating zone on the peripheral portion of each bipolar plate throughout the duration of the securing process. Such a pressure force also allows good thermal diffusion without penetrating the bipolar plates and therefore without damaging the carbon fibers of the bipolar plates.

In a preferred embodiment of the invention, the first bipolar plate being subjected to an implementation pressure force during its manufacture, the pressure force applied by the pressure member is less than or equal to the implementation pressure force, advantageously making it possible to limit damage to the composite assembly.

In a preferred embodiment, the second assembly device comprises a heating member having a peripheral shape, the heating member being configured to perform heating according to a peripheral heating zone on the peripheral portion of the second bipolar plate of so as to melt the matrix of the second bipolar plate and form a peripheral weld bead extending outside the central portion and being strictly included in the peripheral portion of the second bipolar plate.

Two similar assembly devices mounted opposite each other make it possible to reduce the heating times, which advantageously makes it possible to limit thermal diffusion in the bipolar plates and thus to limit the risks of deconsolidation of the composite material. Such a configuration also makes it possible to heat the two bipolar plates symmetrically. Thus similar mechanical properties are retained on the two bipolar plates.

In one embodiment, the second assembly device comprises a pressure member configured to apply a pressure force according to a pressure zone at least on a part of the peripheral portion of the second bipolar plate, so as to compress the first bipolar plate and the second bipolar plate between the first assembly device and the second assembly device, the heating member being mounted on the pressure member, the heating zone being in the vicinity of the pressure zone.

In one embodiment, the thickness of the pressure member of the first assembly device is preferably between 10 and 100 mm, making it possible to ensure that the pressure member applies a pressure force according to a zone enough pressure to hold the bipolar plates in compression. Thanks to such a thickness, the pressure member only applies the pressure force on the peripheral portion of the first bipolar plate, which makes it possible to preserve the central conductive portion from any force which might damage it.

• une étape de chauffage, au moins par l’organe de chauffage du premier dispositif d’assemblage, pendant une première durée prédéterminée de chauffage, l’étape de chauffage étant réalisée selon une zone de chauffage périphérique sur la portion périphérique de la première plaque bipolaire de manière à former un cordon de soudage périphérique s’étendant extérieurement à la portion centrale et étant strictement inclus dans la portion périphérique de la première plaque bipolaire.

The invention also relates to a method for securing a first bipolar plate and a second bipolar plate so as to form a bipolar module of an electrochemical device, the electrochemical device being configured to implement an electrochemical reaction, the method connection being carried out by means of the connection system as described above, the connection method comprising:

• a heating step, at least by the heating member of the first assembly device, for a first predetermined heating time, the heating step being carried out in a peripheral heating zone on the peripheral portion of the first bipolar plate so as to form a peripheral weld bead extending outside the central portion and being strictly included in the peripheral portion of the first bipolar plate.

The method according to the invention advantageously allows a simple and rapid connection of two bipolar plates to form the bipolar module. The process makes it possible to ensure the joining of two bipolar plates while guaranteeing to preserve the conductivity characteristics of the central portion of each bipolar plate which has reinforcing fibers exposed on the surface. Thanks to the invention, the connection of two bipolar plates made of composite material is also carried out reliably by ensuring the tightness of the channels internal to the bipolar module. In addition, the joining is carried out without adding material, which makes it possible to limit the costs, to overcome the precise positioning of an adhesive joint for example and to limit the number of steps necessary for the formation of the bipolar module. The joining process according to the invention also makes it possible to very significantly reduce the duration of the welding of two bipolar plates, which makes it possible to increase the production rates.

Preferably, the first predetermined heating time is less than or equal to 20 seconds, making it possible to limit the heating time and therefore the risks of significant thermal diffusion in the bipolar plates, which can generate effects of deconsolidation of the composite material on areas away from the weld zone. In other words, such a first duration makes it possible to limit the risks of damage to the composite assembly of each bipolar plate. The process thus makes it possible to preserve the characteristics of mechanical resistance of a bipolar plate of thin thickness comprising reinforcing fibers impregnated in a polymer resin.

Preferably again, the first predetermined duration of heating is less than 2 seconds.

In one embodiment, the method comprises, prior to the heating step, a step of applying, at least by a pressure member of the first assembly device, a pressure force, the pressure force being applied according to a pressure zone at least on a part of the peripheral portion of the first bipolar plate, so as to compress the first bipolar plate and the second bipolar plate. The application of the pressure device ensures that the bipolar plates remain immobile throughout the joining process.

In one embodiment, after the heating step, the pressure member of the first assembly device maintains the pressure force according to the pressure zone for a second predetermined cooling time. Maintaining the pressure force makes it possible to ensure the solidification of the weld bead before removing the pressure member, thus making it possible to limit the risks, for example of slipping and therefore of shifting of a bipolar plate with respect to to each other or detachment of the two bipolar plates which would be due to an unconsolidated composite matrix.

Preferably, the second predetermined cooling time is less than or equal to 5 seconds.

Preferably, the heating step is carried out simultaneously by the heating member of the first assembly device on the peripheral portion of the first bipolar plate and by the heating member of the second assembly device on the peripheral portion of the second bipolar plate. Thus the duration of application of the two heating elements is reduced.

Preferably, the step of applying a pressure force is performed simultaneously on the peripheral portion of the first bipolar plate by the pressure member of the first assembly device and on the peripheral portion of the second bipolar plate by the pressure member of the second assembly device.

Preferably, the distance between the peripheral heating zone and the central portion of each bipolar plate is greater than or equal to 0.5 mm. Such a distance advantageously makes it possible to limit the risk of the heating member affecting the polymer matrix of the central portion and thus altering its conductive properties.

Preferably, the distance between the peripheral heating zone and the central portion of each bipolar plate is less than 30 mm. Such a distance makes it possible to secure two bipolar plates in the peripheral portion closest to the central portion, which has the advantage of increasing the sealing in the bipolar module, making it possible to limit the risks of mixing of the different fluids in the electrochemical device.

PRESENTATION OF FIGURES

The invention will be better understood on reading the following description, given solely by way of example, and referring to the accompanying drawings given by way of non-limiting examples, in which identical references are given to similar objects. and on which:

FIG. 1 is a schematic representation of a stack of three cells and of a bipolar module of an electrochemical device;

Figure 2 is a schematic representation of a bipolar plate of the bipolar module of Figure 1;

FIG. 3 is a schematic representation of a view along a section plane A: A of the bipolar plate of FIG. 2;

Figure 4 is a schematic representation of a bipolar plate comprising a central portion and a peripheral portion;

FIG. 5 is a schematic representation of a view along a section plane B: B of the bipolar plate of FIG. 4;

Figure 6 is a schematic representation of a top view of the bipolar plate of Figure 4;

FIG. 7A is a schematic representation of a first embodiment of a system for securing two bipolar plates according to the invention;

FIG. 7B is a schematic representation of a bottom view of a first device for assembling the securing system of FIG. 7A;

FIG. 7C is a schematic representation of a second embodiment of a system for securing two bipolar plates according to the invention;

FIG. 7D is a schematic representation of a bottom view of a first device for assembling the securing system of FIG. 7C;

FIG. 8 is a schematic representation of a third embodiment of a system for securing two bipolar plates according to the invention;

Figure 9 is a schematic representation of a bottom view of a first assembly device of the securing system of Figure 8;

FIG. 10 is a schematic representation of a close-up view along a section plane C: C of the first assembly device of FIG. 8;

FIG. 11 is a schematic representation of a close-up view of the securing system of FIG. 8 according to the embodiment for the assembly of two bipolar plates of FIG. 4;

FIG. 12 is a schematic representation of a close-up view of the securing system of FIG. 8 according to an alternative embodiment for assembling two bipolar plates of FIG. 4;

FIGS. 13 to 18 are schematic representations of the steps of a method for securing two bipolar plates according to the invention.

It should be noted that the figures expose the invention in detail to implement the invention, said figures can of course be used to better define the invention if necessary.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a system for securing two bipolar plates made of composite material of an electrochemical device.

Subsequently, as described previously, the term "electrochemical device" designates equally well a fuel cell, a proton exchange membrane electrolyser, an oxidation-reduction flow battery or any other device making it possible to implement an electrochemical reaction.

As previously described, an electrochemical device comprises a stack of a plurality of cells, each comprising a membrane-electrode assembly and two bipolar plates, also called separator plates, which sandwich the membrane-electrode assembly. Each cell is supplied with heat transfer fluid for thermal regulation of the electrochemical device. For this, two adjacent bipolar plates of two adjacent cells are fastened together so as to form a bipolar module defining several internal channels which allow the passage of the heat transfer fluid between the cells.

The invention relates to a system for joining two bipolar plates of a bipolar module to guarantee the tightness of the internal channels which allow the passage of the heat transfer fluid.

Referring to Figure 4, each bipolar plate 1 extends longitudinally along an X axis, laterally along a Y axis and vertically along a Z axis, so as to form an orthogonal mark (X, Y, Z).

According to the invention, each bipolar plate 1 is made of composite material and comprises conductive reinforcing fibers impregnated in a polymer resin. In a preferred embodiment, each bipolar plate 1 comprises carbon fibers impregnated in a thermoplastic resin, forming a polymer matrix. The carbon fibers are electrically conductive so as to conduct the electrical charges necessary or produced by the oxidation-reduction reaction in the electrochemical device.

Referring to Figures 4 to 6, each bipolar plate 1 comprises a central portion 2 electrically conductive and a peripheral portion 3 electrically non-conductive. The central portion 2 is preferably rectangular.

The central portion 2 is intended to carry out exchanges in the electrochemical device and for this purpose comprises conductive reinforcing fibers exposed at the surface so as to allow high electrical conductivity.

The central portion 2 has a thickness Ec of between 0.1 and 1 mm, defined along the vertical axis Z and represented in FIG. 5 and making it possible to give the bipolar plate 1 a thin and light reinforced zone. The bipolar plate 1 comprising a plurality of channels to allow the passage of fluids, as described above, its thickness Ec varies while being less than 1 mm.

The peripheral portion 3 extends externally to the central portion 2 so as to form the periphery of the bipolar plate 1, as shown in FIG. 4. The peripheral portion 3 comprises unexposed reinforcing fibers, so as to form a non-conductive portion. For this, the peripheral portion 3 comprises a surplus of material, designated residual layer of polymer matrix 31, preferably on either side of the thickness of the bipolar plate 1 (in other words in this example along the Z axis at the -above and below the bipolar plate 1), which will be used for joining two bipolar plates 1 as will be described in more detail later. Preferably, the residual polymer matrix layer 31 has a thickness Er of between 0.03 and 0.1 mm. Also, the peripheral portion 3 has a thickness Ep along the vertical axis Z shown in Figures 4 and 5, strictly greater than the thickness Ec of the central portion 2. The peripheral portion 3 preferably comprises a rectangular inner edge and a rectangular outer edge.

In other words, the overall thickness of each bipolar plate 1 is between 0.1 and 1.2 mm, which allows a light and compact bipolar plate 1 in the electrochemical device.

In a preferred embodiment of the invention, the peripheral portion 3 extends over a width L (shown in Figures 4 and 6) preferably between 10 and 100 mm, allowing a sufficient surface to allow contact of the system connection S while ensuring a sufficient quantity of excess polymer matrix 31 to allow the connection of two bipolar plates 1.

In a preferred embodiment, with reference to Figure 6, the peripheral portion 3 comprises a welding portion 32 corresponding to the portion which will be in contact with a heating member of the attachment system S, as will be described in more detail. afterwards. Such a welding portion 32 extends over the entire peripheral portion 3 of the bipolar plate 1. In other words, the welding portion 32 has a peripheral shape. Preferably, the welding portion 32 extends over a width e of between 0.1 and 15mm, preferably less than 5mm.

In addition, the welding portion 32 is preferably positioned in the peripheral portion 3 at a distance d between 0.5 and 30 mm, more preferably still greater than 0.8 mm from the central portion 2. Such a distance d allows advantageously to limit the risk that the securing system S affects the thermoplastic matrix of the central portion 2 and thus alters its conductive properties.

As described previously, the connection system S according to the invention makes it possible to connect a first bipolar plate 1A and a second bipolar plate 1B, to form a bipolar module M.

With reference to FIG. 7A, the securing system S according to the invention comprises a first assembly device 4 and a second assembly device 5, mounted opposite the first assembly device 4. During joining the two bipolar plates 1A, 1B, the first assembly device 4 is configured to be in contact with the first bipolar plate 1A (in this example the upper plate) and the second assembly device 5 to be in contact with the second bipolar plate 1B (in this example the lower plate).

Referring to Figure 7B, showing a sectional view of the first assembly device 4, the latter comprises a welding member 41, configured to allow the welding of the two bipolar plates 1A, 1B. The welding member 41 makes it possible to carry out heating according to a peripheral heating zone C on the peripheral portion 1A of the first bipolar plate 1A as will be described in more detail later.

In a preferred embodiment, with reference to FIGS. 7C to 9, the first assembly device 4 comprises a pressure member 42, configured to hold the two bipolar plates 1A, 1B stationary. The pressure member 42 is configured to apply a pressure force F according to a pressure zone P at least on part of the peripheral portion 3A of the first bipolar plate 1A. In this embodiment, the heating member 41 is mounted on the pressure member 42 and the heating zone C is in the vicinity of the pressure zone P.

Preferably, the pressure force F is between 0.1 and 1.5 MPa, so as to avoid excessive pressure which could cause material to move out of the weld portion.

In one embodiment, shown in Figures 7C and 7D, the pressure member 42 has a parallelepipedic shape. The pressure zone P extends both over the central portion 2A and over part of the peripheral portion 3A of the first bipolar plate 1A, and the peripheral heating zone C extends over the peripheral portion 3A of the first bipolar plate 1A outside the pressure zone P, as represented in FIG. 7D.

In a preferred embodiment, shown in Figures 8 and 9, the pressure member 42 has a peripheral shape. The pressure member 42 is configured to apply the pressure force F according to a pressure zone P extending peripherally on the peripheral portion 3A of the first bipolar plate 1A, as shown in FIG. 9. more preferably, the pressure zone P is configured to extend only over the peripheral portion 3A of the first bipolar plate 1A.

In this example, the heating member 41 is preferably mounted on the pressure member 42. The heating zone C is thus in the vicinity of the pressure zone P. The heating zone C extends internally or externally to the pressure zone P. In a preferred embodiment, shown in Figure 9, the heating zone C is included in the pressure zone P, as will be described in more detail later.

The securing system S is described below according to this last preferred embodiment, in which the first assembly device 4 comprises a pressure member 42 and in which the peripheral heating zone C is strictly included in the pressure zone P device.

In this example, with reference to Figures 9 and 10, the pressure member 42 comprises a main body 421 of peripheral shape and an interior cavity 422 extending in this example vertically throughout the pressure member 42. This document presents the example of a pressure member 42 according to a rectangular pressure zone P (as represented in FIG. 9), however it goes without saying that the pressure member 42 could just as well have a different peripheral shape, so to be able to be adapted to any shape of bipolar plate 1 (circular, ovoid, trapezoidal or even a more complex shape).

The pressure member 42 has, in this example, over the entire periphery, a thickness k preferably between 10 and 100mm. Such a thickness k advantageously makes it possible to ensure that the pressure member 42 applies a pressure force F along a peripheral pressure zone P having a sufficient surface to maintain the bipolar plates 1A, 1B in compression, while ensuring that the pressure force F is only applied to the peripheral portion 3A of the first bipolar plate 1A.

The pressure member 42 is configured to be maintained at an operating temperature lower than or equal to the melting temperature of the polymer resin of the composite material of each bipolar plate 1, lowered by 20° C., so as not to melt the resin when pressed. In a first embodiment, the pressure member 42 is made of a thermally non-conductive material, so as to limit the transfer of heat between the heating member 41 and the pressure member 42. By way of example , in a non-exhaustive manner, the pressure member 42 is made of a thermoplastic material such as polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyetherketone (PEK), Teflon ®, or in an organic composite material, a material inorganic refractory, or by machining MICA, graphite, ceramics. In a second embodiment, the pressure member 42 comprises a cooling device (not shown), for example a liquid or gaseous cooling circuit integrated or external to the pressure member 42, to regulate the operating temperature of the pressure member 42 by maintaining it, for example, at ambient temperature. Such a cooling device also makes it possible to limit the transfer of heat between the heating member 41 and the pressure member 42.

Referring to Figure 10, in this example, the heating member 41 is mounted in the inner cavity 422 of the pressure member 42. This makes it possible to carry out heating according to a heating zone C which is compressed in an optimal manner. as will be presented later.

In a preferred embodiment, the heating member 41 is slidably mounted in the interior cavity 412 of the pressure member 42, so as to be able to be easily removed and brought into contact with the first bipolar plate 1A when implementation of the joining process.

Analogously to the pressure member 42, as shown in Figure 9, the heating member 41 according to the invention has a peripheral shape and is configured to perform heating according to a peripheral heating zone C in a manner in melting the residual layer of polymer matrix 31 of the peripheral portion 3A of the first bipolar plate 1A to secure the first bipolar plate 1A to the second bipolar plate 1B. Alternatively, the heating member 41 can make it possible to melt the residual layer of polymer matrix 31 both of the peripheral portion 3A of the first bipolar plate 1A and of the peripheral portion 3B of the second bipolar plate 1B.

In this example, the peripheral heating zone C is strictly included in the peripheral pressure zone P so as to form on the bipolar module M a peripheral welding bead extending externally to the central portion 2A and being strictly included in the portion peripheral 3A of the first bipolar plate 1A. In other words, the pressure zone P of the pressure member 42 encompasses the heating zone C of the heating member 41 so as to locally compress the first bipolar plate 1A and the second bipolar plate 1B on either side of the heating member 41 around the heating zone C.

Referring to Figure 10, the heater 41 comprises a main body 411 and a welding head 412. The welding head 412 forms the heating zone C and is configured to come into contact with the welding portion 32 of the peripheral portion 3A of the first bipolar plate 1A during a welding operation as will be described in more detail later. The welding head 412 preferably has a width g of between 0.1 and 10mm, preferably less than 5mm. Heating member 41 is preferably centered relative to pressure member 42 so that heating zone C is centered in pressure zone P as illustrated in Figures 9 and 10.

Preferably, the heater 41 is configured to perform heating, for example by convection, radiation, induction, conduction or ultrasonic vibration.

Preferably, the heating member 41 is configured to be maintained at a temperature between the melting temperature of the polymer resin and the degradation temperature of said polymer resin. Such a temperature advantageously makes it possible to locally melt the residual layer of polymer matrix 31 of the first bipolar plate 1A.

In a preferred embodiment, the heating member 41 is configured to apply to the welding portion 32 of the peripheral portion 3A of the first bipolar plate 1A, a pressure force, designated welding pressure force, of between 0 .1 and 1.5 MPa Such a pressure force keeps the bipolar plates joined during the welding phase, without the pressure force damaging them. The pressure force also makes it possible to minimize the effects of deconsolidation in each bipolar plate linked to the melting of the polymer and the release of residual stresses in the composite material of each bipolar plate. This further helps prevent unwanted movement of the resin out of the weld area.

In a preferred embodiment, still with reference to Figure 10, the heating member 41 comprises a positioning device 43 configured to come into abutment against the pressure member 42 when the heating member 41 slides in the cavity. 422 of the pressure member 42. In this example, the positioning device 43 is in the form of a shoulder projecting laterally from the heating member 41. Such a positioning device 43 advantageously makes it possible to control the position of the heater 41 relative to the first bipolar plate 1A during the welding operation. In other words, when the heating member 41 slides in the interior cavity 422 of the pressure member 42, the positioning device 43 allows the heating member 41 to come into contact with the peripheral portion 3A of the first plate. bipolar 1A, without the welding head 412 passing through the first bipolar plate 1A, so as to limit the damage to the reinforcing fibers and the resistance of the composite material.

Referring to Figure 11, according to a first embodiment, the second assembly device 5 is mounted opposite the first assembly device 4 and is configured to come into contact with the second bipolar plate 1B, so as to allow with the first assembly device 4 to simultaneously compress the first bipolar plate 1A and the second bipolar plate 1B.

In this example, the second assembly device 5 is simply in the form of a support, configured to support the second bipolar plate 1B placed under the first bipolar plate 1A in order to resist the pressure applied by the first device. assembly 4.

In this embodiment, the heating member 41 of the first assembly device 4 is configured to melt the thickness Ep of the peripheral portion 3A of the first bipolar plate 1A and the thickness Ep of the peripheral portion 3B of the second bipolar plate 1B. The heating member 41 of the first assembly device 4 is then configured to form the bipolar module M.

The assembly devices 4, 5 of the securing system S can be different, as shown in Figure 11, or similar, as shown in Figure 12.

In a second embodiment, represented in FIG. 11, the second assembly device 5 is similar to the first assembly device 4. As such, the second assembly device 5 comprises a heating member 51. Preferably the second assembly device 5 further comprises a pressure member 52 and a positioning member 53. The heating member 51, the pressure member 52 and the positioning member 53 of the second assembly device 5 have in this case the plurality of features described above for the heating member 41, the pressure member 42 and the positioning member 43 of the first assembly device 4. Also these will not be described in more detail.

In this embodiment, the first assembly device 4 and the second assembly device 5 are mounted symmetrically with respect to the first bipolar plate 1A and to the second bipolar plate 1B. In other words, the first assembly device 4 and the second assembly device 5 are configured to compress the first bipolar plate 1A and the second bipolar plate 1B on either side between the pressure member 42 of the first device. assembly 4 and the pressure member 52 of the second assembly device 5, as shown in Figure 12.

The welding head 512 of the second assembly device 5 is then mounted opposite the welding head 412 of the first assembly device 4, so as to simultaneously melt the thickness Ep of the first bipolar plate 1A by means of the welding head 412 of the first joining device 4 and the thickness Ep of the second bipolar plate 1B by means of the welding head 512 of the second joining device 5, as shown in FIG. 12. Simultaneous heating of the first heating member 41 and of the second heating member 51 on the two bipolar plates 1A, 1B advantageously makes it possible to reduce the duration of application of the heating members 41, 51 on the peripheral portion 3A, 3B of each bipolar plate 1A, 1B.

• contrôler l’effort de pression F de chaque organe de pression 42, 52 appliqué sur la première plaque bipolaire 1A et la deuxième plaque bipolaire 1B,
• commander le coulissement de chaque organe de chauffage 41, 51 dans la cavité intérieure 422, 522 de chaque organe de pression 42, 52, ou bien encore
• commander la durée d’application de l’organe de chauffage 41, 51 sur la portion de soudage 32 des plaques bipolaires 1A, 1B.

Preferably, the securing system S further comprises an electronic device 6 (shown in FIGS. 11 and 12), electrically connected to the first assembly device 4 and to the second assembly device 5. Such an electronic device 6 is configured for example for:

• control the pressure force F of each pressure member 42, 52 applied to the first bipolar plate 1A and the second bipolar plate 1B,
• control the sliding of each heating member 41, 51 in the interior cavity 422, 522 of each pressure member 42, 52, or even
• control the duration of application of the heater 41, 51 on the welding portion 32 of the bipolar plates 1A, 1B.

In one embodiment, the electronic device 6 is further configured to control the position of each heating member 41, 51 relative to the pressure member 42, 52 on which it is mounted, so as to control the force pressure applied by the heating member 41, 51 on the peripheral portion 3A, 3B of each bipolar plate 1A, 1B, without requiring the addition of a stop 43, 53.

The securing system S according to the invention simultaneously allows maintenance over the entire periphery of the bipolar plates 1A, 1B and local heating allowing a partial overhaul of the residual layer of thermoplastic matrix present on each face of the peripheral portion 3 of each plate. bipolar 1A, 1B, without damaging the central portion 2 of each. Such a securing system S also makes it possible to dispense with the addition of additional material during the formation of the bipolar module M, which represents a saving of time and limits the number of steps necessary for the formation of the bipolar module M .

There will now be described a method for securing two bipolar plates 1A, 1B, so as to form a bipolar module M, with reference to FIGS. 13 to 18. In this example, the securing system S comprises a first assembly device 4 and a second assembly device 5 similar, mounted facing each other, on either side of the two bipolar plates 1A, 1B as illustrated in FIG. 12. In this example, the first joining device 4 and second joining device 5 are mounted vertically along the Z axis, that is to say so that the two bipolar plates 1A, 1B extend horizontally in the plane ( X, Y).

The fastening method is described for the example of a fastening system S in which each assembly device 4, 5 comprises a pressure member 42, 52 configured to apply a pressure force F according to a peripheral pressure zone P only on the peripheral portion 3A, 3B of each bipolar plate 1A, 1B and in which the heating member 41, 51 is configured to heat according to a heating zone C strictly included in the pressure zone P.

The first assembly device 4 and the second assembly device 5 are controlled analogously, preferably simultaneously. For the sake of clarity and conciseness, only the steps relating to the first assembly device 4 will be presented, these being analogous for the second assembly device 5.

The method comprises a first step of positioning E1 (shown in FIG. 13) of the first assembly device 4 with respect to the peripheral portion 3A of the first bipolar plate 1A so that the heating member 41 is aligned with the welding portion 32 of the first bipolar plate 1A described previously.

As illustrated in Figure 10, the first assembly device 4 is preferably positioned so as to place the interior cavity 422 (and incidentally the heating member 41) of the pressure member 42 at a distance h between between 0.5 and 30 mm from the central portion 2A of the first bipolar plate 1A. Such positioning advantageously makes it possible to limit the risks of heating of the conductive central portion 2A of each bipolar plate 1A, 1B, thus making it possible to limit the risks of melting the thermoplastic matrix of each central portion 2A, 2B during the joining of the two bipolar plates 1A, 1B. Thus the conductive properties of each central portion 2A, 2B are not altered and the risks associated with the deconsolidation of each composite bipolar plate 1A, 1B are minimized. The second assembly device 5 is positioned analogously.

Referring to Figure 14, during a compression step E2, the pressure member 42 of the first assembly device 4 and the pressure member 52 of the second assembly device 5 apply a pressure force F similar according to each zone of peripheral pressure P against the bipolar plate 1A, 1B with which it is in contact, so as to keep the first bipolar plate 1A stationary against the second bipolar plate 1B. In other words, the two bipolar plates 1A, 1B are compressed at least in part over their entire peripheral portion 3A, 3B between the pressure member 42 of the first assembly device 4 and the pressure member 52 of the second assembly device 5. During the compression step E2, the heating member 41 is in an offset position with respect to the pressure member 42 and thus does not heat.

As illustrated in Figure 15, in this example, the heating member 41 then slides in the interior cavity 422 of the pressure member 42, during a displacement step E3. The movement is stopped when the positioning device 43 comes into abutment against the pressure member 42 so as to position the heating member 41 in optimum contact with the bipolar plate 1A. The heater 41 is in an aligned position with respect to the pressure member 42 in order to act synergistically. In such a position, each heating member 41, 52 applies a pressure force along the peripheral heating zone C on each welding portion 32 of each bipolar plate 1A, 1B.

Referring to Figure 16, each heating member 41, 52 heats, in a heating step E4, along the peripheral heating zone C so as to melt the matrix of each bipolar plate 1A, 1B to secure the first bipolar plate 1A with the second bipolar plate 1B and form the bipolar module M.

In a preferred embodiment, each heating member 41, 52 heats up to a temperature between the melting temperature of the polymer resin and the melting temperature increased by 40° C., for a first predetermined duration of heating that is less than or equal to equal to 20 seconds, so as to melt the polymer resin to weld the bipolar plates 1A, 1B without deconsolidating the thermoplastic assembly of each, which could damage it.

Alternatively, steps E3 and E4 are carried out simultaneously. In such an embodiment, each heating member 41, 52 heats up and is pressed, once having reached a predetermined temperature, against each bipolar plate 1A, 1B for the first predetermined duration.

After the first predetermined heating time, with reference to FIG. 17, during a displacement step E5, each heating member 41, 51 is moved in the opposite manner in step E3 so as to withdraw the member from heating 41, 51 of each bipolar plate 1A, 1B. The welding portion 32 of each bipolar plate 1A, 1B cools for a second predetermined cooling time during which each pressure member 42, 52 maintains the pressure force F. The second predetermined time is preferably less than or equal to 5 seconds, so as to allow consolidation of the weld bead formed by each heating member 41, 51.

Referring to Figure 18, after the second predetermined cooling time, during a withdrawal step E6, each pressure member 42, 52 is moved inversely to step E2. Each pressure member 42, 52 is removed from each bipolar plate 1A, 1B, so as to no longer compress them.

Such a joining process advantageously allows simple and rapid welding of two bipolar plates to form the bipolar module. The method according to the invention makes it possible to ensure the welding of two bipolar plates while guaranteeing to preserve the conductivity characteristics of the central portion of each bipolar plate comprising reinforcing fibers impregnated in a polymer resin and having a central portion comprising exposed reinforcing fibers. Thanks to the invention, the welding of two bipolar plates as described in this document is also carried out reliably by ensuring the tightness of the channels internal to the bipolar module. In addition, the welding is carried out without adding material, which makes it possible to dispense with the precise positioning of the adhesive joint for example and limits the number of steps necessary for the formation of the bipolar module. The joining method according to the invention also makes it possible to very significantly reduce the duration of the welding of two bipolar plates.

Claims (15)

System for securing (S) a first bipolar plate (1A) and a second bipolar plate (1B) so as to form a bipolar module (M) of an electrochemical device, the electrochemical device being configured to implement an electrochemical reaction, each bipolar plate (1A, 1B) being made of a composite material comprising conductive reinforcing fibers impregnated in a polymer resin, each bipolar plate (1A, 1B) comprising:

• a central portion (2A, 2B), electrically conductive, intended to carry out exchanges in the electrochemical device, and
• a peripheral portion (3A, 3B), electrically non-conductive, extending outside the central portion (2A, 2B),
• the securing system (S) comprising:
  • a first assembly device (4) configured to be in contact with the first bipolar plate (1A), and
  • a second assembly device (5) configured to be in contact with the second bipolar plate (1B),
  • the first assembly device (4) comprising a heating member (41) having a peripheral shape and configured to carry out heating according to a peripheral heating zone (C) on the peripheral portion (3A) of the first bipolar plate (1A ) so as to melt the matrix to secure the first bipolar plate (1A) with the second bipolar plate (1B) and form a peripheral weld bead extending externally to the central portion (2A) and being strictly included in the portion peripheral (3A) of the first bipolar plate (1A).

Securing system (S) according to claim 1, in which the first assembly device (4) comprises a pressure member (42) configured to apply a pressure force (F) according to a pressure zone (P) at least on a part of the peripheral portion (3A) of the first bipolar plate (1A) so as to compress the first bipolar plate (1A) and the second bipolar plate (1B) between the first assembly device (4) and the second assembly device (5), the heating member (41) being mounted on the pressure member (42), the heating zone (C) being in the vicinity of the pressure zone (P). Securing system (S) according to claim 2, in which, the pressure member (42) having a peripheral shape, the pressure zone (P) extends peripherally only over the peripheral portion (3A) of the first bipolar plate (1A), and the peripheral heating zone (C) is strictly included in the peripheral pressure zone (P). Securing system (S) according to one of Claims 2 and 3, in which the pressure member (42) of the first assembly device (4) comprising an internal cavity (412), the heating member ( 41) of the first assembly device (4) is slidably mounted in the internal cavity (412) of the pressure member (42). Connection system (S) according to one of Claims 2 to 4, in which, the heating member (41) being configured to come into contact with the first bipolar plate (1A), the heating member (41) comprises a positioning device (43) configured to abut against the pressure member (42) so as to precisely define the position of the heating member (41). Securing system (S) according to one of Claims 1 to 5, in which the heating member (41) comprising a welding head (422), the welding head (422) has a section (g) lower or equal to 5mm. Securing system (S) according to one of Claims 1 to 6, in which the heating member (41) is configured to apply a pressure force of between 0.1 and 1.5 MPa depending on the heating zone (C ) device. Securing system (S) according to one of Claims 1 to 7, in which the second assembly device (5) comprises a heating member (51) having a peripheral shape, the heating member (51) being configured to perform heating according to a peripheral heating zone on the peripheral portion (3B) of the second bipolar plate (1B) so as to melt the matrix of the second bipolar plate (1B) and form a peripheral weld bead extending externally to the central portion (2B) and being strictly included in the peripheral portion (3B) of the second bipolar plate (1B). Method for securing a first bipolar plate (1A) and a second bipolar plate (1B) so as to form a bipolar module (M) of an electrochemical device, the electrochemical device being configured to implement an electrochemical reaction , the securing process being carried out by means of the securing system (S) according to one of claims 1 to 8, the securing process comprising:

• a step of heating (E4), at least by the heating member (41) of the first assembly device (4), for a first predetermined duration of heating, the step of heating (E4) being carried out according to a zone heating device (C) on the peripheral portion (3A) of the first bipolar plate (1A) so as to form a peripheral weld bead extending externally to the central portion (2A) and being strictly included in the peripheral portion ( 3A) of the first bipolar plate (1A).

Method of securing according to claim 9, comprising, prior to the heating step (E4), a step of applying (E2), at least by a pressure member (42) of the first assembly device (4), d a pressure force (F), the pressure force (F) being applied according to a pressure zone (P) at least on a part of the peripheral portion (3A) of the first bipolar plate (1A), so compressing the first bipolar plate (1A) and the second bipolar plate (1B). Method of securing according to claim 10, in which, after the heating step (E4), the pressure member (42) of the first assembly device (4) maintains the pressure force (F) according to the pressure zone (P) for a second predetermined cooling time. Method of securing according to claim 11, in which the second predetermined cooling time is less than or equal to 5 seconds. Method of securing according to one of Claims 9 to 12, in which the heating step (E4) is carried out simultaneously by the heating member (41) of the first assembly device (4) on the peripheral portion (3A ) of the first bipolar plate (1A) and by the heating member (51) of the second assembly device (5) on the peripheral portion (3B) of the second bipolar plate (1B). Method of securing according to one of Claims 9 to 13, in which the distance between the peripheral heating zone (C) and the central portion (2A, 2B) of each bipolar plate (1A, 1B) is greater than or equal to 0 .5mm. Method of securing according to one of Claims 9 to 14, in which the first predetermined duration of heating is less than or equal to 20 seconds.