FR3059473A1 - FUEL CELL WITH INTEGRATED COOLING CIRCUIT AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

The present invention relates to a fuel cell (1) having a stack of cells (A) stacked on each other, each cell (A) having in superposition: ° a first bipolar plate (2a), ° an anode (3a ), An electrolyte (4), a cathode (3b), and a second bipolar plate (2b), the first (2a) and second (2b) bipolar plates having orifices (20) on their periphery in which pass thermally conductive and electrically insulated heat transfer fluid conduits (10).

Description

© Publication number: 3,059,473 (to be used only for reproduction orders) (© National registration number: 16 61511 ® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY

COURBEVOIE © Int Cl ⁸ : H 01 M 8/0258 (2017.01), H 01 M 8/2475

A1 PATENT APPLICATION

©) Date of filing: 25.11.16. © Applicant (s): VALEO THERMAL SYSTEMS (© Priority: Simplified joint stock company - FR. @ Inventor (s): DE VAULX CEDRIC, MONNET VERO- NIQUE and AZZOUZ KAMEL. (47) Date of public availability of the request: 01.06.18 Bulletin 18/22. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ® Holder (s): VALEO THERMAL SYSTEMS related: Joint stock company. ©) Extension request (s): © Agent (s): VALEO THERMAL SYSTEMS.

(54J FUEL CELL WITH INTEGRATED COOLING CIRCUIT AND MANUFACTURING METHOD THEREOF.

FR 3 059 473 - A1 _ The present invention relates to a fuel cell (1) comprising a stack of cells (A) stacked on top of each other, each cell (A) comprising in superposition:

⁰ a first bipolar plate (2a), ⁰ an anode (3 a), ⁰ an electrolyte (4), ⁰ a cathode (3b), and ⁰ a second bipolar plate (2b), the first (2a) and second (2b ) bipolar plates having orifices (20) on their periphery in which pass conduits (10) of thermally conductive and electrically insulated coolant.

Fuel cell with integrated cooling circuit and method of manufacturing the same

The invention relates to a fuel cell in particular for a motor vehicle. More particularly, it relates to a fuel cell comprising an integrated cooling circuit as well as its manufacturing process.

As shown in FIG. 1, a fuel cell 1 comprises a stack of cells A in which an electrochemical reaction takes place between dihydrogen and gaseous oxygen. The stack of cells A is generally compressed and held between two clamping plates 7 by means of tie rods 70.

As shown in Figure 2, each cell A has an anode 3a and a cathode 3b between which is placed an electrolyte 4, for example a proton exchange membrane. At the anode 3a and at the cathode 3b is also arranged a catalyst in order to accelerate the chemical reaction. At the anode 3a is disposed a first bipolar plate 2a having circulation channels 22a which allow the circulation of dihydrogen. At the cathode 3b is disposed a second bipolar plate 2b comprising circulation channels 22b which allow the circulation of the oxygen and the evacuation of the water resulting from the electrochemical reaction.

The electrochemical reaction within cells A is exothermic and it is therefore necessary to cool these cells A. For this, a heat transfer fluid passes between cells A for example by means of cooling plates 5 comprising pipes 50 for circulation of a heat transfer fluid arranged between the bipolar plates 2a, 2b of two contiguous cells A.

However, this type of cooling is not entirely satisfactory because it requires the use of a non-conductive heat transfer fluid, of extreme purity and free of ions in order to reduce the risks of short circuit. Thus, it is necessary to constantly filter the heat transfer fluid in order to eliminate any ion enrichment of the heat transfer fluid, for example during its passage through a heat exchanger or a pump. This generates complexity and a significant cost for manufacturing the fuel cell 1.

One of the aims of the present invention is therefore to at least partially remedy the drawbacks of the prior art and to propose an improved fuel cell as well as its manufacturing process.

The present invention therefore relates to a fuel cell comprising a stack of cells stacked on top of each other, each cell comprising in superposition:

° a first bipolar plate, ° an anode, ° an electrolyte, ° a cathode, and ° a second bipolar plate, the first and second bipolar plates having orifices on their periphery through which pass heat-conducting and electrically insulated heat transfer fluid conduits .

The presence of these heat transfer fluid conduits on the periphery of the bipolar plates allows the bipolar plates to directly transfer the heat resulting from the electrochemical reaction to the heat transfer fluid in order to cool the cells or conversely to bring heat to the cells if one needs to warm them up. It is thus possible to cool or heat the cells without going through a complex thermal management circuit passing between the cells and requiring a non-conductive and very pure heat transfer fluid. It is thus possible to use a conventional heat transfer fluid which reduces the production and use costs of the fuel cell.

According to one aspect of the invention, the heat transfer fluid conduits are tubes of aluminum or aluminum alloy, said heat transfer fluid conduits being anodized on their outer surface.

According to another aspect of the invention, the first and second bipolar plates are made of aluminum or aluminum alloy.

According to another aspect of the invention, the heat transfer fluid conduits are held in the orifices by a mechanical fastening linked to an expansion of said heat transfer fluid conduits.

According to another aspect of the invention, in the stack of cells, the second bipolar plate of a first cell is merged with the first bipolar plate of a second contiguous cell.

According to another aspect of the invention, the fuel cell comprises between each cell a thermally conductive plate, said thermally conductive plate having orifices on its periphery through which also pass the heat transfer fluid conduits.

According to another aspect of the invention, the thermally conductive plates are made of aluminum or aluminum alloy.

According to another aspect of the invention, a fuel cell comprises, on either side of the stack of cells, a coolant collector into which the coolant conduits open.

According to another aspect of the invention, the collectors comprise a collecting plate, said collecting plate comprising orifices through which the heat transfer fluid conduits pass, the ends of the heat transfer fluid conduits being flared at the base of said orifices.

According to another aspect of the invention, the openings of the collector plates include compressible seals.

According to another aspect of the invention, the fuel cell comprises, on either side of the stack of cells, a current collector comprising orifices through which the heat transfer fluid conduits pass.

The present invention also relates to a method of manufacturing a fuel cell as described above, said method comprising the following steps:

° stacking of the cells so that the heat transfer fluid conduits are inserted into the orifices, ° compression of the cell stack, ° expansion of the heat transfer fluid conduits.

According to one aspect of the method according to the invention, the manufacturing method comprises an additional step of setting up a collector on either side of the stack of cells.

According to another aspect of the method according to the invention, the additional step of setting up a collector comprises:

° a first sub-step of fitting collector plates, ° a second step of flaring the ends of the heat-transfer fluid conduits, ° a third step of fitting covers.

According to another aspect of the method according to the invention, the first sub-step of installing collector plates is carried out before the step of expanding the heat transfer fluid conduits.

Other characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and nonlimiting example, and of the appended drawings among which:

• Figure 1 shows a schematic representation of a fuel cell of the prior art, • Figure 2 shows a schematic representation of a stack of cells of the prior art, • Figure 3 shows a schematic representation in section transverse of a stack of cells according to a first embodiment of the invention, • Figure 4 shows a schematic representation of an internal face of a bipolar plate, • Figure 5 shows a schematic representation in cross section of a stack of cells according to a second embodiment of the invention, • Figure 6 shows a schematic representation in cross section of a stack of cells according to a third embodiment of the invention, • Figure 7 shows a representation schematic in longitudinal section of a fuel cell according to the invention.

Identical elements in the different figures have the same references.

The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the characteristics apply only to a single embodiment. Simple features of different embodiments can also be combined to provide other embodiments.

In the present description, it is possible to index certain elements or parameters, such as for example first element or second element as well as first parameter and second parameter or even first criterion and second criterion etc. In this case, it is a simple indexing to differentiate and name elements or parameters or criteria that are similar but not identical. This indexing does not imply a priority of an element, parameter or criterion over another and one can easily interchange such names without departing from the scope of this description. This indexing does not imply an order in time for example to assess such or such criteria.

As shown in Figure 3, the fuel cell 1 according to the invention comprises a stack of cells A stacked on top of each other. Each cell A has in superposition:

• a first bipolar plate 2a, • an anode 3a, • an electrolyte 4, for example a proton exchange membrane, • a cathode 3b, and • a second bipolar plate 2b.

In the present description, the first bipolar plate 2a is spoken of as being the bipolar plate in relation to the anode 3a and allowing the supply of dihydrogen at the level of said anode 3a by means of circulation channels.

22a. Similarly, we speak of a second bipolar plate 2b as being the bipolar plate in relation to the cathode 3b and allowing the supply of oxygen at the level of said cathode 3b by means of circulation channels 22b. Structurally, the first 2a and the second 2b bipolar plates are preferably identical and arranged in a mirror symmetrically with respect to the plane formed by the anode 3a, the electrolyte 4 and the cathode 3b.

In order to ensure the tightness of the cells A, compressible seals 24 are preferably arranged between the first 2a and second 2b bipolar plates and the electrodes 3a, 3b to which they face.

The first 2a and second 2b bipolar plates have orifices 20 on their periphery through which pass conduits 10 of thermally conductive and electrically insulated coolant. The fact that these heat transfer fluid conduits 10 are electrically insulated makes it possible to avoid short circuits between the cells A.

The orifices 20 of the bipolar plates 2a, 2b are preferably aligned so that a conduit 10 of rectilinear heat transfer fluid can pass through an orifice 20 of the assembly of the bipolar plates 2a, 2b.

These heat transfer fluid conduits 10 are preferably tubes made of aluminum or aluminum alloy in order to have good thermal conduction. In order to electrically isolate these conduits 10 while retaining good thermal conduction, the conduits 10 of heat transfer fluid made of aluminum or aluminum alloy can be anodized on their outer surface in particular in contact with the bipolar plates 2a, 2b. However, other types of electrical insulation can be used, such as a plastic film for electrical insulation.

The bipolar plates 2a, 2b are also preferably made of aluminum or aluminum alloy in order to have good thermal conductivity.

The presence of these heat transfer fluid conduits 10 on the periphery of the bipolar plates 2a, 2b allows the bipolar plates 2a, 2b to directly transfer the heat resulting from the electrochemical reaction to the heat transfer fluid in order to cool the cells A or conversely to provide heat to cells A if you need to heat them. It is thus possible to cool or heat the cells A without going through a complex thermal management circuit passing between the cells A and requiring a non-conductive and very pure heat transfer fluid. It is thus possible to use a conventional heat transfer fluid which reduces the production and use costs of the fuel cell 1.

In addition, the heat transfer fluid conduits 10 are held in the orifices 20 preferably by a mechanical fixing linked to an expansion of the heat transfer fluid conduits 10 within the orifices 20. This makes it possible to maintain the stack of cells A because the conduits 10 of heat transfer fluid pass through all the cells A. It is therefore not necessary to use clamping plates 7 and tie rods 70 to maintain the stack of cells A.

According to a first embodiment illustrated in FIG. 3, each cell A comprises a first bipolar plate 2a and a second bipolar plate 2b which are clean and distinct from one cell A to another. The second bipolar plate 2b of a cell A is then in contact with the first bipolar plate 2a of a contiguous cell.

FIG. 4 shows an internal face 200 of a bipolar plate 2a, 2b (also shown in FIG. 3), that is to say the face in contact with an electrode 3a, 3b and which comprises circulation channels 22a, 22b. The bipolar plate 2a, 2b, comprises a supply line 26a and a discharge line 26b of a first gas, dihydrogen if it is a first bipolar plate 2a and dioxygen if it is a second bipolar plate 2b. Between the supply pipe 26a and the delivery pipe 26b of the first gas is disposed a circuit of circulation channels 22a, 22b on the internal face 200 of the bipolar plate 2a, 2b in order to distribute the first gas against one of the electrodes 3a , 3b. The supply pipes 26a and delivery pipes 26b of the first gas and the circulation channel circuit 22a, 22b are preferably surrounded by a seal 24 allowing sealing with its associated electrode 3a, 3b.

The supply lines 26a and the discharge lines 26b are through and are used to supply the first gas to the other bipolar plates 2a, 2b of the cell stack A and to discharge it.

The bipolar plate 2a, 2b also comprises a supply line 27a and a discharge line 27b of a second gas, dihydrogen if it is a second bipolar plate 2b and dioxygen if it is of a first bipolar plate 2a. A seal 24 also allows sealing around this supply line 27a and this discharge line 27b. The supply lines 27a and the discharge lines 27b are through and serve to supply the second gas from the other bipolar plates 2a, 2b of the cell stack A and to its discharge.

The orifices 20 through which the heat transfer fluid conduits 10 pass are preferably arranged over the entire periphery of the bipolar plate 2a, 2b for a uniform circulation of heat. However, it is not excluded from the invention, that the distribution of the orifices 20 and the conduits 10 of heat transfer fluid is different depending on the space constraints within a motor vehicle. Thus, the orifices 20 and the conduits 10 of heat transfer fluid can be arranged only on one or more sides of the bipolar plates 2a, 2b and therefore of the fuel cell 1.

According to a second embodiment illustrated in FIG. 5, in the stack of cells A, the second bipolar plate 2b of a first cell A 'is merged with the first bipolar plate 2a of a second contiguous cell A'. Thus, between two cells A, there are not two bipolar plates 2a, 2b joined to each other but a double bipolar plate 2c which has circulation channels 22a on each of its two faces. A first face of this double bipolar plate 2c is then in contact with the anode

3a of a first cell A ’and its second face is in contact with the cathode 3b of a second cell A’ adjacent to the first cell A ’.

In FIG. 5, only two cells A ’and A” are shown, but it is obviously obvious that a double bipolar plate 2c can be used for stacks of a greater number of cells A.

According to a third embodiment illustrated in FIG. 6, the fuel cell 1 can comprise between each cell A a thermally conductive plate 8. This thermally conductive plate 8 has orifices 80 on its periphery in which also pass the fluid conduits 10 coolant. This thermally conductive plate 8 is preferably made of a material having a very good thermal conductivity such as for example aluminum or aluminum alloy. This thermally conductive plate 8 allows better thermal management of the cells A, in particular when the bipolar plates 2a, 2b, are made of a material having a reduced thermal conductivity.

Figure 7 shows a fuel cell 1 as a whole. On either side of the cell stack A, the fuel cell 1 comprises a current collector 11. These current collectors 11 may also have orifices 110 through which the conduits 10 for heat transfer fluid pass.

The fuel cell also includes, on either side of the stack of cells A, a collector 9 of heat transfer fluid into which the conduits 10 of heat transfer fluid open. These heat transfer fluid collectors 9 allow the distribution of the heat transfer fluid to the conduits 10 and the collection and evacuation of the heat transfer fluid from the conduits 10.

These collectors 9 include in particular a collector plate 91 and a cover 92 fixed in leaktight manner to the collector plate 91 and defining a chamber 90. The collector plate 91 comprises orifices 910 through which the conduits 10 of heat transfer fluid pass. In order to fix the manifold 9 to the cell stack A, the ends of the heat transfer fluid conduits 10 can be flared directly above the orifices 910 in the chamber 90.

In order to ensure the seal between the coolant conduits 10 and the collector plate 91, the openings 910 may include compressible seals 93.

The present invention also relates to a method for manufacturing a fuel cell 1 as described above. The manufacturing process notably includes the following steps:

• stack of cells A so that the heat transfer fluid conduits 10 are inserted into the orifices 20, • compression of the stack of cell A so as to compress the seals 24 between the bipolar plates 2a, 2b and the electrodes 3a, 3b .

• expansion of the heat transfer fluid conduits 10.

This expansion step of the heat transfer fluid conduits 10 can be carried out by passing an olive through the conduits 10. This expansion step allows the conduits 10 to be fixed to the bipolar plates 2a, 2, and also allows good conductivity. thermal between these bipolar plates 2a, 2b and the conduits 10. In addition, this expansion makes it possible to keep the cells A together in compression and thus to maintain the seal.

The manufacturing process can also include an additional step of setting up a collector 9 on either side of the stack of cells A. This step of setting up the collector can be divided into two sub-steps:

• A first sub-step of installing the collecting plates 91.

This sub-step can in particular be carried out before the step of expanding the conduits 10 of heat transfer fluid. The expansion of the conduits 10 allowing the compression of the compressible seals 93 to ensure sealing.

• A second step of flaring the ends of the conduits 10 of heat transfer fluid in order to fix the collecting plates 91.

• A third step of fitting covers 92.

Thus, it can be seen that the fuel cell according to the invention, owing to the fact that it is the bipolar plates 2a, 2b which serve directly as a thermal bridge between the electrochemical reaction and conduits 10 of heat transfer fluid, allows the reuse of a standard heat transfer fluid which does not need to be non-electrically conductive and does not need to be constantly filtered. In addition, the conduits 10 allow the cells A to be held together, which makes it possible to dispense with clamping plates 7 and tie rods 70. The manufacturing process is also simple and does not require the installation of a complicated thermal management circuit between A cells.

Claims (15)

Claims 1. Fuel cell (1) comprising a stack of cells (A) stacked on top of each other, each cell (A) comprising in superposition: ° a first bipolar plate (2a), ° an anode (3 a), ° an electrolyte (4), ° a cathode (3b), and ° a second bipolar plate (2b), characterized in that the first (2a) and second (2b) bipolar plates have orifices (20) on their periphery through which pass conduits (10) of heat transfer fluid thermally conductive and electrically insulated. 2. Fuel cell (1) according to the preceding claim, characterized in that the conduits (10) of heat transfer fluid are tubes of aluminum or aluminum alloy, said conduits (10) of heat transfer fluid being anodized on their outer surface . 3. Fuel cell (1) according to one of the preceding claims, characterized in that the first (2a) and second (2b) bipolar plates are made of aluminum or aluminum alloy. 4. Fuel cell (1) according to one of the preceding claims, characterized in that the conduits (10) of heat transfer fluid are held in the orifices (20) by a mechanical fixing linked to an expansion of said conduits (10) coolant. 5. Fuel cell (1) according to one of the preceding claims, characterized in that in the stack of cells (A), the second bipolar plate (2b) of a first cell (A ') is coincident with the first bipolar plate (2a) of a second contiguous cell (A ”). 6. Fuel cell (1) according to one of claims 1 to 4, characterized in that it comprises between each cell (A) a thermally conductive plate (8), said thermally conductive plate (8) having orifices ( 80) on its periphery through which also pass the conduits (10) of heat transfer fluid. 7. Fuel cell (1) according to the preceding claim, characterized in that the thermally conductive plates (8) are made of aluminum or aluminum alloy. 8. Fuel cell (1) according to one of the preceding claims, characterized in that it comprises on either side of the stack of cells (A) a collector (9) of heat transfer fluid into which the heat transfer fluid conduits (10). 9. Fuel cell (1) according to the preceding claim characterized in that the collectors (9) comprise a collecting plate (91), said collecting plate (91) comprising orifices (910) through which the conduits (10) pass. heat transfer fluid, the ends of the conduits (10) of heat transfer fluid being flared at the base of said orifices (910). 10. Fuel cell (1) according to the preceding claim characterized in that the openings (910) of the collector plates (91) have compressible seals (93). 11. Fuel cell (1) according to one of the preceding claims, characterized in that it comprises on either side of the stack of cells (A) a current collector (11) comprising orifices (110 ) through which the heat transfer fluid conduits (10) pass. 12. Method for manufacturing a fuel cell (1) according to one of the preceding claims, said method comprising the following steps: ° stack of cells (A) so that the conduits (10) of heat transfer fluid are inserted into the orifices (20), ° compression of the stack of cell (A), ° expansion of the conduits (10) of heat transfer fluid. 13. The manufacturing method according to the preceding claim, characterized in that it comprises an additional step of setting up a collector (9) on either side of the stack of cells (A). 14. Manufacturing method according to the preceding claim, characterized in that the additional step of setting up a collector (9) comprises: ° a first sub-step of fitting collector plates (91), ° a second step of flaring the ends of the conduits (10) of heat transfer fluid, ° a third step of fitting covers (92). 15. The manufacturing method according to the preceding claim, characterized in that the first sub-step of installing collector plates (91) is carried out before the step of expanding the conduits (10) of heat transfer fluid. 1/4 70 A AT