Bipolar separator plate for fuel cell, fuel cell related thereto, and manufacturing method

Abstract

The present invention relates to a channel-type bipolar separator plate (4) for a fuel cell formed by two unit plates superimposed on each other, each unit plate having a fixed surface facing the other unit plate and a flow surface (18) facing away from the other unit plate and defining at least one channel (20) for the flow of reactive gases. The bipolar separator plate (4) - adhesive placed between the two unit plates (14) to assemble the two unit plates; - a metal insert (28) sandwiched between two unit plates, protruding from the edge of the bipolar separator plate (4) and contacting a portion of the adhesive; Further provided are:

Description

Technical Field

[0001] The present invention relates to a channel-type bipolar separator plate for a fuel cell, which is provided with channels for distributing a reactive fluid in the fuel cell.

[0002] The present invention also relates to a fuel cell including the bipolar separator plate.

[0003] The present invention also relates to a method for manufacturing the bipolar separator plate.

Background Art

[0004] A polymer electrolyte fuel cell includes at least one electrochemical cell. Each electrochemical cell is formed by a membrane-electrode assembly (also abbreviated as "AME" or "MEA" which is an abbreviation of the English term "Membrane Electrode Assembly") sandwiched between two separator plates.

[0005] Each membrane-electrode assembly is layered and includes an ion-exchange separation polymer membrane sandwiched between two electrodes. Each electrode has an active layer and a gas diffusion layer adjacent to the membrane. Each membrane-electrode assembly has an anode side where the electrode forms an anode and a cathode side where the electrode forms a cathode.

[0006] Each separator plate is provided with channels that define flow channels for the reactive fluid between the separator plate and the membrane-electrode assembly in contact with the membrane-electrode assembly on the surface of the side to which the membrane-electrode assembly is attached.

[0007] The reactive fluid includes a fuel fluid containing fuel and a combustion-supporting fluid containing a combustion-supporting substance.

[0008] The reactive fluid is generally a reactive gas. In that case, the channels located on the surface of the separator plate are generally called the gas flow field (or "Gas Flow Field" in English terms). The electrode forming the anode and the electrode forming the cathode are electrically connected through an electrical circuit, including charges supplied by the fuel cell.

[0009] During the operation of the fuel cell, the fuel fluid flows through the channels of the separator plate located on the anode side, and the supporting combustion fluid flows through the channels of the separator plate located on the cathode side.

[0010] In the electrochemical process of generating electrical energy by the fuel cell, the flow of the fuel substance on the anode side is converted into the flow of electrons and ions within each electrochemical cell. Electrons are generated in the active anode layer of the electrode forming the anode, and then are transported to the anode of the fuel cell through the diffusion layer of the electrode forming the anode and within the separator plate by electron conduction. Ions are transported through the membrane by ion conduction and combine with the supporting combustion substance and the electrons flowing from the anode to the cathode through the electrical circuit to form at least one product.

[0011] The fuel cell is, for example, of the PEMFC ("Proton Exchange Membrane Fuel Cell (proton exchange membrane type fuel cell)") type. In this case, the ion exchange membrane is a proton exchange / conduction membrane. During operation, hydrogen is supplied to the channels of the separator plate on the anode side, and air or oxygen is supplied to the channels of the separator plate on the cathode side. Protons and electrons transported from the anode to the cathode are generated from hydrogen. The protons combine with the electrons supplied from the anode to the cathode on the cathode side, and oxygen generates water.

[0012] The fuel cell is formed, for example, by alternately laminating separator plates and membrane-electrode assemblies. Each of the joints formed by the membrane-electrode assemblies sandwiched between two electrochemical cells forms an electrochemical cell.

[0013] Such a fuel cell includes a separator plate called a "bipolar" type, and each bipolar separator plate is positioned between two membrane - electrode assemblies.

[0014] Each bipolar separator plate has a surface in contact with the electrode forming the anode of the membrane - electrode assembly and a surface in contact with the electrode forming the cathode of another membrane - electrode assembly, and the two surfaces are provided with channels for the reactive fluid to flow through.

[0015] Each bipolar separator plate is preferably conductive so as to electrically connect the electrodes forming the anode and cathode of the membrane - electrode assemblies sandwiching it. By doing so, the stacked electrochemical cells are electrically connected in series.

[0016] Each bipolar separator plate is formed, for example, by assembling two overlapping unit plates. Advantageously, the two unit plates define channels for the cooling fluid to circulate between them. Summary of the Invention Problems to be Solved by the Invention

[0017] To ensure the sealing performance between unit plates, it is known to use a sealing seal that requires a large mechanical force during the manufacture of each bipolar separator plate, and an additional step of positioning the seal is also required during manufacture.

[0018] It is also known to use an epoxy - based adhesive between unit plates. However, the implementation of such adhesion is by no means easy, and it is necessary to ensure perfect contact between the two unit plates, taking the risk of generating stress during the tightening of the stack forming the fuel cell.

[0019] Furthermore, it is also possible to attach silicone in a string-like manner using a robot. However, for such attachment, drying and polymerization steps are required. Such steps are costly in terms of man-hours and perfect reproducibility cannot be achieved either.

[0020] Also, it is desirable to be able to measure the individual voltage of each electrochemical cell of a fuel cell, for purposes such as verification of its operation.

[0021] Therefore, it is possible to create by machining holes for inserting test needles for voltage measurement on the side surface of the separator plate. However, such a method causes problems regarding manufacturing reproducibility.

Means for Solving the Problems

[0022] Therefore, one of the objects of the present invention is to propose a bipolar separator plate that can be manufactured more easily and quickly in a reproducible and reliable manner.

[0023] Therefore, the present invention relates to a channel-type bipolar separator plate for a fuel cell formed by two unit plates overlapping each other, wherein each unit plate has a fixed surface facing the other unit plate and a flow surface facing in the opposite direction to the other unit plate, the flow surface defining at least one channel for the flow of a reactive gas. In the bipolar separator plate, an adhesive disposed between the two unit plates for assembling the two unit plates and a metal insert sandwiched between the two unit plates and protruding from the edge of the bipolar separator plate, with a part of the adhesive contacting the metal insert are further provided.

[0024] According to another embodiment, the bipolar separator plate includes one or more of the following optional features independently or in any technically possible combination. That is, - The metal insert can be connected to a voltage measurement unit. - The adhesive is an adhesive tape with a thickness of less than 0.05 mm, particularly less than 0.04 mm. - The adhesive contains a foamed acrylic resin or consists of a foamed acrylic resin. - The metal insert is a finger-shaped piece with a thickness of less than 2 mm, preferably less than 1 mm. - Each unit plate is made of a composite material containing a matrix reinforced with a filler, particularly a filler of carbon or graphite, such as a filler made of carbon fiber or graphite.

[0025] The present invention relates to a fuel cell comprising at least one bipolar separator plate and at least two electrode-membrane assemblies as defined above, wherein each electrode-membrane assembly is applied to the flow surface of any one unit plate, and a voltage measurement unit is connected to the metal insert.

[0026] The present invention also relates to a method for manufacturing a bipolar separator plate for a fuel cell, - Supplying a first unit plate having two opposing surfaces including a fixed surface and a flow surface defining at least one channel for the flow of a reactive gas; - Placing a metal insert on the fixed surface of the first unit plate such that the metal insert protrudes from the edge of the first unit plate; - Applying an adhesive to the fixed surface of the first unit plate such that a part of the adhesive contacts the metal insert; - Supplying a second unit plate having two opposing surfaces including a fixed surface and a flow surface defining at least one channel for the flow of a reactive gas; - Superposing the second unit plate on the first unit plate such that the two fixed surfaces face each other, and the unit plates are assembled by the adhesive; and relates to a method including at least the above steps.

[0027] According to another embodiment, the manufacturing method includes one or more of the following features, each independently or in any technically possible combination. That is, - The adhesive is an adhesive tape adhered to the fixing surface of the first unit plate by cold rolling. - The method further includes a step of pressing the bipolar separator plate after the superimposing step.

[0028] The present invention and its advantages will be better understood by reading the following description, which is given by way of example only and with reference to the accompanying drawings.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0030] Referring to FIG. 1, the fuel cell 2 has a stack of a separator plate 4 and a membrane / electrode assembly 6. Such a stack is generally called a "fuel cell stack" in English terms.

[0031] Each membrane / electrode assembly 6 is disposed between two separator plates 4. Each joint formed by the separator plate 4 and the membrane / electrode assembly 6 defines a unit electrochemical cell 8 of the fuel cell 2.

[0032] Each membrane / electrode assembly 6 forms a flat, layered joint body including an ion exchange membrane 10 and two electrodes 12 disposed so as to be in direct contact with both sides of the membrane 10.

[0033] The membrane 10 is particularly a proton exchange membrane, and the fuel cell is of the PEM ("Proton Exchange Membrane") type.

[0034] Each electrode 12 is conductive. Each electrode 12 includes an active layer and a gas diffusion layer. One of the electrodes 12 defines an anode, and the other defines a cathode.

[0035] The separator plate 4 serves a function of electrical conduction. The separator plate 4 is conductive and is in electrical contact with the electrode 12.

[0036] The separator plate 4 serves a function of distributing reactive gas on both sides of the membrane - electrode assembly 6 and further serves a function of discharging the product.

[0037] The separator plate 4 shown in FIG. 1 is of the "bipolar" type, and each separator plate 4 is disposed between two membrane - electrode assemblies 6.

[0038] When there is only one surface of the separator plate in contact with the membrane - electrode assembly, the separator plate 4 is said to be of the "monopolar" type. Such a monopolar type separator plate (not visible in the figure) is at both ends of the stack of the fuel cell 2.

[0039] Each bipolar separator plate 4 is formed by two unit plates 14 superimposed on each other.

[0040] Each unit plate 14 is preferably made of a composite material containing a matrix reinforced with a filler, especially a filler of carbon or graphite, for example, a filler made of carbon fibers or graphite powder.

[0041] Each unit plate 14 has a fixed surface 16 facing the other unit plate 14 and a flow surface 18 facing away from the other unit plate 14.

[0042] Each separator plate 4 is in contact with an electrode 12 that forms an anode of one membrane - electrode assembly 6 by one of its flow surfaces 18, and further in contact with an electrode 12 that forms a cathode of the other membrane - electrode assembly 6 by the other of its flow surfaces 18.

[0043] Each flow surface 18 defines at least one channel 20. Each channel 20, together with the adjacent membrane - electrode assembly 6, defines a supply line for the flow of reactive gas in contact with the membrane - electrode assembly 6.

[0044] Different reactive gases are individually supplied to the channels 20 of the flow surface 18 of each separator plate 4. Fuel such as hydrogen is supplied to the channels 20 of the flow surface 18 in contact with the electrode 12 forming the anode, and a supporting combustion substance such as oxygen or air is supplied to the channels 20 of the other flow surface 18 in contact with the electrode 12 forming the cathode.

[0045] The channels 20 of the flow surface 18 of the separator plate 4 in contact with the electrode 12 forming the anode define an anode compartment, and are in fluid communication with each other. The channels 20 of the flow surface 18 of the separator plate 4 in contact with the electrode 12 forming the cathode define a cathode compartment, and are in fluid communication with each other.

[0046] Each separator plate 4 includes a supply port for supplying reactive gas to each channel 20 and a discharge port for discharging unconsumed reactive gas and products resulting from the operation of the fuel cell.

[0047] In particular, as shown in FIG. 2, the separator plate 4 has a channel 20 on its flow surface 18 that includes an inlet section 22 for receiving the supply of reactive gas at a supply port 24A (defining the supply port) and an outlet section 26 that opens at a discharge port 28A (defining the discharge port).

[0048] The channel 20 enables the flow of reactive gas along the membrane - electrode assembly from the inlet section 22 to the outlet section 26.

[0049] Channel 20 extends along a meandering path, here a serpentine path, between its inlet section 22 and its outlet section 26.

[0050] Supply port 24A penetrates separator plate 4. When a plurality of separator plates 4 are stacked, supply ports 24A are aligned to define a supply header that extends through the stack of fuel cells 2.

[0051] Discharge port 28A penetrates separator plate 4. When a plurality of separator plates 4 are stacked, discharge ports 28A are aligned to define a discharge header.

[0052] Separator plate 4 includes another supply port 24B and another discharge port 28B that are in fluid communication with channels on the opposite side that are not visible in FIG. 2 and not in fluid communication with channels 20 of flow surface 18 shown in FIG. 2.

[0053] During operation, fuel is supplied to one of supply ports 24A, 24B and a supporting combustible substance is supplied to the other.

[0054] As can be seen in the figures, separator plate 4 according to the present invention further includes an adhesive 26 and a metal insert 28 as shown in FIG. 3.

[0055] Adhesive 26 is disposed between two unit plates 14 to assemble and integrate the two unit plates 14 to form bipolar separator plate 4.

[0056] As can be seen in FIG. 3, adhesive 26 is specifically disposed on fixing surface 16 of each unit plate 14 along the outer peripheral edge of fixing surface 16.

[0057] Adhesive 26 is disposed, in particular, in grooves formed within fixing surface 16, such as in the form of channels provided within fixing surface 16, and particularly in grooves formed along the outer peripheral edge of fixing surface 16.

[0058] Preferably, as shown in FIG. 3, the adhesive 26 extends along a closed line. Thereby, the sealing property between the two unit plates 14 in the zone inside the closed line can be ensured.

[0059] In an advantageous embodiment not shown, the adhesive 26 extends around each port 24A, 24B, 28A, 28B along a closed contour. Thereby, the sealing property around each port 24A, 24B, 28A, 28B can be ensured.

[0060] The adhesive 26 is advantageously an adhesive tape having a thickness of less than 0.05 mm, especially less than 0.04 mm.

[0061] In one example, the adhesive 26 contains or consists of a foamed acrylic resin.

[0062] The metal insert 28 is disposed between the two unit plates 14 and protrudes from the edge of the separator plate 4.

[0063] More specifically, the metal insert 28 has a fixing portion disposed between the two unit plates 14, and a protruding portion protrudes from the edge of the separator plate 4.

[0064] Advantageously, the separator plate 4 has a recess confined between the two unit plates 14, and the metal insert 28, or more specifically its fixing portion, is received in that recess between the two unit plates 14.

[0065] The recess is formed, for example, by making a notch 32 that opens at the edge of the fixing surface 16 in only one of the two unit plates 14, or by providing such a notch 32 in the fixing surface 16 of each of the two unit plates so that the two notches 32 face each other.

[0066] The metal inserts 28 arranged between the unit plates 14 are in electrical contact with at least one of those unit plates 14 and, in particular, with each of the unit plates 14. The metal inserts 28 are at the same potential as the unit plates, that is to say the separator plates 4.

[0067] As shown in FIG. 1, the metal inserts 28 are connected to the voltage measuring unit 30.

[0068] Therefore, as can be seen from each figure, the metal inserts 28, more specifically their protruding parts, protrude from the edge of the separator plate 4, and the voltage measuring unit 30 is connected to the protruding parts. This protruding part forms the connection terminal of the separator plate 4 and enables the connection of the voltage measuring unit 30.

[0069] The voltage measuring unit 30 is configured to measure the voltage between two metal inserts 28 provided on two adjacent separator plates 4 located on both sides of the same membrane-electrode assembly 6 and to measure the voltage generated by the membrane-electrode assembly 6. The voltage measuring unit 30 is, for example, a voltmeter.

[0070] The metal inserts 28 preferably contain copper, in particular rough copper or gold-plated copper.

[0071] The metal inserts 28 are in particular in the form of finger-like pieces. The fixed part and the protruding part form two separate sections in the finger-like piece-shaped metal insert 28.

[0072] The finger-like piece-shaped metal insert 28 has a thickness of less than 2.0 mm, preferably less than 1.0 mm. Thereby, the insertion of the metal insert 28 between the two unit plates 14 is facilitated.

[0073] The metal inserts 28 extend in particular over a length of 1.0 cm to 4.0 cm and preferably over a length of 1.0 cm to 2.0 cm.

[0074] The metal insert 28 protrudes outside the separator plate 4 with a length of 1.0 cm to 2.0 cm. This corresponds to the length of the protruding part of the metal insert 28.

[0075] As can be seen from FIG. 3, a part of the adhesive 26 is in contact with the metal insert 28.

[0076] In particular, the metal insert 28 fits into the notch 32, and the adhesive 26 is applied to the fixing surface 16 so as to cover the fixing part of the metal insert 28 accommodated in the notch 32. The adhesive 26 thus placed holds the metal insert 28 in the recess in this way.

[0077] In the embodiment shown in FIG. 3, the metal insert 28 extends in the inner and outer directions of the separator plate 4 from each side of the adhesive 26.

[0078] In a variation, the metal insert 28 extends only from one side of the adhesive 26 towards the outside of the separator plate 4.

[0079] In an advantageous embodiment, as is already known, each separator plate 4 of the fuel cell 2 comprises an internal cooling pipe provided in the separator plate 4 for circulating a cooling fluid. The cooling pipe is defined by, for example, a channel made in one or each fixing surface 16 of the unit plate of the separator plate 4.

[0080] The cooling pipe receives the supply of the cooling fluid through a cooling inlet port and opens into a cooling outlet port through the separator plate 4.

[0081] When the separator plates 4 are stacked, the cooling inlet port and the cooling outlet port are aligned and each defines a cooling inlet header and a cooling outlet header.

[0082] In that case, the adhesive 26 preferably extends along a closed contour around the subsequent cooling line as well as around the subsequent inlet and outlet ports. Thereby, the tightness of the cooling line can be ensured, in particular the tightness between the cooling line and the ports provided through the unit plate 14 for the reactive gas.

[0083] From here on, a method for manufacturing the bipolar separator plate 4 according to the invention will be described.

[0084] First, a first unit plate 14 having a notch 32 for receiving a metal insert 28 is provided.

[0085] The metal insert 28 is placed in the notch 32 provided in the fixing surface 16 of the first unit plate 14 such that the metal insert 28 protrudes from the edge of the first unit plate 14.

[0086] Next, an adhesive 26 is applied to the fixing surface 16 of the first unit plate 14 such that a part of the adhesive 26 contacts the metal insert 28, in particular so as to partially cover the metal insert 28. In particular, the adhesive 26 is applied along a line passing through the notch 32 so as to cover the metal insert 28 received in the notch 32.

[0087] Thereby, the adhesive 26 holds the metal insert 28 in a fixed position within the notch 32.

[0088] In particular, the adhesive 26 is in the form of an adhesive tape applied along a line extending along the outer peripheral edge of the fixing surface 16, as can be seen in FIG. 3.

[0089] The adhesive tape has, for example, two surfaces, at least one of which is a protective tape for preventing the adhesive tape from sticking and is covered with a protective tape that can be peeled off in order to adhere the adhesive tape.

[0090] Subsequently, the adhesive tape is placed on the fixing surface 16, for example, by bringing the exposed surface of the adhesive tape into contact with the fixing surface 16 of the first unit plate 14, and further adhered by cold rolling.

[0091] Subsequently, the protective tape covering the opposite surface of the adhesive tape is peeled off from the adhesive tape.

[0092] Next, the second unit plate 14 is supplied.

[0093] The second unit plate 14 is superposed on the first unit plate 14 such that the two fixing surfaces 16 face each other. Thereby, the fixing surface 16 of the second unit plate 14 comes into contact with the adhesive tape.

[0094] The two unit plates 14 are assembled by the adhesive 26, thereby forming the bipolar separator plate 4.

[0095] Next, advantageously, the bipolar separator plate 4 is pressed to ensure good adhesion between the two unit plates 14.

[0096] Therefore, the present invention is considered to have a certain number of advantages.

[0097] In fact, the manufacturing method according to the present invention is easy to implement.

[0098] Furthermore, this manufacturing is carried out quickly and requires only a small number of man-hours.

[0099] Therefore, the present invention enables a large time gain in the assembly stage of the fuel cell 2.

[0100] In addition, the method according to the present invention is easy to automate and has excellent reliability. Furthermore, the bipolar separator plate 4 according to the present invention makes it even easier to adjust the interface using an industrial voltage measuring device.

[0101] Therefore, the present invention is suitable for industrial use with reproducibility and reliability.

Explanation of Reference Numerals

[0102] 2 Fuel cell 4 Separator plate 6 Membrane electrode assembly, membrane electrode junction 8 Unit electrochemical cell 10 Ion exchange membrane 12 Electrode 14 Unit plate 16 Fixed surface 18 Flow surface 20 Channel 24A, 24B Supply port 26 Adhesive 28 Metal insert 28A Discharge port 30 Voltage measurement unit

Claims

1. A channel-type bipolar separator plate (4) for a fuel cell (2) formed by two unit plates (14) overlapping each other, wherein each unit plate (14) has a fixed surface (16) facing the other unit plate (14) and a flow surface (18) facing away from the other unit plate (14), the flow surface (18) defining at least one channel (20) for the flow of a reactive gas. In the bipolar separator plate (4), - an adhesive (26) disposed between the two unit plates (14) for assembling the two unit plates (14), - a metal insert (28) sandwiched between the two unit plates (14) and protruding from the edge of the bipolar separator plate (4), the metal insert (28) having a part of the adhesive (26) in contact therewith The bipolar separator plate (4) further comprising.

2. The bipolar separator plate (4) according to claim 1, wherein the metal insert (28) is connectable to a voltage measurement unit (30).

3. The bipolar separator plate (4) according to claim 1 or 2, wherein the adhesive (26) is an adhesive tape having a thickness of less than 0.05 mm.

4. The bipolar separator plate (4) according to any one of claims 1 to 3, wherein the adhesive (26) is an adhesive tape having a thickness of less than 0.04 mm.

5. The bipolar separator plate (4) according to any one of claims 1 to 4, wherein the adhesive (26) contains a foamed acrylic resin or consists of a foamed acrylic resin.

6. The bipolar separator plate (4) according to any one of claims 1 to 5, wherein the metal insert (28) is a finger-shaped piece having a thickness of less than 2 mm.

7. The bipolar separator plate (4) according to any one of claims 1 to 6, wherein the metal insert (28) is a finger-shaped piece having a thickness of less than 1 mm.

8. The bipolar separator plate (4) according to any one of claims 1 to 7, wherein each unit plate (14) is made of a composite material containing a matrix reinforced with a filler.

9. The bipolar separator plate (4) according to claim 8, wherein the filler is a carbon or graphite filler.

10. The bipolar separator plate (4) according to claim 8 or 9, wherein the filler is made of carbon fiber or graphite.

11. - At least one bipolar separator plate (4) according to any one of claims 1 to 10, - At least two electrode / membrane assemblies (6), each of which is an electrode / membrane assembly (6) applied to the flow surface (18) of any one of the unit plates (14), - A voltage measurement unit (30) connected to the metal insert (28) A fuel cell (2) comprising.

12. A method for manufacturing a channel-type bipolar separator plate (4) for a fuel cell (2), - Supplying a first unit plate (14) having two opposing surfaces including a fixed surface (16) and a flow surface (18) defining at least one channel (20) for the flow of reactive gas; - Placing a metal insert (28) on the fixed surface (16) of the first unit plate (14), such that the metal insert (28) protrudes from the edge of the first unit plate (14); - Applying an adhesive (26) to the fixed surface of the first unit plate (14), such that a part of the adhesive (26) contacts the metal insert (28); - Supplying a second unit plate (14) having two opposing surfaces including a fixed surface (16) and a flow surface (18) defining at least one channel (20) for the flow of reactive gas; - Superimposing the second unit plate (14) on the first unit plate (14) such that the two fixed surfaces (16) face each other, and the unit plates (14) are assembled by the adhesive (26); A method including at least.

13. The manufacturing method according to claim 12, wherein the adhesive (26) is an adhesive tape adhered to the fixed surface (16) of the first unit plate (14) by cold rolling.

14. The manufacturing method according to claim 12 or 13, further including the step of pressing the bipolar separator plate (4) after the superimposing step.

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