Bipolarplatte

Abstract

The invention relates to a bipolar plate (7) for a fuel cell. The bipolar plate (7) comprises a first half-shell (3), a second half-shell (5), and a contact strip (9) with a contact region (10) arranged between the first and second half-shells (3, 5) and electrically connected to the two half-shells (3, 5). The contact strip (9) has at least one end (11) that projects beyond the half-shells (3, 5). The invention further relates to a fuel cell having a bipolar plate (7) and to a method for producing a bipolar plate (7).

Description

The invention relates to a bipolar plate for a fuel cell. The invention further relates to a fuel cell having a bipolar plate and to a method for producing a bipolar plate.DE 10 2021 207 245 A1 discloses a bipolar plate for an electrochemical system.The bipolar plate for a fuel cell according to the invention comprises a first half shell, a second half shell and a contact strip. The contact strip has a contact region which is arranged between the first and the second half shell and is electrically connected to the two half shells. Furthermore, the contact strip has at least one end which projects beyond the half shells.The contact strip creates a technically simple possibility of making electrical contact with the half shells, for example in order to be able to carry out electrical measurements. Corresponding measurement systems can be connected to the contact strip via the protruding end. This is advantageous above all in bipolar plates made of brittle materials, since a direct connection of plugs or terminals to the bipolar plates can lead to these being cracked or even parts breaking out of them.In one variant, the first and the second half shell consist of a nonmetallic conductive material, for example of graphite or a graphite composite material. When such materials are used, the use of the contact strip has proven to be particularly advantageous since the contact strip can be embedded simply between the half shells and an only negligibly small contact resistance is established between the half shells and the contact strip.The contact strip is formed, for example, by a metal strip. Copper strips and aluminium metal strips have proved to be particularly advantageous since they have good electrical properties and are not very susceptible to corrosion. Such metal strips are technically simple to produce, inexpensive and robust.The metal strip preferably has a thickness of at most one millimeter, particularly preferably at most 0.5 millimeter. As a result, the metal strip is flexible and easy to process.The width of the metal strip is, for example, between 0.5 cm and 2 cm, preferably 1 cm. The length of the metal strip is, for example, between 2 cm and 5 cm. It has been shown that metal strips having these dimensions can be integrated technically easily between the two half shells and can be electrically connected to them.The contact strip preferably has at least one fixing geometry in the contact region. This makes it possible to ensure that the contact strip is fixed mechanically stably between the half shells and cannot slip out even if forces act on the contact strip, for example if a measuring system is connected to the latter.The fixing geometry is formed, for example, by at least one opening in the contact strip or metal strip. It is of course also possible for a plurality of openings to be provided in the metal strip in the longitudinal and / or transverse direction. Openings as a fixing geometry can be produced in a particularly simple and resource-saving manner, for example by punching the metal strip. It has been found that with such a fixing geometry a stable mechanical anchoring of the contact strip between the half shells can be achieved.It can furthermore be provided that the contact strip has a plug contact geometry at its end projecting beyond the half shells. As a result, it can be connected to a measurement system in a particularly simple manner. The mechanical forces which act on the contact strip during the contacting by means of the plug contact geometry and are at least partially transmitted to the half shells are low, whereby the risk of damage is further reduced.The fuel cell according to the invention comprises at least two membrane electrode assembly (MEA) and at least one bipolar plate according to the invention which is arranged between the membrane electrode units.The advantages mentioned for the bipolar plate according to the invention apply in the same way to the fuel cell according to the invention.The two membrane electrode units can be contacted separately from one another via the bipolar plate or the contact strip of the bipolar plate and their electrical parameters can be determined or monitored, for example by connecting a corresponding measuring device to the contact strip of the bipolar plate and to a further contact strip of a further bipoloar plate or a current collector plate arranged on an opposite side of the relevant membrane electrode units.Of course, the fuel cell according to the invention can also have more than two membrane electrode units and more than two bipolar plates which are alternately stacked one on top of the other and form a fuel cell stack. The voltage can then be tapped via the contact strips of the bipolar plates, for example, via a part of the fuel cell stack. Thus, the electrical parameters of individual or of a plurality of membrane electrode units and / or cells connected to one another can be determined and monitored in a technically simple manner.The method according to the invention for producing a bipolar plate according to the invention comprises at least the steps:providing the first and second half-shells;positioning the contact strip such that the contact region of the contact strip lies between the first and the second half shell and the at least one free end of the contact strip protrudes beyond the half shells; andconnecting the first half shell to the second half shellThe half shells can be glued, welded or pressed together, for example, in order to connect them to one another.It is possible in principle to produce the bipolar plates as separate components.Alternatively, the half shells and contact strips can also be alternately layered with the membrane electrode units to form a fuel cell stack. The connecting step can then take place in the fuel cell stack, for example by the ends of the fuel cell stack being pressed together by means of a clamping device.Preferred exemplary embodiments are explained in more detail with reference to the following figures. This showsFIG. 1 shows a schematic illustration of an exemplary embodiment of a fuel cell according to the invention in a side view;FIG. 2 shows a schematic illustration of an exemplary embodiment of a bipolar plate according to the invention in an exploded illustration;FIG. 3 shows a schematic illustration of a contact strip with strip-shaped fixing geometries;FIG. 4 shows a schematic illustration of a contact strip having a plurality of circular fixing geometries; andFIG. 5 shows a schematic illustration of an exemplary embodiment of a method according to the invention.The fuel cell 1 shown in FIG. 1 includes a first current collector plate 2 serving as an anode contact of the fuel cell 1.Adjacent to the first current collector plate 2, a first half shell 3 made of a nonmetallic conductive graphite composite material is arranged. More specifically, the first half shell 3 is an anode half shell made of a mixture of graphite and a thermoplastic and having distribution channels for distributing hydrogen. This is not to be understood as restrictive. Alternatively, the first half shell 3 can also consist of pure graphite or other suitable materials.The fuel cell 1 further includes a second current collector plate 4 serving as a cathode contact of the fuel cell 1.Adjacent to the second current collector plate 4, a second half shell 5 made of a nonmetallic conductive graphite composite material is arranged. More specifically, the second half shell 5 is a cathode half shell made of a mixture of graphite and a thermoplastic and having distribution channels for distributing oxygen. This is also, of course, not to be understood as restrictive. Alternatively, the second half shell 5 can also consist of pure graphite or other suitable materials, preferably of the same materials as the first half shell 3.Furthermore, the fuel cell 1 comprises a plurality of membrane electrode units 6 and a plurality of bipolar plates 7 according to the invention, which are arranged between the two current collector plates 2, 4.The membrane electrode units 6 and the bipolar plates 7 form a fuel cell stack 8, wherein two adjacent membrane electrode units 6 are in each case spatially separated from one another by one of the bipolar plates 7 and electrically connected to one another.FIG. 2 shows one of the bipolar plates 7 in an exploded illustration.The bipolar plate 7 comprises a first half shell 3, which is preferably structurally identical to the first half shell 3 already mentioned above.The bipolar plate 7 further comprises a second half shell 5, which is preferably structurally identical to the second half shell 5 already mentioned above.In addition, the bipolar plate 7 comprises a contact strip 9.The contact strip 9 has a contact region 10 which is arranged between the first half shell 3 and the second half shell 5 and is electrically connected to the two half shells 3, 5. The contact region 10 is embedded, for example, between the first half shell 3 and the second half shell 5.Furthermore, the contact strip 9 has a free end 11 which projects beyond the two half shells 3, 5.In the described embodiment variant, the contact strip 9 is formed by a metal strip 12, for example by a copper strip or an aluminum strip.The contact strip 9 or the metal strip 12 is, for example, 1 cm wide, 3 cm long and projects 1 cm beyond the two half shells 3, 5.The thickness of the contact strip 9 or of the metal strip 12 is 0.5 mm. Due to the small thickness, the contact strip 9 is flexible and can be embedded well between the half shells 3, 5.The contact strip 9 of the bipolar plate 7 shown in FIG. 2 has a fixing geometry 13 in the contact region 10, which fixes it mechanically stably between the two half shells 3, 5. The fixing geometry 13 ensures that the contact strip 9 cannot slip out between the half shells 3, 5, even if tensile forces act on the free end 11, for example when a measuring instrument is coupled to or uncoupled from it.The fixing geometry 13 is formed by a circular opening 14 in the contact strip 9. This can be produced with very little effort, for example by punching the metal strip 12.Of course, alternatively, other opening shapes and / or types of fixing geometries 13 can also be used.In order to illustrate this, FIGS. 3 and 4 show schematic representations of contact strips 9, each of which has a plurality of fixing geometries 13 designed as strip-shaped or circular openings 14.Depending on the material used for the half shells 3, 5 and the length and width of the contact strip 9, different fixing geometries 13 can be used in order to achieve the most stable possible anchoring of the contact strip 9 between the half shells 3, 5.Optionally, the contact strips 9 can also have a plug contact geometry 15 at their ends 11 protruding beyond the half shells 3, 5.As shown in FIG. 4, this can be formed by a narrowing in the width of the metal strip 12 and / or by additional recesses in or at the free end 11 of the contact strip 9.Alternatively, the plug contact geometry 15 can also be formed by a separate component which is soldered or screwed to the metal strip 12, for example.FIG. 5 shows a schematic illustration of an exemplary embodiment of a method according to the invention, with which the bipolar plate 7 shown in FIG. 2 is produced. The method is briefly explained below.In a first step S 1 of the method, the first and the second half shell 3, 5 are provided.In a second step S 2 of the method, the contact strip 9 is positioned between the half shells 3, 5 in such a way that it partially protrudes beyond the latter. In other words, the contact strip 9 is arranged offset with respect to the half shells 3, 5, so that it lies with its contact region 10 between the first half shell 3 and the second half shell 5 and protrudes with a free end 11 beyond the two half shells 3, 5.In a third step S 3 of the method, the first and the second half shell 3, 5 are connected to one another, for example pressed, bonded, welded or screwed.In principle, bipolar plates 7 can be produced as separate components by means of the method.Alternatively, the half shells 3, 5 and contact strips 9 can, however, also be layered alternately with the membrane electrode units 6, for example in order to form a fuel cell stack 8. The connecting step can then take place in the fuel cell stack 8, for example by applying a force to its ends and pressing them together or clamping them together in order to create a mechanical and electrical connection between the adjoining first and second half shells 3, 5.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2021 207 245 A1

[0002]

Claims

Bipolar plate for a fuel cell (1), comprising a first half shell (3), a second half shell (5), and a contact strip (9) with a contact region (10), which is arranged between the first and the second half shell (3, 5) and is electrically connected to the two half shells (3, 5), and with at least one end (11), which protrudes beyond the half shells (3, 5).The bipolar plate of claim 1, wherein the first and second half shells (3, 5) are made of a non-metallic conductive material.Bipolar plate according to claim 2, wherein the first and the second half shell (3, 5) consist of graphite or a graphite composite material.Bipolar plate according to one of the preceding claims, wherein the contact strip (9) is formed by a metal strip (12).The bipolar plate of claim 4, wherein the metal band (12) has a thickness of a maximum of one millimeter.Bipolar plate according to one of the preceding claims, wherein the contact strip (9) has at least one fixing geometry (13) in the contact region (10).Bipolar plate according to claim 6, wherein the fixing geometry (13) is formed by at least one opening (14) in the contact strip (9).Bipolar plate according to one of the preceding claims, wherein the contact strip (9) has a plug contact geometry (15) at its end (11) projecting beyond the half shells (3, 5).Fuel cell comprising at least two membrane electrode units (6) and at least one bipolar plate (7) according to one of the preceding claims, which is arranged between the membrane electrode units (6).Method for manufacturing a bipolar plate (7) according to any one of claims 1 to 8, comprising the steps of: - providing the first and second half-shells (3, 5); - positioning the contact strip (9) such that the contact area (10) of the contact strip (9) lies between the first and second half-shells (3, 5) and the at least one free end (11) of the contact strip (9) protrudes beyond the half-shells (3, 5); and - connecting the first half-shell (3) to the second half-shell (5).

Images