WO2002065572A2

WO2002065572A2 - Electrochemical cell stack

Info

Publication number: WO2002065572A2
Application number: PCT/DE2002/000560
Authority: WO
Inventors: Matthias Bronold; Uwe Schattauer; Christian Leu; Wilhelm Thom
Original assignee: Heliocentris Energiesysteme Gmbh
Priority date: 2001-02-13
Filing date: 2002-02-13
Publication date: 2002-08-22
Also published as: WO2002065572A3; AU2002249072A1

Abstract

The invention relates to an electrochemical element, especially a fuel cell or a stack of fuel cells, wherein engaging or interlocking, oppositely conical or skewed guiding and fixing means (13,14) are disposed on both sides in or on the frame elements (2) of the membrane-electrode unit (1) and on the biopolar and current collector plates (3,4) for accurately positioned provision, assembly and mutual fixing of adjacent components during mounting. During mounting, the recesses and cavities (13, 14) are automatically guided into each other, initially sliding with a large amount of slip, whereupon they are subsequently positioned in an exact fit and sealed in relation to each other. Mounting is made significantly easier by a seal (10) which is integrated into the frame element (2).

Description

description

Electrochemical element

The invention relates to an electrochemical element formed from a plurality of electrochemical cells, which comprises membrane electrode assemblies sealingly held on a frame element, alternatingly arranged bipolar plates and a current collector plate and an end plate on both sides, with openings in the edge region of the frame element and the plates for the formation of feed and discharge channels for at least one of the reactants are provided, which are connected to open fluid distribution channels molded into the bipolar and current collector plates and adjoining the anode or cathode layer of the membrane electrode assembly.

Such electrochemical elements, in which the fluid is transported between the supply and discharge channels and the fluid distribution channels via channels provided in the current transfer and current collector plates, are sufficiently known from the prior art. DE 199 26 026 also describes a membrane electrode unit for fuel cells, membrane electrolysers and membrane compressors designed in this way, which is kept gas-tight in its non-active edge region between two stiffening plates which form a frame element and are connected by hot melt adhesive layers. The frame elements which can be produced from plastic can be produced inexpensively and make a considerable contribution to simplifying the assembly of the electrochemical cell comprising a plurality of membrane electrode units and bipolar plates. Nevertheless, the assembly is difficult in that the in the Frame elements, current transfer and current collector plates and end plates provided openings for the exact formation and sealing of the feed and discharge channels for the reactants must lie congruently one above the other. Precise assembly is practically not possible with automatic production and can only be achieved manually with a considerable amount of time.

A fuel cell is also known from JP 07249417 A, in which the fluid transport between the supply and discharge channels and the fluid distribution channels formed in the current transfer and current collector plates and open to the membrane electrode unit via channels provided in the frame elements - follows. The frame elements are designed to be strong enough to accommodate the connecting channels. Accordingly, the strength of the current transfer and current collector plates in the region of the frame element was reduced, while the part of these plates provided with the fluid distribution channels projects into a recess delimited by the vertical inner edge of the frame element. This design of the frame elements and current transfer or current collector plates is disadvantageous insofar as the frame elements and plates also have to be made to size in the area of the active membrane surface, that is to say they have to fit into one another in order to ensure a tight connection between the connecting channel in the frame element and the fluid distributor. to ensure channel in the current transfer or current collector plate. In addition, the assembly of such a fuel cell is also difficult and time-consuming, since the fluid distribution channel region of the current transfer and current collector plates has to be laboriously fitted into the recess in the frame element. Automatic assembly is also unthinkable in this case. In the case of a quick, simple, yet exact installation, the installation of the seals required between the frame elements and the bipolar / current collector plates also prepares the situation. In a seal known from DE 198 29 142 AI is on the frame member

Seal bead applied from curable silicone or an epoxy resin and then connected to the adjacent bipolar plate by curing the sealing material by gluing. This complex process is not suitable for the rapid, as automated as possible, assembly of a fuel cell stack. In the fuel cell described in DE 199 10 487 C1, sealing elements are injection molded onto the bipolar plates in a two-stage process. Although the molded seals can simplify assembly, the manufacturing process is complex or the sealing effect is insufficient or the membrane electrode assembly can be damaged due to the high contact pressure required, so that leaks occur.

The invention has for its object to provide an electrochemical element of the type mentioned in such a way that with precise, safe and congruent positioning of the individual components and the media-carrying channels a simple, less time-consuming assembly is possible and yet an exact seal is guaranteed.

According to the invention, the object is achieved with an electrochemical cell designed according to the features of patent claim 1. Further features and advantageous refinements of the invention result from the subclaims.

The main idea of the invention is with others

Words that the individual components of the burner Material cell, namely the frame elements, the bipolar plates, current collector plates and end plates during the assembly and in the assembled state, corresponding to one another, firstly performing a guiding function and then a holding function in the form of recesses in one part and elevations engaging in them in the adjacent part or are also formed by elevations spanning the outer edge of the adjacent part. The mutual guidance during assembly and the mutual mounting and precise positioning after the components have been assembled can also be brought about by the region of the fluid distributor channels being molded onto the bipolar and current collector plates as a truncated cone-like elevation, while the frame element forms a correspondingly shaped recess for precisely fitting the elevation. During assembly, the framed membrane electrode assemblies and the bipolar or current collector plates automatically slide with a large amount of play to a precisely fitting end position that seals against the bevelled side edges, in which the connection channels and the flood distribution channels are exactly aligned. The bevelled side surfaces can be flat or can be convex or concave in the mounting direction in order to further facilitate sliding into one another. An inventive feature which considerably simplifies assembly and also ensures the secure sealing between the assembled components also consists in the use of a frame element, on the surfaces of which facing the adjacent components, an elastically formed elevation is integrally formed or formed as a seal. The electrochemical element, for example a fuel cell or a fuel cell stack, can thus be easily and quickly, in particular also automatically, with a high degree of accuracy and sealing effect and thus without impairing functionality. be installed during operation of the electrochemical element.

An embodiment of the invention is explained in more detail with reference to the drawing. Show it:

1 shows a fuel cell stack composed of several individual cells in section; and

Fig. 2 is a side view of a membrane electrode unit held in a frame element.

3 shows a partial view of a fuel cell stack in section, specifically in an exploded view of a membrane electrode assembly with a bipolar plate arranged on both sides;

FIG. 4 shows a side view of a membrane electrode unit according to FIG. 1 in a first embodiment variant;

FIG. 5 shows a side view of a membrane electrode unit according to FIG. 1 in a second embodiment; and

Fig. 6 is a partial view of a fuel cell stack as in Fig. 1, but in a third embodiment of the membrane electrode assembly and the bipolar plates.

7 shows a plan view of a membrane electrode unit held in a frame element with a circumferential seal which is integrally formed on both sides of the frame element and which is also guided around the opening of the feed channel and the discharge channel for the reactants; and 8 is an exploded sectional view of part of a fuel cell stack, consisting of a membrane electrode unit arranged between two bipolar plates with seals molded onto their frame element.

The fuel cell stack initially comprises a plurality of membrane electrode units 1, each of which is held in a frame element 2 comprising two frame parts (not shown) sealingly connected by means of a hot-melt adhesive layer, bipolar plates (current transfer plates) 3 arranged between them and on the outer membrane electrode Units arranged current collector plates 4 and finally end plates 5, via which the fuel cell stack is held together with clamping bolts (not shown) which are guided in bores 12. In Fig. 1, the feed channel 6 and the discharge channel 7 for the first reactant, which are formed from openings which are provided in the plates and frame elements 2 to 5 and are aligned one above the other, are shown. The connection between the feed channel 6 or the discharge channel 7 and the fluid distribution channel 9 for the first reactant is established via a connecting channel 8 in the frame element 2. Sealing elements 10 are arranged for sealing. The fluid distribution channels for the second reactant are identified by reference number 11. The associated connecting channels to the supply and discharge channels 14, 15 (FIG. 2) for the second reactant cannot be seen in the selected sectional view (FIG. 1).

The recess 13 formed by the frame element 2 in the area of the active surface of the membrane-electrode unit 1 is - like the elevation 14 formed by the area of the fluid distribution channels 9, 11 - designed as a truncated cone by chamfered edges 17, 18. The frame elements 2 and the bipolar plates or current collectors Mer plates can therefore be joined together with a large amount of play and thus in a simple manner, and yet after assembly they lie tightly together and at the connection points of the fluid distribution channels to the connecting channels.

For the sake of simplicity, FIGS. 3 and 6 only show part of a fuel cell stack, that is to say a membrane electrode unit 1 held in a frame element 2 with bipolar plates 3 shown on both sides at a distance from it. The fuel cell stack actually consists of several alternately and with the help of seals (not shown), gas-tight membrane electrode units and bipolar plates, each with a current collector plate (anode or cathode plate) and an end plate (each not shown) on the outer membrane electrode units ) connect. In the edge area of the end plates, current collector plates and bipolar plates as well as the frame element 2 of the membrane electrode unit 1 there are openings for the formation of a feed and a discharge channel 6 and 7 for the anode reactant and a feed and discharge channel 15 and 16 for the cathode reactant , From the feed channels, the anode or cathode reactant flows via fluid distribution channels 9 or 11 in the bipolar plates 2 (and current collector plates) via the anode side or the cathode side of the membrane electrode unit 1, which is covered on both sides with a gas distributor 19. Unit 1 is in its outer, inactive edge area in the

Frame element 2 held, which consists of two, essentially stiff plates joined together via a hot melt adhesive layer (not shown). The non-active edge region of the membrane electrode unit 1 is also embedded in this hot melt adhesive layer. According to FIGS. 3 to 6, male and female guiding and fixing elements in the form of recesses 13 and elevations 14 opposite these in the fuel cell stack are provided on the frame element 3 and the bipolar plates 3 on both sides. These guiding and fixing means 13 and 14 are each arranged at a distance from the outer edge or directly on the outer edge (FIG. 6). They can be punctiform (Fig. 4) or elongated (Fig. 5). They are dimensioned so that they are in the assembled, gas-tight

The fuel cell stack lies in one another or in one another essentially without play. A mutual lateral displacement is not possible after assembly. The supply and discharge channels for the reactants are arranged in alignment and the seals (not shown) are arranged exactly around the openings for forming the supply and discharge channels. Of course, the recesses 13 can also be provided in the frame elements 2 and the elevations 14 in the bipolar plates 3, or the bipolar plate 3 and the frame element 2 can have a recess (depression) on one side and an elevation on the other side. In addition, the guiding and fixing means 13 and 14 are also formed in the current collector plates and on the inside of the end plates (not shown in each case).

It can also be seen from the drawing that the recesses 13 and the elevations 14 are designed with oblique side surfaces, that is to say they taper conically towards the interior of the recess 13 and towards the tip of the elevation 14, so that adjacent guide and fixing elements 13 , 14 are initially guided into one another with a large amount of play and, after the fuel cell stack has been braced over the end plates, a congruent and secure arrangement of all plates is nevertheless ensured. The arrangement of the tapered J ⁾ t to P ¹

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in fact from two frame parts (not shown) which are glued to one another on the mutually facing surfaces with the aid of a hot melt adhesive and between which the membrane electrode unit 1 is held. The frame parts with the seals 20, 20a are produced in a molding tool in a single process step. The elasticity of the seal required for the sealing effect is achieved both by the selection of a suitable frame material and by the cross-sectional shape of the seal. Due to the fact that the frame element 2 with the integrated seal 20, 20a and the bipolar plate 3 abut directly against one another, a sufficient contact pressure for the necessary sealing effect, that is to say, counterpressure of the bipolar plate can be applied to the molded seal 20, 20a without the Membrane electrode unit 1 can be destroyed and the sealing effect is impaired. In the exemplary embodiment, the seal 20, 20a is shown as an integrally formed oval, elastic sealing strand, which - starting from an originally round strand - assumes this shape only under the effect of the contact pressure in the assembled fuel cell stack and thus a wide elastic sealing surface on the adjacent bipolar plate 3 forms. The cross-sectional area of the seal 20, 20a can of course also have any other shape that results in an elastic deformation and thus a good seal, for example in the form of a sealing lip. The frame element with an integrated seal also has the essential advantage that the fuel cell or the fuel cell stack can be installed quickly and easily, since the frame elements with the integrated seals are easy to handle and the time-consuming application of the seal is eliminated. LIST OF REFERENCE NUMBERS

Membrane-electrode unit frame element bipolar plate current collector plate end plate supply channel (first reactant) discharge channel (first reactant) connecting channel 11 fluid distribution channel sealing element bores for clamping bolts recess elevation supply channel (second reactant) discharge channel (second reactant), 18 chamfered edges of 13, 14 gas distributor, 20a integrated poetry

Claims

claims

1. An electrochemical element, in particular a fuel cell or a fuel cell stack formed from a plurality of electrochemical cells connected in series, the membrane electrode units held in a sealing manner on a frame element, alternating bipolar plates arranged between them, between the bipolar or current collector plates and seals arranged on the frame element and on both sides each comprise a current collector plate and an end plate, openings being provided in the edge region of the frame element and the plates for forming feed and discharge channels for at least one of the reactants which are molded into the bipolar and current collector plates and open fluid distribution channels adjoining the anode or cathode layer of the membrane electrode unit are connected, characterized in that on or in the assembled state on or on the frame elements (2) and the current collector and bipolar plates (3)interlocking guiding and fixing means for the correct feeding, joining and mutual fixing of these components are formed during assembly, while the seal (20, 20a) on the frame element (2) is integrally formed on both side surfaces as a circumferential elastically deformable strand or from the Frame material is molded.

2. Electrochemical element according to claim 1, characterized in that the guiding and fixing means are designed as recesses (13) and elevations (14) in or on the respective component.

3. Electrochemical element according to claim 2, characterized in that the recesses (13) towards the bottom and the elevations (14) towards the tip are conical and interlock with one another during the assembly with play and in the assembled state essentially without play.

4. Electrochemical cell according to claim 3, characterized in that the side surfaces of the recesses are convex and the side surfaces of the elevations are concave.

5. Electrochemical cell according to one of claims 2 to 4, characterized in that the recesses (13) and the elevations (14) are each punctiform or elongated.

6. Electrochemical cell according to claim 2, characterized in that the recesses (13) and the elevations (14) are formed on the outer edge of the components which are respectively joined together.

7. Electrochemical cell according to claim 1, characterized in that formed on the outer edge of a component ridges overlap the outer edge of the adjacent component.

8. Electrochemical cell according to claim 6 and 7, characterized in that the mutually facing side surfaces of the elevation and the outer edge or the recess are chamfered in the same direction.

9. Electrochemical cell according to claim 1, characterized in that for mutual guidance and fixation of the adjacent components, the area of the Fluid distribution channels (9, 11) of the bipolar and current collector plates (3, 4) is designed as a truncated cone-like elevation (14), which is formed in a truncated cone-like recess (13) in the region of the diaphragm formed by chamfered inner edges of the frame element (2). Electrode unit (1) engages, the membrane electrode units (1) and bipolar / current collector plates (3, 4), which are initially brought together with play, lie precisely against one another in the assembled state, with the feed elements in the frame elements (2) and discharge channels connecting channels (8) for connection to the fluid distribution channels (9, 11) are formed.

10. Electrochemical element according to claim 9, characterized in that in the frame element, starting from the supply or discharge channel (6, 7; 15, 16), two or more connecting channels (8) which are individually connected to fluid distribution channels (9, 11) are trained.

11. Electrochemical element according to one of claims 9 and 10, characterized in that the obliquely extending lateral surfaces of the recess (13) and the elevation (14) are concave or convex in the assembly direction.

12. Electrochemical element according to claim 1, characterized in that the frame element (2) with an integrated seal (20, 20a) consists of an elastically deformable material.

13. Electrochemical element according to claim 1, characterized in that the integrated seal (20, 20a) has a resilient cross-sectional shape or is formed with an elastic sealing lip.

14. Electrochemical element according to claim 1, characterized in that the integrated seal (20, 20a) is formed on the edge of the frame element (2) and on the peripheral edge of the feed and discharge channels (15, 16).