Separating device, and method for separating bipolar plates and membrane-electrode assemblies of a fuel-cell stack

Abstract

The invention relates to a separating device (10) for separating bipolar plates and membrane-electrode assemblies (101) of a fuel-cell stack (100), the separating device comprising: a first separating tool (12) which is designed to separate, in regions, a bipolar plate (101) connected to a membrane-electrode assembly from a membrane-electrode assembly, or a membrane-electrode assembly from a bipolar plate (101), thereby forming an initial gap between the bipolar plate (101) and the membrane-electrode assembly; and a second separating tool (26) which is designed to penetrate into the initial gap formed by the first separating tool (12).

Description

[0001] R.413781

[0002] - 1 -

[0003] Description

[0004] Separation device and method for separating bipolar plates and membrane electrode assemblies of a fuel cell stack

[0005] Technical field

[0006] The invention relates to a separation device for separating bipolar plates and membrane electrode assemblies of a fuel cell stack, characterized by a particularly safe separation process that is mechanically gentle on the bipolar plates and membrane electrode assemblies, especially during automated separation. Furthermore, the invention relates to a method for separating two bipolar plates connected by an interposed membrane electrode assembly, as well as membrane electrode assemblies, which enables a particularly gentle separation process.

[0007] State of the art

[0008] Within the framework of alternative drive concepts, hydrogen drives are known, for example, for commercial vehicles that use fuel cell stacks as part of the energy conversion system from chemical to electrical energy. Such a fuel cell stack typically consists of a large number of fuel cells arranged one above the other. Each fuel cell, in turn, consists of two bipolar plates and a membrane electrode assembly (MEA) located between the bipolar plates. The MEA is mechanically connected to the respective bipolar plate via sealing elements and sealed against it.

[0009] For example, to replace or recycle the components or parts contained in such fuel cell stacks after the end of their service life, or if individual cells of the stack are damaged, it is necessary to separate the bipolar plates and membrane electrode assemblies of the fuel cell stack. For this reason, corresponding devices are already described in the prior art R.413781.

[0010] - 2 -

[0011] This technique has become known. For example, it is known from EP 1 478043 A1 to insert a strip-shaped, wedge-shaped separating tool from opposite sides of the fuel cell stack. This tool engages in a gap between two superimposed bipolar plates and separates the bipolar plates by moving the two separating tools against each other. The known separating tool has a length that extends across the entire width of the fuel cells or the aforementioned gap between the bipolar plates.

[0012] Furthermore, US patent 2020 / 0373590 A1 discloses cutting tools acting on opposite sides of the fuel cell stack, which, in plan view, are fork-shaped with two projections or prongs spaced apart from each other.

[0013] In both documents mentioned, the separation tools are identically designed and are typically moved to about the middle of the fuel cell stack to enable (complete) separation of the bipolar plates.

[0014] Disclosure of the invention

[0015] The separation device according to the invention for separating cell layers of a cell stack, in particular bipolar plates and membrane electrode units of a cell stack of an electrochemical cell, preferably of a fuel cell stack of a fuel cell with the features of claim 1, makes it possible to separate the bipolar plates and membrane electrode units connected to each other by sealing elements in a particularly simple and process-reliable way without damaging the bipolar plates and membrane electrode units.

[0016] The cell layers are preferably bipolar plates and / or membrane electrode assemblies. The cell stack is preferably a cell stack or a fuel cell stack. Within the scope of the present invention, an electrochemical cell particularly comprises a fuel cell and / or an electrolysis cell and / or a battery cell. It should be noted that R.413781

[0017] - 3 -

[0018] The cell stack can also be that of a cooler or heat exchanger, without leaving the scope of the present invention.

[0019] The invention is based on the idea – in contrast to the prior art mentioned above – of using two differently designed and / or serving different purposes separation tools, which are moved from the same side of the fuel cell stack between the bipolar plates and membrane electrode assemblies to be separated. While the first separation tool is designed to create an initial gap between two superimposed bipolar plates and a membrane electrode assembly in order to subsequently enable the insertion of a second separation tool, the second separation tool is optimized to enable complete separation of the bipolar plates or the membrane electrode assemblies from the bipolar plates when an initial gap already exists.

[0020] In light of the above explanations, a separating device according to the invention for separating bipolar plates and membrane electrode assemblies of a fuel cell stack with the features of claim 1 therefore comprises a first separating tool which is configured to separate a bipolar plate connected to a membrane electrode assembly from the membrane electrode assembly or a membrane electrode assembly from a bipolar plate by forming an initial gap between the bipolar plate and the membrane electrode assembly.

[0021] Furthermore, a second separating tool is provided, which is designed to penetrate the initial gap formed by the first separating tool and to separate the bipolar plate from the membrane electrode assembly or the membrane electrode assembly from the bipolar plate at least almost completely by moving the second separating tool in a feed motion.

[0022] Advantageous further developments of the separation device according to the invention for separating bipolar plates and membrane electrode units of a fuel cell stack are listed in the dependent claims.

[0023] The second separating tool has a separating body that has a wedge-shaped cross-section, at least in some areas. The wedge-shaped design of R.413781

[0024] - 4 -

[0025] The separating body, during its (horizontal) movement, causes a successive separation of the bipolar plate from the membrane electrode unit arranged below it, or of the membrane electrode unit from the bipolar plate arranged below it.

[0026] In a preferred geometric embodiment of the proposal presented above, the wedge-shaped cross-section has a separating surface that extends at an angle to a bottom surface for interaction with an upper bipolar plate or the membrane electrode assembly. Preferably, the angle is between 20° and 40°, more preferably 30°.

[0027] With regard to the separating body of the second separating tool, this is preferably designed in the shape of a strip with a constant cross-section and has a length that corresponds at least to a width of the bipolar plates and membrane electrode units to be separated from each other, wherein a fastening section for attaching the second separating tool to a drive mechanism is attached to the separating body.

[0028] To achieve a long service life for the second cutting tool and to minimize the mechanical stress on the bipolar plates and membrane electrode assemblies caused by friction with the second cutting tool, it is preferably provided that the second cutting tool is made of steel, in particular stainless steel. Alternatively, it is also possible to use other non-metallic materials that have similar properties.

[0029] With regard to the geometric design of the first separating tool, it has proven advantageous, with a view to minimizing the risk of damage to the bipolar plates and membrane electrode assemblies when the first separating tool is applied, if the first separating tool is knife-shaped with a knife tip for penetrating between a bipolar plate and a membrane electrode assembly and has a width that is less than the width of the bipolar plate or the membrane electrode assembly. R.413781

[0030] - 5 -

[0031] In a preferred embodiment of such a first cutting tool, it is provided that the first cutting tool is connected to a drive mechanism which is designed to move the first cutting tool perpendicular to a first feed direction of the first cutting tool in the direction of a second feed direction in order to form the initial gap. Both feed directions run in the plane of the bipolar plates.

[0032] In order to widen the initial gap for inserting the second cutting tool in such a way that the second cutting tool does not come into contact with the first cutting tool during its movement, it is further provided that the first cutting tool can additionally be raised and lowered perpendicular to the two feed directions, i.e. perpendicular to the plane of the bipolar plates.

[0033] The invention further comprises a method for separating two interconnected cell layers of a cell stack, in particular bipolar plates and membrane electrode assemblies of a cell stack of an electrochemical cell, preferably a fuel cell stack of a fuel cell, in particular by means of a separation device designed according to the invention as described above, wherein the method comprises at least the following steps: First, a first separation tool penetrates between a bipolar plate and a membrane electrode assembly to create an initial gap. Then, a second separation tool penetrates the initial gap and moves between the bipolar plate and the membrane electrode assembly towards the side of the fuel cell stack facing away from the initial gap until the bipolar plate or membrane electrode assembly is preferably completely separated.

[0034] A preferred embodiment of the method provides that the first separating tool for forming the initial gap is first moved over a partial area of ​​a width and length of the bipolar plate between the bipolar plate and the membrane electrode unit in a first feed direction and subsequently in a second direction perpendicular to the first feed direction in the plane of the bipolar plate R.413781

[0035] - 6 -

[0036] is used to form the initial gap across the entire width of the bipolar plate or the membrane electrode assembly.

[0037] To enable the second cutting tool to penetrate the initial gap as easily as possible without collision with the first cutting tool, a further preferred embodiment of the method provides that the initial gap is enlarged by raising the first cutting tool in a direction perpendicular to the plane of the bipolar plates and that the second cutting tool is moved into the initial gap below the first cutting tool.

[0038] In order to minimize the mechanical stress on the lower of the two bipolar plates to be separated or the membrane electrode units, it is further preferably provided that the second separation tool is moved above or below the membrane electrode unit, wherein a separation surface of the second separation tool interacts with the upper bipolar plate or the membrane electrode unit and separates it from the membrane electrode unit or the lower bipolar plate.

[0039] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings.

[0040] Brief description of the drawings

[0041] Fig. 1

[0042] and

[0043] Fig. 2 shows, in simplified perspective views, a separation device for separating bipolar plates and membrane electrode units of a fuel cell stack during different phases of separation.

[0044] Fig. 3 shows a perspective view of a first cutting tool of the cutting device according to Figs. 1 and 2.

[0045] Fig. 4 shows a perspective view of a second separating tool of the separating device according to Figs. 1 and 2, R.413781

[0046] - 7 -

[0047] Fig. 5 shows a cross-section through the second cutting tool in the area of ​​its cutting body and

[0048] Fig. 6 shows a flowchart to explain the separation of two bipolar plates using the separation device according to Figs. 1 and 2.

[0049] Embodiments of the invention

[0050] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0051] Figures 1 and 2 show, in a highly simplified manner, a separating device 10 for separating bipolar plates 101 arranged one above the other and connected to each other in the area of ​​seals (not shown), as well as membrane electrode assemblies of fuel cells of a fuel cell stack 100. Each fuel cell of the fuel cell stack 100 is formed by two bipolar plates 101 and a foil-like membrane electrode assembly arranged between the two bipolar plates 101 and connected to the bipolar plates 101 via the aforementioned seals, as is known from the prior art.

[0052] The fuel cell stack 100 is shown, by way of example, arranged or mounted on a platform 103. The bipolar plates 101 and membrane electrode assemblies typically each have a semicircular indentation 105 on one side facing the separating device 10, in the area of ​​which a separation gap 106 is formed between the membrane electrode assembly and the bipolar plate 101 arranged below and above it, which enables the use of the separating device 10.

[0053] The separating device 10 comprises a first separating tool 12, which is configured to penetrate the separating gap 106 in the region of the notch 105 between a bipolar plate 101 and the membrane electrode assembly. The first separating tool 12 is coupled to a drive mechanism 14 and is thereby movable in the three spatial directions x, y, and z of a Cartesian coordinate system. R.413781

[0054] - 8 -

[0055] The first cutting tool 12, also referred to as the primary tool 15, shown in detail in Fig. 3, is designed in the form of a flat cutting blade 16 with a thickness d of, for example, 1.5 mm. Furthermore, the first cutting tool 12 has a length I of, for example, 140 mm and a width b of, for example, 20 mm. The length I of the first cutting tool 12 is less than the length L of the bipolar plates 101 and membrane electrode assemblies and is, for example, (only) between 20% and 40% of the length L of the bipolar plate 101 and membrane electrode assemblies. Likewise, the width b of the first cutting tool 12 is less than the width B of the bipolar plate 101 and the membrane electrode assemblies and is, for example, only 20% of the width B of the bipolar plates 101 and membrane electrode assemblies.

[0056] As shown in Fig. 3, the first cutting tool 12 has a longitudinal axis 18 along which two knife sections 20, 21 run opposite each other. The knife sections 20, 21 form a knife tip 22 on the side facing the fuel cell stack 100. The knife tip 22 is formed solely by the first knife section 20. Both knife sections 20, 21 have side edges 23, 24 on the side facing the knife tip 22, which are arranged at an acute angle α, β of, for example, between 10° and 30°. Furthermore, the second knife section 21 is offset relative to the knife tip 22, so that a distance α is created between the two side edges 23, 24 in the region of the longitudinal axis 18.

[0057] Furthermore, the separating device 10 comprises a second separating tool 26, which is also movable by means of a drive mechanism 28 at least in the x-direction, i.e. parallel to the plane of the bipolar plates 101 and the membrane electrode units, preferably also in the z-direction, i.e. perpendicular to the plane of the bipolar plates 101 and membrane electrode units.

[0058] The second separating tool 26, shown in detail in Figures 4 and 5, is also referred to as the secondary tool 29 and has a separating body 30 with a triangular cross-sectional area. The cross-section of the separating body 30 is constant over its entire length c. In particular, the length c is at least equal to the width B of the bipolar plate 101 and membrane electrode assembly. [Reference to the separating body 30: R.413781]

[0059] - 9 -

[0060] A fastening section 32 is attached to one side, which serves to attach the second separating tool 26 to the drive mechanism 28.

[0061] The cross-section of the separating body 30 is characterized by an acute angle y of approximately 30°. Furthermore, the cross-section of the separating body 30 is formed in the shape of a right-angled triangle, such that angle A is 90° and angle A is approximately 60°.

[0062] The separating body 30 has a bottom surface 34 extending parallel to the plane of the bipolar plates 101 and membrane electrode assemblies, and an inclined separating surface 36. Furthermore, the separating body 30, or the second separating tool 26, is preferably made of steel, in particular stainless steel. The longitudinal axis 38 of the strip-like separating body 30 is aligned parallel to the side edges 108 of the bipolar plates 101 and membrane electrode assemblies over their entire width B.

[0063] The separation process of the uppermost bipolar plate 101 from a membrane electrode assembly and of the membrane electrode assembly from the bipolar plate 101 arranged below it of the fuel cell stack 100 can be explained with reference to Figs. 1 and 2 in conjunction with the flow diagram according to Fig. 5, using the separation process of the upper bipolar plate 101 from the membrane electrode assembly arranged below it as an example:

[0064] In a first step 1001, as shown in Fig. 1, the first separating tool 12 penetrates the separation gap 106 between the upper bipolar plate 101 and the membrane electrode assembly located below it (not shown in Fig. 1) in the area of ​​the indentations 105 by moving the first separating tool 12 in a first feed direction in the x-direction. As soon as the first separating tool 12 has penetrated, for example, one-third or half of its length I between the bipolar plate 101 and the membrane electrode assembly, the first separating tool 12 is moved in a second feed direction, i.e., in a positive or negative y-direction, until an initial gap is created between the (upper) bipolar plate 101 and the membrane electrode assembly across its entire width B. Subsequently, in step 1003, the first R.413781 is lifted according to the illustration in Fig. 2.

[0065] - 10 -

[0066] The separating tool 12 is moved in the z-direction to facilitate the insertion of the second separating tool 26 into the initial gap formed between the upper bipolar plate 101 and the membrane electrode assembly, which remains attached to the lower bipolar plate 101. In a subsequent step 1004, the second separating tool 26 is moved in the feed direction in the x-direction between the (upper) bipolar plate 101 and the membrane electrode assembly. During this movement, the separating surface 36 of the second separating tool 26 comes into contact with the underside of the upper bipolar plate 101 and separates it from the membrane electrode assembly. Preferably, the second separating tool 26 is moved in the x-direction until the (upper) bipolar plate 101 is completely separated from the membrane electrode assembly. It is also preferably the case that, before the complete removal or...Releasing the upper bipolar plate 101, for example, by gripping the bipolar plate 101 using a gripper not shown, so that the upper bipolar plate 101 can be removed after separation from the fuel cell stack 100.

[0067] After the two separating blades 12, 26 are returned to their initial position, steps 1001 to 1004 are carried out analogously for the membrane electrode assembly and the lower bipolar plate 101 of a fuel cell located below it. Thus, a bipolar plate 101 and a membrane electrode assembly are separated alternately.

[0068] The separating device 10 described so far can be modified or adapted in a variety of ways without deviating from the inventive concept.

[0069] Thus, it may not be necessary to move the second separating tool 26 over the entire length L of the bipolar plates 101 and membrane electrode units if the adhesion between a bipolar plate 101 and a membrane electrode unit has already been eliminated due to the arrangement of the aforementioned seals, or if the upper bipolar plate 101 or membrane electrode unit, which may still have a slight connection with the membrane electrode unit or the lower bipolar plate 101, can be easily removed from the bipolar plate 101 or membrane electrode unit by means of the gripper also mentioned.

Claims

R.413781 - 11 - Claims 1. Separating device (10) for separating cell layers (101) of a cell stack (100), in particular bipolar plates (101) and membrane electrode assemblies of a cell stack (100) of an electrochemical cell, preferably of a fuel cell stack (100) of a fuel cell, comprising a first separating tool (12) configured to selectively separate the cell layers (101), in particular a bipolar plate (101) connected to a membrane electrode assembly from a membrane electrode assembly or a membrane electrode assembly from a bipolar plate (101) by forming an initial gap between the bipolar plate (101) and the membrane electrode assembly, and a second separating tool (26) configured to penetrate the initial gap formed by the first separating tool (12) and to separate the cell layers (101),in particular to separate the bipolar plate (101) from the membrane electrode unit or the membrane electrode unit from the bipolar plate (101) by moving the second separating tool (26) in a feed motion at least largely, in particular almost completely or completely from each other.

2. Separating device according to claim 1, characterized by that the second separating tool (26) has a separating body (30) which has a wedge-shaped cross-section at least in some areas.

3. Separating device according to claim 2, characterized by that the wedge-shaped cross-section has a separating surface (36) extending at an oblique angle (y) to a bottom surface (34) for interaction with an upper cell layer (101), in particular an upper bipolar plate (101) or the membrane electrode assembly.

4. Separating device according to claim 3, characterized by R.413781 - 12 - that the oblique angle (y) is between greater than or equal to 20° and less than or equal to 40°, preferably 30°.

5. Separating device according to one of claims 2 to 4, characterized by that the separating body (30) is designed in a strip-like shape with a constant cross-section and has a length (c) that corresponds at least to a width (B) of the cell layers (101) to be separated from each other, in particular bipolar plates (101), and that a fastening section (32) for attaching the second separating tool (26) to a drive mechanism (28) is connected to the separating body (30).

6. Separating device according to one of claims 1 to 5, characterized by that the second cutting tool (26) is made of steel, in particular stainless steel.

7. Separating device according to one of claims 1 to 6, characterized by that the first separation tool (12) is knife-shaped with a knife tip (22) for penetrating between one of the cell layers (101), in particular the bipolar plate (101) and the membrane electrode assembly, and has a width (b) that is less than the width (B) of the cell layer (101), in particular the bipolar plate (101) and the membrane electrode assembly.

8. Separating device according to claim 7, characterized by that the first cutting tool (12) is connected to a drive mechanism (14) which is designed to move the first cutting tool (12) perpendicular to a first feed direction of the first cutting tool (12) in the direction of a second feed direction of the first cutting tool (12) in order to form the initial gap.

9. Separating device according to claim 8, characterized by R.413781 - 13 - that the first cutting tool (12) is additionally arranged to be raised and lowered perpendicular to the two feed directions.

10. Method for separating cell layers (101) of a cell stack (100), in particular bipolar plates (101) and membrane electrode assemblies of a cell stack (100) of an electrochemical cell, preferably of a fuel cell stack (100) of a fuel cell, in particular by means of a separation device (10) designed according to any one of claims 1 to 9, comprising at least the following steps: Penetration of a first separation tool (12) between the cell layers (101), in particular a bipolar plate (101) and a membrane electrode unit to create an initial gap; Penetration of a second separation tool (26) into the initial gap and movement of the second separation tool (26) between the cell layers (101), in particular the bipolar plate (101) and the membrane electrode assembly in the direction of the side of the cell stack, in particular the fuel cell stack (101) facing away from the initial gap, until preferably complete separation of the cell layers (101), in particular the bipolar plate (101) and the membrane electrode assembly.

11. Method according to claim 10, characterized by that the first separating tool (12) for forming the initial gap is first moved over a partial area of ​​a width (B) and a length (L) of the cell layers (101), in particular the bipolar plate (101) between the bipolar plate (101) and the membrane electrode assembly in the direction of a first feed direction and subsequently in a second direction perpendicular to the first feed direction in the plane of the cell layer (101), in particular the bipolar plate (101), in order to form the initial gap over the entire width of the cell layer (101), in particular the bipolar plate (101) or the membrane electrode assembly.

12. Method according to claim 10 or 11 , characterized by that the initial gap is created by lifting the first separating tool (12) in a direction perpendicular to the plane of the cell layers (101), in particular bipolar plates R.413781 - 14 - (101) is enlarged in the direction of the first cutting tool (12) and the second cutting tool (26) is moved into the initial gap below the first cutting tool (12).

13. Method according to any one of claims 10 to 12, characterized by that the second separating tool (26) is moved above or below a lower cell layer (101), in particular a membrane electrode assembly, wherein a separating surface (36) of the second separating tool (26) interacts with the upper cell layer (101), in particular the upper bipolar plate (101) or the membrane electrode assembly, and separates it from the membrane electrode assembly or the lower bipolar plate (101).

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