Cell frame for an electrochemical cell and method for producing a cell frame

Abstract

Cell frame (1) for an electrochemical cell of an electrolyzer which is made of a composite material comprising at least one thermoplastic and continuous glass fibers.

Description

[0001] Cell frame for an electrochemical cell and method for manufacturing a cell frame

[0002] Description:

[0003] The present invention relates to a cell frame for an electrochemical cell of an electrolyzer. It further relates to a method for manufacturing such a cell frame.

[0004] With the use of renewable energies, technologies for storing the generated electrical energy are becoming increasingly important. One possibility is storage in the form of hydrogen, which is produced using an electrolyzer. Depending on their design, such electrolyzers can consist of stacks of electrochemical cells. Typically, each cell has a steel frame, which can be circular or rectangular, surrounding the electrochemical cell and holding the bipolar separator plate.

[0005] Manufacturing and finishing such cell frames with a diameter of, for example, 1.6 m requires expensive lathes. Mass production of cell stacks is not yet practical.

[0006] It is an object of the present invention to provide a cell frame for an electrochemical cell of an electrolyzer that can be manufactured simply and cost-effectively and also exhibits the necessary stability and robustness. Furthermore, a method for manufacturing such a cell frame, which is particularly suitable for mass production, is to be provided.

[0007] This problem is solved by the subject matter of the independent patent claim. Advantageous embodiments and further developments are the subject matter of the dependent claims. According to one aspect of the invention, a cell frame for an electrochemical cell of an electrolyzer is provided, which is formed from a composite material comprising at least one thermoplastic and continuous glass fibers.

[0008] As it turns out, combining a thermoplastic with continuous glass fibers makes it possible to provide a sufficiently stable cell frame that exhibits favorable properties in terms of stability and thermal expansion. Continuous glass fibers are understood to be, for example, glass fibers with a length of at least 50 mm, often considerably longer, which are typically available wound on a reel and can be processed into layups of virtually any dimensions using winding methods.

[0009] Furthermore, such a cell frame is significantly lighter than a steel cell frame and requires no complex forming of the component. By selecting appropriate materials, high corrosion resistance and resistance to alkaline liquids can also be achieved. In addition, the production of the cell frame can be very energy- and cost-efficient.

[0010] In one embodiment, the continuous glass fibers are wound around an axis perpendicular to the plane of the cell frame. By using a winding technology, the cell frame can be manufactured very simply and cost-effectively. Favorable mechanical properties are achieved through the choice of materials, the geometry of the cell frame, and the winding technology.

[0011] In thermoplastic winding, for example, a thermoplastically pre-impregnated tape is passed through a preheating section, causing the thermoplastic polymer matrix to melt and the tape to become less rigid. Alternatively, heating can be achieved by laser irradiation.

[0012] Winding processes typically refer to technologies in which rotationally symmetric bodies are deposited onto a rotating mold core using fibers embedded in resin. In particular, depending on the core geometry and the winding angle, unidirectionally reinforced semi-finished products with a width of 5-25 mm are used.

[0013] Since the components for the cell frame are only 10-20 mm wide, a wide-band winding technology can be used, in which the winding strip is exactly as wide as the component. This means that only a large number of individual strip layers need to be wound on top of each other to produce the cell frame. Such winding methods allow for precise control of the fill level of the composite material and have already been proven.

[0014] According to one embodiment, the fill level of the composite material is 40-60%. The fill level is defined as the volume fraction of glass fibers in the composite material. It has been found that a fill level of 40-60% achieves sufficient stability and favorable coefficients of thermal expansion for the cell frame.

[0015] According to one embodiment, the cell frame has a plurality of frame elements that are connected to each other by material bonding and / or form-fitting.

[0016] In this embodiment, the cell frame is subdivided into a plurality of individual elements, which are manufactured and assembled in separate or successive winding steps. This allows the production of even complex cell frame geometries. In particular, it allows the integration of the bipolar separator plate into the cell frame.

[0017] According to one embodiment, the cell frame has a first frame element and a second frame element, wherein the two frame elements are arranged on two sides of a bipolar separator plate of the electrochemical cell and the bipolar separator plate is held between the first and the second frame element.

[0018] In this embodiment, the bipolar separating plate can be integrated into the geometry of the frame elements in a material-bonded and / or form-fit manner such that it is stably held to the cell frame. According to one embodiment, the cell frame has a further frame element that surrounds the first and second frame elements from the outside and mechanically connects them.

[0019] In this embodiment, different functions of the cell frame are performed by different frame elements: while the first and second frame elements located further inside hold the bipolar separating plate, the further frame element can ensure sealing to the outside and to adjacent cells.

[0020] According to one embodiment, the cell frame further comprises at least one electrically conductive contacting element embedded in the composite material, which contacts the bipolar separator plate of the electrochemical cell and is exposed on a top side of the frame.

[0021] In a steel cell frame, the bipolar separator plate can be contacted via the frame itself. The electrodes of adjacent cells can then be contacted via the cell frame with a sufficiently high current-carrying capacity. However, in the case of a cell frame constructed from composite material, the problem of electrical contacting can be solved by incorporating at least one electrically conductive contact element into the cell frame, particularly by wrapping it in during the winding process. This electrically conductive contact element is exposed on one side of the frame, thus enabling contact with the adjacent electrochemical cells.

[0022] According to one embodiment, the composite material further comprises at least one layer of a material that increases the gas tightness of the cell frame. Such a so-called liner can be particularly advantageous for sealing against readily diffusing hydrogen. Such a layer can simply be inserted between individual layers of tape and wound along with the tape during the winding process.

[0023] According to one aspect of the invention, an electrolyzer is provided, comprising at least one stack of electrochemical cells, each having the described cell frame. This can, in particular, be an alkaline electrolyzer.

[0024] According to one embodiment, the cell frames have at least one inner frame element and one outer frame element, wherein the outer frame element surrounds the at least one inner frame element from the outside, because several adjacent cell frames of the stack have a common, one-piece formed outer frame element within which several inner frame elements of adjacent cells are arranged.

[0025] This embodiment has the advantage that the outer ring for several electrochemical cells can be wound onto the existing inner frame elements simultaneously and reliably connects them, so that assembly by screwing is not necessary.

[0026] According to one aspect of the invention, a method for manufacturing a frame for an electrochemical cell of an electrolyzer is specified, which is formed from a composite material comprising at least a thermoplastic and continuous glass fibers, wherein the continuous glass fibers are wound around an axis that is perpendicular to the plane of the cell frame.

[0027] The cell frame can have a plurality of frame elements that are wound in separate process steps.

[0028] According to one embodiment, the cell frame has at least one inner frame element and one outer frame element, wherein the outer frame element surrounds the at least one inner frame element from the outside and is wound onto the at least one previously wound inner frame element.

[0029] Embodiments of the invention are described below by way of example with reference to schematic drawings.

[0030] Figure 1 shows a cell frame for an electrochemical cell according to a first embodiment of the invention, Figure 2 shows a cell frame for an electrochemical cell according to a second embodiment of the invention,

[0031] Figure 3 shows a cell frame for an electrochemical cell according to a third embodiment of the invention,

[0032] Figure 4 shows a cell frame for an electrochemical cell according to a fourth embodiment of the invention,

[0033] Figure 5 shows a cell frame for an electrochemical cell according to a fifth embodiment of the invention and

[0034] Figure 6 shows a cell frame for an electrochemical cell according to a sixth embodiment of the invention.

[0035] Figure 1 shows a cross-section through a cell frame 1 for an electrochemical cell of an electrolyzer according to a first embodiment of the invention. The cell frame 1 can be, in particular, annular or rectangular. The cell frame 1 serves to enclose an interior space 18 of the electrochemical cell. Furthermore, the bipolar partition 6 is mounted on the cell frame 1. The bipolar partition 6 separates a first side 20 of the interior space 18 from a second side 22 of the interior space 18. The bipolar partition 6 prevents the mixing of hydrogen and oxygen that occur at the cathode and anode, respectively. It also allows current flow between the anode and the cathode and increases the mechanical stability of the electrochemical cell.

[0036] In the embodiment shown in Figure 1, the cell frame 1 is composed of three frame elements: the outer frame element 2, the inner frame element 3, and the inner frame element 4. The outer frame element 2 is arranged radially further outward than the inner frame elements 3 and 4. The outer frame element 2 surrounds the inner frame elements 3 and 4 and connects directly to them. All frame elements 2, 3, and 4 are made of a composite material comprising at least one thermoplastic and continuous glass fibers. The continuous glass fibers are coated with a thermoplastic and wound in a multiple of layers 5 using a wide-band winding technique, with the winding taking place around the axis L, which is perpendicular to the plane of the cell frame 1.

[0037] In the illustrated embodiment, the inner frame elements 3, 4 are wound first. The outer frame element 2 is then wound onto these, connecting them. The bipolar separating plate 6 is inserted into a gap 16 between the inner frame elements 3, 4. This can be done before the outer frame element 2 is wound onto them.

[0038] In the embodiment shown in Figure 1, an O-ring seven is arranged on the outer frame element 2, which seals the cell frame 1 against adjacent cell frames 1.

[0039] Figure 2 shows a second embodiment of the cell frame 1. This differs from the one shown in Figure 1 in that the bipolar divider plate 6 has an angled end 8 with which it is positively engaged in the inner frame element 3, 4. This embodiment thus has the advantage of a particularly secure mounting of the bipolar divider plate 6.

[0040] Figure 3 shows a third embodiment of the cell frame 1, which differs from that shown in Figure 2 in that a contacting element 9 is wrapped within the inner frame elements 3 and 4. The contacting element 9 is made of an electrically conductive material and can, for example, have the form of a metallic rod. The contacting element 9 serves to contact the bipolar separator plates 6 of adjacent cells with each other. For this purpose, contact areas 10 are exposed at its ends, which are not embedded within the inner frame elements 3 and 4. In the embodiment shown in Figure 3, two contacting elements 9 are provided, one of which is arranged within each of the inner frame elements 3 and 4, respectively, so that the bipolar separator plate 6 is contacted from both sides.

[0041] Figure 4 shows a fourth embodiment of the cell frame 1, which differs from the embodiment shown in Figure 3 in that only one continuous contacting element 9 is provided. This is arranged on the outside of the bipolar separator plate 6 and is in contact with it via the angled end 8.

[0042] The contact elements 9 shown in Figures 3 and 4 can already be incorporated into the inner frame elements 3, 4 during the winding process. Alternatively, they can be inserted into them after winding.

[0043] Figure 5 shows a fifth embodiment of the cell frame 1. This differs from the embodiments shown in Figures 1 to 4 in several respects. In this embodiment, the bipolar partition plate 6 extends outwards through the frame elements 3, 4. According to this embodiment, the bipolar partition plate 6 extends through a gap 16 formed between the frame elements 3, 4. In this embodiment, the interior is sealed by means of glazing rings 7 on the inner areas of the frame elements 3, 4. The sealing function is thus performed by the frame elements 3, 4. They also bear the axial load during assembly.

[0044] Figure 6 shows another embodiment of the cell frame 1, in which the sealing function is also ensured by inner frame elements 3, 4. This embodiment differs from that shown in Figure 5 in that the bipolar separator plate 6 does not extend to the outside, but is held in the inner frame elements 3, 4. Furthermore, an outer frame element 2 is wound onto the outside of the inner frame elements 3, 4, connecting them to each other. This embodiment has the advantage that the outer frame element 2 can be wound for a plurality of adjacent cells. The winding can, for example, be carried out on the existing structure consisting of the inner frame elements 3, 4 and the bipolar separator plate 6. A separate connection of adjacent cells to form a stack, for example by screws, is then unnecessary.

[0045] The features of the embodiments shown in Figures 1 to 5 can also be combined with one another in ways other than those explicitly shown. List of reference symbols:

[0046] 1 cell frame

[0047] 2 outer frame element 3 inner frame element 4 inner frame element 5 position

[0048] 6 Separating plate

[0049] 7 O-ring

[0050] 8 angled end

[0051] 9 Contact element 10 Contact area

[0052] 11 outer frame element 12 outer frame element 13 edge

[0053] 16 columns

[0054] 18 Interior

[0055] 20 first page

[0056] 22 second page

Claims

Patent claims:

1. Cell frame (1 ) for an electrochemical cell of an electrolyzer, which is made of a composite material comprising at least a thermoplastic and continuous glass fibers.

2. Cell frame (1) according to claim 1 , wherein the continuous glass fibers are wound around an axis L which is perpendicular to the plane of the cell frame (1).

3. Cell frame (1) according to claim 2, wherein a broadband is formed from the continuous glass fibers, the width of which corresponds to the width of the wound component.

4. Cell frame (1) according to any one of claims 1 to 3, where the fill level of the composite material is 40 to 60%.

5. Cell frame (1) according to any one of claims 1 to 4, comprising a plurality of frame elements (2, 3, 4) which are connected to each other by material interlocking and / or form interlocking.

6. Cell frame (1) according to claim 5, comprising a first frame element (3) and a second frame element (4), wherein the two frame elements (3, 4) are arranged on two sides of a bipolar separating plate (6) of the electrochemical cell and the bipolar separating plate (6) is held between the first and the second frame element (3, 4).

7. Cell frame (1) according to claim 6, further comprising a further frame element (2) that externally surrounds the first frame element (3) and the second frame element (4) and mechanically connects them together.

8. Cell frame (1) according to any one of claims 1 to 7, further comprising at least one electrically conductive contacting element (9) embedded in the composite material, which contacts a bipolar separating plate (6) of the electrochemical cell and is exposed on one side of the cell frame (1).

9. Cell frame (1) according to any one of claims 1 to 8, wherein the composite material further comprises at least one layer (5) of a material increasing the gas tightness of the cell frame (1).

10. Electrolyzer comprising at least one stack of electrochemical cells comprising cell frames (1) according to any one of claims 1 to 9.

11. Electrolyzer according to claim 10, wherein the cell frames (1 ) have at least one inner frame element (3, 4) and one outer frame element (2), wherein the outer frame element (2) surrounds the at least one inner frame element (3, 4) from the outside, wherein several adjacent cell frames (1) of the stack have a common, integrally formed outer frame element (2), within which several inner frame elements (3, 4) of adjacent cells are arranged.

12. Method for producing a cell frame (1 ) for an electrochemical cell of an electrolyzer, which is formed from a composite material comprising at least a thermoplastic and continuous glass fibers, wherein the continuous glass fibers are wound around an axis that is perpendicular to the plane of the cell frame (1).

13. Method according to claim 12, wherein the cell frame (1) has a plurality of frame elements (2, 3, 4) which are wound in separate process steps.

14. Method according to claim 13, wherein the cell frame (1) has at least one inner frame element (3, 4) and one outer frame element (2), wherein the outer frame element (2) surrounds the at least one inner frame element (3, 4) from the outside and is wound onto the at least one previously wound inner frame element (3, 4).

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