Thin PEM water electrolysis cell and process

Abstract

The invention relates to a cell (1) for PEM water electrolysis, which has at least one sequence of a GDL anode (GDLA), an MEA, a cathode (GDLK) in a frame (10), wherein the end faces (26, 28) of the anode (GDLA) and cathode (GDLK) are provided with a seal (25, 27), which are placed under pressure close to the frame (10), as well as bipolar plates (BPP) on the anode (GDLA) and under the cathode (GDLK).

Description

[0001] The invention relates to a thin cell for PEM water electrolysis and a method.

[0002] In PEM water electrolysis, the aim is to build as small and thin a system as possible to minimize space requirements, resource consumption, and short electrical paths. This allows for the construction of efficient systems.

[0003] Currently, O-rings are often inserted into the cells, or flat gaskets are used between the frame and the bipolar plate. These require additional indentations / grooves in the frame or are relatively thick, as is the case with a flat gasket.

[0004] This results in a high level of complexity on its side, for example due to elaborate milling or complex injection molding for the recesses for the O-ring.

[0005] An additional problem is the tolerance between the gas diffusion layer (GDL) and the cell frame. This allows the GDL to move and not always remain in the same position. This can lead to problems and should be avoided. Particularly on the cathode side, a large gap between the frame and the GDL can cause problems because the membrane is not supported there. In this area, the likelihood of membrane tears or similar defects is increased. Membrane tears lead to cell failure.

[0006] The problem of the unsupported diaphragm has largely been solved by using a large carbon fleece (soft component) as part of the GDL cathode. This large carbon fleece ensures a zero gap between the frame and the GDL cathode, thus providing excellent diaphragm support. However, this carbon fleece is not ideal either, as the material interface between the stainless steel GDL cathode and the carbon fleece results in high ohmic resistance.

[0007] It is therefore the purpose of the invention to solve the problem mentioned above.

[0008] The problem is solved by a cell according to claim 1 and a method according to claims 4, 6.

[0009] The dependent claims list further advantageous measures which can be combined arbitrarily to achieve further advantages.

[0010] They show Fig. 1 a state-of-the-art cell, Fig. 2 a cell according to the invention and Fig. 3 a process step.

[0011] The figures and description represent only exemplary embodiments of the invention.

[0012] The Fig. Figure 1 shows a state-of-the-art cell 1'. A bipolar plate (BPP), a GDL anode (GDL), a membrane (MEA), a GDL cathode (GDL), and another bipolar plate (BPP) appear in sequence.

[0013] The cathode and anode are enclosed and held by a frame 10'. Within the frame 10' are several recesses 11, 12, 13, each containing a seal 14.

[0014] Two external recesses 11, 13 in the frame 10' are provided for sealing against the bipolar plate (BPP) and there is an internal recess 12 for sealing against the MEA.

[0015] The frame 10' must therefore have a corresponding thickness so that it can contribute to sufficient mechanical stability in a stack of several cells because of the cutouts of material for the recesses 11, 12, 13.

[0016] In Fig. Figure 2 shows a cell 1 according to the invention. The frame 10 has only one recess 12 in the area of ​​the MEA.

[0017] The end faces of the GDL anode (GDLA) preferably already have a seal 25 before installation in the frame 10. The same applies to the cathode (GDLK) with a seal 27.

[0018] This means that the two outer recesses 11, 13 are close to the BPP ( Fig. 1) no longer necessary, so the frame can be made 10 thinner because the absence of the recesses still provides sufficient mechanical stability. Therefore, the cathode and anode can also be made thinner.

[0019] The metallic GDL is surrounded on the respective end faces 26, 28 with a seal 25, 27, in particular made of FKM, PDM, PTFE, FKM, silicone, ..., so that the GDL is completely wetted with sealing material at the edge.

[0020] This should preferably be applied in such a way that a slight overhang is formed in the horizontal and vertical directions.

[0021] The GDLs can then be pressed into frame 10.

[0022] By pressing, the seal 25, 27 is deformed to such an extent (approx. 10% - 40% compression is preferred) that a sealing effect is achieved between GDLA and GDLK and frame 10.

[0023] This clearly defines the position of the GDL and there is no gap between the frame and the GDL.

[0024] The membrane is optimally supported on the cathode side. A carbon fleece is no longer needed for this.

[0025] The seal can now be pressed down with a bipolar plate (BPP). This also allows cell 1 to be sealed between the bipolar plate (BPP) and the seal.

[0026] The application of the seal 25, 27 to the GDL can be carried out by overmolding, injection molding, brushing or additive manufacturing.

[0027] This is in Fig.Figure 3 shows a nozzle 30 spraying plastic onto the GDL, here GDLA.

[0028] A seal 25 has already been applied to one side surface of the GDLA.

[0029] The plastic may need to be cured.

[0030] In additive thickening, the GDL is introduced into the corresponding printer.

[0031] The advantages of this cell according to the invention 1: • Thinner, simpler frame possible • The membrane is optimally supported • Carbon fleece is not required for tolerance compensation

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