Method for producing an electrochemical cell, and electrochemical cell

Abstract

The invention relates to a method for producing an electrochemical cell (1), in particular a fuel cell or an electrolysis cell, comprising a plurality of layers and / or plies (2) arranged one on top of the other in order to form two electrodes (3) with an intermediate separator (4). According to the invention, at least one of the two electrodes (3) is made from an electrode material (5) and a fibre material (6), wherein a water-soluble fibre material (6) is used. This water-soluble fibre material is a) coated with the electrode material (5) or b) integrated into the electrode material (5). In a subsequent method step, the water-soluble fibre material (6) is at least partly removed again using water, so that cavities (7) are formed. The invention also relates to an electrochemical cell (1).

Description

[0001] R.415617

[0002] - 1 -

[0003] Description

[0004] Methods for manufacturing an electrochemical cell and electrochemical cell

[0005] The present invention relates to a method for manufacturing an electrochemical cell with the features of the preamble of claim 1. The electrochemical cell can, in particular, be a fuel cell or an electrolysis cell. Furthermore, an electrochemical cell is specified.

[0006] The preferred application area of ​​the invention is fuel cell or electrolysis systems.

[0007] State of the art

[0008] Electrochemical cells, particularly fuel cells and electrolysis cells, have a layered structure with two electrodes and a separator positioned between them, which electrically isolates the electrodes. The separator can be a membrane, which together with the electrodes forms a membrane-electrode array. One electrode forms the anode and the other the cathode.

[0009] In a fuel cell, hydrogen and oxygen are converted into electrical energy, heat, and water. The hydrogen is supplied to the anode, and the oxygen to the cathode. In an electrolysis cell, water is split into hydrogen and oxygen using electrical energy. In this case, the water is supplied to the anode.

[0010] The electrodes of an electrochemical cell often consist of an electrically conductive base material, which is coated with an R.415617.

[0011] - 2 - catalytic material is functionalized. The catalytic material can also be applied directly to the separator, so that a catalyst layer is formed on one or both sides of the separator, which acts as an electrode. Since the electrodes and the separator are very delicate and therefore susceptible to damage, high process requirements are placed on the application of the catalytic material and / or the assembly of the electrodes and the separator.

[0012] The efficiency of the electrochemical reactions taking place at the electrodes, as described above, depends on the transport of the gases and / or liquids involved in the reactions to and from the electrodes. For this reason, electrochemical cells typically have additional layers that facilitate the transport of the gases and / or liquids. These layers can include, in particular, gas diffusion layers, microporous layers, and / or porous transport layers.

[0013] The present invention aims to further improve the material transfer of gases and / or liquids involved in electrochemical reactions within an electrochemical cell. The result is an increase in the efficiency of the electrochemical cell.

[0014] To solve the problem, the method with the features of claim 1 is proposed. Advantageous embodiments of the invention are described in the dependent claims. Furthermore, an electrochemical cell produced according to a method according to the invention is described.

[0015] Disclosure of the invention

[0016] A method for manufacturing an electrochemical cell, in particular a fuel cell or an electrolysis cell, is proposed, comprising several superimposed layers and / or layers to form two electrodes with an intermediate separator. According to the invention, at least one of the two electrodes is manufactured from an electrode material and a fiber material, wherein a water-soluble fiber material is used. This is R.415617

[0017] - 3 - a) coated with the electrode material or b) integrated into the electrode material.

[0018] In a subsequent process step, the water-soluble fiber material is at least partially dissolved again using water, so that cavities are formed.

[0019] The cavities created by the process increase the surface area of ​​at least one electrode and the reaction area for the respective medium. This, in turn, increases the efficiency of the electrochemical cell. Furthermore, the cavities structure the surface, shortening the diffusion paths within the electrode and to the catalytic material. This accelerates the electrochemical reactions, leading to a further increase in efficiency.

[0020] The formation of cavities using the proposed method offers the particular advantage of being especially gentle, thus preventing damage to the delicate layers and / or strata, particularly the separator. Such damage could impair the function of these layers and / or strata. The proposed method avoids this because the electrode is initially manufactured and, if necessary, assembled without cavities. The cavities are then formed in the electrode only in a subsequent process step. Furthermore, the method eliminates the need for a subtractive manufacturing process of subsequently introducing the cavities. This process also carries a high risk of damaging the delicate layers and / or strata.

[0021] Since the proposed method uses water to dissolve fiber material from at least one electrode, the process is particularly simple and gentle. Due to its design, water is not an aggressive medium for the delicate layers and / or strata of the electrochemical cell, as these come into contact with water during operation anyway. R.415617

[0022] - 4 -

[0023] Preferably, in the proposed method, in case a), before coating the fiber material with the electrode material, the fiber material is arranged on the separator or a carrier film, and during the subsequent coating process, the fiber material is bonded to the separator or carrier film using the electrode material. In this way, a bond between the electrode and the separator or carrier film can be created in a single step. In the first case, one step is eliminated. In the latter case, the bond with the separator can be achieved via the carrier film. The carrier film has a stiffening effect and thus simplifies the handling of the electrode.

[0024] In case b), the electrode material is preferably applied to the separator or a carrier film before the fiber material is integrated. Integrating the fiber material after the electrode material has been applied to the separator or carrier film is particularly easy, as the fiber material can be introduced into the electrode material, for example, by sinking or pressing it in. The typically low-viscosity electrode material is also stabilized by the separator or carrier film. Furthermore, the fiber material can only be inserted once the low-viscosity electrode material has already undergone a certain degree of pre-solidification, thus enabling more precise positioning of the fiber material within the electrode material.

[0025] Preferably, the electrode is indirectly connected to the separator via the carrier film, for example by lamination. This applies if the fiber material and / or the electrode material is not applied directly to the separator, but to a carrier film. The carrier film stabilizes the fiber material and / or the carrier material and thus simplifies its handling. The bond between the electrode and the separator can then be easily achieved indirectly via the carrier film. A lamination process is particularly suitable for this purpose.

[0026] Advantageously, regularly arranged cavities are formed by a net- or grid-like arrangement of the fiber material. The fiber material is thus distributed over the surface, and cavities are formed by subsequently removing the fiber material (R.415617).

[0027] - 5 - are arranged in a net-like or grid-like pattern. The cavities thus extend across the surface of the electrode. Sufficient electrode material remains between the cavities to ensure the electrode's function.

[0028] Preferably, the regularly arranged cavities are spaced 20–120 µm apart. If the cavities are too closely spaced, i.e., <20 µm, the electrode surface has an insufficient volume fraction of electrode material for the electrochemical reactions. Conversely, if the cavities are spaced >120 µm apart, they are so far apart that the described advantageous effects are no longer sufficiently achieved.

[0029] In a further development of the invention, it is proposed that at least one water-soluble polymer, for example starch, gelatin, agarose, or casein, or a polymer from the group consisting of polyethylene oxides, dextrans, or poloxamers, be used to produce the fiber material. All of the polymers described are substances that are particularly soluble in water and can therefore be readily extracted from the electrode material. The polymers and polymer groups described are also particularly easy to process and can be produced in the form of a fiber material. In particular, polymers can be produced by linking them to any desired length, so that the size and length of the fiber material can be precisely adjusted according to requirements.

[0030] Preferably, fibers with a thickness of 5-30 pm are formed from the fiber material. The width and / or depth of the cavities can be adjusted via the fiber thickness. Whether one or multiple fibers are used to form a cavity also plays a role. Fibers of the specified thickness are particularly easy to produce, especially in an atomization process, for example, by electrospinning or electrospraying. In these processes, the atomization is supported by applying an electromagnetic force. In this way, the fiber shape, length, and thickness can be controlled and precisely adjusted. R.415617

[0031] - 6 -

[0032] Furthermore, a solvent-containing electrode material is preferably used to produce the electrode, and the electrode material is dried before the downstream process step, i.e., the at least partial removal of the water-soluble fiber material. The addition of the solvent makes the electrode material viscous, particularly low-viscosity, so that in case a) the coating of the fiber material or in case b) the integration of the fiber material is simplified. Drying the solvent-containing electrode material before the downstream process step ensures that the electrode material is not removed along with the water during the downstream process step.

[0033] Preferably, the electrode material is dried under the influence of heat before the subsequent process step. Drying under heat offers the advantage of faster process times.

[0034] Furthermore, a preferred electrode material is used for the production of the electrode which

[0035] - Carbon particles,

[0036] - metallic nanoparticles and / or

[0037] - contains a proton-conducting polymer. The carbon particles ensure the electrode's mechanical strength and are electrically conductive, allowing for complete contact. The carbon particles also form a porous structure with a large surface area. This facilitates mass transport and accelerates electrochemical reactions. The metallic nanoparticles adsorb the gas phase and further accelerate electrochemical reactions. The proton-conducting polymer balances the charge and promotes water formation.

[0038] In an advantageous embodiment of the invention, it is proposed that the at least one electrode and / or the separator be manufactured as strip material and only cut to a predetermined final dimension after manufacture. In this way, in practical application, a R.415617

[0039] - 7 - A very high number of electrodes and / or separators can be produced, which is particularly advantageous in mass production. In particular, economies of scale can be exploited, helping to save time and costs. In addition, the tape material can be adapted to the size of the electrochemical cell during cutting.

[0040] Furthermore, an electrochemical cell, in particular a fuel cell or an electrolysis cell, is proposed, which has been manufactured according to a method according to the invention. For the reasons stated above, an electrochemical cell manufactured according to a method according to the invention exhibits increased efficiency.

[0041] The invention and its advantages are described in more detail below with reference to the accompanying drawings and figures. These show:

[0042] Fig. 1 shows a schematic cross-section through an electrochemical cell according to the invention during its manufacture,

[0043] Fig. 2 shows a schematic cross-section through the cell of Figure 1 during its manufacture after a further process step and

[0044] Fig. 3 is a schematic top view of the cell of Figure 2.

[0045] Detailed description of the drawings

[0046] Figure 1 shows a schematic cross-section through an electrochemical cell 1 during its manufacture according to a method according to the invention. The electrochemical cell 1 shown has several layers 2. These include two electrodes 3 and a separator 4 arranged between the electrodes 3. At least one of the electrodes 3 (the upper electrode in Figure 1) of the electrochemical cell 1 has an electrode material 5 and a water-soluble fiber material 6.

[0047] The electrode material 5 can, for example, consist of carbon particles, metallic nanoparticles and / or a proton-conducting polymer R.415617.

[0048] - 8 - be produced. The fiber material 6 is produced in the form of fibers from a water-soluble polymer by means of an atomization process, for example by electrospinning or electrospraying.

[0049] The electrode 3 can be manufactured in various ways. The fiber material 6 can be arranged on the separator 4 and then coated with the electrode material 5, thus connecting the electrode 3 to the separator 4. Alternatively, the fiber material 6 can first be arranged on a carrier material (not shown) and then coated with the electrode material 5. The electrode 3 can therefore be connected to the separator 4 directly or indirectly via the carrier film.

[0050] Furthermore, the electrode material 5 can initially be arranged on the separator 4 or the carrier film (not shown). The fiber material 6 is then subsequently inserted or pressed into the electrode material 5.

[0051] In a subsequent process step, the fiber material 6 is then at least partially dissolved from the electrode material 5 using water, so that cavities 7 are formed in the electrode 3.

[0052] In an electrochemical cell 1 according to the invention, one or both electrodes 3 can have an electrode material 5 and a water-soluble fiber material 6, which is at least partially dissolved again in a subsequent process step.

[0053] Figure 2 shows the electrochemical cell 1 from Figure 1 after the removal of the water-soluble fiber material 6. The resulting cavities 7 increase the surface area of ​​the electrode 3. Furthermore, this reduces the diffusion pathways within the electrode 3, thereby accelerating the mass transfer. Consequently, the efficiency of the electrochemical cell 1 increases. R.415617

[0054] - 9 -

[0055] Figure 3 shows a top view of the electrochemical cell 1 of Figure 2, that is, after the removal of the fiber material 6. It is evident that the cavities 7 have a net-like or grid-like arrangement. The material transport to and from the cell is thus facilitated across the surface and can be accelerated in this way.

Claims

R.415617 - 10 - Claims 1. A method for producing an electrochemical cell (1), in particular a fuel cell or an electrolysis cell, comprising several superimposed layers and / or layers (2) to form two electrodes (3) with an intermediate separator (4), characterized in that at least one of the two electrodes (3) is produced from an electrode material (5) and a fiber material (6), wherein a water-soluble fiber material (6) is used which a) is coated with the electrode material (5) or b) is integrated into the electrode material (5), and wherein in a subsequent process step the water-soluble fiber material (6) is at least partially dissolved again using water, so that cavities (7) are formed.

2. Method according to claim 1, characterized in that, prior to coating the fiber material (6) with the electrode material (5), the fiber material (6) is arranged on the separator (4) or a carrier film and is connected to the separator (4) or the carrier film during the subsequent coating process using the electrode material (5).

3. Method according to claim 1, characterized in that the electrode material (5) is applied to the separator (4) or a carrier film before the integration of the fiber material (6).

4. Method according to one of claims 2 or 3, characterized in that the electrode (3) is indirectly connected to the separator (4) via the carrier film, for example by lamination. R.415617 - 11 - 5. Method according to one of the preceding claims, characterized in that a net- or grid-like Arrangement of the fiber material (6) regularly arranged cavities (7) are formed, which are preferably arranged at a distance of 20-120 pm from each other.

6. Method according to one of the preceding claims, characterized in that at least one water-soluble polymer, for example starch, gelatin, agarose or casein, or a polymer from the group consisting of polyethylene oxides, dextrans or poloxamers, is used to produce the fiber material (6).

7. Method according to one of the preceding claims, characterized in that fibers with a fiber thickness of 5-30 pm are formed from the fiber material (6), preferably in an atomization process, for example by means of electrospinning or electrospraying.

8. Method according to one of the preceding claims, characterized in that a solvent-containing electrode material (5) is used to produce the electrode (3) and the electrode material (5) is dried before the downstream process step, preferably under the influence of heat.

9. Method according to one of the preceding claims, characterized in that an electrode material (5) is used to produce the electrode (3) which Contains carbon dioxide particles, metallic nanoparticles and / or a proton-conducting polymer.

10. Method according to any of the preceding claims, R.415617 - 12 - characterized in that the at least one electrode (3) and / or the separator (4) is manufactured as strip material and is only cut to a predetermined final dimension after manufacture.

11. Electrochemical cell (1), in particular fuel cell or Electrolysis cell manufactured according to a method according to one of the preceding claims.

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