Method and system for producing an electrode assembly for a cell of an electrochemical energy converter

Abstract

The presented invention relates to a production method (100) for an electrode assembly (300) for a cell of an electrochemical energy converter, the production method (100) comprising: - applying (101) a first electrode dispersion to a first transfer roller (201), - applying (103) a second electrode dispersion to a second transfer roller (203), - transferring (105) the first electrode dispersion and the second electrode dispersion onto a membrane (207) fed between the first transfer roller (201) and the second transfer roller (203), in order to form the electrode assembly (300), wherein: the first transfer roller (201) has a first surface texture by means of which, during the transferring (105) of the first electrode dispersion onto a first side of the membrane (207), a surface texture corresponding to the first surface texture is formed in a first electrode (301) formed by the first electrode dispersion; the second transfer roller (203) has a second surface texture by means of which, during the transferring of the second electrode dispersion onto a second side of the membrane (207), a surface texture corresponding to the second surface texture is formed in a second electrode (303) formed by the second electrode dispersion.

Description

[0001] Description

[0002] title

[0003] Method and system for manufacturing an electrode arrangement for a cell of an electrochemical energy converter

[0004] The presented invention relates to a manufacturing method for an electrode arrangement for a cell of an electrochemical energy converter, a system for manufacturing an electrode arrangement for a cell of an electrochemical energy converter and an electrode arrangement for a cell of an electrochemical energy converter, according to the attached claims.

[0005] State of the art

[0006] A catalyst-coated membrane, called a catalyst-coated membrane or CCM, is a central element of a cell in an electrochemical energy converter, such as a fuel cell system or an electrolysis system.

[0007] Such a membrane consists largely of a fluoropolymer, perfluorosulfonic acid (PFSA), which is referred to as an ionomer. The catalyst is a component of highly porous gas diffusion electrodes in which process gases react during operation, thus generating charge carriers.

[0008] Such a catalyst typically consists of nanoscale platinum particles deposited on a carbon black particle as a support, on whose surface the catalysis takes place. Electrons generated in this process flow away via a network of carbon black particles. Another component of a gas diffusion electrode is an ionomer, similar to those used in membranes. Hydrogen ions generated during catalysis are transported via the ionomer.

[0009] Both electron and ion conductivity are crucial for the performance of the electrodes.

[0010] Processes are known for the production of electrode arrangements in which catalyst particles are mixed with an ionomer dissolved in one or more solvents, so that they form a low-viscosity electrode dispersion which can be used on an industrial and economical scale for coating a membrane.

[0011] The liquid coating is then solidified by removing the solvents. The ionomer spreads into the spaces between the catalyst particles, thus reducing the porosity of the gas diffusion electrode.

[0012] The catalytic reaction of the gases takes place at the catalytically active surface of the catalyst, usually platinum or platinum alloy particles. The size of the total active surface is a factor in the electrode's performance. Another significant factor is the microstructure of the gas diffusion electrodes, as it determines the amount of gas that can reach the catalytically active surface.

[0013] The gas diffusion electrodes exhibit a porosity with a specific pore size distribution through which the reaction gases are transported to the catalyst surface. This porosity results from a network of catalyst particles. The ionomer contained within the pores of the gas diffusion electrodes reduces their porosity to varying degrees depending on the quantity. The solvents used have a significant influence on the distribution of the ionomer within the gas diffusion electrode and thus on its microstructure. Accordingly, improving the ionic conductivity of the electrode by increasing the quantity and distribution of the ionomer comes at the expense of the electrode's porosity and therefore gas diffusion within the electrode. Disclosure of the invention

[0014] Within the scope of the presented invention, a manufacturing process for an electrode arrangement for a cell of an electrochemical energy converter, a system for manufacturing an electrode arrangement for a cell of an electrochemical energy converter, and an electrode arrangement for a cell of an electrochemical energy converter are presented. Further features and details of the invention will become apparent from the respective dependent claims, the description, and the drawings. Features and details described in connection with the manufacturing process according to the invention naturally also apply in connection with the system and the electrode arrangement according to the invention, and vice versa, so that the disclosure regarding the individual aspects of the invention is always, or can always be, mutually referenced.

[0015] The presented invention serves to provide an electrode arrangement with improved gas transport properties.

[0016] Thus, according to a first aspect of the presented invention, a manufacturing process for an electrode arrangement for a cell of an electrochemical energy converter is presented.

[0017] The presented manufacturing process comprises applying a first electrode dispersion to a first transfer roller, applying a second electrode dispersion to a second transfer roller, transferring the first electrode dispersion and the second electrode dispersion to a membrane passing between the first and second transfer rollers to form the electrode arrangement, wherein the first transfer roller has a first surface texture by which, upon transfer of the first electrode dispersion to a first side of the membrane, a surface texture corresponding to the first surface texture is formed in a first electrode formed by the first electrode dispersion, and wherein the second transfer roller has a second surface texture.by which, during the transfer of the second electrode dispersion to a second side of the membrane, a surface texture corresponding to the second surface texture is formed in a second electrode created by the second electrode dispersion.

[0018] In the context of the presented invention, a surface texture is understood to be a spatially changing surface that, for example, comprises a multitude of individual structures rising from a base surface, e.g., a plane.

[0019] According to the invention, the surface texture of the respective transfer rollers is transferred, e.g., imprinted, into an electrode formed by a respective electrode dispersion, so that the surface texture of a respective transfer roller is reflected in a respective electrode or the electrode itself shows the surface texture or a negative of the surface texture.

[0020] The presented manufacturing process allows the gas transport properties of the electrodes of an electrode unit to be adjusted largely independently of their ionic conductivity. For this purpose, an electrode dispersion is applied to a transfer roller. Optionally, a large portion of the solvent from the electrode dispersion is first removed from the transfer roller, and the electrode dispersion is then transferred to a membrane with a defined residual solvent content.

[0021] The residual solvent content in the electrode dispersion determines the adhesion of an electrode formed from it to the membrane.

[0022] According to the invention, transfer rollers are used that have a surface texture which shapes the surface of the electrodes, hereinafter also referred to as gas diffusion electrodes. This means that the surface texture of a respective transfer roller determines or shapes the surface texture of an electrode formed by the transfer roller, so that a spatial pattern is formed in the electrode, maximizing the gas inlet area of ​​the electrode, in particular increasing it compared to a flat electrode. Accordingly, the presented manufacturing process provides an electrode arrangement that exhibits improved gas transport into the gas diffusion electrodes compared to known or flat electrode arrangements, thereby maximizing the energy efficiency and longevity of a corresponding electrochemical energy converter in which electrode arrangements produced by the presented manufacturing process are used.

[0023] In particular, the presented manufacturing process enables improved control of a microporous structure of the respective electrodes by transferring the electrode dispersion to the membrane in a pressure zone which, due to the roller arrangement provided according to the invention, is limited to a narrow line. Accordingly, the electrode arrangement is only under pressure for a very short time, thereby reducing the mechanical stress and deformation to a minimum.

[0024] It may be provided that the first surface structure and / or the second surface texture is formed by a multitude of individual structures, wherein the individual structures have a lateral extent between 10 pm and 100 pm and a depth between 50 pm and 100 pm.

[0025] For example, the individual structures can form grooves, inverted pyramids, hexagons, caps or even more complex three-dimensional geometries.

[0026] It may also be provided that the first transfer roller and the second transfer roller are rotated at a distance between 0 mm and 1 mm from each other.

[0027] The transfer of the electrode dispersions from the two transfer rollers to the membrane is achieved, in particular, by the transfer rollers rolling along opposite sides of the membrane, so that both electrodes are formed simultaneously or in parallel, and the two transfer rollers exert a pressure on the electrode arrangement, especially through their distance from each other and / or the elasticity of their surfaces. It may also be provided that, before the first and second electrode dispersions are transferred to the membrane, they are dried until a predetermined residual solvent content is reached.

[0028] Electrodes for PEM fuel cells, for example, consist of a catalyst, usually platinum or platinum alloys, in the form of small particles (< 5 nm) on larger carbon black particles (< 100 nm) as a support and electron conductor, and a hydrogen ion-conducting polymer, the ionomer. Both materials are dispersed in a solvent mixture of water and alcohol, such as ethanol, propanol, or glycol. By drying, for example using a drying device such as a blower or an infrared heater, the proportion of the solvent mixture in the electrode dispersion can be reduced sufficiently to allow it to be shaped and transferred to a membrane.

[0029] In particular, it may be provided that at least one drying unit is used for drying the first electrode dispersion and the second electrode dispersion, which is arranged at a distance of between 1 mm and 100 mm from the first transfer roller and / or the second transfer roller.

[0030] For example, different or differently adjusted drying units can be used to dry the first electrode dispersion and the second electrode dispersion, so that different electrode dispersions are adjusted to a specific solvent content.

[0031] It may also be provided that the first and second transfer rollers are heated to a temperature between 50 °C and 200 °C. Heating the transfer rollers serves two purposes: firstly, it dries the respective electrode dispersion, and secondly, it facilitates the easy removal and deformation of the electrode dispersion or electrodes.

[0032] It may also be provided that the first transfer roller and the second transfer roller each have a diameter between 1 meter and 4 meters and are rotated at a circumferential speed between 0.5 meters per minute and 1 meter per minute.

[0033] By selecting a sufficiently large roller diameter, the application, drying and subsequent transfer of electrode dispersion to the membrane can take place in one revolution of the transfer rollers.

[0034] The transfer of the electrode to the membrane is supported by a special design of the surface of the transfer rollers such that they exhibit low surface energy and defined elasticity.

[0035] It may further be provided that the first electrode dispersion is applied to the first transfer roller and / or the second electrode dispersion is applied to the second transfer roller by an apparatus from the following list of apparatus: slot nozzle arranged perpendicular or at an angle of less than 90° to the roller surface and at a distance between 0.1 mm and 1 mm from the roller surface, engraved roller, cylindrical screen mesh, spray device.

[0036] The geometry of the slot nozzle, the engraved roller or the sieve fabric, or the delivery rate of the spray device and the composition of the electrode dispersion significantly determine the platinum content of the gas diffusion electrodes required for the function of, for example, a fuel cell.

[0037] According to a second aspect, the presented invention relates to a system for manufacturing an electrode arrangement for a cell of an electrochemical energy converter. The presented system comprises a first transfer roller, a second transfer roller, and a membrane feeder, wherein the membrane feeder is configured to guide a membrane between the first transfer roller and the second transfer roller, wherein the first transfer roller is configured to transfer a first electrode dispersion to a first side of the membrane, and wherein the first transfer roller has a first surface texture configured to form a corresponding surface structure in a first electrode formed by the first electrode dispersion, and wherein the second transfer roller is configured toto transfer a second electrode dispersion to a second side of the membrane, wherein the second transfer roller has a second surface texture configured to form a corresponding surface texture in a second electrode formed by the second electrode dispersion.

[0038] Thus, the system according to the invention offers the same advantages as those already described in detail with reference to the manufacturing process according to the invention.

[0039] The presented system serves in particular to carry out the presented procedure.

[0040] It may be provided that the first transfer roller and / or the second transfer roller is coated with at least one material from the following list of materials: PTFE, ETFE, EPDM, PEN, PET.

[0041] Plastics, such as PTFE, ETFE, EPDM, PEN or PET, allow for particularly easy and safe or damage-free removal of an electrode dispersion from a transfer roller, as they are particularly smooth and / or particularly flexible or soft.

[0042] It may also be provided that the first transfer roller and / or the second transfer roller has a surface that has a surface energy between 15 mN / m and 30 mN / M and a high modulus of elasticity of 1 to 100 MPa at a low hardness of 50 to 100°ShoreA.

[0043] Due to a low surface energy between 15 mN / m and 30 mN / m, particularly between 19 mN / m and 25 mN / m, the electrode assembly being transferred detaches very easily from the transfer roller, leaving no residue. The high elasticity, with a modulus of elasticity of 1 to 100 MPa, particularly between 30 and 60 MPa, and a low hardness between 50 and 100 Shore A, particularly between 70 and 90 Shore A, distributes the pressure acting on the electrode assembly across the surface of the transfer roller, thus protecting it from excessive mechanical stress. In particular, this elasticity allows for at least partial deformation of the transfer roller's surface, enabling the electrode dispersion to detach very easily.

[0044] It may also be provided that the system is configured to carry out a possible embodiment of the presented manufacturing process.

[0045] According to a third aspect, the presented invention relates to an electrode arrangement for a cell of an electrochemical energy converter.

[0046] The presented electrode arrangement comprises a membrane, a first electrode arranged on a first side of the membrane and a second electrode arranged on a second side of the membrane opposite the first side, wherein the electrode arrangement is produced by a possible embodiment of the presented manufacturing process.

[0047] Due to the presented manufacturing process, the presented electrode arrangement exhibits a texture, in particular a characteristic pattern, on the surfaces of its electrodes, which includes, for example, a code, i.e., an alphanumeric or number-letter or machine-readable code. Advantages described in detail with respect to the manufacturing process for an electrode arrangement for a cell of an electrochemical energy converter according to the first aspect of the invention apply equally to the system for manufacturing an electrode arrangement for a cell of an electrochemical energy converter according to the second aspect of the invention and to the electrode arrangement for a cell of an electrochemical energy converter according to the third aspect of the invention, and vice versa.

[0048] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination.

[0049] They each show schematically:

[0050] Figure 1 shows a representation of a possible embodiment of the presented manufacturing process,

[0051] Figure 2 shows a possible embodiment of the presented system, and

[0052] Figure 3 shows a detailed view of an embodiment of the presented electrode arrangement produced according to the presented manufacturing process.

[0053] Fig. 1 shows a manufacturing process 100 for an electrode arrangement for a cell of an electrochemical energy converter.

[0054] The manufacturing process 100 comprises a first application step 101 in which a first electrode dispersion is applied to a first transfer roller, a second application step 103 in which a second electrode dispersion is applied to a second transfer roller, and a transfer step 105 in which the first electrode dispersion and the second electrode dispersion are transferred to a membrane passed between the first transfer roller and the second transfer roller to form the electrode arrangement.

[0055] The first transfer roller has a first surface texture, which, when the first electrode dispersion is transferred to a first side of the membrane, forms a surface texture corresponding to the first surface texture in a first electrode formed by the first electrode dispersion.

[0056] Furthermore, the second transfer roller has a second surface texture, which, when the second electrode dispersion is transferred to a second side of the membrane, forms a surface texture corresponding to the second surface texture in a second electrode formed by the second electrode dispersion.

[0057] Fig. 2 shows a system 200 for manufacturing an electrode arrangement for a cell of an electrochemical energy converter.

[0058] System 200 comprises a first transfer roller 201, a second transfer roller 203, and a membrane feeder 205, wherein the membrane feeder 205 is configured to guide a membrane 207 between the first transfer roller 201 and the second transfer roller 203. For this purpose, the membrane feeder 205 includes a feed roller 209, tension rollers 211, and a receiving roller 213 onto which the finished electrode assembly is wound.

[0059] Heating elements 215 are arranged in and around the transfer rollers 201, 203, which heat the membrane 207 and / or dry the electrode dispersion applied to the transfer rollers 201, 203.

[0060] The transfer rollers 201 and 203 each have a diameter between 1 meter and 4 meters and rotate in opposite directions at a circumferential speed between 0.5 meters per minute and 1 meter per minute. They are arranged at a distance of between 0 mm and 1 mm from each other. Electrode dispersion is applied to the transfer rollers 201 and 203 by coating elements 217 and 219, for example, by means of an engraved coating roller, a cylindrical screen mesh, or a spray device.

[0061] Cleaning elements 221 and 223 continuously clean the transfer rollers 201, 203, so that the manufacturing process 100 according to Fig. 1 can run in an uninterrupted process or continuously.

[0062] Fig. 3 shows in detail the shaping of an electrode arrangement 300 by the system 200.

[0063] The electrode arrangement 300 comprises the membrane 207 and electrodes 301, 303 formed on respective sides of the membrane 207.

[0064] Here it is clearly visible that the surfaces of the transfer rollers 201, 203 have a surface texture, e.g. in the form of pyramids, which form a corresponding or correspondingly negative surface texture in the form of offset or negative pyramids in the electrodes 301, 303.

[0065] Due to the surface texture, the gas diffusion area of ​​electrodes 301, 303 is particularly large.

Claims

Claims 1. Manufacturing process (100) for an electrode arrangement (300) for a cell of an electrochemical energy converter, wherein the manufacturing process (100) comprises: Applying (101) a first electrode dispersion to a first transfer roller (201), Application (103) of a second electrode dispersion onto a second transfer roller (203), Transfer (105) of the first electrode dispersion and the second electrode dispersion onto a membrane (207) passing between the first transfer roller (201) and the second transfer roller (203) to form the electrode arrangement (300), wherein the first transfer roller (201) has a first surface texture by which, when the first electrode dispersion is transferred (105) to a first side of the membrane (207), a surface texture corresponding to the first surface texture is formed in a first electrode (301) formed by the first electrode dispersion, and wherein the second transfer roller (203) has a second surface texture by which, when the second electrode dispersion is transferred to a second side of the membrane (207), a surface texture corresponding to the second surface texture is formed in a second electrode (303) formed by the second electrode dispersion.

2. Manufacturing method (100) according to claim 1, characterized in that the first surface structure and / or the second surface texture is imprinted by a plurality of individual structures, wherein the individual structures have a lateral extent between 10 pm and 100 pm and a depth between 50 pm and 100 pm.

3. Manufacturing method (100) according to claim 1 or 2, characterized in that the first transfer roller (201) and the second transfer roller (203) are rotated at a distance between 0 mm and 1 mm from each other.

4. Manufacturing process (100) according to one of the preceding claims, characterized in that, prior to transferring the first electrode dispersion and the second electrode dispersion to the membrane (207), the first electrode dispersion and the second electrode dispersion are dried until a predetermined residual solvent content is reached in them.

5. Manufacturing process (100) according to claim 4, characterized in that at least one drying unit is used for drying the first electrode dispersion and the second electrode dispersion, which is arranged at a distance of between 1 mm and 100 mm from the first transfer roller (201) and / or the second transfer roller (203).

6. Manufacturing method (100) according to one of the preceding claims, characterized in that the first transfer roller (201) and the second transfer roller (203) are heated to a temperature between 50 °C and 200 °C.

7. Manufacturing method (100) according to one of the preceding claims, characterized in that the first transfer roller (201) and the second transfer roller (203) each have a diameter between 1 meter and 4 meters and are rotated at a circumferential speed between 0.5 meters per minute and 1 meter per minute.

8. Manufacturing method (100) according to one of the preceding claims, characterized in that the first electrode dispersion is applied to the first transfer roller (201) and / or the second electrode dispersion is applied to the second transfer roller (203) by an apparatus (217, 219) of the following list of apparatus: slot nozzle arranged perpendicular or at an angle of less than 90° to the roller surface and at a distance between 0.1 mm and 1 mm from the roller surface, engraved roller, cylindrical screen mesh, spray device.

9. System (200) for manufacturing an electrode arrangement (300) for a cell of an electrochemical energy converter, wherein the system (200) comprises: a first transfer roller (201), a second transfer roller (203), a membrane feeder (205), wherein the membrane feeder (205) is configured to guide a membrane (207) between the first transfer roller (201) and the second transfer roller (203), wherein the first transfer roller (201) is configured to transfer a first electrode dispersion to a first side of the membrane (207), wherein the first transfer roller (201) has a first surface texture configured to form a corresponding surface structure in a first electrode (301) formed by the first electrode dispersion, and wherein the second transfer roller (203) is configured to transfer a second electrode dispersion to a second side of the membrane (207).wherein the second transfer roller (203) has a second surface texture configured to form a corresponding surface texture in a second electrode (303) formed by the second electrode dispersion.

10. System (200) according to claim 9, characterized in that the first transfer roller (201) and / or the second transfer roller (203) is coated with at least one material from the following list of materials: PTFE, ETFE, EPDM, PEN, PET.

11. System (200) according to claim 9 or 10, characterized in that the first transfer roller (201) and / or the second transfer roller (203) has a surface having a surface energy between 15 mN / m and 30 mN / M and a modulus of elasticity of 1 to 100 MPa at a low hardness of 50 to 100° Shore A.

12. System (200) according to one of claims 9 to 11, characterized in that the system (200) is configured to carry out a manufacturing process (100) according to one of claims 1 to 8.

13. Electrode arrangement (300) for a cell of an electrochemical energy converter, wherein the electrode arrangement (300) comprises: a membrane (207), a first electrode (301) arranged on a first side of the membrane (207), a second electrode (303) arranged on a second side of the membrane (207) opposite the first side, wherein the electrode arrangement (300) is manufactured by a manufacturing process (100) according to any one of claims 1 to 8.

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