Device for a coating apparatus for depositing functional material

Abstract

The invention relates to a device for a coating apparatus (1) for depositing functional material, having a galvanic trough (3) which can be filled with a liquid electrolyte (2) and at least one counter-electrode (4) arranged in the galvanic trough (3), a substrate carrier (5) which is designed at least partially as a hollow body and has an outer shell enclosing a cavity, and a suction and / or intake device (6) arranged in the cavity for suctioning and / or taking in the electrolyte (2), wherein the outer shell is designed to be open to diffusion and a substrate (7) can be applied to the outside (5B), the substrate carrier (5) projects at least partially into the galvanic trough (3) in an operation-ready state, the substrate carrier (5) is designed as a working electrode or comprises a working electrode, and a voltage can be applied between the counter-electrode (4) and the working electrode, the suction and / or intake device (6) and the galvanic trough (3) are coupled to a pipe system (11), wherein the pipe system (11) is designed to ensure the transport of electrolyte between the suction and / or intake device (6) in the cavity of the substrate carrier (5) and the galvanic trough (3). In this way, a device for metal deposition is provided that permits efficient regeneration of the electrolyte and accelerates and qualitatively improves the deposition process.

Description

[0001] Device for a coating apparatus for the deposition of functional material

[0002] The invention relates to a device for a coating apparatus for the deposition of functional material. In particular, the invention relates to a device for applying a functional material to a substrate. This method is intended to be used for the production of components of an electrochemical energy converter, such as a fuel cell, an electrolyzer, or a battery. Components such as electrolyte-electrode assemblies or other media-permeable substrates, for example, made of expanded metal, sintered material, or perforated material, should be able to be coated.

[0003] Traditionally, the high-volume production of such components requires a batch process or a semi-continuous or continuous process. The coating process can be a substep of several process steps arranged in series to form a production chain. Due to the interlinking of these process steps, the slowest step determines the maximum achievable process speed and can therefore limit the production speed. For sufficiently flexible substrates to be coated, so-called roll-to-roll processes can generally be used. For the coating of less flexible substrates, a movable substrate carrier with a 2D or 3D geometry can be used, depending on the nature of the substrate.

[0004] The description below will be illustrated using the example of the coating of a flexible substrate in a roll-to-roll system. A substrate is unrolled from a roll and gradually processed in a production process into an (intermediate) product, which is then rolled up again for sale or further processing. The substrate to be coated is guided on substrate carriers, e.g. rolls. The production process can include, among other things, functionalization, cleaning, drying and coating steps between the unrolling and the rolling-up side. In the coating step described here, the substrate is immersed in a liquid containing the functional material. During contact between the substrate and the liquid, the coating with the functional material takes place. This material can then be further treated downstream (e.g. cleaning, chemical or physical modifications).The coating of the substrate with functional material can be achieved in various ways and is influenced to varying degrees by migration, diffusion, or convection effects of the functional material in the liquid (electrolyte). This coating is also called deposition and can be of physical or chemical origin.

[0005] When we refer to an electrolyte in this context, we mean any liquid containing a functional material as a particle, as a precursor, in electrostatically charged form, or in ionic form. The deposition of functional material refers to the electrochemical deposition of ions, the electrophoresis of electrostatically charged particles, and / or the deposition of substances from a liquid onto the substrate.

[0006] In the example of functional catalytically active material, catalyst deposition traditionally takes place directly on the substrate during the process. The substrate is immersed in an electrolyte containing catalyst ions, for example in the form of dissolved catalyst salts, which are converted into metallic catalysts by applying current. The process step speed depends largely on the transport of the catalyst ions, which must be transported from the bulk electrolyte to the deposition centers on the substrate surface. During catalyst deposition, the catalyst ions from the near-surface electrolyte are electrochemically reduced to the substrate by the supply of electrons to the substrate, creating metallic material that later serves as catalyst material. This deposition step reduces the concentration of catalyst ions in the near-surface electrolyte.Refilling the now ion-poor electrolyte areas with catalyst ions (electrolyte regeneration) takes a certain amount of time, which is known as the regeneration time. Due to this process, only slow deposition or pulsed deposition via current pulses (e.g., on / off) can be set in the process. Depending on the location of the catalyst ions in the electrolyte, convection due to electrolyte movement, diffusion due to concentration differences, or migration due to the applied electric field dominate as the driving force for ion movement. Convection, in particular, can inhibit process speed because long transport distances in the electrolyte must be covered. This gradual ion transport continues until the concentration in the entire electrolyte is equalized and determines the regeneration time and thus the coating time for the electrochemical deposition (catalyst coating).

[0007] Typically, attempts are made to minimize the ion concentration gradient by mechanical stirring, for example, and thus accelerate the ion transport process, thereby shortening the regeneration time in the electrolyte. However, this process is complicated by the geometry and size of roll-to-roll systems, as vigorous stirring can, for example, lead to the formation of vortexes and inhomogeneities. Due to the remaining regeneration time, a production process using electrochemical catalyst deposition can only achieve slow process speeds, which hinders the process's scale-up and makes it uncompetitive with other approaches, such as chemical catalyst deposition using catalyst powder.

[0008] To avoid slow cycle times in roll-to-roll systems, the substrate can be repeatedly immersed in and removed from an electrolyte via multiple rollers, for example. This increases the substrate surface area in contact with fresh electrolyte and consequently increases the process speed. The key disadvantages, however, are the high investment costs for such electrochemical setups, the increased space requirements, and the high operating costs. Furthermore, the use of large electroplating systems (multiple or long electroplating tanks) requires a large electrolyte volume, which further increases running costs due to the expensive metal-containing electrolytes. Furthermore, large quantities of electrolyte must be technically monitored, conditioned, and controlled, which complicates the process.Mechanical stirring results in a greater susceptibility to errors due to deviations from ideal operating conditions, higher wear on a large number of components and poorer quality of deposited catalyst layers.

[0009] In addition to the complex process control involved in catalyst deposition over large areas and the uneven deposition of catalyst material, the use of auxiliary electrodes may also be necessary. Despite the considerable effort involved, this generally results in only limited process speed and film quality, making the entire process unattractive for large-scale industrial production of components for electrochemical energy converters.

[0010] State-of-the-art metal deposition devices do not currently provide a method for faster electrolyte regeneration that can be easily integrated into conventional roll-to-roll systems. The same applies to systems operating in batch or semi-continuous mode.

[0011] Based on this, the object of the invention is to provide a device for coating with functional material which enables efficient regeneration of the electrolyte and thus increases the process speed and produced layer quality and reduces the investment and operating costs.

[0012] This problem is solved by the subject matter of patent claim 1. Preferred developments can be found in the subclaims.

[0013] According to the invention, a device is thus provided for a coating apparatus for the deposition of functional material, comprising an electroplating tank that can be filled with a liquid electrolyte and at least one counter electrode arranged in the electroplating tank, a substrate carrier that is at least partially designed as a hollow body and has an outer shell enclosing a cavity, wherein the outer shell has an inner side facing the cavity and an outer side facing away from the cavity, and a removal and / or suction device arranged in the cavity for removal orSuction of the electrolyte, wherein the outer shell is designed to be permeable to diffusion and the outside can be supplied with a substrate, the substrate carrier in an operational state protrudes at least partially into the electroplating tank, the substrate carrier is designed as a working electrode or comprises a working electrode, and a voltage can be applied between the working electrode and the counter electrode, the extraction and / or extraction device and the electroplating tank are coupled to a pipe system, wherein the pipe system is designed to ensure, in particular, homogeneous electrolyte transport between the extraction and / or extraction device in the cavity of the substrate carrier and the electroplating tank. When reference is made here to an electroplating tank, this means any structure suitable for electroplating that has a volume into which an electrolyte can be filled. This can also be, for example, an electroplating basin.

[0014] A "substrate carrier" is understood to mean, in particular, a 3-dimensional hollow body that enables substrate contact for a 2-dimensional or 3-dimensional substrate. The substrate carrier can preferably be designed to be movable, for example, by means of a robot arm, and can be used for batch and / or (semi-)continuous processes with a 2D or 3D geometry.

[0015] “Diffusion-open” means a material that is permeable to media.

[0016] When we talk about a pipe system in this case, we mean any type of media-conducting structures and formations, e.g. pipe, hose, nozzle, valve, permeable material, flow guide or channel, or a mere inlet.

[0017] If electrodes are required for the deposition, these are referred to as working and counter electrodes. The arrangement of the counter electrode and working electrode is chosen in such a way that the counter electrode acts as the positive pole or anode, from which metal ions dissolved in the electrolyte are transferred to the working electrode. The working electrode therefore acts as the negative pole or cathode, so that an overall current flow is created between the anode and cathode. The metal ions dissolved in the electrolyte are deposited by electrochemical reduction on the substrate, which is electrically connected to the working electrode or cathode. If the metal ions are catalyst material, catalytically active material is applied to the substrate by reducing the ions, so that the substrate is electroplated with a catalyst layer. During the deposition, the positive and negative poles, if necessary, can also be used.briefly, reversed polarity or pulses can be used during deposition, which allows for further degrees of freedom in the deposition.

[0018] Additionally, auxiliary or reference electrodes can be used for better process control. The working electrode and counter electrode can be placed inside or outside the liquid. The substrate itself can, for example, conduct the electrical current into the liquid, whereby contact with the working electrode can be made outside the liquid. Deposition, e.g., by electrophoresis, can be achieved by generating an electromagnetic field, whereby one or both of the electrodes can be located outside or inside the liquid.

[0019] In this case, it is necessary for the substrate to be in contact with the electrolyte so that the metal ions can be transferred to the substrate. For this purpose, the substrate carrier is arranged in such a way that it extends at least partially into the electroplating tank; in other words, if the electroplating tank is filled with the electrolyte, it is partially immersed in the electrolyte.

[0020] When we refer to a working electrode in this case, we preferably mean an electrical contact located outside the electrolyte. The working electrode is electrically connected to the substrate in such a way that the metal ions are transferred toward the substrate immersed in the electrolyte.

[0021] A "removal and / or suction device" is understood here to mean a device that can suck and / or aspirate the electrolyte, particularly due to a pressure difference. This refers to the flow direction of the electrolyte. If the electrolyte is sucked out, it is sucked from the electroplating tank, through the substrate and through the diffusion-open outer shell of the substrate carrier, into the cavity of the substrate carrier, and from there returned to the electroplating tank. However, if the electrolyte is sucked in, it is sucked out of the electroplating tank, fed into the cavity, and released through the diffusion-open outer shell and through the substrate back to the electroplating tank. The removal and / or suction device is therefore designed to transport the electrolyte in only one of the two flow directions or in both.During operation of the coating device, it is preferably possible to choose between one or both flow directions and / or to switch back and forth between them and / or to temporarily suspend the electrolyte flow. A key aspect of the invention is therefore that, through the continuous or intermittent removal of the electrolyte through the substrate and the substrate carrier immediately after and / or during the deposition of functional material or catalyst material on the substrate surface, the depleted electrolyte is replaced by electrolyte from the volume having the initial concentration. This means that deposition can be continued directly after the previous deposition pulse, and the substrate can be subjected to a new deposition pulse immediately after completion of the previous deposition pulse.This reduces or even eliminates the regeneration time, resulting in continuous deposition, which is the fastest possible deposition method. Furthermore, this approach allows for the control of the penetration depth of the catalyst material into the substrate and the adjustment of the concentration profile of the functional material across the substrate layer depth. Byproducts that can impede homogeneous deposition (e.g., gas bubbles that linger on the substrate surface) can also be easily removed. Furthermore, the pulsed removal and / or the selection of the electrolyte flow rate allow for precise control of the regeneration process in the depleted electrolyte layer, which can again positively influence the deposition result.

[0022] According to a preferred embodiment of the invention, the substrate carrier comprises a hollow cylindrical roller. The substrate carrier is preferably mounted for rotation about its longitudinal axis. The longitudinal direction of the substrate carrier then refers to the length of the cylinder. The substrate can be arranged on the outer surface of the lateral surface. The substrate carrier then rotates about the longitudinal axis of the cylinder. This has the advantage that the substrate can be rolled onto the substrate carrier along a wide surface, thus allowing the surface of the substrate carrier to be used efficiently with a single rotation.

[0023] According to a preferred embodiment of the invention, the outer shell has a plurality of openings, which can be configured, in particular, as slits or holes. A slit-shaped opening is understood here to be an elongated, narrow opening through which the electrolyte can diffuse. The slits can preferably have a length of a few centimeters. Holes can have different sizes and spacings. Furthermore, the substrate carrier can be made of a material that is inherently permeable to diffusion (e.g., sintered material, expanded metal, perforated material, fleece).

[0024] According to a preferred embodiment of the invention, the substrate carrier is arranged on a movement device. The substrate carrier can be moved via the movement device. In particular, the movement device comprises a robot arm, a rod, or a cable.

[0025] According to a preferred embodiment of the invention, the electroplating tank has a base plate to which at least one inlet is arranged, e.g., via a pipe system. This allows the electrolyte to be supplied from below, i.e., from the floor or elsewhere in the electroplating tank, or to be drawn in from below, so that the electrolyte flows through the entire volume of the electroplating tank, eliminating any dead volumes.

[0026] In principle, it is possible to ensure the electrolyte movement through the volume of the electroplating tank by means of a freely generated differential pressure. The electrolyte movement then arises, for example, due to a geodetic height difference, thermal forces, or the rotation of the substrate carrier. Preferably, the suction and / or extraction device comprises a plurality of suction nozzles arranged on the inside of the outer shell or even a single suction nozzle coupled to a suction device, such as a pump. The suction device thus actively draws or pushes the electrolyte out or into the tank.

[0027] According to a preferred development of the invention, it is provided that the suction direction can be varied. During operation of the coating device, it is preferably possible to select between one or both flow directions and / or to switch back and forth between them and / or to temporarily suspend the electrolyte flow. Preferably, the suction power is also variable and adjustable. Changing the suction direction and / or suction power enables the flow profile to be adjusted, which can preferably be set as turbulent, laminar, or a mixture of both, in order to achieve the desired mixing during electrolyte regeneration and deposition.The temporary change in the direction of electrolyte transport can also ensure that products of possible side reactions, such as hydrogen evolution, which prevent or reduce homogeneous and efficient catalyst deposition, can be removed.

[0028] Preferably, the length of the suction and / or extraction device corresponds to the length of the outer surface to which the substrate is applied. In this way, the suction and / or extraction device extends over the entire length of the substrate, allowing the electrolyte to be evenly drawn through the substrate, thus creating a homogeneous flow profile in the electroplating tank.

[0029] According to a preferred embodiment of the invention, the external working electrode comprises a chain having multiple links in the manner of a tank chain. A tank chain is understood to be a chain whose links are each twisted by 90 degrees, so that the chain can lie flat. The chain can therefore be arranged flat on the outer surface of the substrate carrier so that electrical contact can be established between the electrolyte, chain, and substrate, and the electrolyte can be transported across a larger area of ​​the substrate. This increases the contact area between the electrolyte and substrate, which accelerates the deposition process. In addition, the electric field can be homogenized by selecting the 2D or 3D geometry, which can lead to higher layer quality.

[0030] Alternatively, according to a preferred embodiment of the invention, the substrate carrier has contacts for electrically contacting the substrate, so that the substrate itself is designed as a working electrode. The electrical current for deposition can thus be conducted either via the substrate carrier, via an external working electrode in the form of a chain, or via the substrate itself.

[0031] According to a preferred embodiment of the invention, the substrate carrier is designed to be inert. The inert property of a material is characterized by a very limited willingness to undergo chemical reactions. This ensures that no deposition of functional material occurs on the substrate carrier itself. This prevents the loss of functional material, allowing only deposition on the substrate at the desired location. This ensures the most efficient deposition possible.

[0032] Preferably, the use of the device described above for the deposition of functional material for the production of electrolyte electrode assemblies for electrochemical energy converters in a continuous and / or semi-continuous process and / or batch process, such as the roll-to-roll process, is also provided.

[0033] The invention is explained in more detail below using a preferred embodiment with reference to the drawings.

[0034] The drawings show

[0035] Fig. 1 schematically shows a roll-to-roll electroplating apparatus with a device according to a preferred embodiment for flexible substrates of the invention in a perspective view,

[0036] Fig. 2 shows schematically a section of the electroplating apparatus from Fig. 1 in a

[0037] cross-sectional view,

[0038] Fig. 3 shows the space between the electroplating tank and the substrate carrier according to a preferred embodiment of the invention in a perspective view.

[0039] Fig. 1 shows a schematic diagram of a plating apparatus 1 comprising a device for metal deposition. The device includes a plating tank 3 and a roller-shaped substrate carrier 5 that is rotated about its longitudinal axis L. The plating tank can be filled with a liquid electrolyte 2, so that the substrate carrier 5 is immersed in the electrolyte and the substrate is guided through the electrolyte bath. A counterelectrode 4 is also arranged on the circumference of the plating tank 3. The substrate carrier 5, as the working electrode itself, or an electrical contact coupled to the substrate carrier 5, is connected to the substrate. In this way, a current flow can be established between the counterelectrode 4 in the plating tank 3, via the electrolyte, to the working electrode or the substrate to be coated. The use of a reference electrode is also possible by positioning it in the electrolyte close to the substrate.Metal ions must be dissolved in the electrolyte so that they can be transferred to the substrate. If the metal ions are catalyst ions, the substrate is subjected to reduction with a catalytically active material. The reduction takes place in the electrolyte layer close to the surface on the substrate, resulting in a lack of metal ions there. This creates an imbalance in the metal ion concentration in the electrolyte. To compensate for this imbalance and allow the flow of additional metal ions or to regenerate the electrolyte, the electrolyte is transported away at the surface by the removal and / or suction device 6 and reintroduced into the electrolyte volume in a deeper region of the electroplating tank 3, creating a cycle. The removal and / or suction device 6 is shown in Fig. 2.

[0040] Fig. 2 shows a cross-section through the electroplating tank 3 along the longitudinal axis and the substrate carrier 5. The arrows 2A represent the flow of the electrolyte 2 in two possible directions. On the one hand, the electrolyte 2 can be pumped from the electroplating tank 3 through the substrate 7 and through the substrate carrier 5 to the extraction and / or suction device 6 and then fed back into the electroplating tank via a pipe system via two inlets 10 at the bottom of the electroplating tank 3. On the other hand, the electrolyte 2 can also be sucked out of the electroplating tank 3 via the inlets 10 to the extraction and / or suction device 6, and then pumped through the substrate carrier 5 and through the substrate 7 back into the electroplating tank 3 into the area near the surface. So that the electrolyte 2 can diffuse through the substrate carrier 5, the substrate carrier 5 has a plurality of slit-shaped openings 8.Both directional options (dashed arrows) enable continuous electrolyte transport in a circuit so that the metal ion concentration can be homogenized and the metal deposition on the substrate 7 can take place as effectively as possible and there is no delay due to long regeneration times. The openings 8 represent the diffusion openness of the substrate carrier, through which the electrolyte can be transported. Fig. 3 shows the space between the substrate carrier 5 and the electroplating tank 3 in more detail. The area of ​​the electroplating tank 3 shown is filled with the electrolyte and includes an inlet and outlet, which in this case is connected to a pipe system 11. In this way, the electrolyte can be deposited inside the substrate carrier directly after passing through the substrate 7, which rests on the outer side 5B of the substrate carrier.

[0041] 5 A and fed to the electroplating tank via the inlet or outlet 10. The pipe system is designed in such a way that a preferably homogeneous electrolyte exchange is possible over the entire surface of the substrate that is in contact with the electrolyte. For this purpose, the pipe system 11 itself is designed to be permeable to diffusion, e.g. via incorporated slots, holes or other types of media passages, similar to the substrate carrier itself. The required differential pressure for the electrolyte movement 2 A is achieved, for example, via a pump not shown here. The suction direction and the suction power can be varied and controlled during operation, so that the flow profile of the electrolyte can be changed at any time and adapted to specific conditions, which is shown by the arrows 2A.

[0042] List of reference symbols

[0043] 1 coating apparatus

[0044] 2 Electrolyte 2A El ektroly tb directions of movement

[0045] 3 electroplating tanks

[0046] 4 Counter electrode

[0047] 5 substrate carriers

[0048] 5A Inside 5B Outside

[0049] 6 Extraction and / or suction device

[0050] 7 Substrat

[0051] 8 openings

[0052] 9 Base plate 10 Inlet / outlet

[0053] 11 Pipe system

[0054] L Longitudinal axis

Claims

Patent claims 1. Device for a coating apparatus (1) for the deposition of functional material, comprising an electroplating tank (3) which can be filled with a liquid electrolyte (2) and at least one counter electrode (4) arranged in the electroplating tank (3), a substrate carrier (5) which is at least partially designed as a hollow body and has an outer shell enclosing a cavity, the outer shell having an inner side (5A) facing the cavity and an outer side (5B) facing away from the cavity, and a removal and / or suction device (6) arranged in the cavity for removal or suction.Suction of the electrolyte (2), wherein the outer shell is designed to be permeable to diffusion and the outer side (5B) can be supplied with a substrate (7), the substrate carrier (5) in an operational state projects at least partially into the electroplating tank (3), the substrate carrier (5) is designed as a working electrode or comprises a working electrode, and a voltage can be applied between the counter electrode (4) and the working electrode, the extraction and / or extraction device (6) and the electroplating tank (3) are coupled to a pipe system (11), wherein the pipe system (11) is designed to ensure electrolyte transport between the extraction and / or extraction device (6) in the cavity of the substrate carrier (5) and the electroplating tank (3).

2. Device according to claim 1, wherein the substrate carrier (5) comprises a hollow cylindrical roller.

3. Device according to claim 1 or 2, wherein the substrate carrier (5) is rotatable about its longitudinal axis (L).

4. Device according to one of the preceding claims, wherein the outer shell has a plurality of openings (8) or the outer shell is designed to be permeable to diffusion.

5. Device according to one of the preceding claims, wherein the substrate carrier (5) is arranged on a movement device.

6. Device according to one of the preceding claims, wherein the electroplating tank (3) has a base plate (9) and the pipe system (11) is connected to at least one inlet (10) arranged on the base plate (9).

7. Device according to one of the preceding claims, wherein the suction and / or discharge device (6) is designed to change the direction of electrolyte transport.

8. Device according to one of the preceding claims, wherein the working electrode comprises a chain arranged on the outer side (5B) and having a plurality of links in the manner of a tank chain.

9. Device according to one of claims 1 to 7, wherein the substrate carrier (5) has contacts for electrically contacting the substrate and the substrate is designed as a working electrode.

10. Device according to one of the preceding claims, wherein the substrate carrier (5) is inert.

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