METHOD AND DEVICE FOR MANUFACTURING A STACK OF ELECTRODES

Description

[0001] The present invention relates to a method and a device for manufacturing an electrode stack.

[0002] In the manufacture of energy storage devices and energy converters, especially batteries, fuel cells, and capacitors, several foil-shaped electrodes are stacked together to form an electrode stack in a process known as stacking. The individual electrodes are insulated from each other. The electrodes can be individually picked from magazines and placed alternately on the electrode stack by handling systems.

[0003] Methods and devices for producing electrode stacks are known, for example, from US 2021 / 234186 A1, WO 2015 / 079365 A1 and US 7,611,549 B2.

[0004] The precise placement of the individual electrodes, both in terms of their position and orientation, is a critical quality criterion for the manufactured energy storage and energy converter devices. The target accuracy is less than 0.1 mm. Aligning the electrodes in the desired position (target position) has traditionally been a time-consuming and costly sub-step in the stack formation process. For example, it has previously been necessary to precisely record the actual position of an electrode so that the necessary changes in position and orientation to achieve the target position can be determined and subsequently implemented. Precise image processing can be used to record the actual position, but this is associated with high costs.

[0005] In addition, handling systems (robots with grippers) that hold the electrodes, for example using a vacuum, can cause damage to the electrodes, which is disadvantageous.

[0006] Once the target position of the electrode has been achieved, taking into account permissible tolerances, the current technology involves mechanically securing the entire stack of electrodes before the next layer is placed on top of the existing stack. This mechanical securing is also time-consuming and can cause damage to the individual electrodes.

[0007] The object of the invention was therefore to reduce the costs and time required for the production of electrode stacks and to avoid damage to the electrodes during stack formation.

[0008] This object is achieved by a method for producing an electrode stack for an energy storage device or energy converter, in particular for a battery, for a fuel cell or for a capacitor, according to claim 1, in which a plurality of film-shaped, at least partially electrically conductive layers are stacked to form an electrode stack, wherein initially a first layer is placed on a depositing surface and each further layer is placed on the previously deposited layer, in particular the layer deposited immediately beforehand, and wherein an alternating electromagnetic field centering the layer is generated for a time period t before, during and / or after the depositing of at least one layer. Centering is understood in particular to mean moving the layer into a predetermined position and orientation on the depositing surface and / or holding the layer in the predetermined position and orientation on the depositing surface.Centering occurs in particular in a two-dimensional plane parallel to the storage surface.

[0009] The alternating electromagnetic field induces eddy currents in the at least partially electrically conductive layers, which in turn generate a magnetic field that opposes the alternating electromagnetic field. This results in a repulsive force between an element generating the alternating electromagnetic field, such as a coil, and the layers. The inventors have discovered that these repulsive forces can be used excellently for centering the layers. It has been shown that this type of centering can achieve very high precision, i.e. very small deviations between the desired position and the actual position, both in terms of position and orientation. The forces acting on the at least partially electrically conductive layers are not of mechanical origin, so the risk of damage to the layers is significantly reduced.In addition, the centering is extremely fast, much faster than centering with a handling system (gripper) would be possible.

[0010] The method according to the invention is particularly suitable for centering rectangular layers, especially layers with edge lengths of 5 mm to 600 mm and a thickness between 5 µm and 1000 µm. Layers of these dimensions can be precisely centered using the method according to the invention. However, the method according to the invention is also very well suited for centering layers of other shapes, for example, for centering circular or oval layers, especially those with diameters between 5 mm and 600 mm.

[0011] The deposited layers can, for example, be (battery) electrodes with integrated current-conducting current collector layers. These electrodes include cathodes (e.g., aluminum current collectors), anodes (e.g., copper current collectors), and composites of anodes with separator or electrolyte layers and cathodes with separator or electrolyte layers. The method is also suitable for stacking (battery) electrodes in which the active material itself serves as a current collector (e.g., pure lithium metal as a lithium metal anode). A layer deposited immediately beforehand can also be a pure separator layer. Separator layers are non-conductive and are therefore not affected by the alternating electromagnetic field. Within the scope of the present invention, it is possible to deposit separator layers between two at least partially electrically conductive layers using an additional device, for example, a vacuum gripper.If the alternating electromagnetic field is subsequently activated, only the layers that are at least partially electrically conductive are centered.

[0012] Above the storage surface is a storage space. The storage space is the space in which the layers are arranged during the production of the electrode stack to form the electrode stack. The storage space therefore preferably has a height that is adapted to, and in particular corresponds to, the maximum height of the electrode stack. During production, the layers are moved from an area outside the storage space into the storage space and then placed (deposited) on the storage surface or the previously deposited layer. The alternating electromagnetic field has an effective space that preferably encompasses at least the storage space.The effective area of ​​the alternating electromagnetic field is understood to be the space in which the alternating electromagnetic field has a field strength strong enough to exert a force on the layer to be deposited or already deposited that can set the layer in motion, i.e., in particular, to overcome resistance forces between the layer and the process environment during deposit (e.g., air resistance forces, electrostatic forces) and / or adhesion and friction forces between the layer and the deposit surface or between the layer and a previously deposited layer. The effective area of ​​an alternating electromagnetic field generated by a coil extends particularly inside the coil. The effective area can also be referred to as the sphere of influence of the alternating electromagnetic field.

[0013] The effective area can be influenced, for example, by the shape of the coil, the material of the coil, the number of turns of the coil, the diameter of the coil, and the strength of the current flowing through the coil. In addition, there are many other factors that influence the size and shape of the effective area. It is advantageous to adapt the effective area of ​​the alternating electromagnetic field to the shape and size of the electrodes in order to achieve the best possible centering effect.

[0014] The effective area of ​​the alternating electromagnetic field is specifically selected such that the alternating electromagnetic field exerts forces on the layer from at least three directions parallel to the support surface, thereby centering the layer. These forces complement each other in such a way that the position and orientation of the layer in the plane parallel to the support surface are fixed, thus preventing the layer from moving. The position and orientation of the layer in the plane are determined by these at least three forces.

[0015] In advantageous refinements, the effective area of ​​the alternating electromagnetic field partially encloses the deposited layer or its surrounding edge and protrudes outward beyond the edge of the layer at least three times. During their development, the inventors discovered that centering is particularly effective when the alternating electromagnetic field acts on the edge of the deposited layer. Therefore, the effective area of ​​the alternating electromagnetic field can alternatively completely enclose the deposited layer or its surrounding edge. In this case, the alternating electromagnetic field acts from the outside on the entire edge of the layer, thus generating forces from all directions parallel to the deposit surface, achieving exceptionally good centering.

[0016] The alternating current can be generated in two variants (alternatives). In the first variant, the desired frequency and waveform (preferably sine wave or square wave) of the alternating current are generated using a signal generator (alternating current generator). The amplitude of this signal is increased in a connected power amplifier and fed into the coil. The alternating current generates the alternating electromagnetic field in the coil. In the second variant, the coil is converted into an oscillating circuit by a capacitor, and this oscillating circuit is expanded by a charging circuit with a direct current source. The charging circuit with a direct current source continuously charges the capacitor. In a first, preferred embodiment of this variant, the capacitor is discharged in pulses via the coil using a switch between the capacitor and the coil.The resulting high discharge current decays at the natural frequency of the resonant circuit consisting of the capacitor and coil until the capacitor is disconnected from the coil by a switch and recharged by the charging circuit. The high, pulsed discharge current generates a strong alternating electromagnetic field in the coil. In a second, preferable version of this variant, the capacitor and coil are permanently electrically connected and powered by the charging circuit, resulting in an alternating current continuously oscillating at the natural frequency of the resonant circuit, which generates an alternating electromagnetic field in the coil.

[0017] In advantageous further developments, the effective area of ​​the alternating electromagnetic field is adapted to the shape and / or size of the layer to be deposited. If, for example, a rectangular layer is deposited, the effective area of ​​the alternating electromagnetic field is preferably rectangular or substantially rectangular; in particular, the effective area has the shape of a rectangle with rounded corners in a plan view. In practice, this can be achieved by generating the alternating electromagnetic field from a coil whose shape and / or size is adapted to the layer. Furthermore, the extents of the effective area of ​​the alternating electromagnetic field and the layer in directions parallel to the deposit surface are preferably identical, or the extent of the effective area of ​​the alternating electromagnetic field is slightly larger, in particular by up to 10%, particularly preferably up to 5%.The inventors recognized that an even larger effective area does not provide any advantage, but rather leads to lower forces acting on the layer, thus reducing the centering effect. An effective area of ​​the alternating electromagnetic field that is slightly smaller than the layer in directions parallel to the support surface also leads to a lower centering effect. Therefore, a coil is preferably selected whose interior space is only slightly larger in the radial direction than the extension of the layers.

[0018] In the vertical direction, i.e., specifically perpendicular to the stacking surface, the alternating electromagnetic field is designed in such a way that its effective area also encompasses previously deposited layers. This is achieved particularly when the effective area completely encompasses the stacking area. As a result, the already deposited layers are (re)centered by the alternating electromagnetic field. Alternatively, the alternating electromagnetic field can be activated only after the last layer has been deposited, whereupon all electrodes in the stack are centered.

[0019] As already mentioned above, in the prior art, already deposited layers are held by means of a hold-down device. This can lead to mechanical damage. In advantageous developments of the invention, it is provided that the effective space of the electromagnetic alternating field at least partially, in particular completely, encompasses an at least partially electrically conductive deposit part arranged below the deposit space. As a result, eddy currents are also induced in the deposit part. These eddy currents generate their own magnetic field. As described above, a magnetic field is also generated in the layers by the eddy currents induced there. The magnetic fields of the layers and the deposit part are aligned in such a way that the deposit part and the layers attract each other. In this way, the layers are not only centered but also held down.With this type of hold-down, there is no mechanical stress on the layers caused by a gripper or similar device, thus largely avoiding damage to the layers. If non-conductive separator layers are located between deposited, at least partially electrically conductive layers, the separator layers are also held down, as they are held between the at least partially electrically conductive layers and the deposit part.

[0020] Electrically conductive materials are understood to mean materials that have a conductivity of > 10 6 < S / m.

[0021] The time period t during which the alternating electromagnetic field is generated (operated), i.e., during which the alternating electromagnetic field is effective, is preferably between 0.005 and 20 seconds, in particular between 0.005 and 1 second. 20 seconds is sufficient to transport a layer into the storage area and additionally center the layer. A time period of 0.005 seconds, however, is sufficient for centering alone. Preferably, no alternating electromagnetic field is generated between two storage and centering processes, thus limiting energy consumption.

[0022] By inducing eddy currents in the layer and, if applicable, the deposition part, part of the (electrical) energy used is converted into thermal energy (waste heat). The inventors have recognized that it is advantageous to limit the amount of waste heat so that the layers are not damaged. For this purpose, too, it is advantageous if, as described above, no alternating electromagnetic field is generated between two deposition and centering processes. In advantageous developments, the alternating electromagnetic field is additionally or alternatively operated in pulsed mode, wherein the alternating electromagnetic field is alternately activated and deactivated during the time period t. The active time period t active , within which the alternating electromagnetic field is active, is preferably between 0.001 and 10 seconds, in particular between 0.001 and 0.5 seconds.Between each two active time periods t active , there is a pause period t pause , which is between 0.001 and 10 seconds, in particular between 0.001 and 0.5 seconds. It has also been shown that it is highly advantageous if the active time period t active is significantly shorter than the pause period t pause , in particular by a factor of 2 to 10. The shorter active time period is sufficient to center the layer, since centering of the layer takes place extremely quickly. The longer pause period ensures that the heat energy can be dissipated into the device's surroundings, preventing the layers from overheating in the long term.

[0023] The alternating electromagnetic field preferably has a frequency greater than 1 kHz, in particular greater than 10 kHz, and further preferably less than 100 kHz. Below 1 kHz, the resulting eddy currents are often weak, and the centering effect of the inventive method is barely present. Above 10 kHz, the magnetic fields resulting from the eddy currents are sufficiently strong to overcome the attractive forces between the individual layers and center the layers. Above 100 kHz, hardly any improvement in the centering effect can be observed. In addition, such high frequencies generate a lot of waste heat, which is also disadvantageous.

[0024] In advantageous further developments, the support surface is defined by a housing of an electrode cell. The assembly of electrode stack and housing is referred to as an electrode cell. Until now, it was common practice for an electrode stack to first be manufactured independently of a housing and then the electrode stack to be placed into the housing, thus producing an electrode cell. A battery, for example, is then manufactured from several electrode cells. Typically, each energy storage device or converter has a plurality of interconnected electrode cells. The invention makes it possible to manufacture the electrode stack directly in the housing, thereby eliminating one process step—the transfer of a manufactured electrode stack into the housing. Alternatively, the support surface can be defined by the support part itself, in which case it is a surface of the support part.

[0025] The object of the invention is also achieved by a device for producing an electrode stack from a plurality of film-shaped, at least partially electrically conductive layers according to claim 7, which device has a storage part providing a storage surface and an alternating current generator which comprises at least one coil and a power source, wherein the at least one coil is arranged relative to the storage surface in such a way that, when the power source is activated, it generates an alternating electromagnetic field which centers the layers relative to the storage surface at least in a storage space above the storage surface.

[0026] In the device according to the invention, the coil generates the alternating electromagnetic field that centers the layers in the storage space. When layers are deposited in the storage space, particularly on the storage surface or on a previously deposited layer, the alternating electromagnetic field effects the centering described above. In this way, the advantages described above also apply to the device according to the invention.

[0027] The device according to the invention is preferably configured to carry out the method according to the invention. The method according to the invention is preferably carried out using the device according to the invention.

[0028] The effective area of ​​the alternating electromagnetic field is defined in particular by the shape of the coil and its arrangement in space.

[0029] As described above, it is advantageous if the layers are not only centered after deposition but also held down. In advantageous further developments, the deposition part is at least partially electrically conductive and the coil is arranged such that the alternating electromagnetic field at least partially encloses the deposition part. In this way, the alternating electromagnetic field also induces eddy currents in the deposition part, with these eddy currents generating their own magnetic field. This magnetic field interacts with the magnetic field of the eddy currents in the layers in such a way that the layers are held down.

[0030] Alternatively, the storage part is not electrically conductive, and a magnet, in particular an electromagnet and / or a permanent magnet, is arranged beneath the storage part. The magnet is designed to hold down layers deposited on the storage part. The magnet is configured such that it interacts with the magnetic field generated by the eddy currents in the layers in such a way that the layers are held down, i.e., that a force is exerted that presses the layers onto the storage part. With this type of hold-down, there is no mechanical impairment of the layers by a mechanical hold-down device, thus preventing damage.

[0031] A material is not electrically conductive if it has a conductivity of < 10 -8< S / m.

[0032] The storage area preferably corresponds in shape and size to the layers to be deposited (in plan view, i.e., in directions perpendicular to the vertical axis H). The storage area can be slightly larger to accommodate tolerances when depositing the layer before the centering process. The storage area can correspond to the upper surface of the storage part. The shape can also vary slightly. For example, for a rectangular layer, the storage area can also be rectangular with rounded corners.

[0033] The inventors have determined that it is advantageous if the coil or coils are arranged close to the layers to be centered. In advantageous developments of the device according to the invention, it is therefore provided that the coil runs at the level of the storage space, the storage surface and / or the storage part along a closed contour around a vertical axis H running perpendicular to the storage surface, or that several coils are provided (coil arrangement), wherein the coils are evenly distributed along a closed contour around a vertical axis H running perpendicular to the storage surface. With both alternatives, an alternating electromagnetic field can be generated that centers the layers on the storage surface. A single coil simplifies the structure of the device, whereas the device with a plurality of coils can be adapted to complex layer shapes.

[0034] It is also possible to provide, in addition to a single, rotating coil, another coil, for example, located below the storage part. This can also improve the centering effect.

[0035] The closed contour is preferably adapted to the shape and size of the layers, in particular their edge, and is in particular rectangular or substantially rectangular. In this way, the alternating electromagnetic field is generated in the immediate vicinity of the peripheral edge of the layers, which improves the centering effect of the alternating electromagnetic field. With the device according to the invention, electrodes of various shapes and sizes can in principle be centered. The inventors have recognized that it is advantageous to adapt the coil or coil arrangement to the respective layers to be deposited. Rectangular electrodes are often used, which is why the contour is also preferably rectangular or substantially rectangular and in particular runs along a rectangle with rounded corners.

[0036] The coil preferably has at least five, in particular at least 15, turns. It has been shown that a coil with more than five turns results in a good centering effect. Above at least 15 turns, the centering effect is even better, while the resulting heat energy remains within acceptable limits. The coil preferably has fewer than 30 turns, since such a high number of turns generates a lot of waste heat, which can damage the layers.

[0037] The coil or coils are connected to an alternating current source, wherein the alternating current source provides alternating current with a current intensity of preferably at least 2 A, in particular greater than 6 A and preferably less than 100 A and a frequency of preferably greater than 1 kHz, in particular greater than 10 kHz and preferably less than 100 kHz.

[0038] The intensity and resulting centering effect of the alternating electromagnetic field are significantly influenced by the frequency and current of the generating alternating current. The intensity of the alternating electromagnetic field increases with both increasing frequency and current of the generating alternating current. However, due to the inductance of the coil, the frequency and current of the alternating current are inversely related, so high frequencies cause a decrease in the current of the alternating current.

[0039] The inventors have surprisingly discovered that a sufficient centering effect can be generated even below a frequency of 1 kHz if the current intensity is selected to be sufficiently high. This approach has proven successful up to a lower limit of 100 Hz. The current intensity of the alternating electromagnetic field can therefore be up to 100 kA in preferred embodiments. Therefore, an alternating electromagnetic field with a frequency between 100 Hz and 1 kHz and a current intensity between 100 A and 1 kA, and an alternating electromagnetic field with a frequency between 1 kHz and 100 kHz and a current intensity between 2 A and 100 A, have proven particularly advantageous. In both cases, the respective combination of parameters results in a particularly good centering effect with comparatively low heat input.

[0040] A high frequency and simultaneously low current intensity of the generated alternating current are preferably achieved with the first variant for generating the alternating current using a signal generator and power amplifier, or with the second variant of the second variant using a continuous resonant circuit. A high current intensity and simultaneously low frequency of the generated alternating current are preferably achieved with the first variant of the second variant for generating the alternating current using pulsed capacitor discharge in the resonant circuit.

[0041] In advantageous further developments, a bundling device, in particular a circumferential one, is provided radially outside the storage part for bundling the alternating electromagnetic field. The bundling device is made at least partially of a material with high permeability. The bundling device sharply defines the adjacent magnetic fields, thereby further improving the centering effect. Particularly preferably, the bundling device is located radially between the storage part and the coil(s) extending along the contour around the storage part.

[0042] The high-permeability material preferably has a permeability of µ r > 50, especially µ r > 10,000. One material with high permeability is mu-metal (NiFe). The use of mu-metal has proven particularly advantageous because it provides a particularly sharp boundary for the adjacent magnetic fields.

[0043] In advantageous further developments, the bundling device is segmented. This simplifies the structure of the bundling device, as the bundling device can be assembled from several similar parts.

[0044] The bundling device is preferably adapted to the shape and size of the layers to be deposited and, in particular, runs along a rectangular or essentially rectangular contour. This adaptation ensures particularly good centering.

[0045] In advantageous refinements, an amplifier made of a high-permeability material, such as mu-metal, is provided beneath the support section. This amplifier amplifies and focuses the alternating electromagnetic field, significantly improving the centering effect. The forces acting on the layers are then greater, allowing even strong adhesion forces between the layers to be overcome.

[0046] The amplifier is preferably radially enclosed by the focusing device. This enhances the positive effects of the amplifier and the focusing device and ensures a strong and focused alternating electromagnetic field.

[0047] The amplifier can heat up due to the resulting waste heat. Therefore, advantageous developments provide for the amplifier to have a cooling structure, in particular cooling bores and / or cooling grooves, and / or for the device according to the invention to have a cooling device for the amplifier. The cooling device can comprise a coolant that is transported to the amplifier and can absorb thermal energy. The coolant can be air, for example.

[0048] The storage part can also comprise a cooling structure and / or be cooled by a cooling device.

[0049] In advantageous refinements, the amplifier is segmented, i.e., consists of several parts. This allows, in particular, parasitic eddy currents in the amplifier to be avoided, thus enabling reproducible centering of the layers.

[0050] The amplifier is preferably adapted to the shape and size of the layers and, in particular, is rectangular or essentially rectangular in plan view. This allows the alternating electromagnetic field to be even better adapted to the layers, thus improving centering.

[0051] In battery cells, the geometric dimensions of anodes and cathodes often differ, with the anodes generally being larger than the cathodes all the way around. The larger anodes are intended to ensure complete coverage of the cathodes in the electrode stack of the manufactured battery cell, as this coverage is essential for the stability of the electrochemical processes. Likewise, assemblies consisting of anode and separator or cathode and separator, as well as assemblies consisting of anode, separator, and cathode, can have different geometric dimensions to ensure complete coverage in the electrode stack of the manufactured battery cell. Therefore, to center and hold down electrodes or assemblies of different sizes, multiple bundling devices, multiple support parts, and / or multiple amplifiers can be provided, each adapted to different types of layers.For example, two bundling devices, two storage parts and two amplifiers can be provided, wherein a first bundling device, a first storage part and a first amplifier are adapted to a first layer type, in particular to anode layers, and wherein a second bundling device, a second storage part and a second amplifier are adapted to a second layer type, in particular to cathode layers.

[0052] The first bundling device, the first storage part, and the first amplifier form a first assembly, and the second bundling device, the second storage part, and the second amplifier form a second assembly. The assemblies are preferably arranged concentrically so that the respective components can develop their full effect relative to the respective layers. In other words, the storage part of one assembly lies radially outside the bundling device of the other assembly, with the respective bundling device still being arranged radially outside the respective storage part within the assemblies. The same applies to the amplifiers and also to embodiments with more than two assemblies and embodiments without an amplifier or bundling device.

[0053] In advantageous further developments, the device according to the invention comprises a handling device for transporting and depositing the layers. The handling device can be a gripper, for example a vacuum gripper. The layers can be transported into the depositing space by means of the handling device and deposited on the depositing surface or a previously deposited layer. Before, during, and / or after depositing, the alternating electromagnetic field is generated by activating the alternating current source. This centers the deposited layer. Here, too, the invention provides an advantage because the vacuum gripper only needs to be used once, and the subsequent centering is achieved without the mechanical stress caused by the vacuum gripper.

[0054] In particularly advantageous developments of the device according to the invention, the at least one coil and the storage part are components of the handling device for transporting and depositing the layers, wherein either the storage part is at least partially electrically conductive or the storage part is not electrically conductive, wherein a magnet as described above is arranged below the non-electrically conductive storage part. During transport, in both cases, the layer to be deposited is pressed (held down) against the storage part by the alternating electromagnetic field and centered by the alternating electromagnetic field. As a result, the handling device can be moved freely through the space without the layer becoming detached from the storage part. The layer can then be deposited at a destination where other layers may already be located. The centering enables precise deposit of the transported layer.In these further developments, other parts, in particular the amplifier, the power source, the bundling device and the magnet can also be parts of the handling device.

[0055] The at least partially electrically conductive support part preferably consists at least partially of one of the following components: silver, copper, gold, iron, graphene, conductive plastic, conductive composite material, or copper oxide compounds. Support parts that consist at least partially of these components provide a good hold-down effect of the layers.

[0056] The non-electrically conductive storage part preferably consists at least partially of one of the following components: non-conductive plastic, non-conductive composite material, ceramic, glass, non-conductive metal oxides.

[0057] In advantageous refinements, the support part is segmented vertically. The support part then has multiple layers. This allows for highly customized adjustment of the magnetic field generated by the support part. A cooling structure can also be integrated into the support part in this way.

[0058] The storage part is preferably adapted to the shape and size of the layers and preferably corresponds (in plan view) essentially to the shape and size of the layers. The centering and hold-down effect are optimal in this case.

[0059] The invention is illustrated and explained by way of example with reference to the figures. In the figures: Figure 1 shows an embodiment of the device according to the invention in a perspective view Figure 1A shows the device of Figure 1 in a perspective sectional view Figure 2 the device of Figure 1in a further perspective view Figure 3 the device of Figure 1 together with a housing for an electrode cell in a perspective view Figure 4 shows a further embodiment of the device according to the invention in a perspective view Figure 5 shows a further embodiment of the device according to the invention in a schematic view Figure 6 shows a further embodiment of the device according to the invention in a schematic view Figure 7A shows a further embodiment of the device according to the invention in a schematic plan view Figure 7B shows the device of Figure 7A in a sectional side view Figure 8A a further embodiment of the device according to the invention in a schematic plan view Figure 8B the device of Figure 8Ain a sectional view in side view Figures 9A to 9I current density distributions in an electrode in different electromagnetic alternating fields Figure 10A a further embodiment of the device according to the invention in a schematic plan view and Figure 10B the device of Figure 10A in a sectional side view.

[0060] The Figure 1 The device 10 shown for producing an electrode stack from a plurality of foil-shaped, at least partially electrically conductive layers 100 has a support part 20 made of a conductive material, copper. The support part 20 is plate-shaped, thus having a thickness that is significantly smaller than the width and length of the support part 20. The support part 20 is arranged horizontally. The thickness of the support part therefore runs vertically, along a vertical axis H.

[0061] The upper surface of the support part 20 forms a support surface 22 for the layers 100. A support space is located above the support surface 22. The support space is the space in which the layers are arranged during the manufacture of the electrode stack to form the electrical stack.

[0062] An amplifier 30 is arranged under the storage part 20, which has the same width and length as the storage part 20 (see Figures 1a and 2 ). The amplifier 30 is cuboid-shaped and made of mu-metal.

[0063] A bundling device 40 runs around the storage part 20 and the amplifier 30. The bundling device 40 consists of four segments, two long segments 42 and two short segments 44. The four segments 42, 44 form a closed contour around the storage part 20 and the amplifier 30. The combination of storage part 20, amplifier 30 and bundling device 40 is essentially cuboid-shaped, i.e. rectangular in plan view.

[0064] The device 10 further comprises a coil 50, which is part of an alternating current generator (not shown). The coil 50 is connected to an alternating current source (not shown). For this purpose, the coil 50 has two terminals 52.

[0065] The coil 50 runs at the level of the storage space, the storage surface 22 and the storage part 20 along a closed contour around the vertical axis H running perpendicular to the storage surface 22. The coil 50 has ten turns.

[0066] When the AC power source is activated, alternating current flows through coil 50. Coil 50 then generates an alternating electromagnetic field whose effective area encompasses at least the interior of coil 50. This interior contains amplifier 30, storage part 20, and bundling device 40.

[0067] When layer 100 is placed on the support surface 22 of the support part 20, eddy currents are induced in layer 100 by the alternating electromagnetic field of coil 50. The eddy currents induced in layer 100 generate their own magnetic field, which interacts with the alternating electromagnetic field of coil 50 at all times in such a way that layer 100 is repelled by coil 50. Since coil 50 extends radially along a closed contour around layer 100, layer 100 is centered on the support surface 22.

[0068] Since the support part 20 is made of a conductive material, eddy currents are also induced in the support part 20 by the alternating electromagnetic field. The eddy currents induced in the support part 20 also generate a magnetic field, which interacts with the magnetic field of the layer 100 in such a way that the layer 100 is pressed downward onto the support part 20 and thereby held down.

[0069] If further layers 100 are subsequently deposited on the already deposited layer 100, the induced magnetic fields interact in such a way that the layers 100 are all pressed in the direction of the deposit part 20 and are thereby held down as the resulting electrical stack.

[0070] The bundling device 40 serves to bundle the alternating electromagnetic field. The segments 42, 44 are made of Mu-metal, a material with high permeability. This influences the magnetic field lines of the alternating electromagnetic field of the coil 50 as well as the magnetic fields of the layer 100 and the storage part 20 in such a way that a sharp demarcation between the magnetic fields is created, resulting in a strong centering effect.

[0071] In addition to the eddy currents, the alternating electromagnetic field also generates waste heat, which gradually heats up the components of the device 10 and the layer 100. The amplifier 30 therefore has a plurality of vertical cooling holes 32, which together form a cooling structure (see Figure 2 ). Due to the cooling structure, more air flows around the amplifier 30 during operation and thus cools it, which improves heat dissipation.

[0072] As in Figure 3As shown, a housing 110 of an electrode cell can be arranged on the device 10 according to the invention, i.e., on the support surface 22. The housing 110 forms its own support surface 22. Layers 100 can be deposited on this support surface 22. When the power source is activated, the coil 50 again generates an alternating electromagnetic field. As described above, the alternating electromagnetic field centers the layers 100 and additionally holds the layers 100 down, i.e., exerts a downward force on the layers 100. The housing 110 is typically non-ferromagnetic, i.e., has low permeability, and can, for example, consist of an aluminum composite foil.

[0073] In this way, an electrode stack can be manufactured directly in the housing 110 in which it is to be later arranged in the battery, for example. This eliminates an additional manufacturing step, namely the transfer of the finished electrode stack into a corresponding housing 110.

[0074] The Figure 4 The illustrated embodiment of the device 10 according to the invention comprises a handling device in the form of a multi-axis gripper arm 120. The gripper arm 120 is mounted on a base plate 122 and has at its front end the assembly comprising amplifier 30 (not visible here), bundling device 40, electrically conductive storage part 20, and coil 50. Here, the storage part 20 also comprises a storage surface 22, which is directed downward in the position of the articulated arm 120 shown.

[0075] If a layer 100 (not shown here) is placed on the support surface 22, which also includes bringing the layer closer to the support surface 22 in another way, for example, by moving it counter to the direction of gravity, and the power source is then activated, an alternating electromagnetic field is generated by the coil 50 as described. Here, too, the alternating electromagnetic field induces eddy currents in the support part 20 and in the layer 100, whereupon the support part 20 and layer 100 attract each other due to the magnetic fields generated by the respective eddy currents, thus pressing the layer 100 against the support part 20. The layer 100 is thereby held down on the support part 20 and can be moved to another location by the device 10 according to the invention.

[0076] As mentioned, the eddy currents induced in layer 100 generate a magnetic field that is directed counter to the alternating electromagnetic field. As a result, layer 100 is centered on the support surface 22 in this embodiment as well. This handling device therefore makes it possible to hold a layer 100 without the application of mechanical force and to deposit it precisely at the end of the transport.

[0077] In other embodiments with a handling device, the storage part 20 may also be non-electrically conductive. In this case, the layer 100 is not pressed (held down) against the storage surface by the alternating electromagnetic field. In such embodiments, a different form of holding down, for example, by means of a vacuum, may be used. The alternating electromagnetic field then serves only to center the layer 100 on the storage surface 22.

[0078] In the embodiment of the device 10 according to the invention according to Figure 5 A storage part 20 is again provided, which is completely surrounded in the radial direction by a coil 50. The coil 50 has two connections 52, with which the coil 50 is connected to an alternating current source. In addition to the coil 50, a further coil, a secondary coil 54, is provided, which runs circularly and is arranged below the storage part 20. The secondary coil 54 has two connections 56, by means of which the coil 54 with inverted phase is also connected to the alternating current source. In this way, the secondary coil 54 creates an additional hold-down effect, since it generates a magnetic field that attracts the magnetic fields of the layers 100 and the storage part 20 and thus these components.

[0079] In the embodiment according to Figure 6Four coils 50 are provided, which are evenly distributed along a closed, rectangular contour around the vertical axis H running perpendicular to the support surface 22 of the support part 20. In this embodiment, the coils 50 are all connected to the alternating current source in the same way. As a result, a common alternating electromagnetic field is generated by the coils 50. This alternating electromagnetic field has an effective area that partially encloses the peripheral edge of the layer 100 and projects beyond the edge of the layer at four points, namely once per coil 50. Due to this arrangement of the coils 50, the layer 100 placed on the support surface 22 of the support part 20 is also centered.

[0080] The embodiment of the device 10 according to the invention according to the Figures 7A and 7Bagain comprises a support part 20, which is radially surrounded by a coil 50. In this embodiment, the support part 20 is not electrically conductive. Therefore, no eddy currents are induced there. A centering effect of layer 100 nevertheless occurs, since the alternating electromagnetic field of coil 50 interacts with the field generated in layer 100 and centers layer 100.

[0081] A magnet 60 in the form of an electromagnet 62 is provided below the storage part 20. The electromagnet 62 has an iron core 68 and a magnetic coil 66. The electromagnet 62 generates a magnetic field that interacts with the magnetic field induced by the coil 50 in the layers 100 in such a way that the layers 100 are pressed onto the storage part 20.

[0082] In the embodiment according to the Figures 8A and 8BThe device 10 again comprises a support part 20, which is radially surrounded by a coil 50. Here, too, the support part 20 is not electrically conductive, which means that no eddy currents are induced in the support part 20. The centering effect is not affected and remains unchanged.

[0083] Figure 8B shows three layers 100 placed on top of each other to form an electrode stack. The layers 100 are not drawn to scale with regard to their thickness, namely they are shown as excessively thick.

[0084] A magnet 60 in the form of a permanent magnet 64 is provided beneath the storage part 20. The permanent magnet 64 interacts with the layer 100 deposited on the storage surface 22 in such a way that the layer 100 is pressed onto the storage surface 22.

[0085] The Figures 9A to 9Ishow the simulated current density distribution (current density J) of a layer 100 in various alternating electromagnetic fields. The scale of the current density J ranges from 2 x 10 6< to 8 × 10 8< A / m 2< . The layer 100 is 50 mm wide and 70 mm long and is made of copper. The isolines shown illustrate the current density curve. The arrangement of the layer 100 on the support surface 22 of the device 10 was simulated according to Figure 1 The current of coil 50 (not shown here) was simulated at 15 A.

[0086] In the Figures 9A to 9C A coil with five turns was simulated, in the Figures 9D to 9F a coil with ten turns and in the Figures 9G to 9I a coil with 20 turns. In the Figures 9A , 9D and 9G The alternating electromagnetic field was simulated with a frequency of 500 Hz, in the Figures 9B , 9E and 9H with 5,000 Hz and in the Figures 9C , 9F and 9I at 50,000 Hz.

[0087] As can be seen from the Figures 9A to 9I As can be seen, a higher current density J is obtained with increasing number of turns and increasing frequency. It can also be seen that due to the device 10 according to the invention, the current density in the edge of the layer 100 is considerably higher than in other areas, which is particularly due to the bundling device and leads to a very good centering effect.

[0088] The alternating electromagnetic field of the coil 50 and the magnetic field induced by the eddy currents, particularly in the edge of the layer 100, repel each other and thus interact in such a way that the layer 100 is centered on the support surface 22.

[0089] The Figures 10A and 10Bshow a further embodiment of the device 10 according to the invention. In this embodiment, the device 10 comprises two storage parts 20, each with a storage surface 22, two amplifiers 30, and two bundling devices 40. One storage part 20 and the one amplifier 30 located underneath are arranged centrally. The first, annular bundling device 40 is arranged around this storage part 20 and the amplifier 30. These components form a first assembly.

[0090] Arranged radially outside the first assembly is a second, annular support part 20 with an underlying, also annular amplifier 30. Arranged radially outside these components is a second, annular bundling device 40. These three components form a second assembly. The second assembly is arranged radially outside the first assembly.

[0091] A coil 50 with terminals 52 is arranged radially outside the second assembly. The coil 50 is part of an alternating current generator (not shown in detail), which also includes a power source (not shown).

[0092] Due to their different sizes, the components of the two assemblies are adapted to different types of layers. The first assembly is designed for smaller layers, and the second for larger layers. When these layers alternate during stacking, the design of the Figures 10A, 10B both types of layers are securely centered. List of reference symbols

[0093] 10Device 20Storage part 22Storage surface 30Amplifier 32Cooling holes 40Bundling device 42Long segments 44Short segments 50Coil 52Connections 54Secondary coil 56Connections 60Magnet 62Electromagnet 64Permanent magnet 66Solenoid coil 68Iron core 100Layers 110Housing 120Gripper arm 122Base plate H vertical axis

Claims

1. Method for producing an electrode stack, in particular for a battery, for a fuel cell or for a capacitor, in which a plurality of foil-shaped, at least partially electrically conductive layers (100) are stacked to form an electrode stack, wherein a first layer (100) is initially placed on a deposition surface (22) and each further layer is placed on the previously deposited layer (100), characterised in that an alternating electromagnetic field centring the layer (100) is generated for a period of time t before, during and / or after the deposition of at least one layer (100).

2. Method according to claim 1, characterised in that an effective space of the alternating electromagnetic field partially encloses the deposited layer (100) or its circumferential edge and projects outwards beyond the edge of the layer (100) in at least three places, or in that the effective space of the alternating electromagnetic field completely encloses the deposited layer (100) or its circumferential edge.

3. Method according to one of the preceding claims, characterised in that the effective space of the alternating electromagnetic field at least partially, in particular completely, encloses an at least partially electrically conductive deposition part (20) arranged below the depositing space.

4. Method according to one of the preceding claims, characterised in that the alternating electromagnetic field is operated in pulsed mode, wherein an active time span tAktiv is between 0.001 and 10 seconds and a pause time span tPause is between 0.001 and 10 seconds, wherein in particular the active time span tAktiv is smaller than the pause time span tPause by a factor of 2-10.

5. Method according to one of the preceding claims, characterised in that the deposition surface (22) is defined by the deposition part (20) or by a housing (110) of an electrode cell.

6. Method according to claim 1, characterised in that the alternating electromagnetic field is operated at a frequency between 100 Hz and 1 kHz and a current intensity between 100 A and 1 kA or alternatively at a frequency between 1 kHz and 100 kHz and a current intensity between 2 A and 100 A.

7. Apparatus for producing an electrode stack from a plurality of foil-shaped, at least partially electrically conductive layers (100) with a deposition part (20) providing a deposition surface (22) and with an alternating current generator comprising at least one coil (50, 54) and a current source, wherein the at least one coil (50, 54) is arranged relative to the deposition surface in such a way that, when the current source is activated, it generates an alternating electromagnetic field centring the layers (100) relative to the deposition surface (22) at least in a deposition space above the deposition surface (22).

8. Apparatus according to claim 7, characterised in that the deposition part (20) is at least partially electrically conductive or in that the deposition part (20) is not electrically conductive, wherein a magnet (60), in particular an electromagnet (62) and / or a permanent magnet (64), is arranged below the non-electrically conductive deposition part (20) and is configured to hold down layers (100) deposited on the deposition part (20).

9. Apparatus according to claim 7 or 8, characterised in that the deposition surface (22) corresponds in shape and size to the layers (100) to be deposited or is slightly larger.

10. Apparatus according to one of claims 7 to 9, characterised in that the coil (50, 54) extends at the level of the deposition space, the deposition surface (22) and / or the deposition part (20) along a closed contour about a vertical axis H extending perpendicularly to the deposition surface (22), or in that a plurality of coils (50, 54) are provided, wherein the coils (50, 54) are evenly distributed along a closed contour about a vertical axis H extending perpendicularly to the deposition surface (22), wherein the contour is preferably adapted to the shape and size of the layers (100) and is in particular rectangular or substantially rectangular.

11. Apparatus according to one of claims 7 to 10, characterised in that a bundling device (40) for bundling the alternating electromagnetic field is provided radially outside the deposition part (20), wherein the bundling device (40) consists at least partly of a material with high permeability, for example of Mu-metal (NiFe), wherein the bundling device (40) is segmented and / or wherein the bundling device (40) is adapted to the shape and size of the layers (100) and is in particular essentially rectangular.

12. Apparatus according to one of claims 7 to 11, characterised in that an amplifier (30) made of a material with high permeability, for example Mu-metal (NiFe), is provided below the deposition part (20), wherein preferably the amplifier (30) is enclosed in the radial direction by the bundling device (40) and / or the amplifier (30) has a cooling structure, in particular cooling holes (32) and / or cooling grooves, and / or the apparatus (10) has a cooling device for the amplifier (30) and / or the amplifier (30) is segmented and / or the amplifier (30) is adapted to the shape and size of the layers (100) and is in particular rectangular or substantially rectangular.

13. Apparatus according to one of claims 7 to 12, characterised in that several bundling devices (40), several deposition parts (20) and / or several amplifiers (30) are provided, which are each adapted to different types of layers (100).

14. Apparatus according to one of claims 7 to 13, characterised in that two bundling devices (40), two deposition parts (20) and two amplifiers (30) are provided, wherein a first bundling device (40), a first deposition part (20) and a first amplifier (30) are adapted to a first type of layer, in particular to anode layers, and wherein a second bundling device (30), a second deposition part (20) and a second amplifier (30) are adapted to a second type of layer, in particular to cathode layers.

15. Apparatus according to one of claims 7 to 14, characterised in that the at least one coil (50, 54) and the deposition part (20) are components of a handling device for transporting and depositing the layers (100) and / or in that the deposition part (20) consists at least partially of one of the following components: non-conductive plastic, non-conductive composite material, ceramic, glass, non-conductive metal oxides, conductive plastic, conductive composite material, silver, copper, gold, iron, graphene, copper oxide compounds and / or in that the deposition part (20) is segmented in the vertical direction and / or in that the deposition part (20) is adapted to the shape and size of the layers (100) and in particular essentially corresponds to the shape and size of the layers (100).