DEVICE AND METHOD FOR COMPACTING ELECTRODE MATERIAL APPLIED TO A COLLECTOR TAPE

Description

FIELD OF APPLICATION AND STATE OF THE ART

[0001] The invention relates to a method and a compaction device for compacting electrode material applied to a collector strip. The field of application is battery production. The invention therefore also relates in particular to a method for producing a battery using the aforementioned compaction method.

[0002] The term "battery" originally referred to several galvanic cells connected in series. Today, however, individual galvanic cells are also often referred to as batteries. When a galvanic cell discharges, an energy-producing chemical reaction takes place, consisting of two electrically coupled but spatially separated partial reactions. At the negative electrode, electrons are released in an oxidation process, resulting in an electron flow via an external load to the positive electrode, from which a corresponding amount of electrons is absorbed. A reduction process therefore takes place at the positive electrode. At the same time, an ionic current corresponding to the electrode reaction occurs within the cell. This ionic current is ensured by an ion-conducting electrolyte.In secondary cells and batteries, this discharge reaction is reversible, meaning that it is possible to reverse the conversion of chemical energy into electrical energy during discharge.

[0003] Among known secondary cells and batteries, comparatively high energy densities are achieved, particularly by lithium-ion batteries. Lithium-ion batteries often contain a cell stack consisting of several individual cells. Batteries with very high capacities, in particular, usually feature wound cells (coils or jellyrolls). These can be produced very quickly and, therefore, at comparatively low cost.

[0004] Wound cell technology is suitable for the construction of both prismatic cells and round cells.

[0005] The cells of a lithium-ion battery are usually an assembly of electrodes and separator foils arranged in the sequence positive electrode / separator / negative electrode. Such individual cells are often manufactured as so-called bi-cells with the possible sequences negative electrode / separator / positive electrode / separator / negative electrode or positive electrode / separator / negative electrode / separator / positive electrode. The electrodes typically comprise metallic current collectors, which are usually in the form of flat structures.

[0006] Typically, the described cells for lithium-ion batteries are produced in a multi-stage process. Such processes are known, for example, from DE 102010032770 A1, JP 2013 069637 A, US 2014 / 325833 A1, JP 2014 220113 A, KR 2018 0008451 A, or US 2010 / 0081052 A1.

[0007] In most common processes, the aforementioned electrode foils are produced in a first step and then combined with one or more separator foils to form the aforementioned electrode-separator assemblies. Electrodes and separators are usually bonded together in a lamination step. However, they can also be further processed as a loose assembly.

[0008] To produce the electrode foils, an electrode strip is produced which consists of an electrically conductive collector strip and an electrode material applied to one or both sides thereof. The electrode material is usually applied to the collector strip in the form of a highly viscous mass using a suitable nozzle and / or a doctor blade, with this application of the electrode mass preferably taking place quasi-continuously by guiding the electrode strip along an application station. Typically, edge regions of the collector strip extending in the conveying direction and / or central subregions remain free of electrode material, for example in order to later use these regions, which are referred to as free regions within the meaning of the present invention, as contact regions for arresters or to subsequently cut the electrode strip in the free regions.After the electrode material has been applied, a drying station usually follows, where the carrier solvent escapes from the electrode mass. The remaining dried electrode material is usually permeated with pores, so that compaction usually follows to achieve a higher energy density. This is also described by the term calendering. During compaction, the electrode strip runs through a narrow compaction gap, which is usually formed by two compaction rollers. The force that the edges of this gap, in particular the outer surfaces of the compaction rollers, exert on the electrode material arranged on the collector strip leads to the intended increase in the density of the electrode material and the achievable energy density of the battery produced from it.

[0009] However, the force exerted by the compression gap not only leads to the compression of the electrode material, but also causes a compressive deformation of the collector strip, which is elongated by the compression orthogonally to the plane of the collector strip in the conveying direction and also transversely to it.

[0010] However, in the aforementioned free areas where no electrode material is applied to the collector strip, this deformation of the collector strip does not occur, since the absence of electrode material means that no pressure is exerted on the collector strip by the compaction gap. The uneven deformation of the collector strip in the coated areas and the free areas can lead to the deformation of the collector strip as a whole. In the edge-side free areas, warping and rippling can occur, or such edge-side free areas can bend upwards as a whole relative to adjacent areas of the collector strip. This complicates handling of the electrode strip during subsequent process steps.

[0011] From JP 2014-220113 A, it is known to provide a device for expanding the exposed areas before and after compaction. From DE 102011088824 A1, it is also already known in principle to adapt the uncoated exposed areas of collector strips to the coated area through a forming process. EP 2637238 B1 discloses the use of heat to treat the exposed areas. TASK AND SOLUTION

[0012] The object of the invention is to provide a method for compacting the electrode material that allows deformation of the electrode strip as a whole to be reduced or completely prevented. The method is defined in claim 1, and a corresponding compaction device is defined in claim 8.

[0013] According to the invention, a method for compacting electrode material applied to a collector strip is proposed, which serves the purpose of compacting electrode material which is applied to a collector strip and together with this forms an electrode strip as a partial element of a later battery, wherein the electrode material is applied to the collector strip on at least one side and wherein on this side at least one strip-shaped free area extending in a longitudinal direction of the collector strip is free of electrode material.

[0014] The electrode strip is guided through a compaction gap in a conveying direction parallel to the longitudinal direction of the electrode strip, which compacts the electrode material. As already mentioned above, this compaction gap is preferably defined by two compaction rollers spaced apart by a distance less than the thickness of the electrode strip with the applied and optionally dried electrode material.

[0015] To compensate for the deformation in the collector belt caused by the compression gap, the at least one free area is also subjected to a force in the longitudinal direction, thereby causing the collector belt to stretch in the free area. According to the invention, this is achieved by applying a force to the collector belt downstream of the compression gap in the conveying direction by means of at least one conveyor roller acting on the free area, and simultaneously holding the collector belt back in the conveying direction upstream of the compression gap by a braking device acting on the free area, so that the collector belt is subjected to tensile stress in the free area between the braking device and the conveyor device, thereby causing plastic stretching in the longitudinal direction in the free area.

[0016] While the area of ​​the collector strip coated with electrode material is deformed by the compaction gap, in particular the compaction rollers forming it, a corresponding deformation is generated in parallel in at least one free area by generating a force acting in the conveying direction, which here causes a plastic deformation.

[0017] This is achieved by stretching the section between the braking device in front of the compaction gap and the conveying device behind the compaction gap due to the respective braking force and conveying force. The braking device and the conveying device are adapted to the effect of the compactor rollers in such a way that the free areas and the areas provided with electrode material are elongated approximately equally in the longitudinal direction. In particular, the braking device and the conveying device are preferably each provided with at least one braking roller or conveying roller, which each act selectively on the collector belt in the free area, with the conveying roller in particular conveying faster than the braking roller, so that the desired tension for achieving the plastic elongation of the free area is brought about and permanently maintained.

[0018] The aforementioned adjustment of the conveying device and / or the braking device can be carried out once when setting up the process or can also be subject to dynamic and, in particular, automated adjustments, as will be explained below.

[0019] The tension induced in the free areas according to the invention can not only cause the described plastic strain. It has also been determined that the stress state results in the deformation of the collector strip caused by the compression gap occurring to a greater extent in the conveying direction and to a lesser extent transversely to it. This also promotes the largely uniform plastic deformation of the compacted electrode strip, which is caused by the compression gap on the one hand and by the braking device and the conveying device on the other.

[0020] According to the invention, the tension in the collector belt caused by the braking device and the conveyor in the free area between the braking device and the conveyor in the conveying direction should be sufficiently high to cause plastic expansion of the free area in the conveying direction. The generated tension should be at least 40 MPa for aluminum belts. However, depending on the material, higher tension values ​​are required to reach the elastic yield point and thus achieve the desired plastic deformation.

[0021] Depending on the type of conveyor technology, conveying the electrode strip as a whole can cause a stress state in the conveying direction across its entire width, i.e., even in the areas coated with electrode material. However, this must be distinguished from the stress state created according to the invention in at least one free area between the braking device and the conveyor device, whose stress is preferably at least 20% higher than the stress in the conveying direction in the area of ​​the collector strip coated with electrode material.

[0022] The described compaction serves the particular purpose of reducing the porosity of the electrode material. Particularly when this material has been applied to the collector strip in the form of a solvent-containing paste and has been largely freed of solvent by drying, the aforementioned pores remain, which are reduced by compaction. Preferably, the compaction gap reduces the porosity of the electrode material from more than 40% before the compaction gap to less than 40% after the compaction gap. Particularly preferably, the porosity of the electrode material before the compaction gap is more than 50% and after the compaction gap is less than 30%.

[0023] The process preferably takes place quasi-continuously, with an electrode strip length of at least a few meters, preferably at least 10 meters, and particularly preferably at least 100 meters. The electrode strip is preferably conveyed through the compaction gap at a speed of more than 1 m / min and / or at a speed of less than 100 m / min, with the speed particularly preferably being between 10 m / min and 50 m / min. The stated speeds refer to the feeding of the electrode strip upstream of the compaction device.

[0024] It may also be expedient for the electrode strip to be at least partially heated by a heating device upstream of the braking device, at the braking device, and / or between the braking device and the conveyor device, in order to thereby lower the yield strength of the collector strip material. Heating preferably takes place to a temperature between 20°C and 200°C, particularly preferably to a temperature greater than 30°C and / or a temperature less than 120°C.

[0025] The heating device can be implemented by heating an external heating element, whereby, in particular, a part of the braking device, and in particular a brake roller of the braking device, can be heated to indirectly heat the collector strip in the open area. Inductive heating of the collector strip is also possible.

[0026] The collector strip treated by the method according to the invention must be an electrically conductive strip, as it is intended to enable the flow of current between the electrode material and a conductor during battery operation. The collector strip is preferably designed as a metallic collector strip. If the collector strip is intended for a cathode, it is preferably made of aluminum or an aluminum alloy. In this case, it preferably has an initial thickness of 8 µm to 20 µm, in particular of 8 µm to 12 µm. The thickness of 8 µm to 12 µm is below the previously customary thicknesses in known compaction processes for electrode strips with a free area, in which greater thicknesses were used to reduce the tendency of the collector strip to undesired deformation.However, the process according to the invention also allows the use of such smaller starting thicknesses, which increases the energy density of the batteries produced thereby. If the collector strip is intended for an anode, it is preferably made of copper or nickel, or a copper alloy or a nickel alloy. In this case, the starting thickness is preferably in the range of 3 µm to 12 µm, in particular 3 µm to 5 µm, which is also smaller than the previously usual thicknesses.

[0027] The electrode material provided on the collector strip is preferably in the form of a layer containing electrochemically active particles, with at least one electrode binder and / or a conductive additive, in particular carbon black, graphite, carbon nanotubes, or other conductive carbon materials, preferably additionally being part of the electrode material. Upon application, solvent is usually still present, which, however, is largely evaporated after drying, preferably prior to compaction.

[0028] The width of the collector strip depends largely on the type of subsequent use. Widths in the range of 50 mm to 2400 mm are generally suitable. Smaller widths in the range of 50 mm can be useful if the collector strip is used directly for a battery winding without a subsequent longitudinal cutting process. Larger widths are particularly used when, after compaction, a plurality of strips are to be formed by longitudinal cuts, or when sections are to be cut out by a cutting process, particularly to form an electrode stack.

[0029] The described method is preferably part of a method for producing a battery. This battery manufacturing method involves first producing an electrode strip by applying electrode material to one or both sides of a collector strip.

[0030] After the electrode material is applied in the form of a highly viscous paste, in particular through a slotted nozzle, a drying step can follow, during which the electrode strip is preferably continuously conveyed through a drying system in which solvent is removed from the paste by heat, so that a largely dry layer remains.

[0031] The electrode material is then compacted using the process described above.

[0032] The electrode strip with the dry and compacted electrode material is then formed into the shape required for a battery, for example by winding or stacking, if necessary after a prior cutting process.

[0033] In this form, it is then inserted into a battery housing, with the collector strip or a section cut out of it being galvanically connected to at least one external conductor area of ​​the battery housing. The galvanic connection can be made, in particular, in an area of ​​the collector strip that formed one of the free areas in the previously described process.

[0034] The invention also encompasses a compaction device for compacting electrode material applied to a collector strip, in particular by means of the aforementioned method. Features described with regard to the method and relating to structural elements of the compaction device are accordingly preferably also provided in the compaction device according to the invention. Likewise, the described method according to the invention preferably utilizes a device configured according to the features described below or having at least some of these features.

[0035] According to the described method, the compaction device according to the invention serves the purpose of compacting electrode material which is applied to a collector strip and together with the latter forms an electrode strip, wherein the electrode material is applied to the collector strip on at least one side and wherein on this side at least one strip-shaped free area extending in a longitudinal direction is free of electrode material.

[0036] The compaction device has a conveyor line for conveying the electrode strip in a direction parallel to the longitudinal direction of the electrode strip. The conveyor system can transport the strip via rollers, optionally driven rollers. It is also conceivable for the drive to be provided by an automatic winding machine located downstream of the compaction device.

[0037] The compaction device according to the invention has a compaction gap through which the conveyor line runs and which is bordered on at least one side by a compaction roller, preferably by a compaction roller on each side. This compaction gap serves to compact the electrode material of the electrode strip running through the compaction gap. Their spacing is preferably adjustable in order to be able to compact different types of electrode strips.

[0038] According to the invention, the compaction device has a braking device upstream of the compaction gap in the conveying direction and a conveying device downstream of the compaction gap in the conveying direction. The conveying device has at least one conveyor roller for driving the electrode strip in at least one free area. The braking device is designed to apply a braking force to the free area, so that the conveying device and the braking device are jointly capable of selectively generating plastic longitudinal expansion in the free area between them.

[0039] According to the invention, the conveying device is achieved with a conveyor roller for generating a force acting in the conveying direction and a tension state in the free area. The braking device, which allows the tension state to build up by holding back the collector belt, does not need to have a corresponding roller. Instead, the braking device could, for example, also have brake shoes on both sides of the collector belt, in particular with a surface that prevents static friction, such as a felt surface.

[0040] In practice, however, it is considered the best design if the braking device also has at least one brake roller. This at least one brake roller is designed to allow the tension to build up in the conveying direction by holding the collector belt back in at least one free area. In the simplest case, an electrical or mechanical brake is assigned to the at least one brake roller. A mechanical brake can be designed in a way that is known from vehicles, i.e. in particular in the form of a shoe brake, drum brake or disc brake, with the brake usually being controlled by an electrical actuator. An electric brake can in particular be designed in the form of an eddy current brake or a magnetic brake.

[0041] As an alternative to a brake of this type, the at least one brake roller can also be equipped with a drive motor, provided that this is capable of withstanding the tensile force exerted by the conveyor system in the collector belt in at least one free area. Servomotors or synchronous motors are particularly suitable for this purpose.

[0042] The braking device preferably has at least two brake rollers arranged above and below the free area, which press against each other on the free area of ​​the electrode strip. The electrode strip is thus guided between two such brake rollers. Provision can be made for at least one of these two rollers to be equipped with a brake, while the other merely brakes passively. It is also conceivable for both brake rollers to be equipped with brakes, in particular by driving the two brake rollers by separate drive motors, wherein the drive motors enable a tensile stress to be generated in the free area in the manner described above.

[0043] The braking device is preferably designed such that it has at least two brake rollers above or below the electrode strip, which are positioned corresponding to two different and mutually parallel free areas of the electrode strip. If more than two free areas are provided, preferably as many brake rollers are provided on the top side and / or bottom side as there are free areas on the electrode strip.

[0044] These brake rollers, assigned to the various free areas above or below the electrode strip, can be arranged coaxially to rotate with each other. This can facilitate driving the brake rollers using a common drive motor; however, even if the brake rollers are not arranged coaxially, they can be connected to the output shaft of a common electric motor via a gear. Furthermore, a design is also possible in which several brake rollers on the same side of the electrode strip are driven by several drive motors. This allows for varying degrees of braking action for the different free areas, thus achieving the optimal braking effect for each free area.

[0045] Regarding the arrangement of the conveyor rollers, which are located behind the compaction gap in the conveying direction, the same applies as for the brake rollers. The conveyor system can also have at least two conveyor rollers, arranged above and below the free area, which press against each other on the free area of ​​the electrode strip, so that the free area between the two conveyor rollers is guided and driven. As with the brake rollers, a common drive motor can drive both conveyor rollers, or a separate drive motor can be provided for each. It is also possible for only one of the conveyor rollers to be driven, while its counterpart rolls passively.Furthermore, in the case of more than one free area on one side of the electrode strip, the conveyor device is also provided with at least two conveyor rollers above or below the electrode strip, which are positioned according to the respective free areas of the electrode strip and are preferably arranged coaxially. The conveyor rollers can be driven by a common drive motor or have separate drive motors to generate an individual drive force and, consequently, an individual tensile stress for each free area.

[0046] The conveyor rollers and brake rollers themselves can be made of various materials. Of particular importance is that they are suitable for ensuring slip-free or low-slip contact with the free area of ​​the electrode strip, so that the braking or driving effect is precisely controlled. In particular, the rollers can have an outer surface that comes into contact with the electrode strip, which is made of a metallic material, plastic, ceramic material, or elastomer material, or of a composite material made of a metallic material, plastic, ceramic material, or elastomer material.

[0047] In order to be able to reduce the yield strength in the free region, a heating device is preferably provided which is arranged on the braking device, in front of the braking device or between the braking device and the conveyor device and which is suitable for heating the electrode strip at least in a free region. This can be a resistance heating device which heats the electrode strip indirectly, wherein it is particularly also possible to arrange the heating device in such a way that it heats part of the braking device and in particular a brake roller of the braking device, so that the collector strip is indirectly heated in the free region. Another possibility, however, is to use an inductive heating device which directly inductively heats the collector strip.

[0048] The inventive design with conveyor device and braking device allows the tension and resulting elongation in one or more free areas to be precisely adjusted and adapted to the lengthening effect of the compaction gap on the coated area of ​​the collector belt by targeted configuration of the respective conveying speed or the conveying speed of the conveyor device and the braking effect of the braking device.

[0049] This adjustment can be made manually and once for one or more electrode strips. However, a configuration of the compaction device can also be provided that allows automatic or semi-automatic adjustment, in particular also a control system that adapts the respective parameters on a case-by-case basis during operation. For this purpose, a configuration is considered particularly advantageous in which the compaction device has a detection and control device designed to detect the shape of the electrode strip and, in response to the detected shape, to control the conveying device and / or the braking device and / or the heating device.

[0050] Such a control device has outputs that are connected to the drive motors of the drive and / or the drive motors or brakes of the braking device and can thus control their respective operating parameters, in particular the drive speed or the braking effect. Such a control device can also be provided without an additional detection device in order to be able to use changing parameter sets for operation. However, it is particularly advantageous to combine it with a detection device that examines the electrode strip beyond the drive device or between the drive device and the braking device and, depending on this, changes process parameters by means of the control device, in particular the drive torque or the drive speed of the driving motors. It is considered particularly advantageous if the detection device has at least one camera that examines the shape of the electrode strip.The camera image can be evaluated using pattern recognition, whereby in the simplest case the inclination of the collector belt, whereby the edge-side free areas bend upwards, is interpreted as an indication of insufficient elongation, and the tendency of waviness in the edge-side free areas is interpreted as an indication of excessive elongation. The braking and / or conveying effect of the drive device and the braking device can be adjusted accordingly in order to achieve a greater or lesser stretching of the free areas. Instead of evaluating a camera image, a similar process can also be achieved using a detection device that measures the distance to the free areas, for example using a laser beam, and if necessary using the control device to evaluate the shape of the free areas behind the conveyor device from the results of this distance measurement.

[0051] During operation, an electrode band is located in the compaction device, which is designed according to the above description.

[0052] The compaction device is preferably designed such that it can be adapted to different electrode bands and in particular to different arrangements of free areas.

[0053] For this purpose, it is advantageous if the conveyor rollers and / or brake rollers are movable relative to the compaction gap in a transverse direction orthogonal to the conveying direction and can be fixed in defined positions relative to the transverse direction. It may also be useful to provide conveyor rollers and / or brake rollers that can be attached on a case-by-case basis to allow adaptation of the compaction device to different configurations of the free areas of the electrode strip. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Further advantages and aspects of the invention emerge from the claims and from the following description of preferred embodiments of the invention, which are explained below with reference to the figures. Fig. 1 illustrates the problem underlying the invention, the deformation of the collector strip during the compaction of the electrode material of an electrode strip. Fig. 2A und 2B clearly show the effect of compaction on the collector belt. Fig. 3 shows a compaction device according to the invention in an overall view. Fig. 4A bis 4D show different configurations of brake rollers of a compaction device according to the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] Fig. 1 and 2A and 2B show the basic problem underlying the invention.

[0056] An electrode strip 100 comprises a metallic collector strip 110, on which electrode material is applied on both sides, forming a central strip on the top and bottom sides. On both sides of this, the edge-side free areas 112 of the collector strip 110 are free of electrode material. To achieve a high energy density of a battery, the electrode strip 100 is transported in the direction of arrow 2 within the framework of a continuous process and is guided through a compression gap 20 formed by two compaction rollers 22. This results in a compression of the electrode material 120, as can be seen from the comparison of the Fig. 2A und 2B is evident.

[0057] It is almost impossible to avoid the compaction not only affecting the electrode material 120, but also leading to a compression of the collector belt 110 transversely to its direction of extension. The collector belt 110 is therefore plastically deformed in its main plane of extension in the conveying direction 2 and transversely thereto. However, deformation of the free areas 112 does not occur, since the compactor rollers 22 do not exert any force on the free areas 112. Fig 2B illustrates the compression of the collector strip 110 in the area of ​​the electrode material 120.

[0058] The result is the Fig. 1 The deformation of the free areas 112 is shown as an example to the right of the compactor rollers 22. This complicates further processing of the collector strip, for example, welding of down conductor connections in the free area 112.

[0059] The Fig. 3 A compaction device according to the invention can be seen. In this device, a braking device 40 is provided upstream of the compaction gap 20, and a conveyor device 60 is provided downstream of the compactor rollers 22. The braking device and the conveyor device each have four braking rollers 42 and conveyor rollers 62, respectively, with one conveyor roller 62 being provided above and one conveyor roller 62 below the collector belt 110 in each of the two edge-side free areas 112. The same applies to the braking rollers 42.

[0060] The conveyor rollers 62 and the brake rollers 42 are each driven by drive motors, with one drive motor 64A, 64B being provided for each of the conveyor rollers above and below the electrode strip 100 in the present embodiment. Likewise, two drive motors 44A, 44B are also assigned to the brake rollers 42, with one of the drive motors for the brake rollers 42 being arranged above the electrode strip and one drive motor for the brake rollers 42 being arranged below the electrode strip.

[0061] The conveyor rollers 62 and the brake rollers 42 are driven at slightly different speeds. For example, the speed of the conveyor rollers 62 can be 0.5% higher than that of the brake rollers 42. The speed of the conveyor rollers is adjusted to the elongation of the collector strip in the area coated with electrode material 120.

[0062] The combination of the braking effect of the slower-operating brake rollers 42 and the conveying effect of the faster-operating conveyor rollers 62 causes a section 112' of the free area 112 between the braking device 40 and the conveyor device 60 to be mechanically tensioned. By appropriately adjusting the respective speeds or the respective conveying torques and braking torques, a stress state is achieved in the free areas 112, which leads to plastic strain in the conveying direction 2 in the hatched section 112'.

[0063] In the present exemplary embodiment, two cameras 82 are additionally directed at the electrode belt 100, thereby capturing the two free areas 112 behind the compaction device. A control device 80 evaluates the captured images and controls the drive motors 44A, 44B, 64A, 64B depending on the result. For this purpose, the control device 80 is designed such that it can detect the effects occurring in the free areas 112 due to excessive or insufficient stretching of the free areas 112. Insufficient stretching usually manifests itself in the free areas 112 becoming approximately orthogonal to the electrode material 120. Excessive stretching of the free areas leads to waviness of the edges of the collector belt 110. If such an effect is detected, the conveying torques on the conveyor rollers 62 and / or the braking torques on the braking rollers 42 are adjusted accordingly.

[0064] In a variant not shown, different drive motors are provided for the left and right conveyor rollers or brake rollers, respectively. This allows for the appropriate correction of even asymmetrical errors in the edge-side free areas 112.

[0065] Fig. 4A shows in a partially sectioned view the arrangement of brake rollers 42, which press on the collector strip 110 from above and below in the free areas 112 and are thus able to release only so much of the electrode strip 100 that the desired voltage state occurs in the section 112'. Fig. 4A It can also be seen in a simplified representation that the brake rollers 42 as well as the conveyor rollers 62 are preferably adjustable with regard to their position on their respective drive shaft 45. In the very simple design according to Fig. 4A For this purpose, the drive shafts 45 are provided with a thread 46, and the brake rollers 42 can be attached to the drive shafts 45 at a variable location using nuts 48. In this way, the compaction device can be adapted to different configurations of electrode strips.

[0066] The Fig. 4B und 4C illustrate slightly adapted designs in which the brake rollers 42 are provided with curves 42C or chamfers in the transition area between their end faces 42B and their lateral surfaces 42A. It has been found that the use of such brake rollers 42 is advantageous, since this allows the electrode material 120 to be influenced at the edges in order to achieve the most uniform distribution possible on the collector strip and thereby also to produce a largely uniform effect of the compression gap 20 on the deformation of the collector strip 110.

[0067] In the design according to Figure 4D, it is provided that a lateral surface 42A of the brake rollers 42 is not completely cylindrical, but has a slight conical shape, whereby, in contrast to the design of the brake rollers 42, which is shown somewhat exaggerated for clarity, Fig. 4C Despite the conical section-shaped lateral surface 42A, it rests completely against the free area 112 of the collector belt 110. It has been found that this conical shape promotes the deformation of the collector belt 110 caused by the compression gap to a greater extent in the conveying direction 2 and not transversely thereto.

Claims

1. Method for compressing electrode material (120) applied to a collector tape (110), with the following features: a. the method serves the purpose of compressing electrode material (120) which has been applied to a collector tape (110) and together with it forms an electrode tape (100), wherein the electrode material (120) has been applied to the collector tape at least on one side and wherein on this side at least one free area (112) which is in the form of a strip and extends in a longitudinal direction of the collector tape is free from electrode material (120), and b. the electrode tape is guided in a conveying direction (2), which is parallel to the longitudinal direction of the electrode tape, through a compression gap (20), which brings about a compression of the electrode material (120), and c. force is applied in the longitudinal direction to the at least one free area (112) in order in this way to bring about a stretching of the collector tape in the free area, characterized by the following feature: d. the stretching of the collector tape (110) in the at least one free area (112) in the longitudinal direction takes place by force being applied to the collector tape downstream of the compression gap (20) in the conveying direction (2) by means of at least one conveying roller (62), selectively acting on the free area, and the collector tape simultaneously being restrained upstream of the compression gap (20) in the conveying direction by at least one braking roller (42) of a braking device (40), selectively acting on the free area (112), such that the collector tape (110) is subjected to tensile stress in the free area (112) between the braking device (40) and the conveying device (50) and a plastic strain in the longitudinal direction is thereby brought about in the free area (112).

2. Method according to Claim 1, with the following additional feature: a. the stress in the collector tape (110) that is brought about by the braking device and the conveying device in the free area between the braking device (40) and the conveying device (50) in the conveying direction (2) is at least 40 MPa, preferably with the additional feature: b. the stress in the collector tape (110) that is brought about by the braking device and the conveying device in the free area between the braking device (40) and the conveying device (50) in the conveying direction (2) is at least 20% higher than the state of stress in the conveying direction (2) in the area of the collector tape (110) that is coated with electrode material.

3. Method according to Claim 1 or 2, with at least one of the following additional features: a. the porosity of the electrode material (120) is reduced by the compression gap (20), preferably from more than 40% upstream of the compression gap (20) to less than 40% downstream of the compression gap (20), and / or b. the electrode tape (100) is conveyed through the compression gap (20) at a speed of more than 1 m / min and / or at a speed of less than 100 m / min, preferably at a speed between 10 m / min and 50 m / min.

4. Method according to one of Claims 1 to 3, with the following additional feature: a. the electrode tape (100) is at least partially heated by means of a heating device (30) upstream of the braking device (40) and / or between the braking device (40) and the conveying device (50), preferably to a temperature between 20°C and 200°C, particularly preferably to a temperature greater than 30°C and / or a temperature less than 120°C, preferably with the following additional feature: b. the heating device is designed for heating part of the braking device, and in particular a braking roller of the braking device, such that the collector tape (110) is thereby indirectly heated in the free area (112).

5. Method according to one of Claims 1 to 4, with at least one of the following additional features: a. the collector tape (110) is formed as a metal collector tape (110), and / or b. the electrode material (120) takes the form of a layer with electrochemically active particles, which preferably additionally comprises at least one electrode binder and / or a conductive additive, in particular carbon black, graphite or carbon nanotubes, and / or c. the at least one free area (112) forms a peripheral free area (112) at one of the side edges of the collector tape (110), wherein a peripheral free area (112) is preferably provided at both side edges of the collector tape (110), and / or d. the collector tape (110) is formed as a collector tape of aluminium or an aluminium alloy and preferably has a starting thickness of 8 µm to 12 µm, or e. the collector tape (110) is formed as a collector tape of copper or nickel or a copper alloy or a nickel alloy and preferably has a starting thickness of 3 µm to 5 µm, or f. the collector tape (110) has a width between 50 mm and 2400 mm, and / or g. the at least one free area (112) has a width in the transverse direction of at least 5 mm.

6. Method for producing a battery, with the following features: a. at least one electrode tape (100) is produced by electrode material (120) being applied to one or both sides of a collector tape (110), and b. the electrode material (120) applied to the collector tape (110) is compressed, and c. the electrode tape (100) or a subportion of the electrode tape (100) is inserted into a battery housing, wherein the collector tape (110) is galvanically connected to at least one outer collector area of the battery housing, characterized by the following feature: d. the compression of the electrode material (120) on the collector tape (110) takes place by means of the method according to one of Claims 1 to 5.

7. Method according to Claim 6, with at least one of the following features: a. the application of the electrode material (120) takes place in the form of a highly viscous electrode paste, wherein a drying step is provided after application of the electrode paste and before the compression, and / or b. the electrode tape is introduced into the battery housing in the form of a coil which is produced by winding it or a subportion of it, or c. the electrode tape is introduced into the battery housing in the form of a stack which is produced by cutting out subportions from it and stacking them.

8. Compression device for compressing electrode material (120) applied to a collector tape (110), with the following features: a. the compression device serves the purpose of compressing electrode material (120) which has been applied to a collector tape (110) and together with it forms an electrode tape (100), wherein the electrode material (120) has been applied to the collector tape (110) at least on one side and wherein on this side at least one free area (112) which is in the form of a strip and extends in a longitudinal direction is free from electrode material (120), and b. the compression device has a conveying section for conveying the electrode tape (100) in the direction of a conveying direction (2) parallel to the longitudinal direction of the electrode tape (100), and c. the compression device has a compression gap (20), through which the conveying section runs and which is bounded at least on one side by a compressor roller (22) for the compression of the electrode material (120) of the electrode tape (100) running through the compression gap (20), characterized by the following features: d. the compression device has a braking device (40) upstream of the compression gap (20) in the conveying direction (2) and a conveying device (60) downstream of the compression gap (20) in the conveying direction (2), and e. the conveying device (60) has at least one conveying roller (62), which selectively acts on the at least one free area and is intended for driving the electrode tape (100) in the at least one free area (112), and the braking device (40) has a braking roller (62), which selectively acts on the free area and is designed for making a braking force act on the free area (112), such that the conveying device (60) and the braking device (40) are together capable of producing between them a plastic strain in the longitudinal direction in the free area (112).

9. Compression device according to Claim 8, with the following additional feature: a. the braking device (40) has at least one braking roller (42) for braking the electrode tape, preferably with at least one of the following features: b. the at least one braking roller (42) is assigned an electrical or mechanical brake, or c. the at least one braking roller (42) is provided with a drive motor.

10. Compression device according to Claim 9, with at least one of the following additional features: a. the braking device (40) has at least two braking rollers (42), which are arranged above and below the free area (112) and, directed towards one another, press onto the free area (112) of the electrode tape (100), wherein the two braking rollers (42) are preferably driven by means of separate drive motors (44A, 44B), and / or b. the braking device has at least two braking rollers (42) above or below the electrode tape (100), which are positioned to correspond to two different, mutually parallel free areas (112) of the electrode tape (100), wherein the two braking rollers (42) are preferably driven by a common drive motor or by separate drive motors, and / or c. the braking rollers (42) have an outer side which comes into contact with the electrode tape (100) and consists of a metal material, of plastic, of a ceramic material or an elastomer material or is of a composite material comprising a metal material, plastic, a ceramic material or an elastomer material.

11. Compression device according to one of Claims 8 to 10, with at least one of the following additional features: a. the conveying device (60) has at least two conveying rollers (62), which are arranged above and below the free area (112) and, directed towards one another, press onto the free area (112) of the electrode tape (100), wherein the two conveying rollers (62) are preferably driven by means of separate drive motors (64A, 64B), and / or b. the conveying device (60) has at least two conveying rollers (62) above or below the electrode tape (100), which are positioned to correspond to two different, mutually parallel free areas (112) of the electrode tape (100), wherein the two conveying rollers (62) are preferably driven by a common drive motor or by separate drive motors, and / or c. the conveying rollers (62) have an outer side which comes into contact with the electrode tape (100) and consists of a metal material, of plastic, of a ceramic material or an elastomer material or is of a composite material comprising a metal material, plastic, a ceramic material or an elastomer material.

12. Compression device according to one of Claims 8 to 11, with the following additional feature: a. a heating device (30) is provided, arranged on the braking device (40), upstream of the braking device (40) or between the braking device (40) and the conveying device (60) and suitable for heating the electrode tape (100) at least in a free area (112), preferably with the following additional feature: b. the heating device is designed for heating part of the braking device, and in particular a braking roller of the braking device, such that the collector tape (110) is thereby indirectly heated in the free area (112).

13. Compression device according to one of Claims 8 to 12, with the following additional feature: a. a detection and control device (80) is provided, designed for detecting the shaping of the electrode tape (100) and, in response to the detected shaping, controlling the conveying device (60) and / or the braking device (40) and / or the heating device (30), preferably with the additional feature: b. the detection and control device (80) has at least one camera (82) for detecting the shaping of the electrode tape (100).

14. Compression device according to one of Claims 8 to 13, with the following further feature: a. placed in the compression device is an electrode tape (100), which has a collector tape (110) of a conductive material, in particular of aluminium or copper, and which is provided on at least one side with an electrode material (120), wherein the electrode material (120) has been applied to the collector tape (110) at least on one side and wherein on this side at least one free area (112) which is in the form of a strip and extends in a longitudinal direction is free from electrode material (120).

15. Compression device according to one of Claims 8 to 14, with at least one of the following further features: a. the conveying roller (62) and / or the braking roller (42) is displaceable with respect to the compression gap (20) in relation to a transverse direction orthogonal to the conveying direction (2) and / or conveying rollers (62) and / or braking rollers (42) are provided, placeable on a case-by-case basis to allow an adaptation of the compression device to different configurations of free areas (112) of the electrode tape (100), and / or b. the compression gap (20) is defined by two compressor rollers (22), one of which is arranged below and one above the conveying section.