Current collector arrangement, battery cell for a motor vehicle and method for providing a current collector arrangement

Abstract

Current collector arrangement (10) for a battery cell (14) designed as a cylindrical cell, wherein the current collector arrangement (10) comprises an electrically conductive current collector film (20) having a length (L) and a width (B) perpendicular to the length (L), wherein the current collector film (20) has a collecting area (22) and an edge area (24) adjoining the collecting area (22) in the direction of the width (B) and extending in the direction of the length (L), and which provides a contact area (38) for electrically conductive contact with a current collector surface (36) of the battery cell (14), the current collector film (20) having a fold (42) in the edge area (24) having a first and a second fold end (44, 46), wherein the first fold end (44) directly adjoins the collecting area (22) and the second fold end (46) has a fold over the first fold end (44, 46). Foil edge (48) of the current collector foil (20) includes,wherein the first and the second fold ends (44, 46) are attached to each other, characterized in that the fold (42) is designed as a fold (42) forming an eyelet (40).

Description

[0001] The invention relates to a current collector arrangement for a battery cell designed as a round cell, wherein the current collector arrangement comprises an electrically conductive current collector foil having a length and a width perpendicular to the length, wherein the current collector foil has a collecting region and an edge region adjoining the collecting region in the width direction, which edge region extends in the length direction and which provides a contact region for electrically conductive contact with a current collector surface of the battery cell. Furthermore, the invention also relates to a battery cell with such a current collector arrangement and a method for providing a current collector arrangement.

[0002] Battery cells, such as lithium-ion cells, typically have an interior coil made up of a specific layer sequence. Such a battery cell typically comprises two electrodes, a cathode and an anode, each provided by a current collector foil, on which a corresponding electrode coating is arranged on both sides: an active anode material in the case of the anode and an active cathode material in the case of the cathode. The current collector foil of the anode is typically provided by a copper foil, and that of the cathode is usually provided by an aluminum foil. Furthermore, the anode and cathode are separated from one another by separators. To provide a cell coil, for example, an anode can be provided first, followed by a separator, then a cathode, and then another separator, and this layer sequence can be rolled up to form the cell coil.

[0003] Furthermore, the respective current collector foils of the electrodes are contacted with a current collector surface of the battery cell. Such a current collector surface can be provided, for example, by a part of the cell housing or a disk or something similar. The cell pole taps, via which the cell voltage can be tapped externally, can be provided via these respective current collector surfaces. There are several options for connecting the respective current collector foils to such a current collector surface. Firstly, there are electrodes with a so-called tab. A battery cell then typically has two tabs, one for the cathode and one for the anode. Such a tab represents a type of tab or card that is welded to the corresponding current collector foil, i.e., to the copper foil or the aluminum foil, and protrudes, for example, at the end of the winding.The disadvantage of such cylindrical battery cells with tab electrodes is that electrons can only enter or exit through such a tab. The current collectors of cylindrical battery cells, on the other hand, are very long—up to eight meters in length for some cell types, for example—and therefore the electrical resistance of such tab electrodes is relatively high, especially compared to, for example, prismatic cells. Another disadvantage is that only these tabs are sufficiently thermally connected to the battery casing, but not the copper and aluminum foil in the cell itself. The separators are usually both electrically and thermally insulating.

[0004] However, tableless cells or tableless electrodes are also known from the prior art that do not require such a tab, as described, for example, in US 7,700,222 B2 and US 2020 / 0144676 A1. In this case, the current collector foils themselves have a projecting area, which can provide several such contact points and which can itself be connected to a current collector surface. In other words, a current collector foil can be shaped in the edge area such that it can be mechanically connected directly to a current collector surface. The edge area of ​​such a current collector foil can be divided into several segments by incisions. The areas of the

[0005] Current collector foils are thus electrically connected in parallel. This design reduces electrical and thermal resistance, and can provide a huge reduction in energy losses. This, in turn, leads to less heat generation and a more uniform temperature within the battery cell, which in turn has a positive effect on the cell's service life. A further advantage is that the fast-charging capability of such a battery cell can be improved due to the reduced heat generation. This enables faster charging and shorter charging times for electric cars, for example. Consequently, charging with higher power is possible. The electrical output power is also increased. This enables electric motors with higher power and torque, and better acceleration of the electric car.

[0006] Consequently, such tableless electrodes offer enormous advantages over those with tabs. However, one problem with providing such tableless electrodes is that the current collector foils are typically extremely thin, for example, in the range of 12 micrometers thick. The contact surfaces provided by these foils for contacting the current collector surface are accordingly very sensitive and can be easily damaged by bending, for example. The contact surfaces to the current collector surface should be as flat and large as possible to increase efficiency, but this is not easily achieved due to the sensitive, thin foil ends.

[0007] Furthermore, EP 2 219 248 A1 describes an electrode arrangement in which the current collector foils are provided by a plastic film with a conductive coating on both sides. The ends of these current collector foils are extended from the layer sequence and folded over several times to establish electrically conductive contact between the electrically conductive coatings on the two different sides of the plastic film. These repeatedly folded over ends can then be connected to a contact surface for providing the cell poles, for example, by ultrasonic welding. This process causes the current collector foils to be folded several times, which in turn increases the risk of damage.

[0008] JP H-04 324 248 A describes a battery with a current collector foil having an exposed, folded end.

[0009] GB 1 332 944 A describes an electrode arrangement with a collector foil having a free edge region which is slotted.

[0010] The object of the present invention is therefore to provide a current collector arrangement, a battery cell and a method which enable the most efficient possible bonding of a current collector foil to a current collector surface of a battery cell.

[0011] This object is achieved by a current collector arrangement, a battery cell, and a method having the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description, and the figures.

[0012] A current collector arrangement according to the invention for a battery cell designed as a round cell has an electrically conductive current collector foil which has a length and a width perpendicular to the length. The current collector foil further has a collecting region and an edge region which adjoins the collecting region in the width direction and runs in the length direction and which provides a contact region for electrically conductive contact with a current collector surface of the battery cell. In the edge region, the current collector foil has a fold which forms an eyelet and has a first and a second fold end, wherein the first fold end directly adjoins the collecting region and the second fold end comprises a film edge of the current collector foil folded over the first fold end, wherein the first and second fold ends are fastened to one another.

[0013] This design of the edge region of the current collector foil advantageously provides a contact area for electrically conductive contact with a current collector surface of the battery cell. On the one hand, the contact area, thanks to the fold forming the eyelet, provides a very large contact surface. This contact area also has a high degree of stability. This is because the fold forming the eyelet prevents kinks in the current collector foil, and additional stability is provided by the fastening of the fold ends to one another. The current collector foil can therefore, for example, have a type of drop-shaped loop or bow in the edge region, in particular with a certain minimum bending radius. The current collector foil is therefore bent over in the edge region, but in such a way that a certain minimum bending radius is not undercut. The foil is therefore folded in such a way that no kink occurs in this folding area, but rather a rounded shape.This curve has several advantages. This curve also provides the contact surface through which the electrically conductive contact with the current collector surface of the battery cell is to be established. If this folded area is pressed with its rounded outer side against such a surface, a widening contact surface is created, similar to a drop of water hitting a flat surface. This curve can therefore provide a very large contact surface between the current collector foil and the current collector surface. At the same time, the curve can also minimize the risk of potential damage to the current collector foil, as this curve prevents the foil from kinking, especially in this contact area. By attaching the two folded ends to each other, the fold can be further stabilized.Even during the arrangement of the current collector arrangement on such a current collector surface, it can then advantageously be ensured that areas of the current collector foil, particularly in the edge region, do not slip against each other, and instead the desired widening of the contact area takes place as described above. By widening this contact area, however, not only can a large-area contact be advantageously provided between the cover and the current collector surface, but it can also advantageously be achieved that individual sections of this cover, which lie adjacent to one another in the radial direction, i.e., when the current collector arrangement is in a wound state, also contact each other.Because these respective segments contact each other in a radial direction, contact resistance can be further minimized and the efficiency of the battery cell increased. Furthermore, the advantages mentioned above for such a tableless electrode also apply to this current collector arrangement, which also provides a tableless electrode. In other words, the contact area is also provided by a portion of the current collector foil itself, and not by a contact tab or similar device arranged separately on the foil. For example, the entire edge area along the length of the current collector foil can also be used as the contact area, which minimizes contact resistance and thus maximizes efficiency.

[0014] The current collector foil can further be provided as part of an electrode. Such an electrode can further comprise a corresponding electrode material, for example in the form of a coating, which is preferably arranged on both sides of the current collector foil, in particular in the collecting region of the current collector foil. A part of the current collector foil, namely the edge region, remains free of electrode material, i.e., it has no electrode material coating. In other words, the edge region can represent the uncoated part of the current collector foil, and the collecting region can represent the area of ​​the current collector foil coated on both sides. Furthermore, the current collector foil can be provided both as part of an anode and as a corresponding part of a cathode. Thus, in the first case, the current collector foil can preferably be a copper foil, and in the second case, for example, an aluminum foil.In general, the current collector foil can be formed with a thickness in the range between 10 and 30 micrometers. If the current collector foil is provided as a copper foil, for example, and thus provides the current collector for the anode, it can have a thickness of 12 micrometers, for example. If, on the other hand, the current collector foil is an aluminum foil for providing a current collector for the cathode, it can have a thickness of 22 micrometers, for example. Furthermore, the current collector arrangement is preferably used in a battery cell designed as a round cell. For this application, the current collector arrangement is provided in wound form. It is preferred that the current collector foil, including further layers described below, is wound in the direction of its length.In the wound state, the current collector foil is therefore curved along its length, while it continues to extend essentially in a straight line in the direction of its width. Accordingly, when the current collector arrangement is arranged in a cell housing to provide a round cell, the width of the current collector foil points in the direction of the height of the round cell, which runs essentially parallel to an axis of the round cell and perpendicular to its radial direction. In the wound state of the current collector foil, the length of the foil is therefore curved, for example in a helical shape, and always essentially perpendicular to its width. More precisely, the length of the current collector foil in the wound state of the current collector foil always runs tangential to a radial direction relative to a winding axis of the wound current collector foil, wherein the winding axis runs parallel to the width of the current collector foil.In the unwound state of the current collector foil, it has an essentially rectangular geometry, with a straight length and a perpendicular, straight width.

[0015] In a further advantageous embodiment of the invention, the fold is segmented in the length direction by at least one incision running in the width direction, wherein the at least one incision runs from an edge of the fold facing away from the collecting region in the width direction up to a maximum of a fastening region in which the first and second fold ends are fastened to one another. Such an incision can advantageously simplify the rolling up of the current collector arrangement. Especially if the current collector arrangement is to be used in a round cell, it is preferred for the fold to have numerous such incisions in the length direction. This allows the current collector arrangement and in particular the fold of the current collector foil to be rolled up particularly easily in the length direction.These incisions can advantageously prevent damage to the very thin current collector foil during winding. If the wrap has several such incisions along its length, these can be arranged equidistant from one another along its length, for example. This simplifies production. However, they can also be arranged at different distances from one another. For example, the incisions closer to the center of the winding can be spaced closer together than the incisions in the outer region of the winding. This is due to the fact that the radii of curvature of the wrap are significantly smaller in the center of the winding than in the outer region of the winding. The distances between the incisions can therefore advantageously be dimensioned according to requirements in order to enable simple, damage-free winding of the current collector arrangement.

[0016] In a further particularly advantageous embodiment of the invention, the first and second fold ends are sewn together, i.e., in particular, fastened to one another by at least one seam. To provide the fold, one fold end, namely the second fold end, which also encompasses the open edge of the current collector foil, is folded over the other fold end, i.e., the first fold end. The first fold end, as defined, represents the area of ​​the current collector foil immediately adjacent to the collecting area. These two ends can also be fastened to one another in other ways, for example by welding, or, more preferably, by gluing. For example, these fold ends can also be welded together using ultrasound, although this is comparatively expensive. A better solution is to glue these ends together.However, it is particularly advantageous if these turn-up ends are sewn together. This has numerous advantages: Firstly, sewing is very cost-effective and only minimally increases the price of the assembly and the overall price of a battery cell, which is particularly advantageous when used for a high-voltage battery in an electric vehicle, as such a high-voltage battery usually has a large number of such individual cells. Another particularly large advantage of sewing is that it can provide a very good, mechanically stable structure, so that the sewn-together layers are securely and sufficiently connected to one another. Another very large advantage is that sewing is easy to industrialize, and many experiences from the textile industry can be adopted. In addition, suitable sewing threads are known, which preferably have a diameter around the diameter of a human hair.In other words, the sewing thread has a diameter in the range of 0.02 to 0.08 millimeters, preferably 0.06 millimeters. A material with good mechanical strength, similar to fishing line, such as nylon, polyvinylidene fluoride (PVDV), also known as fluorocarbon, polyethylene, Dyneema, Spectra, Kevlar, to name a few, or even metallic materials such as stainless steel or titanium, can be used as the sewing thread.

[0017] In a further very advantageous embodiment of the invention, the current collector arrangement has at least one first separator for arrangement between an anode and a cathode of the battery cell, wherein the at least one first separator has at least a first region arranged between the first and second folded ends of the current collector foil. Before the current collector arrangement is rolled up, the current collector arrangement can, for example, provide a layer sequence of anode, separator, cathode, separator, wherein the aforementioned first separator can then represent one of the two aforementioned separators and the current collector foil can be part of the anode and / or the cathode, as already described above.

[0018] The first separator can therefore advantageously also protrude beyond the region with the electrode material in the width direction. This has the great advantage that this first separator, i.e. the at least one first region of this separator, can be arranged between the first and second turn-up ends of the turn-up of the current collector foil. This means that this at least one first region of the separator is arranged in the fastening region in which the first and second turn-up ends are fastened to one another. This has the great advantage that, especially in the case of fastening by sewing, greater stability of this arrangement can be provided in the fastening region. Such a separator is electrically non-conductive and, precisely for this purpose, has very good mechanical properties. The separator can therefore simultaneously function as a structural layer in the seam region.The separator can, for example, have a thickness in the range of 10 to 30 micrometers, preferably 20 micrometers. This provides greater stability for the very thin collector foil, especially in this mounting area.

[0019] In a further very advantageous embodiment of the invention, the first separator has a first separator edge region that is arranged at least partially to overlap the edge region of the current collector foil, wherein the first separator edge region of the first separator has a separator fold-over that forms a separator eyelet, runs within the fold-over of the current collector foil, and has a first and a second separator fold-over end, wherein the first and second separator fold-over ends are fastened to one another. This fastening can be carried out in the same way as the fastening of the fold-over ends of the current collector foil. In other words, both the separator fold-over ends and the fold-over ends of the current collector foil can be fastened to one another with one and the same seam.The separator can therefore be arranged as a layer over the edge region of the current collector foil and folded over together with this current collector foil to form a fold-over with an eyelet, in such a way that the separator fold-over is then located within the fold-over of the current collector foil. This means, for example, that in the fastening area, two separator layers are arranged between the fold-over ends of the current collector foil. This design, in turn, has several advantages. In addition, the stability in the fastening area can be further increased, since by folding the separator end between the fold-over ends of the separator foil, a double separator layer is provided. In addition, the fold-over of the current collector foil is formed around the fold-over of the separator, thus also providing more stability for the fold-over of the current collector foil.The overall wall thickness in the envelope area can be at least doubled, for example. This provides significantly more stability, especially in the contact area. In other words, the separator envelope stabilizes the envelope of the current collector foil from the inside.

[0020] In a further very advantageous embodiment of the invention, the current collector arrangement has a second separator for arrangement between an anode and a cathode of the battery cell, wherein the at least one second separator has a second region which, together with the at least one first region of the first separator, is arranged between the first and second folded ends of the fold of the current collector foil. In other words, the second separator can also be used to stabilize at least the fastening region. For example, the first separator, together with the current collector foil, can be folded over in the edge region around this edge region of the second separator. This means that there are three separator layers in the fastening region, for example, two separator layers that are assigned to the first separator and one layer that is assigned to the second separator.Alternatively, the second separator can also be designed such that it too forms a fold in the edge region providing an eyelet. In other words, both the first and the second separator can be arranged at least partially overlapping the current collector foil in the edge region, and this layer arrangement can be folded over, for example so that four separator layers are located in the fastening region between the fold-over ends of the current collector foil. These two separators can therefore provide additional stability, especially in the contact area of ​​the current collector foil. The two fold-over areas of the respective separators can have different fold-over radii and, for example, can also be designed so that they do not lie adjacent to one another in some areas. The separators can also be folded over multiple times in order to provide additional separator layers between the fold-over ends of the current collector foil.Depending on the desired thickness and / or stability or requirement, a suitable design can be easily selected and implemented.

[0021] In a further advantageous embodiment, an electrically insulating, deformable strand element extending the length of the current collector foil provided by the foldover, and in particular within the separator eyelet, is arranged at least within the eyelet of the current collector foil, in particular having a substantially circular cross-section in the undeformed state. Such a strand element can be provided, for example, as a type of rubber hose or similar and simplifies the folding of the current collector foil while ensuring a certain minimum bending radius. In other words, kinking of the foil in the foldover area can be prevented even more effectively by such a strand element guided in the eyelet. Nevertheless, appropriate stability to prevent such kinking can also be achieved by the corresponding foldovers of the separators, as described above, for example.

[0022] Furthermore, the invention also relates to a battery cell, in particular a round cell, for a motor vehicle, wherein the battery cell has a current collector arrangement according to the invention or one of its embodiments.

[0023] Such a battery cell is preferably used for a high-voltage battery of a motor vehicle. Accordingly, a high-voltage battery with such a battery cell, as well as a motor vehicle with such a battery cell, in particular with a high-voltage battery comprising at least one such battery cell, are also considered to be part of the invention. The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.

[0024] In an advantageous development of such a battery cell, the battery cell comprises a cell housing and a first current collector surface. The current collector arrangement is rolled up into a coil along the length of the current collector foil and is arranged in the cell housing of the battery cell such that the part of the current collector foil's fold facing away from the collecting area makes surface contact with the current collector surface, and in particular, adjacent segments of the fold in the radial direction of the coil touch each other. This allows contact resistance to be reduced and efficiency to be optimized.

[0025] The battery cell can be designed as already described and, for example, have a first electrode and a second electrode. For example, the first electrode comprises the current collector foil, on which a first electrode layer is arranged in the collecting area, in particular on both sides. The first electrode can, for example, represent an anode or a cathode. The second electrode can also have such a current collector foil, as well as a second electrode layer arranged on the second current collector foil, again preferably on both sides.

[0026] Furthermore, it is possible for both the electrode and the anode to be geometrically similar with regard to providing the corresponding contact area for contacting the corresponding current collector surface, in particular as described within the scope of the invention. In other words, both the anode and the cathode can each be designed as tableless electrodes. However, only one of the two electrodes, preferably the anode, is preferably designed as such a tableless electrode. The reason for this is that the efficiency can be enormously increased by designing it as a tableless electrode. However, the increase in efficiency when the other of the two electrodes is also designed as a tableless electrode is rather small. In other words, designing only one of the two electrodes as a tableless electrode is particularly efficient in terms of cost-benefit ratio. Nevertheless, this is also conceivable.

[0027] Furthermore, it is preferred that the contact area between the current collector surface and the current collector foil wrap is preferably at least 200 micrometers in the radial direction relative to the winding. This provides a very large contact area or surface width, which can significantly reduce the contact resistance. This allows for particularly efficient operation of the battery cell.

[0028] Furthermore, the invention also relates to a method for providing a current collector arrangement for a battery cell designed as a round cell, wherein an electrically conductive current collector foil is provided which has a length and a width perpendicular to the length, wherein the current collector foil has a desired region and an edge region which adjoins the collecting region in the direction of the width and runs in the direction of the length and which provides a contact region for electrically conductive contact with a current collector surface of the battery cell. Furthermore, the current collector foil is folded over in the edge region, so that a fold forming an eyelet is provided in the edge region, which fold has a first fold end which directly borders the collecting region and a second fold end which comprises a film edge of the current collector foil folded over onto the first fold end.Furthermore, the first and second ends of the envelope are attached to each other.

[0029] The advantages described for the current collector arrangement according to the invention and its embodiments apply equally to the method according to the invention.

[0030] The invention also includes further developments of the method according to the invention that have features already described in connection with the further developments of the current collector foil according to the invention. For this reason, the corresponding further developments of the method according to the invention are not described again here.

[0031] The invention also encompasses combinations of the features of the described embodiments. The invention therefore also encompasses implementations that each comprise a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.

[0032] Exemplary embodiments of the invention are described below. Shown are: Fig. 1 is a schematic cross-sectional view of part of a current collector arrangement according to an embodiment of the invention; Fig. 2 a schematic and perspective view of the current collector arrangement of Fig. 1 in an unwound state according to an embodiment of the invention; Fig. 3a is a schematic cross-sectional view of a current collector arrangement according to a further embodiment of the invention; Fig. 3b is a schematic cross-sectional view of a current collector arrangement according to a further embodiment of the invention; Fig. 3c is a schematic cross-sectional view of a current collector arrangement according to a further embodiment of the invention; Fig. 4 a schematic cross-sectional view of a battery cell designed as a round cell with a current collector arrangement according to an embodiment of the invention; Fig. 5 a schematic detailed view of the contacting process of the current collector arrangement with a current collector surface according to an embodiment of the invention; Fig. 6 a schematic and perspective representation of an initial state of the current collector arrangement according to an embodiment of the invention; Fig. 7 a schematic and perspective representation of a pressing process for pressing the separators with the current collector foil according to an embodiment of the invention; Fig. 8 is a schematic representation of the current collector arrangement in the non-folded state of the edge region with incisions made centrally in the separator layers and the current collector foil according to an embodiment of the invention; Fig. 9 a schematic and perspective representation of the application of a strand element according to an embodiment of the invention; Fig. 10 is a schematic cross-sectional view of the handling process according to an embodiment of the invention; Fig. 11 is a schematic cross-sectional view of the current collector arrangement with folded edge region according to an embodiment of the invention; Fig. 12 is a schematic cross-sectional view of the sewing of the layers in the fastening area according to an embodiment of the invention; Fig. 13 is a schematic representation of the winding process of the current collector arrangement according to an embodiment of the invention; and Fig. 14 is a schematic representation of the winding process in a cross-sectional view of the current collector arrangement according to an embodiment of the invention.

[0033] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0034] In the figures, the same reference symbols designate elements with the same function.

[0035] Fig. 1 shows a schematic cross-sectional view of a part of a current collector arrangement 10 according to an embodiment of the invention and Fig. 2 shows a perspective view of this current collector arrangement 10, in particular in the unwound or unrolled state, according to an embodiment of the invention. The current collector arrangement 10 represents a cell winding for a battery cell 14 (see Fig. 4), in particular a battery cell 14 designed as a round cell, wherein the current collector arrangement 10 is shown in Fig. 2 is shown in the unwound state. The current collector arrangement 10 has a first electrode 16, for example an anode, and a second electrode 18, for example a cathode. In this example, the first electrode 16 is designed as the anode and the second electrode 18 as the cathode. However, the examples explained below can also be implemented in the same way if the first electrode 16 represents the cathode and the second electrode 18 represents the anode. The anode 16 has a current collector foil 20, which is designed, for example, as a copper foil with a thickness d1 of, for example, 12 micrometers. This current collector foil 20 further has a collecting region 22, which designates the region of the current collector foil 20 on which an electrode layer 26 is arranged on both sides.This collection area 22 is immediately adjacent to an edge area 24 of the current collector foil 20 in the direction of a width of the current collector foil 20, which extends here in the direction of the z-axis shown. This edge area 24 of the current collector foil 20 represents the part of the current collector foil 20 not coated with the electrode material 26.

[0036] The second electrode 18 also has a current collector foil 28 coated on both sides with an electrode material 30. In the case of the cathode as the second electrode 18, the current collector foil 28 is an aluminum foil, for example, with a thickness d2 in the y-direction of 22 micrometers. The electrode layers 30 of the second electrode 18 can furthermore have a layer thickness in the illustrated y-direction of, for example, 64 micrometers. The electrode layers 26 of the first electrode 16 can each have a layer thickness of, for example, 39 micrometers in the y-direction. In the case of a lithium-ion battery cell 14, the cathode material 30 is provided, for example, by LiFePO4, and the anode material 26 is provided, for example, by LiC6. A first separator 32 is arranged between the first and second electrodes 16. A second separator 34 is also arranged in the y-direction after the second electrode 18.This is also located between the second electrode 18 and the first electrode 16 when the current collector arrangement 10 is in the wound state. In the wound state, in particular, the winding shown in . Fig. 1, or rather the section of the current collector arrangement 10 in the y-direction, continues analogously on both sides. Accordingly, on the right side of the first electrode 16 in Fig. 1 again shows a portion of the second separator 34. The first and second separators 32, 34 are each formed from an electrically non-conductive material. These separators 32, 34 can each have a thickness in the y-direction of, for example, 20 micrometers. Furthermore, they can also be provided as films.

[0037] In this example, the first electrode 16 is advantageously designed as a so-called tableless electrode 16. This means that it does not have a separately manufactured contact lug for connecting the electrode 16 to a current collector surface 36 of the battery cell 14. Instead, the contact area 38 to this current collector surface 36 is provided by the current collector foil 20 itself, in a particularly advantageous manner, as will now be explained in more detail below. For this purpose, the current collector foil 20 has a fold 42 forming an eyelet 40 in the edge area 24. This fold 42 further comprises a first fold end 44, which directly borders the collecting area 22, and a second fold end 46, which comprises a foil edge 48 folded over the first fold end 44. These two fold ends 44, 46 are further advantageously fastened to one another in a fastening area 50, in the present example by sewing them together.A corresponding sewing thread is designated 52. At the same time, regions of the separators 32, 34 are also passed through this fastening region 50 and, on the one hand, stabilize the eyelet 40 provided by the fold 42 and, on the other hand, the fastening 52 itself. In this example, the first separator 32 also has an edge region 54 with a fold 56, which also provides an eyelet 58. The separator fold 56 runs within the fold 42 of the current collector foil 20. Accordingly, the first separator 32 also has two first regions 60, 62, which are located in the fastening region 50 between the two fold ends 44, 46 of the current collector foil 20 and which are fastened to one another.In addition, in this example, a second region 64 of the second separator 34 is inserted between these two first regions 60, 62 of the first separator 32 and is also connected to the remaining regions 60, 62 or turn-up ends 44, 46 of the current collector foil 20. In other words, the two turn-up ends 44, 46, as well as the two first regions 60, 62 of the first separator 32 and the second region 64 of the second separator 34 are sewn together in the fastening region 50 using a common seam and thus fastened to one another. These additional separator layers 60, 62, 64 between the two turn-up ends 44, 46 can provide additional stability for this seam region 50. In addition, the separators 32, 34 are used to stabilize the turn-up area 42 of the current collector foil 20.This advantageously makes it possible to ensure a certain minimum radius of curvature of this current collector foil 20 in the fold-over region 42, thereby preventing kinks and thus reducing the likelihood of damage to the very thin foil 20. Furthermore, in this example, an elastic strand element 66 is guided through the eyelets 40, 58 of the current collector foil 20, as well as of the separator 32, in this example in the x-direction. In the undeformed initial state, this elastic strand element 66 may, for example, have a round cross-section and further inhibit the formation of kinks in the fold-over region 42. This provides additional stability in the contact area 38.In order to establish contact between the current collector foil 20 in this transition region 42 and the current collector surface 36, the transition region 42 can be pressed against this current collector surface 36 with its end 68 providing the contact region 38 during battery cell assembly. The original teardrop shape of this transition region 42, visible in cross-section, as shown, for example, in . Fig. 2, thus flattens on the underside, i.e. in the direction of the current collector surface 36, when pressed, as shown in Fig. 1. This provides a flat contact point between the contact area 38 and the current collector surface 36, which has a width d3 in the y-direction, as shown in Fig. 1, of at least 200 micrometers. Such a large width can advantageously be achieved by the folded region 42 provided according to the invention. This reduces contact resistance, which in turn increases efficiency, reduces waste heat, and enormously increases the overall performance of the battery cell 14. By flattening the folded region 42, it is also possible to ensure that adjacent regions of this folded region 42 touch one another in the radial direction, which here corresponds to the y-direction shown, when the current collector arrangement 10 is in the wound state, as will be illustrated in more detail below. This allows the efficiency to be further increased.

[0038] Fig. Figure 2 schematically shows, as already mentioned, the current collector arrangement 10 in the non-rolled or non-wound state. Also illustrated here are the width B of the current collector arrangement 10 or the current collector foil 20, which extends in the z-direction shown here, and its length L in the x-direction shown, where Fig. 2 only a part of the current collector arrangement 10 is shown in the x-direction and thus only a part of the length L. Furthermore, in Fig. 2 that the fold 42 of the current collector foil 20, as well as the inner separator fold 56, have a plurality of incisions 70 in the direction of length L, which extend in the direction of width from the end 68 of the fold 42 up to a maximum of the fastening area 50. Such incisions 70 can simplify the subsequent winding of the current collector arrangement 10 in the longitudinal direction. The strand element 66 can also be seen in the undeformed state with a round cross-section.

[0039] Although such a strand element 66 is very advantageous, the current collector arrangement 10 can also be provided without such a strand element 66, as is shown, for example, in Fig. 3a, Fig. 3b and Fig. 3c. In particular, further embodiments of the current collector arrangement are illustrated in a schematic cross-sectional view. These can be distinguished by the differences described below, such as Fig. 1 and Fig. 2 described. In Fig. 3a, both the first and the second separator 32, 34 are folded over, i.e., in this example, the second separator 34 also has such a folded area 72, which in turn forms an eyelet 74. This can provide an additional stabilizing effect in the folded area 42 of the film 20, whereby the strand element 66 can be dispensed with. The same also applies to Fig. 3b and Fig. 3c. In addition, the ends 76, 78 of the respective separators 34, 32 are folded over a second time and again guided through the fastening area 50. As a result, there are now six separator layers in the fastening area 50. In the example in Fig. 3c, these ends 76, 78 are additionally guided into the area of ​​the eyelet 40, 58, 74 until they come into contact with the inner side of the second separator 34. This can provide an additional support effect during the contacting process, i.e., when the contact surface 38 is pressed against the current collector surface 36.

[0040] When the contact surface 38 is pressed against the current collector surface 36, the cross-sectional geometry of the cover 42 is deformed, as shown in more detail below. Fig. 4 shows a cross-sectional view of a battery cell 14, which is designed in particular as a round cell, and which comprises the current collector arrangement 10 in the form of a cell coil 12. For this purpose, the battery cell 14 has a housing 80 in which the cell coil 12 is arranged. The cell coil 12 is provided in particular by the current collector arrangement 10, as shown for example in Fig. 2, is rolled up in the direction of its length L and is inserted with the contact surfaces 38 of the wraps 42 first through an upper opening in the cell housing 80. The cell housing 80 has a housing cover 98, which is removable or can be placed and fastened after the cell coil 12 has been inserted into the remaining cell housing 80. Alternatively, it is also possible for this opening to be provided on the underside of the cell housing 80. The terms top and bottom refer to the arrangement of the battery cell 14, as shown in Fig. 4. On the underside of the cell housing 80, the current collector surface 36 is also provided by a current collector plate 82 in the form of a disc. The segmented contact surfaces 38 of the envelope 42 are contacted with this current collector surface 36, while the second current collector foil 28 of the cathode can be connected to a top-side current collector surface 84 of the battery cell 14, although this is not explicitly shown in the present example. This connection can be made, for example, via a tab.

[0041] Fig. 5 shows a detailed view of the contacting process of contacting the contact surfaces 38 with the current collector surface 36 in a cross-sectional view. In particular, the images in Fig. 5 each an excerpt from the one marked A in Fig. 4. In the left picture in Fig. 5, the respective contact surfaces 38 are not yet in contact with the current collector surface 36. If the current collector arrangement 10 is pressed further downwards by a force F, and thus the contact surfaces 38 against the current collector surface 36, the respective turn-up sections 42 and thus also the contact surfaces 38 are deformed, as shown in the right-hand image in Fig. 5. The folds 42 in the edge regions 24 of the current collector arrangement 10 are thus initially drop-shaped in cross-section and flatten on the underside due to the pressing against the current collector surface 36. As a result, the contact surface 38 expands, and in addition, in the final state shown in the right-hand image, the folds 42 of the current collector foil 20 are also in mutual contact with each other, i.e., two folds 42 adjacent in the radial direction. The radial direction a runs in particular perpendicular to the z-axis z shown here and refers to the cell coil 12. The z-axis z corresponds to the rotation axis of this cell coil 12 or to the coil axis. Along with the deformation of the fold 42, as shown in Fig. 5, the fold 56 of the first separator 32 is also deformed, while the end 78 of the second separator 34 serves as a support. In addition, the strand element 66 is also deformed.

[0042] In the following, a method for producing or providing such a current collector arrangement 10 will be described. Fig. 6 is a schematic perspective view of the current collector assembly 10 in the initial state. First, the anode 16, the cathode 18 and the two separators 32, 34 are provided and connected to each other, as shown in Fig. 6, arranged one on top of the other. In this example, the first separator 32 is arranged on the anode 16, the cathode 18 on the first separator 32 and the second separator 34 on the cathode 18. The current collector foil 20 of the anode 16 is coated with electrode material 26 exclusively in the collecting area 22, in particular on both sides, but not in the edge area 24. The edge area 24 can extend further in the width direction or be longer than the collecting area 22. To illustrate the size relationships, Fig. 6 additionally a scale 86 is shown. In Fig. The next process step is shown schematically in Figure 7. The areas of the current collector foil 20 and the separators 32, 34 in the edge region 24 of the foil 20, in particular in the later fastening region 50, are deformed or reshaped, which can be done using rollers 88 or similar. The respective layers, i.e., the current collector foil 20, the first separator 32, and the second separator 34, are pressed together in the later fastening region 50. The following step is shown in Fig. 8, in which the incisions 70 in the form of slots are now introduced into the edge region 24 of the current collector foil 20 and the corresponding layers of the separators 32, 34 lying thereabove in the y-direction. These slots 70 can be introduced, for example, using a laser. In other words, these holes 70, in particular elongated holes, can be cut out, for example, using a laser. In the next step, which is shown in Fig. 9 is schematically illustrated, the strand element 66 is placed on the later folding area. This strand element 66 represents an elastic and / or deformable component, in particular with a round cross-section in the initial state, which can, for example, have a deformability like a sponge or a rubber hose, in particular a solid rubber hose, or can be designed as such. This strand element 66 helps with the later folding and ensures a minimum bending radius of the edge. In the following step, which is Fig. 10 is schematically illustrated in the cross-section of the current collector arrangement 10, the folding of the current collector foil 20 takes place in the edge region 24, whereby the fold 42 is formed in the edge region 24. The folding is illustrated in particular by the arrow 90. In particular, three successive time steps t0, t1, t2 of this folding 90 are shown here. The initial state and thus the earliest time step is designated by t0, a later time step by t1, and another later time step by t2. During this folding 90, the two fold ends 44, 46 of the later-formed fold 42 are placed on top of one another. Fig. 11 shows the fold 42 of the current collector foil 20 with the folded ends 44, 46 placed on top of one another or superimposed on one another. At the same time, a fold 56 of the first separator 32 is also provided. After the fold 90, the end region of the second separator 34, also referred to as the second region 64, as well as the two separator fold ends 60, 62 of the first separator 32, also referred to as the first regions 60, 62, are located in the fastening region 50 between the folded ends 44, 46 of the current collector foil 20 in the fastening region 50.

[0043] Subsequently, the layers of the current collector foil 20 and the first and second separators 32, 34 lying one above the other in the fastening area 50 are fastened to one another, in particular sewn to one another by means of a thread 52, as shown in Fig. 12. To illustrate the sewing process, a needle 92 and a sewing thread 94 are also shown. The sewing process is carried out using a sewing machine. The sewing thread can, for example, have a diameter of 0.06 millimeters, and furthermore, a sewing thread 94 made of a material such as nylon, polyvinylidene fluoride (PVDV), also referred to as fluorocarbon, polyethylene, Dyneema, Spectra, Kevlar, or even a metallic material such as stainless steel or titanium can be used for the seam 52. The sewing can be easily industrialized and is therefore feasible with industrial sewing machines. The state of the current collector assembly 10, which in Fig. 12 corresponds to the representation in Fig. 2.

[0044] The current collector arrangement 10 is then rolled up as shown in Fig. 13 is illustrated. Fig. Figure 13 schematically shows the top view of the current collector arrangement 10 onto the contact surface 38 of the cover 42 during the rolling-up process, which is illustrated by the arrow 96. The notches 70 can also be seen here, of which only a few are provided with a reference symbol for reasons of clarity. This rolling-up process 96 is schematically shown again in a cross-sectional view in Fig. 14, in particular again for three different time steps t3, t4, t5. With each rotation of the winding process 96, the number of layers of the resulting cell coil 12 increases. In the first time step t3, the cell coil 12 has only one rotation and thus only one layer arrangement consisting of anode 16, cathode 18, and the separators 32, 34. In the subsequent time step t4, the cell coil 12 already has two such layer arrangements, in the following time step t5, three layer arrangements, and so on. This process can be continued until the current collector arrangement 10 is completely wound and the desired number of layers of the cell coil 12 is provided. Through this winding process 96, the battery cell or the current collector arrangement 10 ultimately acquires its cylindrical shape in the form of the cell coil 12.Through the incisions 70, also called holes, the edges, i.e., the contact surfaces 38 of the envelope 42, can be bent without damaging, or in particular tearing, the copper foil 20. The cell coil 12 thus prepared, also called a Swiss roll, is then mounted or inserted into the housing 80 of the battery cell 14, as described in . Fig. 4 and Fig. 5 has already been described. Without pressure from above, the edges at the bottom of the contact area 38 are still round and not deformed. After installing the metal cap 98 (see Fig. 4) of the cell housing 80 from above, a stationary pressure force F (compare Fig. 5). This deforms the edges, i.e., the undersides of the folds 42, such that the contact surface 38 with the lower current collector disc 82 and with each other is raised or created. The edges, i.e., the undersides of the folds 42, are then no longer round.

[0045] The current collector arrangement according to the invention and its embodiments advantageously make it possible to reduce the electrical and thermal resistance and thus to increase the electrical I 2 R losses can be drastically reduced, where I is the current, R is the electrical resistance and I 2R represents the electrical output accordingly. This results in less heat generation and a more uniform temperature in the cell. Furthermore, it extends the cell's service life. Due to the reduced heat generation, the cell's rapid charging capacity can be improved. This leads to faster or shorter charging times for an electric car. Charging at higher power levels is also possible. The electrical output is also increased, which enables electric motors with higher power and more torque and better acceleration of the electric car. Fastening the folded ends by sewing has the major advantages that sewing is cheap, creates a very good mechanical structure and is easy to industrialize.

[0046] Overall, the examples show how the invention can provide a novel tableless electrode for a lithium-ion battery cell with long service life and super-fast charging capability.

Claims

[1] Current collector arrangement (10) for a battery cell (14) designed as a round cell, wherein the current collector arrangement (10) comprises an electrically conductive current collector foil (20) which has a length (L) and a width (B) perpendicular to the length (L), wherein the current collector foil (20) has a collecting region (22) and an edge region (24) which adjoins the collecting region (22) in the direction of the width (B), which edge region (24) runs in the direction of the length (L) and which provides a contact region (38) for electrically conductive contact with a current collector surface (36) of the battery cell (14), the current collector foil (20) has a fold (42) in the edge region (24) which has a first and a second fold end (44, 46), wherein the first fold end (44) is directly adjacent to the collecting region (22) and the second fold end (46) has a fold on the first fold end (44, 46) folded foil edge (48) of the current collector foil (20),wherein the first and second turn-up ends (44, 46) are secured to each other, characterized by that the cover (42) is designed as a cover (42) forming an eyelet (40). [2] Current collector arrangement (10) according to claim 1, characterized by in that the cover (42) is segmented in the direction of the length (L) by at least one incision (70) running in the direction of the width (B), wherein the at least one incision (70) runs from an edge (68) of the cover (42) facing away from the collecting area (22) in the direction of the width (B) up to a maximum of a fastening area (50) in which the first and the second cover end (44, 46) are fastened to one another. [3] Current collector arrangement (10) according to one of the preceding claims, characterized by that the first and second turn-up ends (44, 46) are sewn together, ie in particular are fastened to one another by at least one seam (52). [4] Current collector arrangement (10) according to one of the preceding claims, characterized by in that the current collector arrangement (10) has at least one first separator (32) for arrangement between an anode (16) and a cathode (18) of the battery cell (14), wherein the at least one first separator (32) has at least a first region (60, 62) which is arranged between the first and second turn-up ends (44, 46) of the turn-up (42) of the current collector foil (20). [5] Current collector arrangement (10) according to claim 4, characterized byin that the first separator (32) has a first separator edge region (54) which is arranged at least partially in overlap with the edge region (24) of the current collector foil (20), wherein the first separator edge region (54) of the first separator (32) has a separator turn-up (56) forming a separator eyelet (58), which runs within the turn-up (42) of the current collector foil (20) and which has a first and a second separator turn-up end (60, 62), wherein the first and the second separator turn-up end (60, 62) are fastened to one another. [6] Current collector arrangement (10) according to one of claims 4 or 5, characterized byin that the current collector arrangement (10) has a second separator (34) for arrangement between an anode (16) and a cathode (18) of the battery cell (14), wherein the at least one second separator (34) has a second region (64) which, together with the at least one first region (60, 62) of the first separator (32), is arranged between the first and second turn-up ends (44, 46) of the turn-up (42) of the current collector foil (20). [7] Current collector arrangement (10) according to one of the preceding claims, characterized by that at least within the eyelet (40) of the current collector foil (20) provided by the fold (42) there is arranged an electrically insulating, deformable strand element (66) extending in the length (L) of the current collector foil (20), in particular which strand element has a substantially circular cross-section in the undeformed state. [8] Battery cell (14) for a motor vehicle, wherein the battery cell (14) has a current collector arrangement (10) according to one of the preceding claims. [9] Battery cell (14) according to claim 8, characterized by in that the battery cell (14) has a cell housing (80) and a first current collector surface (36), wherein the current collector arrangement (10) is rolled up into a coil (12) in the direction of the length (L) of the current collector foil (20), and is arranged in the cell housing (80) of the battery cell (14) in such a way that the part of the envelope (42) facing away from the collecting region (22) makes surface contact with the current collector surface (36), and in particular wherein segments of the envelope (42) arranged adjacent to one another in the radial direction (r) of the coil (12) touch one another. [10] Method for providing a current collector arrangement (10) for a battery cell (14) designed as a round cell, comprising the step: - Providing an electrically conductive current collector foil (20) which has a length (L) and a width (B) perpendicular to the length (L), wherein the current collector foil (20) has a collecting region (22) and an edge region (24) which adjoins the collecting region (22) in the direction of the width (B), which edge region (24) runs in the direction of the length (L), and which provides a contact region (38) for electrically conductive contact with a current collector surface (36) of the battery cell (14), - folding the current collector foil (20) in the edge region (24) so ​​that a fold (42) is provided in the edge region (24), which has a first fold end (44) directly adjacent to the collecting region (22) and a second fold end (46) comprising a foil edge (48) of the current collector foil (20) folded over onto the first fold end (44, 46); and - securing the first and second turn-up ends (44, 46) together; characterized by the fact that the folding of the current collector foil (20) in the edge region (24) is carried out in such a way that the folding (42) is provided as a folding (42) forming an eyelet (40) in the edge region (24).

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