BATTERY CELL

Abstract

A battery cell (100) has a cylindrical housing (110) and an electrode winding (120) with a layered structure (200) wound around a core (190). At least one of the electrodes has a longitudinally projecting current collector (151), wherein the electrode winding (120) is arranged in the housing (110) such that the current collector (151) forms an electrical contact with a positive or negative terminal of the battery cell (100). The current collector (151) is compressed to form a contact surface (150) on a corresponding end face of the electrode winding (120) for the electrical contact, wherein recesses (152) are formed in the current collector (151) such that the contact surface (151) is formed only in partial areas (153) of the end face, while the end face is exposed in the remaining partial areas (154).

Description

[0001] The present invention relates to the field of batteries for electric vehicles. In particular, the invention relates to a battery cell, a battery with several such battery cells, and a vehicle with at least one such battery.

[0002] A key focus in the development of electric or hybrid vehicles, especially those at least partially powered by electric motors, is the battery that powers the electric motor (hence also called "drive battery" or "traction battery"). Various battery cells have been developed for this purpose, such as lithium-ion cells. Several battery cells are typically arranged as a "battery pack" and, through appropriate interconnection, form a battery or battery module. It should be understood that the term "battery" in the following refers specifically to a rechargeable battery ("accumulator" or "rechargeable battery").

[0003] Battery cells can have a rigid casing in various shapes. Common types include prismatic cells (cuboidal) and cylindrical cells. Each cell comprises several layers: an electrode called the "anode" (negative terminal), an electrode called the "cathode" (positive terminal), and a separator located between the two electrodes to electrically separate them (i.e., to prevent electrons from passing through) and to conduct ions. In cylindrical cells, the layers of the individual materials—the electrodes including the separator—are wound in the sequence separator-anode-separator-cathode in a spiral around a core within a cylindrical metal casing to form an electrode coil. In the case of lithium-ion batteries, lithium ions migrate through the separator from the cathode to the anode, creating a current flowing from the negative terminal to the positive terminal.

[0004] Cylindrical battery cells are known in which the electrode ends of like-polarity electrodes, particularly cathodes, which are electrically positive, are electrically connected to a so-called terminal connection. The terminal connection can be located on a base plate of the cell housing, being electrically insulated from the cell housing. Through the terminal connection, an electrically positive pole of the battery cell can be contacted from outside the battery cell. Similarly, the electrode ends of anodes, which are electrically negative, can be electrically connected to the cell housing, which is also electrically conductive, so that the electrically negative pole of the battery cell can be contacted via the cell housing. Alternatively, the terminal connections can also be located on opposite end faces of the battery cell.

[0005] The contact between the electrodes and the respective terminal of the battery cell (e.g., terminal connection or cell casing as explained above) can be established, for example, by having the layer forming the corresponding electrode protrude from the layer structure at one side edge, thus projecting as a current collector at one end of the electrode winding. A lateral edge of the cathode protrudes from the electrode winding at one end, and a lateral edge of the anode at the other. This spiral current collector, created by the winding process, is then further processed on the respective end face of the electrode winding to improve electrical contact and form a contact surface through which the electrical contact between the electrodes and the respective terminals can be established.In particular, contact with the positive pole can be established by means of a welded connection to a connecting disc on the end face of the electrode winding, which acts as a current collector.

[0006] This can be achieved simply by compressing, i.e., pressing down (or "kneading") the protruding edges, especially when simultaneously rotating them around the winding core. However, this disordered compression at the end faces makes it difficult for gases that may form inside the electrode winding during operation to escape. Infiltration with a liquid electrolyte is also hindered.

[0007] Alternatively, notches can be provided in the protruding edges so that the current collectors are formed by a plurality of protruding tabs. These tabs can then be folded or bent over to create a more uniformly compacted and gas-permeable layer.

[0008] To prevent the tabs of the outer winding layers from contacting the cell casing, they are typically folded towards the winding core. However, since the folded tabs of the inner winding layers would then close off the winding core and obstruct each other in the core area, it is known to forgo a current collector or a correspondingly large recess in the conductor in this area. Due to the lack of a current collector in the core area, inhomogeneities can occur during charging and discharging. Furthermore, this places greater stress on the electrode material, for example, through increased heating or lithium deposition in this area, which can result in a shorter battery cell lifespan, especially during rapid charging and discharging processes (i.e., at high C-rates).

[0009] For a high weld quality at the connection between the tabs and the terminal plate, a uniform contact surface formed by the tabs, and thus a uniform bending of the tabs, is required. This necessitates a sufficient number of cuts for the formation of the tabs, even in the outermost areas of the electrode winding, which can also lead to the problems described above.

[0010] Sharp edges of the notches can cause electrode cracks due to the tensile stress during the winding process. Therefore, a rounded shape (i.e., no sharp edge) is generally provided at the end of the notches, which typically requires a minimum gap of 1.5 mm to 2 mm between the tabs. While this wider gap between the tabs can prevent cracking, it can in turn reduce the weldable area and cause weld defects between the tabs and the terminal washers, as the homogeneity of the material beneath the weld surface is highly dependent on weld quality.

[0011] It is an object of the present invention to provide a battery cell, in particular a cylindrical battery cell, with an improved design compared to the prior art. In particular, it is intended to provide a battery cell with improved current collectors on the end faces of the electrode winding.

[0012] The solution to this problem is achieved according to the teaching of the independent claims. Various embodiments and further developments of the invention are the subject of the dependent claims.

[0013] A first aspect of the invention relates to a battery cell comprising a cylindrical housing and an electrode winding with a layered structure wound around a core, wherein the layered structure includes an anode layer, a cathode layer, and at least one separator layer for electrical separation of the anode layer and the cathode layer. At least one of the anode layer and one of the cathode layer has a longitudinally projecting current collector, wherein the electrode winding is arranged in the housing such that the current collector forms an electrical contact with a positive or negative terminal of the battery cell at the corresponding end face of the electrode winding.The current collector is compressed to form a contact surface on a corresponding end face of the electrode winding for electrical contact, with recesses being formed in the current collector so that the contact surface is only formed in parts of the end face, while the end face is exposed in corresponding remaining parts.

[0014] The invention is therefore based on the compression of the current collector to form a contact surface on a corresponding end face of the electrode winding for electrical contact. In particular, this eliminates the need for the previously described tabs that are folded over. This avoids or reduces manufacturing problems, issues with sharp-edged cuts and inhomogeneities, and the associated performance losses. Furthermore, processing the current collectors to form the contact surface by compression is simpler than manufacturing them using tabs, where the tabs first have to be created by incisions and then laboriously folded (bent over).

[0015] Because the contact surface exists only in the areas created by compressing the current collectors, while the remaining areas remain open, the problem of a closed, essentially gas-impermeable layer being formed is avoided. Consequently, venting, gas escape, and infiltration with a liquid electrolyte are improved. At the same time, it has been shown that, despite the open areas, a uniform voltage distribution and a comparable internal resistance of the battery cell can be achieved as with a closed contact surface created by compressing the current collectors.

[0016] The term "vehicle" as used here refers specifically to a passenger car, including all types of motor vehicles, hybrid and battery-powered electric vehicles, as well as vehicles such as sedans, vans, buses, trucks, delivery vans, and the like. The term "electric vehicle" then refers specifically to electric or hybrid vehicles, particularly vehicles that are at least partially powered by an electric motor. An electric vehicle can be, in particular, a passenger car, but also a vehicle such as a van, bus, truck, delivery van, and the like, or a two-wheeler, such as an (electric) motorcycle, (electric) scooter, e-bike, e-scooter, and the like.

[0017] The term "current collector," as used here, refers specifically to an element made of a conductive material, particularly copper or aluminum. It serves to conduct electricity between two geometrically separated points.

[0018] The term "electrode winding," as used here, refers in particular to a device that, as a component of a galvanic cell, especially a battery cell, serves both to store chemical energy and to deliver electrical energy. For this purpose, the electrode winding comprises at least two electrodes, namely an anode and a cathode, and a separator, in particular an electrically insulating separator, which can at least partially absorb an electrolyte. The anode, separator, and cathode are wound around an axis to form an electrode winding. Before electrical energy is delivered, stored chemical energy is converted into electrical energy. During a charging process of the battery cell, electrical energy supplied to the electrode winding is converted into chemical energy and stored.The electrodes can have a current collector, in particular made of aluminum (Al) for the cathode and copper (Cu) for the anode, wherein a thin layer of a mixture of an active material, binder (e.g. PVDF, PTFE, CMC, SBR, LiPAA, PAA, etc.) and conductive additives (carbon black, CNTs, carbon fibers, etc.) can be applied to both sides of the current collector. The current collector can in particular be designed as a foil.

[0019] The term "separator" or "separator layer," as used here, refers in particular to an electrically insulating device that separates and distances an anode from a cathode. Preferably, a separator layer is applied to an anode layer and / or a cathode layer. Preferably, the separator layer is designed as an independent body. The separator or separator layer can also at least partially contain an electrolyte, which preferably contains lithium ions. The electrolyte can also be electrochemically bonded to adjacent layers of an electrode stack or electrode winding. Preferably, a separator is thin-walled, particularly preferably as a microporous film. Preferably, the separator layer or separator is wetted with an additive that also increases the mobility of the separator layer or separator.Wetting with an ionic additive is particularly preferred. Preferably, the separator layer or separator extends at least partially over a boundary edge of at least one electrode. In the layer structure, at least one separator layer is arranged between the cathode layer and the anode layer, and usually another is located on the cathode layer or the anode layer to ensure electrical separation of the electrode layers in the electrode winding. It is understood that the separator layer, as well as the cathode layer and the anode layer, can have a substantially rectangular shape in order to form a cylindrical shape when rolled up. The longitudinal ends are referred to here as the ends in the longitudinal direction.

[0020] The term "active material," as used here, refers in particular to a material that can be electrochemically active and is suitable for coating electrodes for battery cell windings, and into which ions, especially lithium ions, can be incorporated. The active material for the cathode may, in particular, be NMC, NCA, NCMA, LCO, LFP, LMFP, LMO, LNMO, or another material. The active material for the anode may, in particular, be graphite, SiOx, SiC, Si, or another material.

[0021] The terms “comprises”, “includes”, “includes”, “has”, “with”, or any other variant thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or has a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent in such method or apparatus.

[0022] Furthermore, unless explicitly stated otherwise, "or" refers to an inclusive or and not an exclusive "or". For example, a condition A or B is satisfied by one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0023] The terms "ein" or "eine," as used here, are defined as "one or more." The terms "ein anderer" and "ein Weitere," as well as any other variant thereof, are to be understood as "at least one more."

[0024] The term "plural", as used here, is to be understood in the sense of "two or more".

[0025] The terms "configured" or "set up" to perform a specific function (and their respective variations) are understood within the meaning of the invention to mean that the corresponding device already exists in a configuration or setting in which it can perform the function, or at least that it is adjustable—i.e., configurable—so that it can perform the function after appropriate adjustment. Configuration can be achieved, for example, by adjusting parameters of a process sequence or by using switches or similar devices to activate or deactivate functionalities or settings. In particular, the device can have several predetermined configurations or operating modes, so that configuration can be carried out by selecting one of these configurations or operating modes.

[0026] Preferred embodiments of the battery cell according to the first aspect are described below, which, unless expressly excluded or technically impossible, can be combined with each other as desired and with the other described aspects of the invention.

[0027] In some embodiments, the sub-areas extend radially between the winding core and an outer edge of the electrode winding. In particular, they can be essentially circular sectors (especially excluding a cross-sectional area of ​​the winding core). This represents a simple shape for the sub-areas. Specifically, the sub-areas with the contact surface and the free sub-areas can be of the same size. It is understood that other shapes, such as strip-shaped, triangular, or trapezoidal, are possible. In particular, various sizes are conceivable, where the sub-areas with the contact surface are the same size as, smaller than, or larger than the free sub-areas. Other patterns, such as circumferential sub-areas or other non-contiguous sub-areas, can also be provided.The choice of design for the sub-areas may be related in particular to the choice of design for welded joints (see below).

[0028] In some embodiments, the sub-areas are arranged rotationally symmetrically around the winding core. In particular, at least two, e.g., two, three, or four sub-areas with contact surfaces (and thus a corresponding number of free sub-areas) can be provided. This symmetrical arrangement allows for improvements to the aforementioned properties of the battery cell, especially regarding performance.

[0029] In some embodiments, the recesses in the current collector are formed in such a way that the contact surface also extends around the winding core. This area, which can connect radially extending sub-sections, such as those essentially shaped like circular sectors, allows for improvements to the aforementioned properties of the battery cell, particularly with regard to voltage flow. In known solutions with bent tabs, this area typically needs to remain clear to prevent the bent tabs from protruding into the winding core. This protrusion is unlikely to occur, or hardly occurs, during compression, especially when combined with a rotary movement of the tool around the winding core as the axis of rotation.

[0030] In some embodiments, the electrode winding is connected to the positive terminal by means of a connecting disc arranged on its end face. This connecting disc is linked to the electrode winding, and in particular to the current collector, by welds in the contact area. The design of the contact area (and thus the design of the current collector) can therefore be related to the design of the welds. The (positive) connecting disc establishes electrical contact between the electrode winding (or more precisely, the anode) via the contact surface and a terminal of the battery cell, which forms the positive terminal of the battery cell. It can, in particular, extend over the entire surface of the end face of the electrode winding.

[0031] In some embodiments, both the anode layer and the cathode layer have a corresponding current collector, with the current collector of the anode layer and the current collector of the cathode layer being located on opposite end faces of the electrode winding. This simple spatial separation of the anode and cathode current collectors allows for electrical contact to be established with the respective terminals of the battery cell.

[0032] A second aspect of the invention relates to methods for manufacturing a battery cell, in particular a battery cell according to the first aspect of the invention. For this purpose, a cylindrical housing and an electrode winding with a layered structure wound around a core are provided, wherein the layered structure comprises an anode layer, a cathode layer, and at least one separator layer for electrical separation of the anode layer and the cathode layer, wherein at least one of the anode layer and the cathode layer has a longitudinally projecting current conductor.

[0033] Recesses are formed in the current collector to create a contact surface. This surface is located on a corresponding end face of the electrode winding, providing electrical contact to the positive or negative terminal of the battery cell only in certain areas, while the remaining areas of the end face are exposed. The layered structure is then wound around a core to form the electrode winding. The current collector is then compressed, particularly in conjunction with a rotational movement around the core as the axis of rotation, to create the contact surface. The electrode winding is positioned in the housing, and the current collector establishes electrical contact with the positive or negative terminal of the battery cell via the contact surface, particularly through welded connections in the contact area, for example, via a terminal plate.

[0034] A third aspect of the invention relates to a battery for an electric vehicle, in particular a traction battery, which comprises at least one battery cell according to the first aspect of the invention and / or at least one battery cell produced according to the method according to the second aspect of the invention.

[0035] A fourth aspect of the invention relates to an electric vehicle which includes at least one battery according to the third aspect of the invention as a drive battery for an electric motor of the electric vehicle.

[0036] The features and advantages explained in relation to the first aspect of the invention also apply accordingly to the other aspects of the invention.

[0037] Further advantages, features and possible applications of the present invention will become apparent from the following detailed description in conjunction with the drawings.

[0038] This shows: Fig. 1 a cross-section through a cylindrical battery cell (“round cell”); Fig. 2 schematically a layer structure for an electrode winding in top view; Fig. 3 schematically a front face of an electrode winding according to a first embodiment; Fig. 4 schematically shows an end face of an electrode winding according to a second embodiment; and Fig. 5 schematically a front face of an electrode winding according to a third embodiment.

[0039] The same reference numerals are used throughout the figures for the same or corresponding elements of the invention.

[0040] Fig. Figure 1 shows a schematic cross-sectional view of a cylindrical battery cell 100 (round cell), particularly for use in an electric vehicle battery. It could, for example, be a lithium-ion cell. Typically, several battery cells 100 are combined to form a battery pack, which constitutes a battery for an electric vehicle (not shown), specifically a traction battery for the electric motor of the electric vehicle. The battery cell 100 can, for example, have a diameter of 46 mm and a length of 95 mm.

[0041] The battery cell 100 has a housing 110 in the form of a hollow cylinder made of an electrically conductive material. An electrode winding 120 is arranged in the housing 110, which is formed by winding a corresponding layer structure (see Figure 1). Fig. 2) can be formed around a winding core 190. An anode of the electrode winding 120 is connected to a base plate 130 of the housing 110 via a contact surface 150 and corresponding electrical connections 140. The base plate 130, like the anode contact surface 150, can be made of copper, and the battery cell 100 can be electrically connected from outside the battery cell 100 via the base plate 130.

[0042] Similarly, a contact plate 170 is arranged on a side of the hollow cylinder 110 opposite the base plate 130. This contact plate has an electrically conductive material and is electrically connected to the cathode via a cathode contact surface 160 through electrical connections 180, so that the battery cell 100 can be electrically connected from outside the battery cell 100 via the contact plate 170. The contact plate 170 and the electrical connections 180 are made of aluminum. It is understood that corresponding alternative configurations of the battery cell are conceivable, in which, for example, connecting discs on the end faces and corresponding terminal connections can be used instead of the electrical connections 140, 180 with the base plates 130, 170.

[0043] The cathode contact surface 160 as well as the previously mentioned anode contact surface 150 can each be produced by compressing appropriate current collectors, as will be explained in more detail below. Fig. 1 in particular shows a sectional view along line AA Fig. 3 dar.

[0044] In Fig. Figure 2 is a schematic, not to scale, top view of a layer structure 200, which, when wound, forms an electrode winding 120. The layer structure 200 comprises an anode layer, a cathode layer, and a separator layer, which electrically separates the anode and cathode layers (layers not shown individually).

[0045] The layered structure 200 has an essentially rectangular basic shape and can be wound, i.e., coiled, from a first longitudinal end 201 to a second longitudinal end 202 (indicated by the arrow). The first longitudinal end 201 is then located at the winding core 190. The current collector 151 projects from the anode, so that the current associated with Fig. The electrical connections described in section 1 can be made.

[0046] It is understood that the current collector 151 with its recesses 152 is shown in a highly simplified form for illustrative purposes. In particular, winding the layer structure 200 would result in Fig. 2 by only three windings which are in Fig. The arrangement shown in Figure 3 is not shown. It is understood that in reality there are significantly more, and the recesses 152 are provided accordingly. Only one current collector 151 is shown on one side. A corresponding structure can also apply to a current collector arranged on the opposite side.

[0047] Fig. Figure 3 schematically shows an end face 121 of the electrode winding 120, which is formed by winding the layer structure 200. By selecting the extent and arrangement of the recesses 152 in the winding direction, corresponding sub-areas 153, 154 of the end face 121 can be formed. Fig. 3. The recesses 152 are located in partial areas 154 of the end face 121, so that the end face 121 of the electrode winding 120 is exposed and therefore no electrical contact can be established. This contact is achieved via the contact surface 150 in the partial areas 153 (the partial areas 153 are shown hatched for better visibility of the structure). Corresponding welded joints (not shown) are therefore provided in the partial areas 153. Two of the partial areas 153 and 154 are provided, which are rotationally symmetrical and circular arc-shaped.

[0048] The contact surface 150 is formed by compressing the current collector 151. This ensures a homogeneous voltage flow. The contact surface 150 is sufficient for this purpose in the sub-areas 153. Sufficient degassing or infiltration with a liquid electrolyte can occur via the exposed sub-areas 154.

[0049] The in Fig. The embodiment shown in 4 is essentially the same as the one shown in Fig. The embodiment shown in Figure 3 is described in the corresponding description. An additional area 155 is formed around the winding core 190, which also includes the contact surface 150. This increases the area for voltage flow, while ensuring that the end face 121 remains sufficiently free in the sub-areas 154.

[0050] The in Fig. The embodiment shown in section 5 is essentially the same as the one shown in Fig. 3. In the embodiment shown, reference is made to the corresponding description. Instead of two, three sub-areas 153 and 154 are provided, which are also rotationally symmetrical and arc-shaped. This allows the welded joints to be distributed more evenly over the end face 121.

[0051] While at least one exemplary embodiment has been described above, it should be noted that a large number of variations exist. It should also be noted that the described exemplary embodiments are merely non-limiting examples, and it is not intended to restrict the scope, applicability, or configuration of the devices and methods described herein. Rather, the preceding description will provide the person skilled in the art with guidance for implementing at least one exemplary embodiment. It is understood that various modifications to the function and arrangement of the elements described in an exemplary embodiment can be made without derogating from the subject matter defined in the appended claims and their legal equivalents. REFERENCE MARK LIST 100 battery cells 110 cases 120 electrode coils 130 Base plate 140 electrical connections 150 contact area anode 151 current collectors 152 exceptions 153 sub-areas front face with contact surface 154 exposed sections of the front face 155 Area of ​​the contact surface around the winding core 160 contact area cathode 170 contact plate 180 electrical connections 190 winding core 200 layer structure 201 first longitudinal end 202 second longitudinal end

Claims

[1] Battery cell (100) comprising a cylindrical housing (110) and an electrode winding (120) with a layer structure (200) wound around a winding core (190), wherein the layer structure (200) comprises an anode layer, a cathode layer and at least one separator layer for electrical separation of the anode layer and the cathode layer, wherein at least one of the anode layer and the cathode layer has a longitudinally projecting current collector (151), wherein the electrode winding (120) is arranged in the housing (110) such that the current collector (151) forms an electrical contact to a positive terminal or negative terminal of the battery cell (100) at the corresponding end faces of the electrode winding (120), wherein the current collector (151) is compressed in order to form a contact surface (150) on a corresponding end face (121) of the electrode winding (120) for electrical contact, and wherein recesses (152) are formed in the current collector (151) so that the contact surface (150) is formed only in partial areas (153) of the end face (121), while the end face (121) is exposed in corresponding remaining partial areas (154). [2] Battery cell according to claim 1, wherein the sub-areas (153) extend in a radial direction between the winding core (190) and an outer edge of the electrode winding (120). [3] Battery cell according to claim 1 or 2, wherein the sub-areas (153, 154) are arranged rotationally symmetrically around the winding core. [4] Battery cell according to one of the preceding claims, wherein the recesses (152) are formed in the current collector (151) such that the contact surface is also formed in a region (155) around the winding core (190). [5] Battery cell according to one of the preceding claims, wherein the electrode winding (120) is connected to the positive terminal by means of a connecting disc arranged at the end face of the electrode winding (120), wherein the connecting disc is connected to the electrode winding (120) by means of welded connections in the area of ​​the contact surface (150). [6] Battery cell according to one of the preceding claims, wherein both the anode layer and the cathode layer have a corresponding current collector (151), wherein the current collector (151) of the anode layer and the current collector of the cathode layer are located on opposite end faces of the electrode winding (120). [7] Method for manufacturing a battery cell (100), in particular a battery cell (100) according to any one of the preceding claims, comprising the following steps: - Providing a cylindrical housing (110) and a layer structure (200) for an electrode winding (120), wherein the layer structure (200) comprises an anode layer, a cathode layer and at least one separator layer for electrical separation of the anode layer and the cathode layer, wherein at least one of the anode layer and the cathode layer has a longitudinally projecting current conductor (151); - Forming recesses (152) in the current collector (151) to form a contact surface (150) which is located on a corresponding end face (121) of the electrode winding (120) for electrical contact to a positive or negative terminal of the battery cell (100) only in partial areas (153) of the end face (121), while the end face (121) is exposed in corresponding remaining partial areas (154); - Winding the layer structure (200) around a winding core (190) to form the electrode winding (120); - Compressing the current collector (151) to form the contact surface (150); - Arranging the electrode winding (120) in the housing (110), wherein the electrical contact to the positive terminal or negative terminal of the battery cell (100) is formed by the current conductor (151) via the contact surface (150). [8] Battery comprising at least one battery cell (100) according to any one of claims 1 to 6 and / or at least one battery cell (100) produced according to the method of claim 7. [9] Electric vehicle with at least one battery according to claim 8 as a traction battery for an electric motor of the electric vehicle.

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