METHOD FOR MANUFACTURING A BATTERY CELL

Description

[0001] The invention relates to a method for producing a battery cell, for example, for producing a pouch cell, comprising an electrode stack with a number of first and second current conductors. The invention further relates to a device for carrying out the method and to a battery cell.

[0002] Electric or electric-powered vehicles, such as electric or hybrid vehicles, typically include an electric motor that can drive one or both axles. To supply electrical energy, the electric motor is typically connected to an on-board (high-voltage) battery that serves as an electrical energy storage device.

[0003] An electrochemical battery, in particular, is understood here and below to mean a so-called secondary battery (secondary battery) of a motor vehicle. In such a (secondary) vehicle battery, consumed chemical energy can be restored by means of an electrical charging process. Such vehicle batteries are designed, for example, as electrochemical accumulators, in particular as lithium-ion accumulators. To generate or provide a sufficiently high operating voltage, such vehicle batteries typically have at least one battery cell module in which several individual battery cells are interconnected in a modular manner.

[0004] Battery cells, for example, are designed as electrochemical (thin-)film cells. These thin-film cells have a layered structure with a cathode layer and an anode layer, with a separator layer sandwiched between them. These components are penetrated, for example, by a liquid electrolyte (liquid electrolyte), which creates an ionically conductive connection between the components and thus a charge balance.

[0005] To manufacture battery cells, for example, a layer of active material or electrode material is applied to a current collector. The current collectors are often designed as metal foils, with copper foil typically used for the anode layers and aluminum foil for the cathode layers. Current collectors coated in this way are used as stacked electrodes (electrode stacks). The current collectors of the electrode or cell stack are electrically connected to each other to form a common anode and a common cathode, which are also referred to below as current collectors.

[0006] The individual conductor flags or current conductors are usually connected by laser or ultrasonic welding.

[0007] However, ultrasonic welding is disadvantageous in that it induces (mechanical) vibrations, which can cause stack tolerance imbalance and even deformation of the (current) collector foils. Therefore, it is necessary, for example, to use clamping units for the electrode stacks to prevent or at least reduce these vibrations. Furthermore, ultrasonic welding is highly dependent on the surface quality of the collector. The presence of oxide, moisture, dirt, or an oil film can significantly impair the quality of the weld.

[0008] The disadvantage of laser welding is that part of the light beam is reflected by the metal surface of the current collector, reducing efficiency. Therefore, a high energy input is required to melt the material during laser welding. Laser welding is therefore a comparatively energy-intensive process. It melts the collector, such as copper and aluminum, which are highly (thermally) conductive materials. The heat generated during welding can thus be transferred to the active material and also creates a zone of high heat impact at the collector.

[0009] Furthermore, during laser welding, only a small area of ​​the collector is welded with a linear seam. Other areas of the collector are not welded. Since welding is only performed locally, this area heats up more quickly, as all electrons in the battery current flow through this weld area when entering or exiting the electrode during operation.

[0010] Furthermore, during the laser welding process, the collector material melts, resulting in the formation of oxide particles, which cause an oxide layer that adversely reduces the conductivity of the weld. The resistance in the laser weld seam is therefore often several times higher than the resistance of the collector material (copper or aluminum). This means that a comparatively high (ohmic) power loss occurs in the area of ​​the laser weld seam.

[0011] DE 10 2014 226 806 B3 discloses a method for producing an electrically conductive connection, in which the surfaces of the joining partners are cleaned and subsequently coated with an adhesive polymer. The coated joining partners are then mechanically pressed together during a curing process of the polymer layers, resulting in the formation of electrically conductive microcontacts between the joining partners in the joining area due to surface irregularities.

[0012] DE 10 2019 111 410 A1 discloses a method for reaction metallurgical welding. The welding method involves providing a reactive material between and in contact with a first and second workpiece. In a first position, the workpieces and the reactive material are pressed together, heated, and held between first and second tools to form a first RMJ weld between the workpieces. Subsequently, in a second position, the workpieces are pressed together, heated, and held between the tools to form a second RMJ weld that overlaps the first RMJ weld.

[0013] CN 110 224 176 A discloses a manufacturing method for a secondary battery. The secondary battery has a positive plate with a positive active substance layer formed on the positive core and a positive collector connected to the positive core. The laminated positive core has a connecting portion connected to the positive collector. When the product of the thickness of a piece of the portion of the positive core not connected to the positive collector and the number of layers of the positive core in the connecting portion is set to Tp1, the connecting portion has a first region with a thickness smaller than Tp1 and a second region with a thickness greater than Tp1 in the lamination direction of the positive core.

[0014] DE 10 2019 106 988 A1 describes a stack assembly comprising a battery tab with a localized weld seam, as well as a method for its manufacture. The assembly is manufactured by a method including the steps of arranging a plurality of battery tabs into a stack assembly, providing a resistive coating on at least one of the inner surfaces and the outer surfaces of the battery tabs, and resistively heating the stack assembly. The resistive coating is a nickel-phosphorus (Ni-P) alloy having a phosphorus content of 5 to 7 wt.%. The resistive heating involves reacting the Ni-P alloy with an electric current to generate concentrated heat localized between adjacent battery tabs, such that the Ni-P alloy undergoes solid-state bonding with the Cu in the first tab.

[0015] The invention is based on the object of providing a particularly suitable method for producing a battery cell. In particular, a simple and reliable joint between the collectors is to be enabled, which preferably has a low electrical resistance. The invention is further based on the object of providing a particularly suitable device for carrying out the method and a particularly suitable battery cell.

[0016] With regard to the method, the object is achieved according to the invention with the features of claim 1, and with regard to the device 9 and the battery cell with the features of claim 11. Advantageous embodiments and further developments are the subject of the respective subclaims.

[0017] If method steps are described below, advantageous embodiments for the device result in particular from the fact that it is designed to carry out one or more of these method steps.

[0018] The method according to the invention is intended for, and is suitable and designed for, the production of a battery cell. The battery cell is, in particular, a pouch, bag, or soft pack cell. The battery cell comprises a cell housing and an electrode stack accommodated therein, with a number of first and second current conductors.

[0019] The electrode stack comprises a number of thin-film cells stacked one above the other, each comprising a cathode layer and an anode layer, as well as a separator layer (separator) interposed therebetween. For example, an active material or electrode material layer is applied to the current collectors. The current collectors are embodied, for example, as metal foils, with copper foils suitably used for the anode layers and aluminum foils for the cathode layers. Preferably, high-silicon-based anode layers are used in order to realize a battery cell with the highest possible power density and, on the other hand, to enable rapid charging of the battery cell. In the following, the first current collectors are understood to mean, in particular, aluminum foils, and the second current collectors are understood to mean, in particular, copper foils.

[0020] According to the process, the first current conductors are joined to form a common cathode, and the second current conductors are joined to form a common anode, using a melt-free, material-to-material bond. In particular, the conductor tabs (electrode conductor tabs) of the current conductors are joined. "Melt-free" or "melt-free" refers in particular to a material-to-material bond without one or both joining partners entering a melting phase. This means that the joining partners are, if possible, not melted during the joining process.

[0021] A "material bond" or a "material bond" between at least two interconnected parts is understood here and below in particular to mean that the interconnected parts are held together at their contact surfaces by material union or cross-linking (for example due to atomic or molecular bonding forces), possibly under the effect of an additive.

[0022] According to the invention, the first and second current conductors are joined to the cathode and anode by means of solid-state welding. "Solid-state welding" or a "solid-state welding process" refers in particular to a joining process in which the joint is created by applying pressure alone or by a combination of heat and pressure. If heat is used, the temperature in this process is below the melting point or melting temperature of the metals to be welded (hot diffusion welding). Furthermore, no filler material is used.

[0023] According to the invention, the collectors are connected or joined by pressure welding, in particular by hot-pressure welding. Preferably, the collectors, or the anode and cathode, are trimmed to their final dimensions during the solid-state welding process. According to the invention, laser or ultrasonic welding is thus replaced by pressure welding or hot-pressure welding. This creates a particularly suitable method for producing a battery cell.

[0024] The method according to the invention eliminates the need for energy-intensive laser welding, thereby reducing the heat input into the electrode stack or the active layers (cathode layer, anode layer). Solid-state welding of the collector results in a surface weld rather than a linear seam weld as with laser welding. Thus, compared to a laser weld seam, a (large-area) contact and connection of the current collectors is possible, which advantageously reduces ohmic heat losses during battery operation. In contrast to ultrasonic welding, no vibrations occur during pressure welding according to the invention, so that the joining or welding process does not negatively affect the dimensional accuracy of the battery cell.

[0025] Furthermore, pressure or hot-pressure welding of the individual conductor tabs or current collectors enables a material-to-material bond between the materials without the inclusion of particles or air, thus ensuring that the conductivity of the joined cathodes or anodes is not adversely affected. The use of pressure or hot-pressure welding thus increases the current flow through the collectors, thereby increasing the performance of the manufactured battery cell.

[0026] The method according to the invention also makes it possible to eliminate the need for an additional arrester tab with pre-sealing tape during battery cell production. In other words, it is no longer necessary to join the collectors with a separate arrester tab to avoid excessive thermal stress on the pre-sealing tape. This eliminates the need for a separate "arrester tab with pre-sealing tape" component, creating significant cost savings potential. Pressure or hot-press welding creates a block from the individual arrester tabs, which can be used as an arrester or collector. This not only eliminates the need for the "arrester tab," but also reduces the weight of the battery cell.

[0027] To prevent galvanic corrosion, the anode and / or cathode are coated with a protective layer after pressure or hot-pressure welding, for example. In particular, a tin coating is applied to the copper side, i.e., the anode side, immediately after solid-state or pressure welding. In other words, the anode is coated with a layer of tin as a protective layer. Alternatively, a nickel coating on the anode is also conceivable.

[0028] The pressure or hot-pressure welding according to the invention makes it possible to weld the individual conductor tabs of the electrodes into a solid block (cathode, anode). This means that the resulting welded connection has high mechanical rigidity. In particular, pressure or hot-pressure welding creates a connection with a particularly long service life. In principle, the number of layers, i.e. the number of current conductors stacked one above the other, is not important for solid-state welding. However, with a small number of layers, cracks can occur in the conductor tabs or current conductors due to the (joining) pressure. In a suitable embodiment, it is therefore provided that the first and second current conductors are arranged in at least ten layers, in particular in more than 20 layers, preferably between 30 and 50 layers.In other words, at least ten, in particular 20, and preferably between 30 and 50, first and second current collectors are joined to the cathode and anode, respectively. With this number of layers, there is essentially no risk of cracking.

[0029] The pressure or hot-pressure welding process depends on the surface quality (cleanliness) of the materials. This means that the process or welding parameters (pressure, duration, and temperature) depend on the surface quality of the joining partners. With a clean surface, the welding process requires less energy. Therefore, a practical design provides for pre-cleaning of the current conductors. This involves cleaning the first and second current conductors before contacting or before the melt-free, material-to-metal joining process to remove any contaminants such as grease from the surfaces.

[0030] In other words, the current collectors are freed of surface contaminants. For example, the surfaces of the current collectors are freed of contaminants using plasma cleaning. In a preferred embodiment, the first and second current collectors are cleaned, particularly in an ultrasonic bath, before solid-state welding. Additionally or alternatively, it is possible, for example, to perform mechanical cleaning of the current collectors, for example using brushes. This ensures that as little contaminants as possible are present in the joining area. The clean surfaces improve the quality of the joint and thus the quality of the electrical contact.

[0031] In one embodiment according to the invention, the first and second current conductors are heated before joining or welding. This means that the temperature of the current conductors is increased for solid-state welding. The copper anode of the second current conductor is preheated, for example, to up to 600°C to 700°C, whereas the aluminum cathode of the first current conductor is preheated, for example, to 300°C to 350°C. This means that less heating power is required during pressure or hot-pressure welding. In particular, preheating thus reduces the process time of pressure or hot-pressure welding. For example, the process time is reduced from approximately 20 seconds to approximately five seconds. In one conceivable further development, the first and second current conductors are (pre-)heated inductively, for example using a coil.Alternatively, it is possible, for example, to generate the preheating by means of a pressure stamp that is pressed onto the current collector, wherein the heating is effected by current flow due to resistance heating. To avoid damage to the active coating of the electrodes, an embodiment of the method according to the invention further provides for the electrode stack to be cooled during the joining or welding process, in particular also during the preheating. For this purpose, a cooling connection, i.e. a thermal coupling, of the electrode stack to a cooling device, in particular to a cooling plate, is provided. The cooling plate can, for example, extend over the entire area of ​​the active material, although designs with smaller cooling plates are also possible.

[0032] To prevent oxide formation, preheating and pressure or hot-pressure welding are carried out in a shielding gas or under vacuum. It is particularly important that no oxygen is present in the environment to prevent oxide formation. In a suitable embodiment of the process, hot-pressure welding is carried out in a nitrogen atmosphere, i.e., in a nitrogen environment.

[0033] The device according to the invention is intended for carrying out a method described above, and is suitable and configured for this purpose. The statements made in connection with the method also apply mutatis mutandis to the device, and vice versa.

[0034] According to the invention, the device comprises a housing and a stamping device accommodated therein, each with an upper stamping die and a lower stamping die for hot-press welding the first and second current conductors. This means that there is an upper and lower stamping die for the first current conductors, and an upper and lower stamping die for the second current conductors, so that the current conductors can be joined to the cathode and anode essentially simultaneously. This creates a particularly suitable device for producing a battery cell.

[0035] In a suitable further development, a pneumatic cutting die for cutting the cathode and anode is integrated into the upper pressure dies. This allows the collectors to be trimmed to the desired final size during hot-press welding.

[0036] The battery cell according to the invention is designed, in particular, as a pouch cell. The battery cell is intended, for example, for use in a vehicle battery of an electrically powered or drivable motor vehicle.

[0037] The battery cell comprises an electrode stack with a number of first and second current collectors, and a cell housing accommodating the electrode stack. The first current collectors are joined to a common cathode, and the second current collectors are joined to a common anode in a melt-free manner. The cell housing comprises, for example, two circumferentially joined housing halves, from which the cathode and the anode protrude at least partially. In the areas of the cathode and the anode, the housing halves suitably each have a pre-sealing strip, which is joined to the respective collector in a materially bonded manner. This results in a particularly suitable battery cell. The advantages and configurations cited with regard to the method and / or the device can also be applied analogously to the battery cell, and vice versa.

[0038] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. In schematic and simplified representations, the drawings show: Fig. 1 shows a flow chart of a method according to the invention for producing a battery cell, Fig. 2 shows a battery cell, Fig. 3 shows a cleaning process of the method, Fig. 4 shows a preheating process of the method, Fig. 5 shows a hot-press welding process of the method for contacting a collector, and Fig. 6 shows a separation process of the hot-press welding process.

[0039] Corresponding parts and sizes are always provided with the same reference symbols in all figures.

[0040] The Fig. 1 shows in a schematic and simplified flow diagram a method 2 according to the invention for producing a battery cell 4 ( Fig. 2 ). The following based on the Figures 2 to 5The method described in this embodiment comprises, for example, nine consecutive method steps OP1, ..., OP9. A device not further designated for carrying out method 2 or method steps OP1, ..., OP9 is also described below with reference to the Figures 2 to 5 explained in more detail.

[0041] The battery cell 4 has an electrode or cell stack 6 with a number of thin-film cells stacked one above the other, each having a cathode layer and an anode layer, as well as a separator layer (separator) inserted between them. For example, an active material or electrode material layer is applied to a current collector 8, 10. The current collectors 8, 10 are designed, for example, as metal foils, with copper foils being suitably used for the anode layers and aluminum foils for the cathode layers. The current collectors 8, 10 project from the edges of the electrode stack 6 as collector tabs or electrode collector tabs. In the following, the current collectors 8 are to be understood as aluminum foils in particular, and the current collectors 10 are to be understood as copper foils in particular.

[0042] The Fig. 3shows process step OP1 of process 2 in successive representations. In process step OP1, the surface of the current collectors 8, 10 is cleaned using ultrasound. During surface cleaning, oxides, moisture, and oily products are removed from the surface of the current collectors 8, 10.

[0043] For this purpose, the device comprises an ultrasonic cleaner 12 with an ultrasonic bath 14. An ultrasonic generator 16 for frequencies up to 40 kHz (kilohertz) is arranged in the ultrasonic bath 14, wherein the ultrasonic bath 14 is filled with a liquid 18. The liquid 18 is, for example, distilled water with alkaline solvents or additives for oxide cleaning. During operation, the ultrasonic generator 16 generates an ultrasonic wave 20, which has the greatest amplitude in the area of ​​the immersed current collectors 8, 10. The ultrasonic wave 20 generates rapidly moving cavitation bubbles 22 in the liquid 18, which move at the ultrasonic frequency and remove dirt and oily substances from the surfaces of the current collectors 8, 10. The alkaline additives in the liquid 18 help to remove oxides on the surfaces.

[0044] The ultrasonic bath 14 is covered with a lid 24. The lid 24 is made of rubber and has slots for guiding the current collectors 8, 10. In the area of ​​the lid 24, cleaning roller brushes 26 with polyamide fibers are provided for the mechanical cleaning of the current collectors 8, 10. The cleaning roller brushes 26 are moved by contact with the current collectors 8, 10.

[0045] The electrode stack 6 is secured by a gripper 28 in a guide plate 30 for ultrasonic cleaning. The electrode stack 6 is lowered by means of the guide plate 30 so that the current collector 8 dips through the slotted cover 24 into the ultrasonic bath 14 and is cleaned of the cavitation bubbles 22 and the cleaning roller brushes 26. The electrode stack 6 is then moved vertically upwards by means of a gripper 32 and pivoted by 180° by means of a joint 34. The current collector 10 is then immersed in the ultrasonic bath 14 and cleaned. The electrode stack 6 is accommodated in a protective cover 36 so that as little liquid 18 as possible comes into contact with the electrode stack 6. Finally, the electrode stack 6 is removed from the guide plate 30 by a gripper 38 and guided to process step OP2.

[0046] As an alternative to the method step OP1 described above, it is conceivable, for example, to clean the current collectors 8, 10 by means of a plasma.

[0047] Once the surface has been cleaned, it is preheated in process step OP2 by induction or resistance heating under an inert nitrogen atmosphere ( Fig. 4 ). In resistance heating, for example, two energizable stamps are pressed against the current conductors 8, 10. The stamps are made, in particular, of graphite, titanium, or tungsten.

[0048] For the copper anode of the current collector 10, preheating occurs, for example, to up to 600°C. For the aluminum cathode of the current collector 8, preheating occurs, for example, to up to 300°C. For this purpose, the device has a heating chamber as a housing 40. The heating chamber 40 contains a gas 42 within it.

[0049] The inert gas 42 is embodied as nitrogen, for example, and is introduced into the heating chamber 40 under an overpressure of, for example, 15 mbar (millibars). To prevent undesired heating of the electrode stack 6, two cooling plates 44 are provided. The cooling plates 44 are pressed against the electrode stack 6 on both sides by means of a gripper 46 with a clamping force shown as arrows, so that the electrode stack 6 is tempered to a maximum temperature of 50 °C during preheating. The cooling plates 44 are cooled by a water and glycol suspension, with the temperature being adjusted or regulated based on the water cooling rate.

[0050] The current collectors 8, 10 are each preheated by means of a heating device 48. The heating device 48 heats the current collectors 8, 10, for example, via induction or via an electrical (heating) resistor.

[0051] After preheating or preheating, the current conductors 8, 10 are pressed in the process step OP3 within the heating chamber 40 with a heated stamping device 50, 52 ( Fig. 5 ). The stamping devices 50, 52 each have a movable (pressure) stamp 54 and a fixed stamp 56 as a counterbearing. The stamps 56 are supported on a base plate 58. Both the fixed and the movable stamp 54, 56 are heated by heating cartridges 60 embedded in a ceramic cover or a ceramic jacket. The stamps 54, 56 are made of graphite, for example, for low pressures and of carbide and / or titanium for high pressures.

[0052] The stamp 54 of the stamping device 50 is heated in particular to a temperature between 350 °C and 600 °C, for example up to 400 °C, and generates a pressure of, for example, 4 bar to 6 bar on the current conductors 8. The stamp 54 of the stamping device 52 is heated in particular to a temperature between 550 °C and 750 °C, for example up to 700 °C, and generates a pressure of, for example, 6 bar to 7 bar on the current conductors 10.

[0053] On the copper side of the current collector 10, the temperature is preferably 500°C to 700°C, although higher pressure is required at lower temperatures. The punches 54 are designed, for example, as pneumatic cylinders, which generate the necessary force for welding. The punch 54 or pneumatic cylinder requires approximately 4 bar of air pressure for welding copper at 700°C. At 550°C, approximately 6 bar of air pressure is required. This means that in this temperature range, normal industrial air pressure is sufficient for pressure welding. For welding the aluminum side of the current collector 8, a temperature range of 400 to 600°C is preferably used. At 400°C, approximately 6 bar of air pressure is required in the pneumatic cylinder, whereas at 600°C, approximately 4 bar of air pressure is required.

[0054] The air pressure of the pneumatic cylinders or pistons 54 also depends on the piston surface of the pneumatic cylinder. Larger pneumatic cylinder pistons require less air pressure.

[0055] During operation, the temperature of the stamps 54 is always lower than the melting temperature of the respective current collector material. The stamping devices 50, 52 join the current collectors 8 to form a common cathode 62, and the stamping device 52 joins the current collectors 10 to form a common anode 64 without melting. In particular, pressure welding is performed, with the force 65 required for pressure welding being calculated using the following formula: Collector surface area * Yield stress (approx. 50 MPa) * Factor (5 to 10)

[0056] Suitably, the current collectors 8, 10 are heated to a temperature such that the yield stress is approximately the same, whereby the current collectors 8, 10 can be pressure-welded with essentially the same die pressure. At 700°C for copper and 400°C for aluminum, the yield stress is approximately 50 MPa. During welding, a thickness deformation of approximately 2% occurs. The force required for welding is the yield stress times the welding area times the correction factor. The correction factor is normally 3 to 5, depending on the surface condition. Since aluminum oxide is difficult to weld, the welding temperature for aluminum can be increased to 600°C. Pressure welding is also carried out under the inert nitrogen atmosphere of the gas 42. The electrode stack 6 is cooled to below 50°C by the cooling plates, as in process step OP2.During pressure welding, the collectors 62, 64 are held under the heated punches 54, 56 for three to five seconds.

[0057] During pressure welding, the material of collectors 62, 64 deforms by a maximum of 5%. Due to the shear deformation, the remaining oxide layer breaks open, and atomic contact occurs between the connecting metals. The material is welded using the solid-state diffusion process. It is important that the material is not melted during this welding process, and therefore no intermetallic compounds form in collectors 62, 64.

[0058] Subsequently, the joined collectors 62, 64 are also trimmed after the pressure welding is completed. Fig. 5The trimming shown for anode 64 is performed in the same stroke as pressure welding, with the collector dimensions remaining within tolerance limits. Since trimming occurs at a higher temperature of the joined metal, less cutting force is advantageously required.

[0059] The punch 54 has an integrated cutting punch 66 for separating or trimming the anode 64. The cutting punch 66 is coupled to a pneumatic system with a spring piston 68 and a spring cylinder head 70, wherein the spring cylinder head 70 is mounted with the punch 54 on a press ram 72. The punch 56 is designed with a cutting die 74 as a counterbearing for the cutting punch 66, which is provided with a waste chute 76 for the separated material.

[0060] Subsequently, an optional process step OP4 is performed. A protective coating is applied to the anode 64 as corrosion protection. This optional process step OP4 improves the conductivity and provides galvanic corrosion protection for the anode 64. After the trimming process, the anode or copper collector 64 is immersed in a molten tin bath. Instead of a tin coating, a nickel coating, for example, is also conceivable.

[0061] After process step OP4, the electrode stacks 4 are placed in deep-drawn bags or housing halves (bag half-shells). Two pre-sealing bands 76, 78 are attached to the housing half, which is designed as a deep-drawn bag, in the area of ​​the collectors 62, 64. The pre-sealing bands are suitably provided in process step OP5.

[0062] In process step OP6, for example, a deep-drawing process is carried out, with which an aluminum composite foil is deep-drawn into the housing half, wherein in process step OP7, in particular the provided pre-sealing strips 76, 78 are pre-fixed on the housing half.

[0063] In process step OP8 (not shown in detail), the electrode stack 6 is inserted between two housing halves equipped with pre-sealing strips 106, 108. The housing halves are then brought into contact in the area of ​​edge flanges and joined or sealed to form a cell housing 80 using a heat-sealing process. This eliminates the need for a conductor tab, on which the pre-sealing strip is conventionally arranged. This means that the pressure welding of the current collector foils eliminates the need for a conductor tab.

[0064] As in the Fig. 2As can be seen comparatively clearly, the electrode stack 6 is completely accommodated in the cell housing 80, with only the anode 64 and the cathode 62 protruding from the cell housing 80. The electrode stack 6 is arranged essentially in one half of the cell housing 80, with the other half acting as a free space or gas pocket 82 to accommodate gases generated during operation as a buffer volume.

[0065] The heat-sealing process creates a circumferential sealing edge through the integral bonding of the flanges of the housing halves. In the area of ​​the pre-sealing strips 76, 78, a bond is created between the housing halves and a respective plastic layer. In process step OP9, a metal layer of the pre-sealing strips 76, 78 is welded or bonded to the metallic anode 64 or cathode 62.

[0066] Welding is typically performed using electromagnetic pulse welding (EMP welding). Alternatively, it is also possible to use an external moving device, which is moved at high speed and creates a weld between the pre-sealing band 78 and the collector 64 through impact. The external device is moved by induced magnetic fields. Instead of EMP welding, ultrasonic welding is also possible. Ultrasonic welding can also join polypropylene. If ultrasonic welding is used, the heat sealing process can be avoided. Ultrasonic welding joins the housing halves to each other and to the plastic layers, as well as the metal layers of the pre-sealing bands 76, 78 and the collectors 62, 64. It is important that the strength of the weld seam is tested under vibration load after ultrasonic welding.

[0067] For example, process steps OP8 and OP9 are interchangeable. In other words, the order of OP8 and OP9 can be reversed, with EMP welding first being used to firmly bond the pre-sealing strips 76, 78 to the collectors 62, 64, followed by a heat-sealing process to firmly bond the housing halves.

[0068] In the case of a battery cell 4 with a liquid electrolyte, this is preferably filled into the gas pocket 82 during process step OP8 or OP9 before the cell housing 80 is completely closed and sealed in the area of ​​the collector.

[0069] The claimed invention is not limited to the embodiments described above. Rather, other variants of the invention may be derived from the above by those skilled in the art within the scope of the disclosed claims without departing from the subject matter of the claimed invention. List of reference symbols

[0070] 2 Proceedings 44 Cooling plate 4 Battery cell 46 gripper 6 Electrode stack 48 Heating device 8 Current collector (cathode) 50, 52 Stamping device 10 Current collector (anode) 54, 56 Rubber stamp 12 Ultrasonic cleaner 58 Base plate 14 Ultrasonic bath 60 Heating cartridge 16 Ultrasonic generator 62 Cathode, collector 18 liquid 64 anode, collector 20 Ultrasonic wave 65 Power 22 Cavitation bubble 66 Cutting punch 24 Lid 68 spring piston 26 Cleaning roller brush 70 spring cylinder head 28 gripper 72 Press ram 30 guide plate 74 Cutting die 32 gripper 76 Pre-sealing tape (cathode) 34 joint 78 Pre-sealing tape (anode) 36 protective cover 80 Cell housing 38 gripper 82 Gas pocket 40 Heating chamber 42 gas OP1...OP9 Process step

Claims

1. Method (2) for producing a battery cell (4), comprising an electrode stack (6) having a number of first and second current conductors (8, 10) arranged in layers stacked one above another, - wherein the first current conductors (8) are joined to form a common cathode (62) and the second current conductors (10) are joined to form a common anode (64) in a materially bonded manner without melting by means of hot pressure welding, - wherein the first and second current conductors (8, 10) are heated before joining, and - wherein the electrode stack (6) is cooled during preheating and during the joining process.

2. Method (2) according to Claim 1, characterized in that the first and second current conductors (8, 10) are arranged in at least ten layers, in particular more than 20 layers, preferably between 30 and 50 layers.

3. Method (2) according to Claim 1 or 2, characterized in that the first and second current conductors (8, 10) are cleaned before joining.

4. Method (2) according to Claim 3, characterized in that the first and second current conductors (8, 10) are cleaned in an ultrasonic bath (14).

5. Method (2) according to any of Claims 1 to 4, characterized in that the first and second current conductors (8, 10) are inductively heated before joining.

6. Method (2) according to any of Claims 1 to 5, characterized in that the hot pressure welding is carried out in a nitrogen atmosphere.

7. Device for carrying out a method (2) according to any of Claims 1 to 6, comprising - a housing (40), - a stamping unit (50, 52) accommodated in the housing (40) and having in each case an upper pressure stamp (54) and a lower pressure stamp (56) for the hot pressure welding of the first and second current conductors (8, 10), - a heating device (48) for preheating the first and second current conductors (8, 10), and - a cooling device (44) for cooling the electrode stack (6).

8. Device according to Claim 7, characterized in that a pneumatic cutting punch (66) for cutting the cathode (62) and anode (64) to size is integrated into the upper pressure stamps (54).

9. Battery cell (4), in particular pouch cell, comprising an electrode stack (6) having a number of first and second current conductors (8, 10), and a cell housing (80) accommodating the electrode stack (6), wherein the first current conductors (8) are joined to form a common cathode (62) and the second current conductors (10) are joined to form a common anode (64) by means of pressure welding.