Welding device for battery cells and welding processes

Abstract

The invention relates to a welding device (10) and a method carried out therewith for welding two electrodes (24a, 24b) of two adjacent battery cells (22a, 22b) by means of a cell connector (26), comprising a laser welding device (12) and a hold-down device (16) with at least one spring-loaded pressure piece (18) for pressing the components (26, 24a, 24b) to be welded, wherein the welding device (10) comprises a scanner optics (13) and position detection for detecting the welding points and for aligning the laser welding device (12) and the laser beam (32a, b), furthermore the laser welding device (12) and the hold-down device (16) are structurally connected and the pressure piece (18) has a rounded pressure surface (30) which is designed to enable tolerance compensation for the cell connector (26) when it rests on the electrodes (24a, 24b) to be welded. This enables process-reliable welding of shaped cell connectors (22) for improved component quality, ensuring high-quality welds, particularly with regard to electrical conductivity. In particular, a rotating or tilting movement of the cell connectors (26) is enabled, which can adapt to electrodes of different heights.

Description

The invention relates to a welding device for welding two electrodes of two adjacent battery cells by means of a cell connector, comprising a laser welding device and a hold-down device with at least one spring-loaded pressure piece for pressing the components to be welded on, and to a method for producing a corresponding welded connection. The invention further relates to a welding method using such a welding device.DE 10 2022 000 445 discloses a method for producing a welded connection of in each case two electrodes of two adjacent battery cells of a battery using a cell connector.EP 3 305 460 A1 discloses a welding device for welding electrode lines of mutually facing battery cells of a battery module, having a welding unit for welding two electrode lines of the mutually facing battery cells to one another, and having a holding-down device which presses the two electrode lines to be connected against one another when the welding is carried out.DE 10 2019 127 676 A1 additionally discloses a holding-down device which has a pressure element which is axially prestressed by a spring element, the pressure element loading the electrodes to be welded to one another. The spring-biased pressure element is provided in the region in which the electrodes to be welded are pressed against one another and is mounted axially displaceably and spring-biased. By means of this spring-biased pressure element, the electrodes can be pressed against one another, tolerances being compensated for and overpressing of the electrodes being prevented.It is the object of the invention to make the connection of adjacent battery cells of a battery more reliable. Further, the joining process is to be accelerated.The invention results from the features of the independent claims. Advantageous refinements and refinements are the subject matter of the dependent claims.The object is achieved according to claim 1 in that the welding device comprises a scanner optics with position detection for detecting the welding points and for aligning the laser welding device, the laser welding device and the hold-down device are furthermore structurally connected and the pressure piece has a rounded pressure surface which is designed to enable tolerance compensation for the cell connector when resting on the electrodes to be welded.The scanner optics are responsible solely for welding. A position detection for detecting the welding points and for aligning the laser welding device is provided, which can in principle also be arranged separately, but is arranged here in an integrated manner.This makes it possible to achieve process-safe welding of shaped cell connectors for improved component quality, wherein a welded connection of high quality is ensured, in particular with regard to the electrical conductivity. In particular, a rotational or tilting movement of the cell connectors is made possible, which can adapt to electrodes of different heights. A flexible application is made possible with respect to the number of joints, that is to say depending on the size of the battery or the number of cells. The welding device according to the invention is thus particularly suitable for laser welding cell connectors having a thickness of more than 0.5 mm, which connect prismatic hardcase cells. Furthermore, the holding-down forces can be set as desired by different springs. A thin embodiment of the pressure piece makes possible very good accessibility for the laser beam. This can also be used for integrated, preferably optical, quality assurance systems, which are preferably connected to the scanner optics. There is therefore no threat of shadowing of edge finding systems for seam positioning. The welding device according to the invention is suitable both for welding individual cell connectors and also a plurality of cell connectors by multiple placements, which are combined in a module.According to an advantageous embodiment of the invention, the pressure piece is designed to be electrically insulating. This makes it possible to dispense with structurally more complicated insulators between the pressure piece and the holder.According to an advantageous development of the invention, the welding device is mounted on a robot arm or a gantry installation, which enables very flexible handling.According to an advantageous development of the invention, the hold-down device is fastened to a spacer arm. This ensures a sufficient distance between the holding-down device or its pressure piece and the laser welding device, so that the laser beam can be used to form the two welded connections by deflecting it at both ends of the cell connector.According to an advantageous development of the invention, the hold-down can be provided with replaceable springs for varying the contact pressure. This allows adaptation to different dimensions of batteries or cell connectors that require contact pressures of different magnitude.The object is furthermore achieved by a method for producing a welded connection between two electrodes of two adjacent battery cells of a battery by means of a cell connector, whereinplacing the cell connector on the two electrodes to be connected,the device according to one of the preceding claims is moved centrally against the cell connector in such a way that the pressure piece is pressed against or onto the cell connector, whereby the latter is pressed uniformly against the electrodes,the position of the first welded connection to be produced between the cell connector and the first electrode is determined by means of the scanner optics with position detection,the laser welding device or the laser beam is aligned accordingly,the first welded connection is produced,the position of the second welded connection to be produced between the cell connector and the second electrode is determined by means of the scanner optics with position detection,the laser welding device or the laser beam is aligned accordingly, andthe second welded connection is produced.In this case, the laser beam is deflected for the welding and moved over the components.With a placing process, a cell connector can be electronically contacted completely, with two or more welded seams. The hold-down concept according to the invention enables flexible welding of both fillet and I seams.According to an advantageous development of the method, a cell connector is used whose underside is curved one-dimensionally, so that both ends to be connected to the electrodes are lower than the central region. This ensures that only the outer edges of the cell connector rest on the electrodes.Further advantages, features and details are evident from the following description, in which--where appropriate with reference to the drawings--at least one exemplary embodiment is described in detail. Identical, similar and / or functionally identical parts are provided with the same reference numerals.The following are shown: FIG. 1 : a perspective illustration of the welding device according to the invention; FIG. 2 : a detail view of the lower region of FIG. 1 from another direction; FIG. 3 is a schematic illustration of the area of FIG. 2.FIG. 1 shows a perspective view of a welding device 10 according to the invention, which is attached to a robot arm or gantry axes, not shown. This comprises a laser welding device in the form of a scanner optics 13, a spacer arm 14 with a hold-down 16 fixed at the lower end, at the end of which a pressure piece 18 is pressed downward by means of a compression spring 20. The pressure piece 18 is designed to be electrically insulating and is preferably made of a plastic.Below the welding device 10, two battery cells 22 a, 22 bto be electrically connected are arranged parallel next to one another, which each have upwardly projecting electrodes 24 a, 24 bto be electrically connected. For this purpose, a cell connector 26 is placed on the two electrodes 24 a, 24 band brought into electrical contact therewith and welded by means of the welding device 10 to both electrodes 24 a, 24 bby means of a respective weld seam 28 a, 28 b.As shown in FIG. 3, a cell connector 26 is preferably used, the underside 27 of which is curved one-dimensionally inward (groove-like when viewed from below), so that both ends to be connected to the electrodes 24 a, 24 bare lower than the central region. This ensures that only the outer edges of the cell connector rest on the electrodes.As is shown in FIG. 3, the battery cells 22 a, 22 bor their electrodes 24 a, 24 bmay have different heights due to production or tolerance (shown in exaggerated form in FIG. 3 for illustrative reasons), so that by means of a conventional welding device faults would occur in both welded seams 28 a, 28 b,whether the produced welded seam is fragile and can break during operation by vibrations or impacts or that the welded seam has too great a contact resistance or even ensures no electrical connection to the cell connector 26.The welding device 10 according to the invention is characterized in that the pressure piece 18 has a rounded pressure surface 30 and thus only a point contact acts on the cell connector 26, which is aligned by a rotational or tilting movement between different heights of the cover surfaces of the electrodes 24 a, 24 b, as is represented by the arrow 31, and on both electrodes 24 a, 24 b, reliably evenly acted upon by a suitable force. For this purpose, the pressure piece 18 is pressed as centrally as possible between the two bearing surfaces of the cell connector 26 on the electrodes 24 a, 24 bfrom above against or onto the cell connector 26.If the welding device 10 has thus been moved in such a way that the pressure piece 18 is pressed against the cell connector 26, then the position of the (left-hand in the example shown) edge of the cell connector 26 resting on an electrode 24 a, 24 bmay be determined by means of the scanner optics 13 and the position detection, and the laser welding device 12 may be aligned accordingly in order to produce the left-hand weld seam 28 abetween the electrode 24 aand the cell connector 26 in FIGS. 2 and 3 by means of the laser beam 32 a. The focus position of the laser welding device 12 is readjusted according to the spring-in movement of the pressure piece 18.The position of the right edge of the cell connector 26 is then determined by means of the scanner optics 13 and the position detection, and the right weld seam 28 bin FIG. 2 is produced by means of the laser beam 32 b.Although the invention has been illustrated and explained in more detail by a preferred exemplary embodiment, the invention is not restricted thereby and other variations can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention. It is clear that embodiments mentioned by way of example represent only examples which should not be interpreted in any way as limiting, for example, the scope of protection, the possible applications or the configuration of the invention. Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms, wherein the person skilled in the art, knowing the disclosed inventive concept, can make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, without departing from the scope of protection defined by the claims and their legal equivalents, such as further explanations in the description.List of reference characters10 Welding device 12 Laser welding device 13 Scanner optics 14 Spacer arm 16 Holding-down device 18 Pressure piece 20 Compression spring 22 a,b Battery cells 24 a,b Electrodes 26 Cell connector 27 Underside of the cell connector 28 a,b Weld seam / weld connection 30 Pressure surface 31 Arrow 32 a,b Laser beamReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2022 000 445

[0002] EP 3 305 460 A1

[0003] DE 10 2019,127 676 A1

[0004]

Claims

Welding device (10) for welding two electrodes (24a, 24b) of two adjacent battery cells (22a, 22b) by means of a cell connector (26), comprising a laser welding device (12) and a holding-down device (16) having at least one spring-loaded pressure piece (18) for pressing the components (26, 24a, 24b) to be welded on, characterized in that the welding device (10) comprises a scanner optical unit (13) with position detection for detecting the welding points and for aligning the laser welding device (12) or the laser beam (32a, b), in addition the laser welding device (12) and the holding-down device (16) are structurally connected and the pressure piece (18) has a rounded pressure surface (30) which is designed to enable tolerance compensation for the cell connector (26) when it is placed on the electrodes (24a, 24b) to be welded.Welding device according to claim 1, characterised in that the pressure piece (18) is designed to be electrically insulating.Welding device according to one of the preceding claims, characterized in that the welding device (10) is mounted on a robot arm.Welding device according to one of the preceding claims, characterized in that the holding-down device (16) is fastened to a spacer arm (14).Welding device according to one of the preceding claims, characterized in that the holding-down device (16) can be provided with replaceable springs (20) for varying the contact pressure.Method for producing a welded connection (28a, 28b) between two electrodes (24a, 24b) of two adjacent battery cells (22a, 22b) by means of a cell connector (26), characterized in that - the cell connector (26) is placed on the two electrodes (24a, 24b) to be connected, - the welding device (10) according to one of the preceding claims is moved centrally against or onto the cell connector (26) in such a way that the pressure piece (18) is pressed against the cell connector, as a result of which said cell connector is pressed uniformly against the electrodes (24a, 24b), - the position of the first welded connection (28a) to be produced between the cell connector (26) and the first electrode (24a) is determined by means of the scanner optical unit (13) and the position detection, - the laser welding device (12) is aligned accordingly, the first welded connection (28a) is produced, the position of the second welded connection (28b) to be produced between the cell connector (26) and the second electrode (24b) is determined by means of the scanner optical unit (13) and the position detection, the laser welding device (12) and the laser beam (32a, b) are aligned accordingly, and the second welded connection (28b) is produced.Method according to claim 6, characterised in that a cell connector (26) is used, the underside of which is curved inwardly one-dimensionally.

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