Laser welding system and method of use for welding busbars to a stack of battery cells - Patents.com

Abstract

A laser welding system can include a laser welder having a light emitter configured to emit a laser beam and a scanning head optically coupled to the laser emitter, and a robot having an end effector, the end effector having a body, a resilient member having a first end attached to the body and a second end opposite the first end, a pressure element at the second end of the resilient member, and a laser aperture extending across the body, the resilient member, and the pressure element, wherein the laser beam is directed through the laser aperture by the scanning head when any one of the pole regions is pressed against a corresponding one of the electrodes by the pressure element.

Description

[Technical field]

[0001] The present improvement relates generally to energy storage systems and, more specifically, to the assembly of battery modules. [Background technology]

[0002] Typically, an energy storage system includes one or more packs of battery modules, each containing a number of battery cells held together in an array configuration (i.e., stacked) and bus bars connecting the battery cells in an electrical circuit. Among the existing types of battery cells used in battery modules, the cylindrical shape is perhaps the most widely used. A format that is widely used in some markets, such as electric vehicles, has a cylindrical shape and both the positive and negative poles are accessible at the same end, which can be called the pole end. To stack battery cells, as shown in the examples presented in Figures 1, 1A, and 1B, the axes of the battery cells are parallel to each other, all of the pole ends are facing the same side, and the pole ends are aligned in a common polar plane extending perpendicular to the axes.

[0003] The battery cells, and more specifically the battery poles, can be connected in an electrical circuit using components commonly referred to as busbars. The busbars can be provided in the form of sheet-like elements having positive and negative pole areas with separate conductive paths. The busbars can be aligned parallel to a common pole plane and positioned adjacent to the poles of the battery cells, and the pole areas of the busbars can be welded to the corresponding ones of the poles.

[0004] The busbars and battery cells are manufactured separately and assembled together by a welding process that requires multiple independent welds, at least as many as there are pole areas and poles to be welded. Furthermore, the battery cells are typically at least partially charged during the welding operation, since for many types of batteries, leaving the battery uncharged for an extended period of time will render the battery inoperable. The welding operation described below will require placing the stacked battery cells in the welding area of ​​a welding system, with the poles facing upwards and the busbar extending over the poles and vertically aligning the pole areas with their corresponding ones, and welding the pole-pole area pairs together one by one until all poles are welded to the corresponding pole areas of the busbar to form a battery module. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Pat. No. 1,079,2761 [Patent Document 2] U.S. Pat. No. 1,383,331 [Patent Document 3] U.S. Pat. No. 1,527,805 [Patent Document 4] U.S. Patent No. 9,722,229 [Patent Document 5] US Patent Application Publication No. 2021 / 0273298 [Patent Document 6] US Patent Application Publication No. 2022 / 0040791 Summary of the Invention [Problem to be solved by the invention]

[0006] Although existing welding techniques are satisfactory to some extent, there remains room for improvement. [Means for solving the problem]

[0007] As an increasing portion of energy consumption transitions from fossil fuel energy to electrical energy, it is desirable to manufacture energy storage systems as efficiently as possible, which can involve a variety of aspects.

[0008] As an example, certain standardized battery cell formats are becoming increasingly popular, such as formats 21700 and 18650. Both of these standardized formats have a generally cylindrical body, a projection located in the center of a first generally disc-shaped end face forming a positive electrode, and a negative electrode embodied as an annular tip of a peripheral wall surrounding the positive electrode but spaced radially therefrom, such as that shown in Figures 1A and 1B, the radial spacing of which can be seen in Figure 1A.

[0009] Welding the pole areas of a busbar to the poles of a battery cell using a laser can be particularly interesting from the standpoint of precision and efficiency. However, it may be necessary to press the pole areas against the corresponding poles prior to activating the laser beam for welding in order to ensure good contact between the pole areas and the poles when heated by the laser. This creates the challenge of applying pressure close enough to the areas to be welded in a suitable, i.e. relatively balanced, manner, but without interfering with the path of the laser beam. Furthermore, from a productivity standpoint, there may be a desire to perform all welds as quickly as possible in a manner consistent with specifications.

[0010] According to one aspect, there is provided a laser welding system for welding pole regions of a busbar to electrodes of a battery cell module with a laser beam, the laser welding system receiving the busbar and battery module into a welding area and aligning the pole regions adjacent to corresponding ones of the electrodes, the laser welding system including a laser welder having an emitter configured to emit the laser beam and a scan head optically coupled to the laser emitter, and a robot having an end effector, the end effector having a body, a resilient member having a first end attached to the body and a second end opposite the first end, a pressure element at the second end of the resilient member, and a laser aperture extending across the body, the resilient member, and the pressure element, the laser welding system directing the laser beam through the laser aperture by the scan head when any one of the pole regions is pressed against a corresponding one of the electrodes by the pressure element.

[0011] It may be particularly advantageous for the elastic member to comprise a helical spring having an axis parallel to the battery cell axis, for the pressure element to comprise an annular body of thermally insulating material concentric with the helical spring, the annular body being held at the second end of the helical spring, and for the opening forming the laser beam path to extend along the axis of the helical spring and the annular body.

[0012] According to another embodiment, the end effector can advantageously have two pressure elements, each of which is elastically supported on the body and has a corresponding opening. For example, the first pressure element can be a positive pressure element and the second a negative pressure element. In fact, the movement of the end effector of the robot takes a time that is directly proportional to the speed of the robot, which is usually lower than the speed at which the scanning head of the laser welding machine can move its laser direction. By using an end effector with two pressure elements and a laser welding opening, two welds can be performed one after the other, for example with intermediate movements by the scanning head, without the need to release pressure or move the end effector, which is only moved between the pairs of welding points. This can lead to time savings and a corresponding increase in productivity.

[0013] In some cases, the two pressure elements can be supported independently of each other via corresponding elastic members in a manner that allows the pressure elements to smoothly and naturally adapt to small variations that may occur in the exact height of the positive and negative electrode regions from one battery cell to the next or from one battery module to the next, for example due to the negative electrode being only approximately flat from one battery cell to another.

[0014] By sequentially applying this welding under pressure technique to all of the pole areas of the busbar, all of the pole areas can eventually be securely welded to the corresponding electrodes of the battery module.

[0015] In fact, the weld lines can be performed by laser welding. Laser welding can provide clean and durable weld lines at a relatively fast pace. In an embodiment, the laser welding system has a housing in which a laser beam unit is housed and directed at each pole region. In performing the welding under pressure technique, the housing is moved towards the pole region of the busbar and pressure is applied thereto while the laser beam unit housed within the housing is operated to laser weld the pole region to the electrode below. In such an embodiment, the combined weight of the housing and the laser beam unit housed within it represents a source of inertia that limits the speed of movement from one battery cell to another. According to another embodiment, the laser beam unit can be held stationary and the optics within the unit are configured to move the laser beam from one pole region to another by redirecting the laser beam, while the pressing action is performed by a separate, potentially lightweight, pressing device, improving assembly time.

[0016] According to another embodiment of the present disclosure, there is provided a system for laser welding a busbar on a battery module, the busbar having at least one pair of pole regions disposed over a corresponding pair of electrodes of the battery module, the system including a scanning head such that at least a portion of the busbar is contained within a field of view of the scanning head; and a robot arm having a first end fixed to a base and a second end independent therefrom and movable within the field of view of the scanning head, the second end including an end effector having a first side facing the scanning head and an opposite second side facing the busbar. The system includes a body and a laser aperture extending across the body from a first surface to a second surface, with a plurality of pressure points on the second surface surrounding the laser aperture, and when the end effector is moved within the field of view of the scan head to expose a pair of pole regions of the bus bar to the scan head through the laser aperture, at least some of the pressure points of the end effector are pressed against the bus bar near the pair of pole regions, and the laser welding system is operated to laser weld each of the pole regions of the bus bar to a corresponding one of the electrodes of the battery module through the laser aperture.

[0017] According to another embodiment of the present disclosure, there is provided a method of laser welding a busbar on a battery module, the busbar having at least a pair of pole areas disposed over a corresponding pair of electrodes of the battery module, comprising: directing a field of view of a laser scanning head toward at least a portion of the busbar; moving an end effector within the field of view of the scanning head, the end effector having a body with a laser aperture extending across the body and a second surface having a plurality of pressure points surrounding the laser aperture; exposing the pair of pole areas of the busbar to the laser scanning head through the laser aperture as the end effector moves; and pressing at least some of the pressure points of the end effector against the busbar near the pair of pole areas; and, during the pressing, actuating the laser scanning head to laser weld each of the pole areas of the busbar to a corresponding one of the electrodes of the battery module through the laser aperture of the end effector.

[0018] In accordance with another embodiment of the present disclosure, there is provided an end effector for applying pressure on a busbar having at least a pair of pole regions spaced apart from one another by a given distance, the end effector comprising: a body having a first side and an opposite second side facing the busbar; first and second laser apertures extending across the body from the first side to the second side, the first and second laser apertures being spaced apart from one another by the given distance and having dimensions smaller than dimensions of the pole regions of the busbar; a plurality of pressure points on the second side surrounding each of the first and second laser apertures; and the body having a robot arm anchor for attachment to a robot arm.

[0019] Other and further features and combinations of features related to the present improvements will be apparent to those skilled in the art upon reading this disclosure.

[0020] The diagram is as follows: [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view of an example of a busbar according to the prior art. [Figure 1A] FIG. 1A is a cross-sectional view of the busbar of FIG. 1 taken along section line 1A-1A according to the prior art, showing an underlying battery module. [Figure 1B] FIG. 2 is a top view of a portion of the busbar of FIG. 1 according to the prior art, showing the underlying battery modules and weld lines. [Diagram 2] FIG. 1 is a schematic diagram of an example system for laser welding bus bars to battery modules according to one or more embodiments, showing the laser welding system together with a robotic arm having an end effector. [Diagram 3] FIG. 3 is a side view of the end effector of FIG. 2 according to one or more embodiments. [Figure 3A] FIG. 3 is a partial top view of the end effector of FIG. 2 according to one or more embodiments. [Figure 4] 3 is a graph illustrating the state of the laser welding system and robot arm of FIG. 2 in two successive welding procedures according to one or more embodiments. [Figure 5A] FIG. 13 is a top perspective view of another example end effector according to one or more embodiments. [Figure 5B] FIG. 5B is a perspective view of the end effector of FIG. 5A shown from below, according to one or more embodiments. [Figure 5C] FIG. 5B is a perspective view of the end effector of FIG. 5A shown from below, according to one or more embodiments. [Figure 6] FIG. 13 is a top view of another example system for laser welding bus bars to battery modules in accordance with one or more embodiments, showing multiple independent robotic arms with individual end effectors moving within the field of view of a single laser welding system. [Figure 7]7 is a graph illustrating the state of the laser welding system and the robot arm of the system of FIG. 6 during successive welding procedures according to one or more embodiments. [Figure 8A] FIG. 13 provides another example embodiment of an end effector configured to operate as an end effector according to one or more embodiments. [Figure 8B] FIG. 13 provides another example embodiment of an end effector configured to operate as an end effector according to one or more embodiments. [Figure 8C] FIG. 13 provides another example embodiment of an end effector configured to operate as an end effector according to one or more embodiments. [Figure 9A] 8A, 8B, and 8C according to one or more embodiments. FIG. [Figure 9B] 8A, 8B, and 8C according to one or more embodiments. FIG. [Figure 10A] 8A-8C according to one or more embodiments. FIG. 8B illustrates an alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 10B] 8A-8C according to one or more embodiments. FIG. 8B illustrates an alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 11A] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 11B] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 12A]8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 12B] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 13A] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 13B] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 14A] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 14B] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 15A] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 15B] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 16A] 8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 16B]8A-8C according to one or more embodiments. FIG. 8B presents another alternative embodiment of an end effector adapted to those end effectors such as those shown in FIGS. 8A, 8B, and 8C. [Figure 17] 1 is a flow chart of an example method of laser welding a busbar to a battery module according to one or more embodiments. [Figure 18] FIG. 2 is a schematic diagram of an example information processing device of a controller in a system for laser welding bus bars to battery modules in accordance with one or more embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] 1 and 1A show an example of an energy storage device, which includes a busbar that is welded to battery cells to form a battery module. In this example, the busbar is provided in the form of a sheet-like element having a plurality of sets of pole areas interconnected via conductive paths. Typically, such a busbar may have, for example, a plurality of negative pole areas interconnected via a negative conductive path and a plurality of positive pole areas interconnected via a positive conductive path. The busbar may be disposed on the arrayed battery cells such that all the pole areas of the busbar are aligned with the corresponding electrodes of the battery cells (see FIG. 1A). The battery module includes a plurality of battery cells, which are cylindrical in this example. As shown, the battery cells have both electrodes, which are accessible at the same end, i.e., the top end. More specifically, a first electrode is provided at the top end of each battery cell in the form of a protrusion located in the center of one of the disk-shaped end faces of the cell, and a second electrode is provided as an edge of a peripheral wall extending between the upper first end of the battery cell and the opposite lower second end of the battery cell. In this example, the first electrode is positive and the second electrode is negative. As shown, the busbar has at least one pair of positive and negative electrode regions that are located above a corresponding pair of electrodes of the battery module when the busbar is suitably positioned above the battery module. In some embodiments, the poles may be reversed or their individual shapes, configurations or sizes may be changed. The battery cells shown in this example are standardized battery cells "size 21700", but any other type of battery cell, such as standardized battery cells "size 18650", may be used in other embodiments, which may be termed alternative examples. FIG. 1B shows a top view of the busbar with the battery cells below it shown in dashed lines. As shown, examples of first and second weld lines for the positive and negative electrodes are also shown in dashed lines.

[0023] 2 illustrates an example of a laser welding system 200 for laser welding a bus bar 202. As illustrated, the laser welding system 200 includes a laser welder 204 having a laser emitter 206 optically coupled to a scanning head 208 having a field of view 210 that includes a welding area A. w 2. In this example, the bus bar 202 is aligned with a horizontal plane H. The scan head 208 is disposed directly above the bus bar 202 and is directed downward toward the bus bar 202. Although it may be desirable in certain embodiments to have the scan head 208 disposed above the bus bar 202, in other embodiments, it may be preferable to have the field of view 210 oriented at an angle relative to the bus bar 202. The field of view 210 of the scan head 208 includes a large number of battery cells 212, for example, more than 25 battery cells or more than 100 battery cells. The scan head 208 may include an enclosure 214 and a beam delivery output 216 disposed within the enclosure 214 for delivering a laser beam 218 when desired. An adjustable mirror assembly may be incorporated into the scan head 208 to receive the laser beam 218 and move it anywhere in the plane of the bus bar 202, i.e., along the x-axis and y-axis. According to certain embodiments, the scan head 208 may have an adjustable focus lens to move the focus of the laser beam along the z-axis. For example, the adjustable mirror assembly may include one or more 1-axis, 2-axis, or 3-axis mirror galvanometer scan heads and / or any other suitable optical components. Finally, the configuration of the scan head 208 may vary from embodiment to embodiment. In this embodiment, the bus bar 202 is positioned within the field of view 210 of the scan head 208 at a distance within the working distance of the scan head 208. Thus, the scan head 208 does not need to be moved to laser weld different portions of the bus bar 202, but rather the laser beam 218 is simply moved by the movement of a mirror in the scan head 208. The working distance of the scan head 208 can be, for example, in the range of 10-100 cm, in the range of 25-75 cm, or about 55 cm.

[0024] The laser welding system 200 includes a robot 220 having a first robot arm 222 having a first end 222a fixed to a base 224 and a second end 222b carrying an end effector 226 and movable within the field of view 210 of the scan head 208. The base 224 may be a table or a manufacturing equipment surface depending on the embodiment. The first robot arm 222 may be any suitable type of manufacturing or industrial robot arm, such as a delta robot arm, a SCARA robot arm, or the like. As shown, the first robot arm 222 may be operated independently of the operation of the scan head 208 and may be moved independently of the operation or movement of the laser beam 218. Thus, the first robot arm 222 may be moved as desired within the field of view 210 of the scan head 208. According to certain embodiments, the laser welding system 200 may also be provided with a second robot arm 228 having a first end 228a fixed to the same base 224 or another base and a second end 228b that holds the scan head 208 for movement thereof. As shown, if the first and second robot arms 222 and 228 are independent of each other, the scan head 208 may be moved in a plane parallel to the plane of the bus bar 202, independent of the second end 222b of the first robot arm 222. According to other embodiments, the second robot arm 228 may be replaced by a gantry system having a holder that holds the scan head 208 and moves the scan head 208 in the xy plane above the stack of battery cells 212.

[0025] A controller 230 may be provided within the laser welding system 200 and communicatively coupled to the laser welding system 200, the first robot arm 222, the second robot arm 228, or a combination thereof. The controller 230 generally includes a processor and memory having instructions stored thereon that, when executed, perform one or more laser welding procedures including, but not limited to, i) moving the first and second robot arms 222 and 228 according to a coordinated motion sequence, ii) redirecting the laser beam 218 using the scan head 208, and iii) activating and deactivating the laser welder 204 as needed. According to certain embodiments, the laser welding system 200 may include a camera 232 communicatively coupled to the controller 230. The camera 232 may be configured to capture one or more two- or three-dimensional images of the busbar 202. The controller 230 can then receive the image(s) and determine the position and orientation of each pair of pole regions of the busbar 202 and use them for the laser welding procedure. In certain embodiments, the position and orientation of the pole regions of the busbar 202 are determined at a modeling station that is spatially separated from the laser welding station. For example, a three-dimensional model of the battery module and its busbar can be created at the modeling station. According to these embodiments, the camera 232 can be used to detect the location of one or more fiducials on the battery module(s) to aid in positioning the three-dimensional model in the coordinate system of the laser welding system 200.

[0026] According to this embodiment, the end effector(s) 226 of the robot 220 may be embodied as a pressure applicator 234. In this embodiment, as best shown in FIG. 3, the end effector 226 has a body 236 having a first side 236a facing the scan head and an opposite second side 236b facing the bus bar 202. The body 236 of the end effector 226 also has one or more openings forming at least one laser aperture 238 that extends across the body 236 from the first side 236a to the second side 236b. The end effector 226 may have one or more portions, which may be referred to as "pressure elements 240," configured to be in contact with the bus bar 202 during application of pressure to the pole region. Each pressure element 240a, 240b may typically have a specific surface area configured to partially or completely surround a pole region in terms of pressure equalization, and may be referred to as having multiple pressure points surrounding the laser aperture 238. The end effector 226 may have a weight of less than 5000 grams, preferably less than 1000 grams, and more preferably less than 500 grams. Limiting the weight of the end effector 226 limits its motion resistance or inertia, which in turn allows for faster end effector displacement. The end effector 226 may be moved by the second end of the first robot arm at a maximum speed of at least 5 m / s, preferably at least 8 m / s, and more preferably at least 12 m / s. In certain embodiments, the time required for one laser welding procedure may be, for example, less than 500 ms, preferably less than 300 ms, and more preferably less than 200 ms.

[0027] In embodiments where both the positive and negative electrodes 241 a and 241 b of the battery cells 212 are accessible on the same side of the battery array, it may be advantageous to have the end effector 226 have both a first positive pressure element 240 a and a second negative pressure element 240 b with laser apertures 238 associated therewith to weld corresponding ones of the positive and / or negative electrode regions 242 a and / or negative electrode regions 242 b of the bus bar 202 sequentially (i.e., without moving the end effector 226 between them) or simultaneously (i.e., with multiple laser beams, if any).

[0028] In certain embodiments, it may be desirable to receive the pressure element by the body 236 of the end effector 226 via the resilient member 246, as this provides some flexibility, e.g., to accommodate relatively small height variations from one pole region to the next, and facilitates application of a generally uniform pressure from one pole region to the next along the weld path. Additionally, in certain embodiments, it may be desirable for the pressure element to be a separate member that is assembled to the resilient member, and not simply implemented as part of the pressure element. This allows the pressure element and the resilient member, for example, to be made of different materials or simply manufactured separately.

[0029] It is noted that in certain embodiments, a minimum charge may be required to remain in the battery cell at all times to maintain the functionality of the battery cell. Thus, electrical energy may be present in the battery cell during a welding operation. In certain embodiments, particularly those in which both the positive pressure element 240a and the negative pressure element 240b are provided on the end effector 226, it may be desirable to electrically isolate the end effector 226 as a whole, or one or both of the positive and negative pressure elements 240a and 240b, from the rest of the mechanical assembly. For example, it may be appropriate to electrically isolate the positive pressure element 240a from the negative pressure element 240b to avoid short circuits between them. Thus, in some embodiments, it may be desirable to electrically isolate either one, or preferably both, of the pressure elements 240a and 240b. According to certain embodiments, this can be achieved by constructing the pressure element 240 from an inherently electrically insulating material, such as a plastic or ceramic material. According to another embodiment, this can be achieved by covering an inherently conductive material, such as a metal, with an electrically insulating coating. 2 S / m, preferably 10 5 A material can be considered conductive if it has a conductivity greater than 10 S / m. -3 S / m, preferably less than 10 -10 A material can be considered electrically insulating if it has a conductivity less than S / m.

[0030] It is further noted that in certain embodiments, since a large amount of heat may be generated by the laser action, it may be desirable to i) make the pressure element(s) 240a and 240b, and possibly also the elastic member(s) 246, heat resistant, i.e. adapted to withstand the potentially high temperatures that may be encountered during the laser welding process, and ii) have the pressure element(s) 240a and 240b act as thermal insulators from the rest of the mechanical assembly. Indeed, the fact that the pressure elements 240a and 240b may be quite close to the area to be welded, and that the thermally conductive metal that makes up the busbar 202 may run straight between them, leads to high temperatures at the pressure points. Therefore, it may be desirable to make the pressure elements 240a and 240b not only from an electrically insulating material, but also from a material that is thermally insulating and potentially able to withstand relatively high temperatures. In certain embodiments, ceramic or high temperature plastic materials may be of particular interest in these circumstances. In the context of this specification, 1 Wm -1 K -1 More than 100 1Wm -1 K -1 A material can be considered thermally conductive if it has a thermal conductivity of more than 1 Wm -1 K -1 Less than 0.1Wm -1 K -1 A material may be considered thermally insulating if it has a thermal conductivity of less than 100° F. As used herein, a material may be considered heat resistant if it maintains its mechanical and structural properties at temperatures above 300° F., and preferably above 500° F.

[0031] The welding process for assembling a battery module may be comprised of a series of welding steps. According to one embodiment, one welding step generally incorporates moving the end effector 226 within the field of view 210 of the scan head to expose the positive and / or negative electrode regions 242a and 242b of the busbar 202 to the scan head through the laser aperture 238 as shown in FIG. 3A and directing a laser beam to the corresponding positive and / or negative electrode regions 242a and 242b. When the end effector 226 reaches the corresponding pole regions, the pole regions of the busbar 202 may be clamped against the positive and / or negative electrodes of the corresponding battery cells, for example by controlling the application of force via a pressure element. The laser welding system may be operated while holding the end effector 226 in position to laser weld the corresponding pole regions of the busbar 202 to the corresponding electrodes of the battery cells through the laser aperture 238. This laser welding procedure can be repeated for a group of battery cells to provide first and second weld lines, one for each pair of positive and negative electrode regions 242a and 242b of the bus bar 202.

[0032] 3A, the first and second laser apertures 238a and 238b of the laser aperture 238 may be sized and shaped to expose corresponding ones of the paired positive and negative pole regions 242a and 242b, respectively. For example, the first laser aperture 238a may be sized and shaped to expose the positive pole region 242a above the positive pole 241a of the battery cell 212, while the second laser aperture 238b may be sized and shaped to expose the negative pole region 242b above the negative pole 241b of the battery cell 212. In certain embodiments, it may be desirable for the second laser aperture 238b to better conform to the shape of the negative pole 241b, such as being elongated and somewhat arcuate. 3 above, it has been found to be advantageous in certain embodiments to have the laser apertures, e.g., first and / or second laser apertures 238a and 238b, tapered from the first surface 236a to the second surface 236b of the end effector 226. This allows the pole regions 242a and 242b of the busbar 202 to be exposed at a larger angle relative to the field of view 210 of the scan head. In certain other embodiments, the body 236 of the end effector 226 may have a thickness below a certain threshold, again allowing for a larger angle of exposure. For example, in certain embodiments, the body 236 of the end effector 226 may be flat and have a thickness in the range of 1-20 mm, preferably in the range of 2-10 mm, and more preferably about 5 mm. In other embodiments, the body 236 may have a different shape.

[0033] 3, a welding sequence can include a transverse motion 250a in a plane parallel to the plane of the busbar 202 through which the end effector 226 is moved into alignment along the XY plane (e.g., horizontal) with a given battery cell 212, a vertical downward motion 250b that can result in the application of force, a period of immobility during which the laser weld is performed (the laser is actuated at the corresponding area), and a vertical upward motion 250c in which the end effector 226 is moved away from the busbar 202 after the laser weld, including pressure relief. In an embodiment having multiple robots, the laser welder can alternate from one end effector to another, allowing one end effector to be displaced while welding is performed with the other end effector.

[0034] In some embodiments, the pressure elements 240a and 240b of the end effector 226 protrude from the second surface 236b of the end effector 226. The pressure elements 240a and 240b may form one or more perimeter lines that may surround either or both of the positive and negative electrode regions 242a and 242b of the bus bar 202 when the end effector 226 is in place. The pressure elements 240a and 240b may also be biased toward the second surface 236b of the body 236, thereby transmitting a tight, repeatable force from one battery cell to another. The biasing mechanism may take a variety of forms depending on the embodiment, and may typically involve one or more resilient members. For example, in the illustrated embodiment, the end effector 226 includes a first coil spring having a first hollow end mounted on the second surface and surrounding the first laser aperture, and a second hollow end on the opposite side and spaced apart from the first hollow end. As shown, the second hollow end of the coil spring includes one or more pressure elements. When in position, the second hollow end surrounds the positive electrode region of the bus bar and presses the positive electrode region against the positive electrode of the underlying battery cell. The end effector also includes second coil springs having a first hollow end mounted on the second surface and interspersed around the second laser aperture, and a second hollow end on the opposite side and spaced apart from the first hollow end. As shown, the second hollow end of the second coil spring includes one or more pressure elements. As such, when the end effector is moved vertically downward, the pressure element can be biased into abutment against the periphery of the negative pole region of the bus bar. Other types of coils or biasing mechanisms can be used in other embodiments.

[0035] In certain embodiments, the robot arm may be configured to move the end effector 226 only in a plane parallel to the bus bar 202, while a second end of the robot arm may have a separate actuator configured to move the end effector 226 across the plane of the bus bar 202 (i.e., along the Z-axis), and in other embodiments, the robot arm may be responsible for free-floating the end effector 226 in three dimensions.

[0036] According to certain embodiments, the second end of the robot arm can have a separate actuator configured to rotate the end effector 226 about an axis perpendicular to the plane of the bus bar 202 (i.e., about the Z axis). The latter separate actuator can help ensure that the first and second laser apertures 238a and 238b of the end effector 226 are aligned with the corresponding pole regions 242a and 242b of the bus bar 202, which can be appropriate, for example, when the robot arm has members that pivot in the X / Y plane. According to certain embodiments, the actuator is pivotally mounted to the second end and / or the end effector using a bearing that has a central laser aperture so that the laser beam can be directed through the central laser aperture.

[0037] In some embodiments, the movement can further include pivoting the end effector about an axis perpendicular to the plane of the busbars to ensure that pairs of positive and negative regions of the busbars that cross corresponding ones of the laser apertures are properly exposed by the laser apertures. In some embodiments, the pivoting can be performed during the transverse movement 250a, during the vertical downward movements 250b and 250c, or sequentially after any one of those movement steps.

[0038] FIG. 4 is a graph 400 illustrating two successive welding sequences 452 that may be performed by the system of FIG. 2. As shown, the first robot arm moves laterally during a first period t1, then moves vertically downward during a second period t2, and then is held in place during a third period t3. The laser welding system is activated during the third period t3 to perform the required weld line. The first robot arm is then moved vertically upward during a fourth period t4. This welding sequence is performed multiple times, so that in time, all pairs of positive and negative electrode regions of the busbar are successfully welded to the corresponding poles of the battery cells. In an exemplary embodiment, the first, second, and fourth periods t1, t2, and t4 each reach 60 ms, while the third period t3 lasts only 20 ms, i.e., the time required for the laser welding system to perform two weld lines, so that the laser welding system is activated for only about 11% of the total time for a given welding sequence. In another embodiment, the first, second and fourth periods t1, t2 and t4 each reach 50 ms, while the third period t3 lasts only 15 ms. It may be noted that in this example, the duration of the entire welding procedure is strongly influenced by the motion of the first robot arm, suggesting that reducing the footprint, and therefore the total weight of the end effector, can have a positive impact on the total duration of the welding procedure with a given robot.

[0039] 5A, 5B, and 5C show an example of an end effector 526 for applying pressure to a bus bar having positive and negative pole regions spaced apart from one another by a given distance. As shown, the end effector 526 has a body 536 having a first surface 536a shown in FIG. 5A and a second surface 536b (shown in FIG. 5B) opposite the first surface 536a. The body 536, in this example, has a flat, triangular-like shape. As shown, the body 536 has first and second laser apertures 538a and 538b that extend across the body 536 from the first surface 536a to the second surface 536b. The first and second laser apertures 538a and 538b, in this example, are spaced apart from one another by a given distance d. The first surface 536a has a recess 556 with first and second laser apertures 538a and 538b formed therein. The body 536 has one or more robot arm anchors 558 for attachment to a second end of a first robot arm. The robot arm anchors 558 are provided in the form of a threaded cavity and may be removably or fixedly attached to the second end of the first robot arm using one or more bolts. In certain embodiments, the first laser aperture 538a has a diameter smaller than a diameter of the positive pole region, while the second laser aperture 538b has a dimension along at least one axis or arc smaller than a corresponding dimension of the negative pole region of the busbar and is adapted to allow a laser beam to form a weld line in a portion of the negative pole region or the positive pole region.

[0040] Also as shown in this embodiment, the first and second laser apertures 538a and 538b of the end effector 526 have a tapered shape that decreases in size from the first surface 536a to the second surface 536b. The first laser aperture 538a has a round shape and is designed to encompass the portion of the busbar pole area directly above the positive terminal of the battery cell. The second laser aperture 538b has a curved shape and is designed to encompass the portion of the busbar pole area directly above a portion of the negative terminal of the battery cell.

[0041] As best shown in Figures 5B and 5C, the second surface 536b has first and second pressure elements 540a and 540b surrounding the corresponding ones of the first and second laser apertures 538a and 538b. The first pressure element 540a has a first helical spring 560, which is attached to the second surface 536b and has a first open end 560a surrounding the first laser aperture and an opposite second open end 560b. In this embodiment, the first pressure element 540a is realized as a circularly curved second open end 560b of the first helical spring 560. In this way, the laser welding beam can be directed along the first coil spring 560 and into its hollow portion during laser welding. The end effector 526 also includes three second coil springs 562 having first open ends 562a attached to the second surface 536b and interspersed around the second laser aperture 238b, and opposite second open ends 562b. In this example, the second pressure element 540b is provided in the form of a pressure plate 564 attached to the second open ends 562b of the second coil springs 562 to provide an even pressure distribution. The pressure plate 564, in this example, can provide one or more pressure points. The pressure plate 564 includes a laser aperture 566 that is horizontally oriented within the perimeter defined by the three second springs 562. As shown, the aperture 566 is sized and shaped to expose an arc of the negative terminal region of the busbar that is directly above a portion of the negative terminal of the battery cell.

[0042] In some embodiments, multiple robots or robot arms may be provided. Here, in the system 600 illustrated in FIG. 6, there are four separate and mechanically independent robots 620, each having a robot arm 622 with its own end effector 626. As shown, the triangular shaped end effectors 626 can provide at least some clearance, allowing each end effector 626 to have increased movement capabilities. The four end effectors 626 are attached to the second ends of the robot arms 622 using cantilever-type members. The cantilever-type members can help to move the field of view of the scan head away from parts of the robot arm that may obstruct the field of view. In this example, each robot arm 622 has a first end 622a fixed to a base on a respective side of the battery module and a second end 622b that can be moved above the pack of battery cells 612 within the field of view 610 of the laser welding system. By using multiple robot arms 622, the time required to laser weld all the pole areas of the busbar to the corresponding electrodes of the battery cells 612 can be significantly reduced. Graph 700 shown in FIG. 7 illustrates the state of the laser welding system and the first robot arm during successive welding sequences 752. As shown, each of the robot arms is performing a similar welding sequence 752, but delayed from each other. This therefore allows the laser welding system to operate four times more times during one welding sequence, thereby reducing the amount of time required to laser weld all the battery cells that make up the module. In certain embodiments, a single first robot arm may be sufficient. According to certain other embodiments, two or more first robot arms may be used to proportionally optimize the laser welding sequence and the overall throughput.

[0043] 8A-8C show yet another example embodiment of an end effector 826 adapted for applying pressure between a pole region of a busbar and an electrode of a stack of battery cells during laser welding of the pole region to a corresponding electrode. The end effector 826, as shown more generally in FIG. 8A, has a proximal end 826a carrying a robot arm anchor configured to secure the end effector 826 to a second end of a robot arm, and a distal end 826b opposite the proximal end 826a. As best shown in FIGS. 8A and 8B, the end effector 826 carries a body 836, a resilient member 860 having a first end attached to the body 836 and a second end opposite the first end, and a pressure element 840a at the second end of the resilient member 860. A laser aperture 838a extends across the body 836, the resilient member 860, and the pressure element 840a. More specifically, in this embodiment, the pressure applying element 840a is the first pressure applying element 840a, and the end effector 826 further includes a second pressure applying element 840b, but the presence of two pressure applying elements is optional. If present, either one of the first and second pressure applying elements 840a and 840b can act as a positive pressure applying element and the other as a negative pressure applying element.

[0044] In the embodiment presented in Figures 8A-8C, the first pressure element 840a is annular in shape, the axis of which can be oriented by the robot during laser operation perpendicular to the plane of the busbar. The elastic member 860 comprises a helical spring that defines a spiral around an axis that coincides with the axis of the ring of the first pressure element. The first pressure element 840a is provided in this example as a separate member from the elastic member 860, since it is attached to the second end of the helical spring. The first pressure element 840a can be made of a heat-resistant material. The first pressure element 840a can be made of a thermally insulating material. The first pressure element 840a can be made of an electrically insulating material. Usually, but not always, a good thermal insulator material is also a good electrical insulator. Materials such as ceramics, high temperature plastics or zirconium (IV) silicate may be advantageously used as the material of the first pressure element 840a. The use of a thermally insulating material may help protect the helical spring 860 from the heat generated by the laser operation. The laser aperture 838a extends along the axis through the laser aperture 838a formed by the ring. Such a geometry may be particularly well adapted for welding of positive electrodes.

[0045] In the embodiment presented in Figures 8A-8C, the second pressure element 840b is adjacent to the first pressure element 840a. As shown, the first pressure element 840a and the second pressure element 840b are held at different distances from the body 836 when free from the busbar. Typically, such a height difference occurs in an embodiment where the positive electrode of the battery cell is slightly elevated with respect to the negative electrode. The second pressure element 840b has a protrusion leading to a pressure tip 868 carrying the laser aperture 838b, with a pressure body that is generally flat and can be directed horizontally by a robot arm. The second pressure element 840b can be attached to the end effector body by a resilient member in the form of a number of springs 862. The springs 862 can circumscribe the laser aperture 838b in a manner that balances the load between them. In the embodiment shown, three springs 862 are used.

[0046] As best seen in FIG. 8B, the pressure tip 868 of the second pressure element 840b, which in this embodiment may be somewhat related to the shape of a cashew, has a generally oval shape (i.e., elongated with rounded ends) and is flexed and curved along its length in a manner that follows the arc shape of the negative electrode, which will be referred to herein as a cashew shape for convenience. The second pressure element 840b may be made of a ceramic material, a high temperature plastic material, or a metal, to name certain examples. If a metal is selected, it may be coated with an electrically insulating material, if appropriate. It is also noted that having the pressure tip protrude from the rest of the pressure body may be useful in certain embodiments to avoid "obstacles", i.e., portions of the busbars and / or battery cells that may impede the movement of the end effector 826.

[0047] According to the illustrated embodiment, the elastic member 862 supporting the second pressure element 840b is separate from the elastic member 860 supporting the first pressure element 840a in this embodiment, which may provide additional versatility for certain embodiments, but is optional. According to certain embodiments, the first and second pressure elements 840a and 840b may have separate laser apertures and / or pressure points, but may be supported by the same elastic member, examples of which are described with reference to Figures 16A and 16B. The use of separate elastic members may be useful, for example, to better accommodate eventual variations in height difference (and / or thickness) between the positive and negative pole regions, such that application of uniform pressure from one pole pair to another is easily achieved.

[0048] 9A and 9B present an alternative embodiment of the end effector 926, which is generally similar to the embodiment depicted in FIGS. 8A-8C, but differs in that the pressure body of the second pressure element 940b is generally rectangular in shape instead of generally triangular, and is supported by four helical springs 962 instead of three. Moreover, the pressure body 940b has a lateral recess 970 configured to absorb the relative displacement of the annular first pressure element 940a. Moreover, the body of the end effector 934 is not only generally cylindrical and flat in shape, but also has a protrusion leading to a helical spring seat 972. With the help of the protrusion, the busbar and parts of the end effector can be pulled away from final obstacles formed by parts of the busbar, battery cells, or other parts of the battery module.

[0049] 10A-10B to 15A-15B present many exemplary potential variations of the second pressure element. The opening and pressure tip in 15A-15B extend along a shorter arc than in the embodiment shown in 10A-10B, for example. 12A-12B have a radially wider opening than in the embodiment shown in 15A-15B. In the case of 11A-11B, 13A-13B, 14A-14B, the pressure element forms an open shape, as opposed to the closed loop shape shown in the other embodiments. Such an open shape can help to avoid obstacles that may be radially outward in some embodiments. In the example of 11A, a partition 1174 is present, which can contribute to a different distribution of the applied pressure. Other variations are possible.

[0050] 8A, 8B and 8C, it is noted that the end effector 826 of the illustrated embodiment has a number of additional optional features. In particular, the body 836 of the end effector 826, which supports the pressure elements 840a and 840b and the elastic members 860 and 862, is disk-shaped and is pivotally mounted, e.g., via ball bearings, in a circular opening 876 such that it can be rotated about a vertical axis V perpendicular to the busbars. Furthermore, a motor, e.g., an air actuator, is provided at a first end 826a of the end effector 826 and is connected to the body via a pulley 878. This mechanical arrangement is adapted to allow the pressure elements 840a and 840b to be robotically rotated in a plane parallel to the busbars such that alignment of the pressure elements 840a and 840b with the corresponding positive and negative regions of the busbars is easily achieved.

[0051] Additionally, laser apertures 838a and 838b extend vertically upwards and into an open ended collector receptacle 880 in the end effector 826. As shown, the collector receptacle 880 extends away from the body 836, i.e., away from the pressurizing elements 840a and 840b. As such, the collector receptacle 880 is in flow communication with the laser apertures 838a and 838b. The collector receptacle 880 may have outwardly tapered walls to provide better clearance for oblique laser beam angles leading to the laser apertures. The collector receptacle 880 may define a gas path 882. An aspirator may be provided with an inlet opening into the collector receptacle 880. This arrangement can be helpful so that "splash" formed by red-hot metal particles that may be caused by laser beam operation can be drawn along the suction conduit more efficiently than if there were no collector receptacle defining a gas path. In certain embodiments, it may be desirable to further provide an inert gas conduit, for example leading into the collector receptacle.

[0052] Another optional feature that may be incorporated into the embodiment depicted in Figures 8A, 8B, and 8C is a load cell 884 that may be provided along a structural member extending from a first end 826a of the end effector 826 to a second end 826b of the end effector 826. In one example, the structural member may be configured as a cantilever. The load cell 884 may provide an indication of the amount of bending stress present at the end effector as a means of determining the amount of pressure being applied by both pressure elements together. The load cell may generate a load cell signal that may be fed back to the robot controller to achieve greater accuracy and consistency in the application of pressure. The anchor at the first end 826a of the end effector 826 may be specialized for attachment to a SCARA SR-6ia robot in this example, or other robots as deemed appropriate.

[0053] 16A and 16B show another example of an end effector 1626. As shown, the end effector 1626 has a body 1636 that receives first and second pressure elements 1640a and 1640b via a resilient member 1690. The resilient member 1690 can be made of any type of resilient material, including but not limited to silicone rubber. The first pressure element 1640a is secured to the body 1636 via the resilient member 1690. The second pressure element 1640b is secured to the body 1636 via the same resilient member 1690. In that regard, the resilient member 1690 has a first end attached to the body 1636 and a second end attached to the pressure elements 1640a and 1640b. The elastic member 1690 may have a sheet-like shape and may act as a mattress for the first and second pressing elements 1640a and 1640b. In this way, the portion of the elastic member 1690 that receives the first pressing element 1640a may be elastically independent from the portion of the elastic member 1690 that receives the second pressing element 1640b. The elastic member 1690 is elastically connected to the first and second pressing elements 1640a and 1640b and may be compressed to fit snugly against the pole regions of the busbars when the end effector 1826 is pressed against the busbars. The elastic member 1690 may thus accommodate height differences between the positive and negative pole regions of the busbars between adjacent battery cells. It is contemplated that the first and second pressing elements 1640a and 1640b are removably attached to the elastic member 1690, which itself is removably attached to the body 1636. This allows the components to be consumable, i.e., replaceable upon damage or after a given operating time threshold condition has been met. In certain embodiments, the body 1636 has a removable portion to which the resilient member 1690 is removably attached. In such embodiments, the removable portion of the body 1636 may be conveniently replaced upon damage.

[0054] As shown, the body 1636 is resiliently mounted to the second end 1626b of the end effector 1626 via a coil spring 1692. As shown, the coil springs 1692 are spatially separated from the first and second laser apertures 1638a and 1638b, which distance can provide an additional layer of protection from laser motion that occurs during operation of the system, thereby avoiding or preventing damage to the resilient member.

[0055] In this embodiment, the body 1636 is disk-shaped and is pivotally mounted, e.g., via ball bearings, within the circular opening 1676 in a manner that allows it to rotate about a vertical axis V. Additionally, a motor, e.g., an air actuator, is provided at the first end 1626a of the end effector 1626 and is coupled to the body 1636 via a pulley 1678. This mechanical arrangement is adapted to allow the pressure elements 1640a and 1640b to be robotically rotated in a plane parallel to the busbar such that alignment of the pressure elements with the corresponding positive and negative regions of the busbar is easily accomplished. As best shown in FIG. 16B, a load cell 1684 is provided along a structural member 1696 extending from the first end 1626a to the second end 1626b of the end effector 1626. The load cell 1684, as discussed above, can provide an indication of the amount of bending stress being experienced by the end effector 1626. In this example, the structural member 1696 is sized and shaped to enhance any mechanical stresses exerted on the first or second ends of the end effector 1626. More specifically, the structural member 1696 has an elongated, thin shape.

[0056] 17 illustrates a flow chart of a method 1700 for laser welding a bus bar to a battery module. In describing method 1700, reference is made to the system of FIG. 2, although it is contemplated that method 1700 may be performed by any other suitable system.

[0057] In step 1702, a field of view of a laser scan head is directed toward at least a portion of the busbar. According to certain embodiments, the laser scan head may be a Raylase® AxialScanFiber30 scan head.

[0058] In step 1704, an end effector is moved within the field of view of the scan head. As previously discussed, the end effector includes a resilient member having a first end attached to a body and a second end opposite the first end, a pressure element at the second end of the resilient member, and a laser aperture extending across the body, resilient member, and pressure element. Step 1704 includes exposing a pair of positive and negative pole regions of the busbar to the laser scan head through the laser aperture, and pressing one or more pressure elements against the busbar near the positive and negative pole regions of the pair.

[0059] In step 1706, during the step of pressing one or more pressure elements against the busbar, in accordance with a step of method 1700, the laser scanning head is activated to laser weld each of the positive and negative electrode regions of the busbar through the laser aperture(s) of the end effector to corresponding electrodes of the battery module.

[0060] In certain embodiments, the end effector is moved to a fixed position relative to the busbar while keeping the field of view of the scan head stationary. The scan head can be moved in a plane parallel to the plane of the busbar in a manner independent of the movement of the end effector. The scan head can be moved during the welding process and preferably during periods when the laser welding system is not operating. The moving step can include holding the scan head stationary while rotating the end effector about an axis perpendicular to the plane of the busbar. The end effector rotation can be described by the position and orientation of the pair of positive and negative pole regions of the busbar, for example, as determined using a camera or according to the design drawings of the battery module.

[0061] Here, according to Fig. 18, the controller of the system of Fig. 2 can be provided as a combination of hardware and software components. The hardware components can be realized in the form of an information processing device 1800, an example of which is described in Fig. 18. The information processing device 1800 can have a processor 1802, a memory 1804, and an I / O interface 1806. Instructions 1808 for controlling at least the first and second robot arms and the laser welding system can be stored on the memory 904 and in a state accessible by the processor 1802.

[0062] The processor 1802 may be, for example, a general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, a programmable read-only memory (PROM), a programmable logic controller (PLC), or any combination thereof.

[0063] The memory 1804 may include any type of computer readable memory, internal or external, such as a suitable combination of random access memory (RAM), read only memory (ROM), compact disc read only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read only memory (EPROM) and electrically erasable programmable read only memory (EEPROM), ferroelectric RAM (FRAM), and the like.

[0064] Each I / O interface 1806 may interconnect the information processing device 1800 with one or more input devices, such as a camera, pressure sensor, or some other sensor, or with one or more output devices, such as robot arm(s), laser welding system(s), etc. For example, a pressure sensor or load cell may be attached to the end effector to provide a real-time measurement of the pressure applied by the end effector or its respective pressure element to the busbar.

[0065] Each I / O interface 1806 may connect to a network (or multiple networks) capable of carrying data, including the Internet, Ethernet, Plain Old Telephone Service (POTS) lines, Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN™), Digital Subscriber Line (DSL), coaxial cable, fiber optics, satellite, mobile, wireless (e.g., Wi-Fi™, WiMAX™), SS7 signaling networks, landlines, local area networks, wide area networks, and the like, or any combination thereof, enabling the controller to communicate with other components, exchange data with other components, access and connect to network resources, service applications, and run other information processing applications.

[0066] The information processing device 1800, as well as any software applications that may be executed by the information processing device 1800, are merely exemplary, as the skilled reader will appreciate that other suitable embodiments of the controller may be provided.

[0067] It is understood that the above described and illustrated examples are merely exemplary and contemplated. For example, the systems and methods described herein may be used to laser weld only one pole region of a busbar per battery cell. Typically, the battery module is kept stationary during the welding procedure. Because the battery module is heavy, moving it is not time or resource efficient. In accordance with at least certain embodiments, the battery module may be moved between laser welding procedures. Although cylindrically shaped battery cells are discussed herein, it is contemplated that the methods and systems described herein may be used to laser weld a busbar(s) to any shape of battery cell, including but not limited to prismatic battery cells. In certain embodiments, one or more pressure elements are applied to the busbar using an end effector. However, in accordance with certain other embodiments, only a single pressure element may be applied to the positive pole region of the busbar and only a single pressure element may be applied to the negative pole region of the busbar. It is noted that it may be desirable to apply at least two pressure elements to at least one or both of the positive and negative pole regions. It may be most desirable in certain embodiments to surround the positive or negative pole regions with three pressure elements and to surround the corresponding pole regions with the three pressure elements. According to certain embodiments, the end effector may have multiple pairs of first and second laser apertures, each pair exposing the positive and negative pole regions of a corresponding battery cell, along with a corresponding pressure element. According to such embodiments, multiple battery cells may be laser welded to corresponding pole regions of the busbar during a single laser welding procedure, thereby increasing the speed of the laser welding procedure. The scope of the invention is indicated by the appended claims.

Claims

1. 1. A laser welding system for welding pole regions of bus bars to electrodes of a stack of battery cells with a laser beam, the laser welding system receiving the bus bars and battery cells into a welding area and aligning the pole regions adjacent to corresponding ones of the electrodes, the laser welding system comprising: a laser welder having a laser emitter configured to emit the laser beam and a scan head optically coupled to the laser emitter; a robot having an end effector, the end effector including a body, a resilient member having a first end attached to the body and a second end opposite the first end, a pressure element at the second end of the resilient member, and a laser aperture extending across the body, the resilient member, and the pressure element; Equipped with A laser welding system in which the laser beam is directed through the laser aperture by the scanning head when one of the pole regions is pressed against a corresponding one of the electrodes by the pressure element.

2. 2. The laser welding system of claim 1, wherein the elastic member comprises a helical spring defining a helix about an axis, and the pressure element is annular and concentric with the axis of the helical spring.

3. 3. The laser welding system of claim 2, wherein the pressure element is made of a thermally insulating material and is separate from and attached to the helical spring.

4. 2. The laser welding system of claim 1, wherein the pressure application element is a first pressure application element, the laser aperture is a first laser aperture, and the end effector further comprises a second pressure application element and a second laser aperture extending across the body and the second pressure application element.

5. 5. The laser welding system of claim 4, wherein the elastic member is a first elastic member, and further comprising a second elastic member having a first end attached to the body and a second end opposite the first end, the second pressure element being attached to the second end of the second elastic member, and the second laser aperture further extending across the second elastic member.

6. 5. The laser welding system of claim 4, wherein the first pressure element is annular in shape and the second pressure element has a cashew-shaped tip carrying the second laser aperture, the cashew-shaped tip being disposed adjacent to the first pressure element in a plane parallel to the busbar.

7. 7. The laser welding system according to claim 6, wherein the second pressure element has a generally flat pressure body having a protrusion leading to the cashew-shaped tip, and the second pressure element is supported by the body via a plurality of helical springs, the helical springs being interspersed around the cashew-shaped tip in the plane.

8. 5. The laser welding system of claim 4, wherein the first pressure element and the second pressure element are held at different distances from the body when free from the bus bar.

9. 5. The laser welding system of claim 4, wherein at least one of the first pressure element and the second pressure element is an electrical insulator.

10. 10. The laser welding system of claim 1, wherein the pressure element is made of an electrically insulating material.

11. 10. The laser welding system of claim 1, wherein the pressure element is made of an electrically conductive material and is covered with an electrically insulating material.

12. 2. The laser welding system of claim 1, wherein the body is rotatable about an axis perpendicular to the bus bar.

13. 2. The laser welding system of claim 1, wherein the end effector further comprises a collector receptacle extending away from the body opposite the pressure application element, the collector receptacle being in fluid communication with the laser aperture.

14. 14. The laser welding system of claim 13, further comprising a suction conduit having an open mouth to the collector receptacle.

15. 14. The laser welding system of claim 13, further comprising an inert gas conduit leading to the collector receptacle.

16. 2. The laser welding system of claim 1, wherein the end effector comprises a structural member extending from a first end carrying a robot arm anchor to a second end carrying the body, and a load cell disposed on the structural member.

17. 1. A method of laser welding a busbar to a battery module, the busbar having at least one pair of pole regions disposed over a corresponding pair of electrodes of the battery module, the method comprising: directing a field of view of a laser scanning head toward at least a portion of the busbar; using a robotic arm to move an end effector within the field of view of the scan head, the end effector having a body, a resilient member having a first end attached to the body and a second end opposite the first end, a pressure element at the second end of the resilient member, and a laser aperture extending across the body, the resilient member, and the pressure element, wherein during the movement, the pair of pole regions of the busbar are exposed to the laser scan head through the laser aperture, and the pressure element of the end effector is pressed against the busbar adjacent the pole regions of the pair; During the pressing, the laser scanning head is operated to laser weld each of the pole regions of the bus bar to a corresponding one of the electrodes of the battery module through the laser aperture of the end effector. method.

18. 20. The method of claim 17, further comprising moving the end effector to a fixed position relative to the busbar while keeping the field of view of the laser scanning head stationary.

19. 20. The method of claim 17, wherein said moving comprises moving said scan head in a plane parallel to a plane of said busbar, said movement of said scan head being independent of said movement of said end effector.

20. 20. The method of claim 17, wherein the laser scanning head is held stationary during the movement of the end effector while rotating the end effector about an axis perpendicular to the plane of the busbar.

Images