DE102020212933A1 - Welding system for producing an electrical contact in a battery module for a high-voltage battery - Google Patents

Abstract

The invention relates to a welding system for producing an electrical contact between at least one cell pole (3) and a busbar (5) of a high-voltage battery module in a welding process in which, in a first process step, the cell pole (3) and the busbar (5) are welded as partners can be brought into a butt joint, and in a second process step the two welding partners (3, 5) are welded to one another at the butt joint. According to the invention, the welding process is implemented as a vacuum laser welding process, in which a laser unit (9) applies a laser beam (11) to the welding point (7). The welding system has an evacuation unit which applies negative pressure to at least the immediate vicinity of the welding point (7) during the welding process.

Description

The invention relates to a welding system for producing an electrical contact between at least one battery cell cell pole and a busbar according to the preamble of claim 1 and a method for producing such a contact according to claim 14.

When assembling a battery module for a high-voltage battery, a number of battery cells are stacked in a stacking direction to form a cell pack. The cell pack is then transferred to a generic welding system in which the cell poles/conductors of the battery cells are welded to busbars/busbars in order to electrically connect the battery cells to one another according to a predetermined wiring diagram.

In the welding process of this type, in a first process step, a cell pole and the busbar are butt-joined as the welding partner. In a second process step, the two welding partners are welded together at the butt joint.

It has been shown that, for example, during laser welding in the atmosphere, welding defects occur, as a result of which the quality of the electrical contact between the cell pole and the busbar is impaired. In this case, post-processing of the electrical contacting is required, which is complex in terms of manufacturing technology.

From the CN 10 695 6076 A a welding system for producing an electrical contact between the battery cell cell poles and a busbar is known.

The object of the invention is to provide a welding system and a welding method by means of which process-reliable and flawless contacting between a cell pole and a busbar of a high-voltage battery is made possible.

The object is solved by the features of claim 1 or 14. Preferred developments of the invention are disclosed in the dependent claims.

The invention is based on a welding process in which, in a first process step, the respective cell pole and the busbar are butt-connected as welding partners, and in a second process step the two welding partners are welded to one another at the butt joint. According to the characterizing part of claim 1, the welding process is implemented as a vacuum laser welding process, in which a laser unit applies a laser beam to the welding point. The welding system also has an evacuation unit, which applies negative pressure to at least the immediate vicinity of the welding point during the welding process.

In general, the invention relates to a laser beam welding device in which parts of the conductors/cell poles to be connected are stored from one or more Li-ion cells to one or more busbars/current collector rails. Within this device, the connection is created under reduced atmospheric pressure or in a vacuum by laser beam welding. The device has at least one beam penetration glass (hereinafter referred to as in-coupling optics), which makes the welding point(s) accessible for the directed laser radiation. Furthermore, at least one bracing element is integrated into the device, which creates a "zero" gap between the welded busbar/current collector rail and arresters/cell poles. In addition, an electrically insulating layer is inserted between the beam penetration glass holder, the bracing element of the welding mask and the components to be welded, which prevents a short-circuit current flow between the cells and/or the device. The openings in the welding mask correspond to the geometry of the desired weld seam shape with oversize. The vacuum chamber has an opening through which the gas present is evacuated from the vacuum chamber and the vacuum in the welding chamber is set above it. In order to be able to save further process time when contacting the arrester/cell poles with the busbar or the current collector rails, it is possible to use several laser units in parallel.

Since the laser beam can propagate freely between the beam exit glass (decoupling optics of the laser unit) and the beam penetration glass (coupling optics) of the welding device, either a housing around the device and the laser beam exit (laser safety cabin) is necessary or there is a laser radiation-tight encapsulation between the beam exit glass of the laser optics and the Beam penetration glass of the device instead. Then no additional housing for protection against laser radiation is necessary. Sensors must be used to ensure that the laser radiation is only released when the laser protection encapsulation is engaged with the device. This laser protection encapsulation can be attached directly to the welding optics or moved from weld to weld using a separate device.

1. 1. Die Schweißvorrichtung(en) verbleibt dauerhaft in der Laseranlage positioniert. Damit ist der Einrichtprozess der Vorrichtung gegenüber dem Laserequipment nur einmal durch zu führen. Dabei wird das Zellenpaket und die Busbars eingelegt oder die Busbars wurde an den Zellstapel bereits angeheftet und anschließend in die Vorrichtung eingelegt. Danach erfolgt die Unterdruck-Erzeugung und anschließend wird geschweißt.
2. 2. In der Anwendung sind mehrere Vorrichtungen in einem Umlaufbetrieb. Dabei findet die Beladung der Vorrichtung(en) mit dem Zellenpaket und Busbar außerhalb der Laseranlage statt. Weiterhin wird die Vorrichtung außerhalb der Laseranlage geschlossen und entlüftet, während sich eine andere Vorrichtung bereits in der Laseranlage befindet und die Schweißungen durchgeführt werden. Dadurch wird Prozesszeit eingespart.
3. 3. Abhängig von der Modul-/ Batteriekonstruktion kann die Einstrahlung des Lasers für das Schweißen simultan durch mehrere Laser oder durch einen Lasersystem erfolgen.

Different application concepts can be implemented for complete (parallelized) and local (individual) laser welding devices:

1. 1. The welding device(s) remains permanently positioned in the laser system. This means that the setup process for the device compared to the laser equipment only has to be carried out once. The cell stack and the busbars are inserted or the busbars have already been attached to the cell stack and then inserted into the device. This is followed by the generation of negative pressure and then welding.
2. 2. In the application, several devices are in circulation. The loading of the device(s) with the cell pack and busbar takes place outside of the laser system. Furthermore, the device outside of the laser system is closed and vented while another device is already in the laser system and the welds are being carried out. This saves process time.
3. 3. Depending on the module/battery construction, the laser beam for welding can be irradiated simultaneously by several lasers or by one laser system.

The contacting of the arrester / cell poles with the current collector bar is made possible by a device in which a vacuum is generated in order to increase the weldability of the materials. Due to the small volume of the device to be evacuated close to the welded joint, the evacuation time is very short. This reduces spatter/pinholes, increasing the electrical connection area. Due to the negative pressure, a higher feed rate can be achieved with the same laser power or the laser power can be minimized with the same feed rate. Due to the higher feed rate or the minimized laser power, the heat input to the components is reduced. As a result, there is little or no drop in strength in the heat-affected zone. This principle works regardless of the number of arresters/cell poles and busbars/current collector bars that are welded simultaneously with a single device. The vacuum welding device can be designed depending on the type of joint to be welded. A large-scale laser protection cabin can be avoided by means of a laser protection encapsulation. A sensor system ensures that the laser radiation is only released when the laser protection encapsulation is engaged with the welding device.

In an alternative embodiment variant, the device can be constructed in such a way that not only the welding area is subjected to a negative pressure, but the entirety of the components to be welded. This negative pressure/vacuum laser chamber is only slightly larger than the envelope geometry of the cells to be welded, including the busbar to be welded. However, in this embodiment variant, the negative pressure/vacuum laser chamber has a much larger volume to be evacuated. As a result, the evacuation time is increased accordingly.

Aspects of the invention are highlighted again in detail below: The evacuation unit can have at least one adapter part, which delimits a vacuum chamber that is open in the direction of the welding point. During the welding process, the adapter part can be placed in a pressure-tight manner with its open chamber side on the side of the butt joint facing the laser unit in such a way that the immediate vicinity of the welding point is subjected to negative pressure. Then the vacuum chamber in the adapter part can be subjected to vacuum.

In a technical implementation, it is preferred if the laser unit is located outside of the adapter part. In this case, the adapter part can have coupling optics. The laser beam generated by the laser unit is coupled into the vacuum chamber through the coupling optics and from there it is guided on to the welding point.

With regard to a perfect welding process, it is preferred if the evacuation unit has a prestressing device, by means of which the adapter part can be brought into direct or indirect pressure contact with the butt joint to be welded (between cell pole and busbar) with a prestressing force.

With a view to perfect formation of weld nuggets at the weld point, it is preferred if the adapter part has a welding mask on its open chamber side, by means of which the weld point is delimited on the peripheral side. An electrically insulating layer may also be provided between the weld mask and the butt joint.

In addition, the adapter part can have an evacuation connection. The vacuum chamber can be fluidically connected to a vacuum source via the evacuation connection in order to apply vacuum to the vacuum chamber.

It is preferred if the laser unit is not directly integrated in the adapter part, but instead is spaced apart from the in-coupling optics of the adapter part by a free beam path. In this case it is preferred if the free beam path between the laser unit and the adapter part is shielded from the outside. This can be implemented, for example, by a laser protection cabin, in which both the decoupling optics of the laser unit and at least the butt joint to be welded (between cell pole and busbar) are housed. As an alternative to this, a laser-radiation-tight encapsulation can also be provided, which extends between the coupling-out optics of the laser unit and the coupling-in optics of the adapter part.

In the battery cell stack, a large number of cell poles are to be welded to busbars. With a view to reducing the duration of the welding process, it is preferable if not just one adapter part, but rather a plurality of adapter parts are provided in the welding system. These can be arranged one behind the other, viewed in the stacking direction of the battery cells. Exactly one butt joint between cell pole and busbar can be assigned to each adapter part. The adapter parts can preferably be connected to a carrier element on which the prestressing device acts. In this way, all adapter parts are brought into the pressure system with the assigned welding partners.

In the above embodiment variant, the laser beam can be radiated into the adapter parts simultaneously by a plurality of laser units. Alternatively, the laser beam can be irradiated by a single laser beam unit. This can be arranged to be movable in the battery cell stacking direction. Therefore, the adapter parts are approached one after the other by the moveable laser unit.

In a further exemplary embodiment, the evacuation unit can have a negative-pressure housing that delimits a negative-pressure space. The vacuum space can be slightly larger than the envelope geometry of the battery cells to be welded. In this case, the entire battery cell stack can be arranged in the vacuum space, which can be connected to a vacuum source. All adapter parts can be fluidically connected to one another and to the vacuum space with their vacuum chambers.

Exemplary embodiments of the invention are described below with reference to the accompanying figures.

• 1 in einer Schnittdarstellung ein fertiggestelltes Batteriezellenpaket nach erfolgtem Schweißprozess;
• 2 eine Anlagenskizze der Schweißanlage mit Evakuiereinheit;
• 3 bis 5 Detailansichten aus der 2;
• 6 bis 11 weitere Ausführungsbeispiele; und
• 12 unterschiedliche Stoßverbindungen mit jeweils daran angepasstem Adapterteil.

Show it:

• 1 a sectional view of a completed battery cell pack after the welding process has taken place;
• 2 a system sketch of the welding system with evacuation unit;
• 3 until 5 Detail views from the 2 ;
• 6 until 11 further exemplary embodiments; and
• 12 different butt joints, each with an adapter part adapted to it.

In the 1 a completed battery module is indicated after the welding process has taken place. The battery module has a cell stack with battery cells 1 stacked one behind the other in the stacking direction. The battery cells 1 are pouch cells, for example. In the 1 the cell poles 3 of the battery cells 1 are welded to one another with busbars 5 at weld points 7 according to a predefined wiring diagram in order to electrically interconnect the battery cells 1 with one another.

The following are based on the 2 until 5 the welding system and the welding process for producing the electrical contact between the cell poles 3 and the busbars 5 are described. First, in a first process step, all busbars 5 are butt-joined to the still unwelded cell poles 3 of the battery cells 1 as weld partners. The battery cell stack that has not yet been welded is then transferred to the welding system, which is located in the 2 is indicated. The welding system has a laser unit 9, by means of which a laser beam 11 can be applied to the respective welding point 7.

The essence of the invention is that the welding process is implemented as a vacuum laser welding process. For this purpose, the welding system has an evacuation unit, by means of which negative pressure is applied to the immediate vicinity of the respective welding point 7 during the welding process.

In the 2 and 3 the evacuation unit is formed from a plurality of adapter parts 15 which are arranged one behind the other as viewed in the stacking direction of the battery cells 1 . Exactly one butt joint between cell pole 3 and busbar 5 is assigned to each of the adapter parts 15 . In addition, all adapter parts 15 are connected to a carrier element 17 . A prestressing device (not shown) acts on the carrier element 17, by means of which all adapter parts 15 can be brought into pressure contact with the associated welding partners 3, 5 with a prestressing force Fv.

In the 4 and 5 an adapter part 15 of the evacuation unit is shown in detail: Dem According to the adapter part 15 limits an open towards the butt joint vacuum chamber 19. During the in the 2 In the indicated welding process, the adapter part 15 is pressure-tight with its open chamber side and placed at a distance from the weld point 7 on the side of the butt joint facing the laser unit 9 . The vacuum chamber 19 is subjected to a vacuum. For this purpose, the adapter part 15 has an evacuation connection 21 ( 3 ) which is connected to a vacuum source, not shown.

On its side spaced apart from the butt joint, the adapter part 15 has coupling optics 23 through which the laser beam 11 generated by the laser unit 9 can be coupled into the vacuum chamber 19 and from there is guided further to the welding point 7 . The adapter part 15 is in the 4 not directly in pressure contact with the butt joint, but rather with the interposition of a welding mask 25 and an electrical insulating layer 27.

How from the 3 As can further be seen, the laser beam 11 is irradiated into the respective adapter parts 15 by a single laser unit 9. This is arranged so that it can be moved in the battery cell stacking direction, so that the adapter parts 15 can be approached by the laser unit 9 one after the other.

How from the 3 shows that the laser unit 9 is spaced apart from the in-coupling optics 23 of the respective adapter part 15 by a free beam path f. To shield the free beam path f points outwards in the 6 the welding system also has a laser protection cabin 29, in which both the laser unit 9 and the entire battery cell stack to be welded are arranged. Alternatively, in the 7 a laser-radiation-tight encapsulation 31 is provided, which extends between the coupling-out optics 33 of the laser unit 9 and the coupling-in optics 23 of the adapter part 15 . The laser radiation-tight encapsulation 31 is in the 8th shown in detail.

In the 9a and 9b a further exemplary embodiment is shown in which the evacuation unit has a vacuum housing 35 . The vacuum housing 35 delimits a vacuum space 37. This is slightly larger than the envelope geometry of the battery cell stack to be welded. Correspondingly, in the 9a and 9b the entire battery cell stack is arranged in the vacuum chamber 37, which can be connected to a vacuum source, not shown. According to the 9 all adapter parts 15 with their vacuum chambers 19 are fluidically connected to one another and to the vacuum space 37 .

In the 10 and 11 are each modifications of the 9 illustrated embodiment shown: so has in the 10 the welding system also has a laser protection cabin 29 in which the free beam path f is shielded from the outside. Alternatively, in the 11 the free beam path f shielded by a laser-radiation-tight encapsulation 31 to the outside, as already based on the 7 is described.

The adapter part 15 according to the invention can be adapted as desired to the geometry of the butt joint to be welded in each case, as is shown in FIGS 11a until 11f is indicated: in the 11a the adapter part 15 is arranged on the side facing the laser unit 9 and is designed for an overlap joint of the welding partners 3, 5. In the 11b the adapter part 15 is also designed for a lap joint, but has a stepped design. In the 11c the adapter part 15 is also positioned only on one side on the side of the butt joint facing the laser unit 9 . The butt joint is implemented as a T-joint. In the 11d the butt joint is implemented as a butt joint, with the adapter part 11 being positioned on both sides on the side facing the laser unit 9 and on the opposite side of the butt joint. Correspondingly, also in the 11e and 11f overlap joints are shown, on which the adapter part 15 is positioned on both sides.

Reference List

1

battery cells

3

cell poles

5

busbars

7

welds

9

laser unit

11

laser beam

15

adapter parts

26

spring bearing

17

carrier element

19

vacuum chamber

21

evacuation port

23

coupling optics

24

spring element

25

welding mask

27

electrical insulating layer

29

laser safety cabin

31

Laser protection encapsulation

33

decoupling optics

35

negative pressure enclosure

37

vacuum room

f

free beam path

FV

preload force

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• CN 106956076A [0005]

Claims (14)

Welding system for producing an electrical contact between at least one cell pole (3) and a busbar (5) of a high-voltage battery module in a welding process in which, in a first process step, the cell pole (3) and the busbar (5) can be butt-joined as a welding partner , and in a second process step the two welding partners (3, 5) are welded together at the butt joint, characterized in that the welding process is implemented as a vacuum laser welding process, in which a laser unit (9) applies a laser beam (11) to the welding point (7 ) applied, and that the welding system has an evacuation unit which applies negative pressure to at least the immediate vicinity of the welding point (7) during the welding process. welding system claim 1 , characterized in that the evacuation unit has at least one adapter part (15) which delimits a vacuum chamber (19) open in the direction of the welding point (7), and in that the adapter part (15) is pressure-tight during the welding process with its open chamber side on the, the Laser unit (9) facing side of the butt joint can be placed, so that the immediate vicinity of the weld (7) can be subjected to negative pressure. welding system claim 2 , characterized in that the laser unit (9) is positioned outside of the adapter part (15) and that the adapter part (15) has coupling optics (23) through which the laser beam (11) generated by the laser unit (9) enters the vacuum chamber (19) can be coupled in and can be guided further up to the welding point (7). welding system claim 2 or 3 , characterized in that the evacuation unit has a clamping device, by means of which the adapter part (15) can be brought into direct or indirect pressure contact with the butt joint with a prestressing force (Fv). Welding system according to one of claims 2 until 4 , characterized in that the adapter part (15) has a welding mask (25) on its open chamber side, by means of which the welding point (7) is limited. welding system claim 5 , characterized in that an electrically insulating layer (27) is provided between the welding mask (25) and the butt joint. Welding system according to one of claims 2 until 6 , characterized in that the adapter part (15) has an evacuation connection (21) via which the vacuum chamber (19) can be connected to a vacuum source. Welding system according to one of claims 3 until 7 , characterized in that the laser unit (9) is spaced apart from the in-coupling optics (23) of the adapter part (15) via a free beam path (f), and in that a laser protection cabin (29) is provided in particular to shield the free beam path (f), in which both the laser unit (9) and at least the butt joint to be welded are housed. welding system claim 8 , characterized in that to shield the free beam path (f) alternatively a laser radiation-tight encapsulation (31) between the decoupling optics (33) of the laser unit (9) and the coupling optics (23) of the adapter part (15) is provided. Welding system according to one of claims 2 until 9 , characterized in that viewed in the stacking direction of the battery cells (1) a plurality of adapter parts (15) are arranged one behind the other, and that each adapter part (15) is assigned exactly one butt joint between a cell pole (3) and a busbar (5), and that in particular the adapter parts (15) are connected to a carrier element (17) on which the prestressing device acts, so that all adapter parts (15) are in pressure contact with the associated welding partners (3, 5). welding system claim 10 , characterized in that the laser beam (11) is irradiated into the adapter parts (15) simultaneously by a plurality of laser units (9), or only by one laser unit (9), which is arranged to be movable in the battery cell stacking direction, so that the adapter parts (15) can be approached in turn by the laser unit (9). Welding system according to one of the preceding claims, characterized in that the evacuation unit has a vacuum housing (35) which delimits a vacuum space (37) which is slightly larger than the envelope geometry of the battery cells (1) to be welded, and that the entire battery cell stack is arranged in the vacuum space (37) which is connected to a vacuum source. welding system claim 12 , characterized in that all adapter parts (15) with their vacuum chambers (19) are fluidically connected to one another and to the vacuum space (37). Method for producing an electrical contact between at least one cell pole (3) and a busbar (5) of a high-voltage battery module, which can be carried out in a welding system according to one of the preceding claims.

Images