Method for manufacturing individual battery cells

Abstract

The invention relates to a method for manufacturing individual battery cells (12) with a stack (1) or a winding of electrodes (2, 3) and separators (4), in which at least one of the electrodes (2, 3) has a conductor tab (5) which projects laterally in one direction from the stack (1) or winding and is welded to one another. The invention is characterized in that the conductor tab (5) is tightly integrated and fastened by welding on the side facing the stack (1) or winding, after which the tightly integrated and welded conductor tab (5') is held by a welding electrode (7) on the side opposite the stack (1) or winding and is wound around the welding electrode (7) in the direction of the stack (1) or winding, after which the cell cover (9) of the individual battery cell (12) is welded to the wound conductor tab (5'). Furthermore, a corresponding individual battery cell (12) is disclosed.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing individual battery cells, as defined in more detail in the preamble of claim 1. [Background technology]

[0002] Individual battery cells, for example in lithium-ion technology, are essentially known from the prior art. They essentially consist of a housing and electrochemically active material arranged in the housing. Typically, the electrochemically active material is a laminate or possibly a winding of a cathode, an anode and a separator, which is introduced into the housing and immersed in an electrolyte solution. The housing is then sealed.

[0003] The electrodes are typically contacted via conductive tabs protruding from the stack or winding, typically with the cathode conductive tab protruding on one side and the anode conductive tab protruding on the other. Depending on the design of the housing, the anode conductive tabs can be welded to each other, the cathode conductive tab can be pressed against the metallic conductive housing, etc. Of course, this can also be done in reverse, or both electrodes can be welded accordingly.

[0004] It is known from the general prior art that during welding, the protruding individual conductor tabs are welded to the current collector, which is then welded to the cell cover, for example, before sealing the individual battery cells, which cell cover can then be welded to the housing. This is relatively cumbersome, requires many welding seams, and requires a relatively large amount of structural space due to the additional current collectors in the individual battery cells. This is a disadvantage, since each welding seam imposes a thermal load on the electrochemistry of the cell. The more material that needs to be melted, the more critical this can be.

[0005] Patent Document 1 also discloses welding conductor tabs without using current collectors. For this purpose, the conductor tabs are held down with an elastic element and directly welded to one another using an ultrasonic welding method. The conductor tab of one electrode protruding on one side of the cell stack and the conductor tab of the other electrode protruding on the other side of the cell stack can be welded directly to one another and to the corresponding stack of the adjacent electrode.

[0006] Patent Document 2 discloses an electrode arrangement for battery cells. In this electrode arrangement, the conductor tabs of the individual electrodes are wound together with the conductors of the individual battery cells and are connected, for example, welded, to the anode conductors or cathode conductors of all the corresponding electrodes in the individual battery cells. The conductor tabs can be separated and pulled out of the housing, for example. Patent document 3 describes an electrochemical cell with at least one electrode, in which the end of each individual electrode foil protruding from the active material is rolled up, thereby simplifying the contact connection of all electrodes of the same polarity of the individual battery cells. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] DE102015209719B4 [Patent Document 2] US2011 / 0206976A1 [Patent Document 3] WO2010 / 030606A2 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to provide a method for manufacturing individual battery cells which further simplifies the structures known from the general prior art, but nevertheless ensures a safer and more reliable electrical contact connection of the conductor tabs. [Means for solving the problem]

[0009] According to the invention, this problem is solved by a method having the features of claim 1, and here in particular the features set out in the characterizing part of claim 1. Advantageous configurations and developments emerge from the claims dependent thereon.

[0010] In the method according to the invention, the conductor tabs are welded, as known from the prior art.

[0011] According to the present invention, the conductor tabs are tightly integrated for this purpose and are first fastened on the side facing the stack or winding by welding, which in a very advantageous embodiment can be implemented as ultrasonic welding, to prevent their position from changing within the stack or winding and to prevent individual electrodes or separators from being pulled out of the stack or winding during production. The conductor tabs fastened in this way via ultrasonic welding are then held by a welding electrode at their end opposite the stack or winding and wound around the welding electrode in the direction of the stack or winding. Finally, the cell covers of the individual battery cells are welded to the wound conductor tabs. This means that the use of additional current collectors to which the individual conductor tabs are welded is omitted. Unlike the above-mentioned prior art, the fastened conductor tabs are not left unprocessed here because they are very thin, highly susceptible to mechanical loads, and can be damaged very quickly, which would significantly impair the electrical conductivity of the structure.

[0012] Instead, in the method according to the present invention, the conductor tab is wound in the direction of the stack and onto the welding electrode located inside this winding. The cell cover can then be welded to the wound or rolled conductor foil, thereby completing this structure directly, i.e., without the need for an intervening current collector. The conductor foil forms a winding welded to the cell cover, resulting in a mechanically stable structure in which the heat generated during welding is only partially transferred to the stack or winding. In particular, the majority of the heat is dissipated via the welding electrode.

[0013] In another highly preferred embodiment of the method according to the invention, grooves in the welding electrode can be used to hold the conductor foil. Such grooves can be provided, for example, in rectangular or circular welding electrodes. The welding electrode is positioned on the stack of fastened conductor tabs so that the ends of the conductor tabs, which are located on the side opposite the stack or winding side of the conductor tabs and are tightly integrated during or after fastening, are located in the grooves. By rotating the welding electrode, the tightly integrated stack of conductor foils is wound around the welding electrode. In another highly preferred embodiment, after welding the wound conductor foil to the cell cover, the welding electrode is removed from the wound conductor foil. However, due to the multi-layer structure, a very stable hollow roll remains, the individual layers of which are welded to each other and to the cell cover in a straight line along the central axis of the welding electrode on the side facing the cell cover.

[0014] This very stable structure consisting of the cell cover and the laminate or winding can then be handled simply and efficiently and introduced into the housing, after which the cell cover is welded to the housing, in particular via laser welding.

[0015] In this case, not only is the conductor foil fastened using ultrasonic welding, but in a very advantageous embodiment of the method according to the invention, the wound conductor foil can also be welded to the cell cover or the cell cover to the wound conductor foil using ultrasonic welding, while the welding of the cover only to the housing can be carried out more efficiently, in particular by laser welding.

[0016] In another highly preferred configuration of the method for manufacturing individual battery cells according to the invention, the conductor foils are fastened at approximately mid-height in the stacking direction or transverse to the winding direction, i.e., rather than being gathered on one side of the stack and then tightly integrated and welded there, as is commonly known today, the conductor foils are gathered in the center in order to fasten the conductor foils to one another as close as possible to the cell stack and with the shortest possible distance of the individual conductor foils to the weld seam.

[0017] In the individual battery cells manufactured according to the method of the present invention, a stack or winding of cathode, anode, and separator is provided, and this stack or winding is arranged in a cell housing sealed by a cell cover, whereby the conductor tab of at least one of the electrodes protrudes from the stack or winding and is configured to be wound in that area and welded to the cell cover. In an advantageous development of the individual battery cell according to the present invention, the cell cover itself can be welded to the housing.

[0018] Advantageous configurations and developments of the method according to the invention and of the individual battery cells produced by means of this method will become apparent from the detailed description of exemplary embodiments which follows, with reference to the accompanying drawings. [Brief explanation of the drawings]

[0019] [Figure 1] 1 shows the production of individual battery cells in a first method step, with a cell stack indicated diagrammatically. [Figure 2]1 shows a second method step, shown similarly to FIG. [Figure 3] 1 and 2, showing a third method step. [Figure 4] 1 shows the finishing of the individual battery cells in the final method step. DETAILED DESCRIPTION OF THE INVENTION

[0020] FIG. 1 shows a portion of a stack 1. This stack 1 contains several different electrodes 2, 3, i.e., anodes and cathodes. Separators 4 are arranged between the electrodes. In the example shown, the cathodes are supported on aluminum foil, which is shown here with a thick solid black line. The ends of the cathodes 2 protrude from the sides of the stack 1 in a direction transverse to the stacking direction S as conductor tabs 5. The ends of the cathodes are grouped together in this region. For the sake of simplicity, only five individual cathodes 2 are shown in this figure. The conductor tabs 5 are grouped together in the center of the stack 1 in the stacking direction S, relative to its height, and are tightly integrated in the region marked with the reference number 5′. On the side of this tightly integrated conductor tab 5 facing the laminate 1, in order to join the tightly integrated conductor tab 5' and in a further step to reliably prevent the electrodes 2, 3 or the separator 4 from being pulled out of the laminate 1, a weld seam or individual weld points are created, here using an ultrasonic welding device 6, along the width of the laminate 1 extending into the plane of the paper in which FIG. 1 is shown.

[0021] The end of the tightly integrated conductor tab 5' facing away from the stack 1 is held by a welding electrode 7, which is formed, for example, as a rod-shaped electrode with a groove 8, by inserting the tightly integrated conductor tab 5' into the groove of the rod-shaped electrode. The welding electrode 7 is then wound in the direction of the stack 1 according to the arrow in FIG. 2, resulting in a roll 5'' consisting of multiple spiral layers of tightly integrated conductor tab 5'. This roll 5'' with the welding electrode 7 inside is brought into contact with the cell cover 9 and welded to it via the cell cover material. This process can also be performed as ultrasonic welding, and a symbolic representation of this welding is again designated by the reference number 6. The wound conductor tab, now designated 5'', which forms a roll after winding, forms a very compact structure that can be easily welded to the cell cover 9 in an efficient and safe process.

[0022] The welding electrode 7 is then pulled out to the side, resulting in a very robust structure consisting of the stack 1 and the cell cover 9, which can then be introduced into a housing 10 that is already filled with electrolyte, as can be seen from the diagram in FIG. 4, for example, or after the stack 1 has been immersed, can be introduced into such a housing 10. This structure is again only shown diagrammatically; the cell stack would of course generally utilize more space inside the housing. The cell cover 9 can then be welded to the housing 10, for example, via laser welding, which is indicated here accordingly by the two triangles 11.

[0023] Basically, the method described above and the individual battery cells 12 obtained therefrom, part of which is shown in Figure 4, can be used accordingly both for circular and for prismatic housings 9. In particular, such individual battery cells 12 are suitable for electrical contact connection between the stack 1 and the cell covers and are therefore preferably suitable for constructions with prismatic housings 10.

[0024] Compared to the prior art, material and manufacturing costs are saved here, since additional welding to the current collectors, as is known from the general prior art, is omitted, while at the same time the proven concept of independent individual battery cells 12 with external electrical contacts is maintained, which offers decisive advantages for scalability and safety that cannot be realized with the last-mentioned prior art.

[0025] Only a portion of the stack 1 or of the individual battery cells 12 can be seen in each of the figures of the drawing. The sides not shown can be identically configured or can be configured in another manner known per se. This applies both to the housing and to the contacting of the respective further electrode 3, i.e., the anode in this case.

Claims

1. A method for manufacturing individual battery cells (12) comprising a stack (1) or a winding of electrodes (2, 3) and separators (4), comprising: At least one of the electrodes (2, 3) has a conductive tab (5), which projects laterally from the stack (1) or the winding in one direction and is welded to each other, the conductor tab (5) is tightly integrated and fastened by welding on the side facing the stack (1) or the winding, then the tightly integrated and welded conductor tab (5') is held by a welding electrode (7) on the side opposite the stack (1) or the winding and wound around the welding electrode (7) in the direction of the stack (1) or the winding, and then the cell cover (9) of the individual battery cell (12) is welded to the wound conductor tab (5'').

2. 2. The method according to claim 1, characterized in that the closely integrated and welded conductor tab (5') is held by means of a groove (8) in the welding electrode (7).

3. 3. The method according to claim 1 or 2, characterized in that the welding electrode (7) is detached from the wound conductor tab (5'') after welding the wound conductor tab (5'') to the cell cover (9).

4. 3. A method according to claim 1 or 2, characterized in that the stack (1) or the winding welded to the cell cover (9) is introduced into a housing (10), after which the cell cover (9) is welded to the housing (10).

5. 5. The method according to claim 4, characterized in that laser welding is used to weld the cell cover (9) to the housing (10).

6. 3. A method according to claim 1 or 2, characterized in that the conductor tabs (5) are welded and fastened using ultrasonic welding.

7. 3. A method according to claim 1 or 2, characterized in that the conductor tab (5) is fastened at approximately mid-height in the stacking direction (S) or in a direction transverse to the winding direction.

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