METHOD FOR MANUFACTURING A SINGLE BATTERY CELL

Description

[0001] The invention relates to a method for manufacturing a single battery cell according to the type defined in the preamble of claim 1

[0002] Individual battery cells, for example, in lithium-ion technology, are fundamentally known from the prior art. They essentially consist of a housing and electrochemically active materials arranged within this housing. Typically, this is a stack or, in some cases, a coil of cathodes, anodes, and separators, which are inserted into the housing and impregnated with electrolyte. The housing is then sealed.

[0003] The electrodes are typically connected via conductor tabs that protrude beyond the stack or coil, with the cathode conductor tabs typically protruding on one side and the anode conductor tabs protruding on the other. Depending on the housing design, the anode conductor tabs can, for example, be welded together, and the cathode conductor tabs can be pressed against a conductive metal housing, or something similar. Of course, this can also be done the other way around, or both electrodes can be welded accordingly.

[0004] It is generally known from the state of the art that during welding, the individual protruding conductor lugs are welded to a current collector, which is then welded to a cell cover, for example, before closing the individual battery cell, where the cell cover can be welded to the housing. This is comparatively complex, requires multiple weld seams, and requires a relatively large amount of installation space due to the additional current collector in the individual battery cell. Each weld seam places thermal stress on the cell's electrochemistry, which is a disadvantage. The more material that has to be melted, the more critical this can be.

[0005] From DE 10 2015 209 719 B4, it is also known to weld the conductor tabs without a current collector. For this purpose, they are held down with a clamp with an elastic element and directly welded together using an ultrasonic welding process. The conductor tabs of one electrode protruding from one side of the cell stack and the conductor tabs of the other electrode protruding from the other side of the cell stack can thus be directly welded to each other and to the corresponding stacks of neighboring electrodes.

[0006] An electrode arrangement for a battery cell is known from US 2011 / 0206976 A1. The conductor tabs of the individual electrodes are wound together with a conductor of the individual battery cell and are connected, e.g., welded, to an anode conductor or cathode conductor for all corresponding electrodes within the individual battery cell. This can then be led out of a housing, for example, in an insulated manner.

[0007] WO 2010 / 030606 A2 describes an electrochemical cell with at least one electrode. The end of each individual electrode foil extending beyond the active material is wound up to facilitate contact between all electrodes of the same polarity in the individual battery cell.

[0008] The object of the present invention is to provide a method for manufacturing a battery cell which further simplifies the structure known from the general prior art and yet ensures safe and reliable electrical contacting of the conductor lugs.

[0009] According to the invention, this object is achieved by the method having the features in claim 1, and in particular in the characterizing part of claim 1. Advantageous embodiments and further developments emerge from the dependent claims.

[0010] The method according to the invention provides for the conductor lugs to be welded, as is known from the prior art. According to the invention, they are compacted for this purpose and first tacked on their side facing the stack or coil by this welding, which according to a very advantageous embodiment can be implemented as ultrasonic welding, in order to prevent their position within the stack or coil from changing and individual electrodes or separators from being pulled out of the stack or coil during production. The conductor lugs tacked in this way by ultrasonic welding are then gripped by a welding electrode at their end facing away from the stack or coil and wound around this welding electrode in the direction of the stack or coil. Finally, a cell cover of the individual battery cell is welded to the wound conductor lugs.The use of an additional current collector, to which the individual conductor lugs are welded, is therefore omitted here. Unlike the aforementioned prior art, the tacked conductor lugs are not left untreated, as they would otherwise be very thin and vulnerable to mechanical stress and could tear very quickly, which would severely impair the electrical performance of the assembly.

[0011] Rather, in the method according to the invention, the conductor tabs are wound toward the stack on a welding electrode located inside this coil. The structure can then be supplemented directly with the cell cover, i.e., without an intermediate current collector, by welding this cell cover to the rolled or wound conductor foils. These then form a coil welded to the cell cover, resulting in a mechanically stable structure that only partially transfers the heat generated during welding to the stack or coil. In particular, a large portion of the heat is dissipated by the welding electrode.

[0012] According to a further very advantageous embodiment of the method according to the invention, the conductor foils can be gripped by means of a groove in the welding electrode. Such a groove can be provided, for example, in a square or round welding electrode. This is positioned on the stack of tacked conductor tabs such that the end facing away from the stack or coil, which was compacted during or after tacking, lies in this groove. By rotating the welding electrode, this compacted stack of conductor foils is then wound around this welding electrode.According to a further very advantageous embodiment, the welding electrode is then removed from the wound arrester foils after the wound arrester foils have been welded onto the cell lid, so that a hollow roll remains which is very stable due to the multi-layer structure, the individual layers of which are welded to one another and to the cell lid in a line along the central axis of the welding electrode on the side facing the cell lid.

[0013] This very stable structure consisting of cell lid and stack or coil can then be handled easily and efficiently and inserted into a housing, after which the cell lid is welded to the housing, preferably by laser welding.

[0014] Not only can the arrester foils be tacked together using ultrasonic welding, but according to a very advantageous embodiment of the method according to the invention, the wound arrester foils can also be welded to the cell cover, or the cell cover to the wound arrester foils, using ultrasonic welding. Only the welding of the cover to the housing can be achieved more efficiently, preferably using laser welding.

[0015] Another very advantageous embodiment of the method for producing the single battery cell according to the invention provides for the arrester foils to be stapled in the stacking direction or transversely to the winding direction at approximately the center height. Thus, the arrester foils are not collected on one side of the stack, where they are compacted and welded, as is largely common today. Instead, they are brought together in the center to tack them together as close as possible to the cell stack, with the individual arrester foils traveling as little distance as possible to the weld seam.

[0016] A single battery cell manufactured according to the method according to the invention now provides a stack or coil of cathodes, anodes, and separators, which is arranged in a cell housing sealed with a cell lid. The conductor tabs of at least one of the electrodes protrude beyond the stack or coil and are rolled up in this area and welded to the cell lid. According to an advantageous development of the single battery cell according to the invention, the cell lid can itself be welded to the housing.

[0017] Advantageous embodiments and further developments of the method according to the invention and of the individual battery cell produced thereby also emerge from the exemplary embodiment which is described in more detail below with reference to the figures.

[0018] Showing: Fig. 1 the production of a single battery cell in a first process step with a schematically indicated cell stack; Fig. 2 a representation analogous to that in Fig. 1 in a second process step; Fig. 3 a representation analogous to that in Fig. 1 and Fig. 2 in a third process step; and Fig. 4 the completion of the individual battery cell in a final process step.

[0019] In the presentation of the Figure 1a section of a stack 1 can be seen. This stack 1 consists of different electrodes 2, 3, i.e. the anodes and the cathodes. Separators 4 are arranged between each one. In the exemplary embodiment shown here, the cathodes are supported on an aluminum foil, which is shown here with a thick, solid black line. The ends of these cathodes 2 protrude laterally beyond the stack 1 as conductor lugs 5, transverse to the stacking direction S. They are grouped together in this area, although only five individual cathodes 2 are shown in the figure in order to simplify the illustration. The conductor lugs 5 are grouped together centrally in relation to the height of the stack 1 in the stacking direction S and are compacted in the area designated 5'.On the side of these compacted conductor lugs 5 facing the stack 1, a weld seam or individual weld points are now created by means of an ultrasonic welding device 6 along the depth of the sheet in the illustration of the . Figure 1 projecting width of the stack 1 in order to connect the compacted conductor lugs 5' and to reliably prevent the electrodes 2, 3 or separators 4 from being pulled out of the stack 1 in the further course.

[0020] The end of the compacted conductor lugs 5' facing away from the stack 1 is now gripped by a welding electrode 7, which is designed, for example, as a rod-shaped electrode with a groove 8, by inserting the compacted conductor lugs 5' into this groove. The welding electrode 7 is then guided according to the arrow in Figure 2wound in the direction of the stack 1, so that a roll 5" is created from several spiral layers of the compacted arrester lugs 5'. This roll 5" with the welding electrode 7 arranged therein is then brought into contact with a cell cover 9 and welded to it through the material of this cell cover 9. This process can also be carried out as ultrasonic welding, which is why the symbolic representation of the welding is again provided with the reference number 6. The wound arrester lugs, which are designated 5" here after winding into the roll, form a very compact structure that can be easily and efficiently welded to the cell cover 9 in a process-reliable manner.

[0021] The welding electrode 7 is then pulled out sideways and a very robust structure is created from stack 1 and cell lid 9, which is then, for example, placed in a housing already filled with electrolyte or, after impregnation of the stack 1, in a housing 10 such as is shown in the illustration of the Figure 4 can be seen. The structure is also shown purely schematically here; typically, the cell stack will naturally utilize more space within the housing. The cell cover 9 can then be welded to the housing 10, for example, by laser welding, which is indicated here by the two triangles 11.

[0022] In principle, the described method and the single battery cell 12 obtainable by this method, which is shown in a partial section in the illustration of the Figure 4As can be seen, it can be used for both round and prismatic housings 9. In particular, it is suitable for electrically contacting a stack 1 with the cell lid and is therefore preferably used for a structure with a prismatic housing 10.

[0023] Compared to the state of the art, this saves material and manufacturing effort, as the additional welding to the current collector, as is common in the general state of the art, is eliminated. At the same time, the proven concept of independent individual battery cells 12, which are then electrically contacted externally, is retained, offering decisive advantages in terms of scalability and safety that are not feasible in the aforementioned state of the art.

[0024] In the illustrations in the figures, only parts of the stack 1 or the individual battery cell 12 are visible. The missing side can be designed identically or in any other known manner. This applies to both the housing and the contacting of the other electrode 3, in this case the anode.

Claims

1. Method for producing an individual battery cell (12) having a stack (1) or winding of electrodes (2, 3) and separators (4), at least one of the electrodes (2, 3) comprising collector tabs (5) which project laterally in one direction beyond the stack (1) or winding and are welded to one another, characterized in that the collector tabs (5) are compacted and attached by welding on their side facing the stack (1) or winding, after which the compacted and welded collector tabs (5') are gripped by a welding electrode (7) on their side facing away from the stack (1) or winding and wound around the welding electrode (7) in the direction of the stack (1) or winding, and after which a cell cover (9) of the individual battery cell (12) is welded to the wound collector tabs (5').

2. Method according to claim 1, characterized in that the compacted and welded collector tabs (5') are gripped by means of a groove (8) in the welding electrode (7).

3. Method according to either claim 1 or claim 2, characterized in that the welding electrode (7) is removed from the wound collector tabs (5") after the wound collector tabs (5") have been welded to the cell cover (9).

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

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

6. Method according to any of claims 1 to 5, characterized in that the collector tabs (5) are welded for attachment by means of ultrasonic welding.

7. Method according to any of claims 1 to 6, characterized in that the wound collector tabs (5") are welded to the cell cover (9) by means of ultrasonic welding.

8. Method according to any of claims 1 to 7, characterized in that the collector tabs (5) are attached at approximately central height in the stacking direction (S) or transversely to the winding direction.