Method for repairing a battery module

Abstract

The invention relates to a method for repairing a battery module (1) with several individual battery cells (2), which comprise electrodes, separators, and electrolyte in a cell housing (8), and of which at least one is defective, wherein the at least one defective individual battery cell is electrically short-circuited. The method according to the invention is characterized in that the at least one defective individual battery cell (2) is brought into a safe state before short-circuiting, in which the electrolyte is drawn out of the cell housing (8) of the individual battery cell (2) through an opening (5, 6, 7) provided in its cell housing.

Description

[0001] The invention relates to a method for repairing a battery module with several individual battery cells according to the type defined in more detail in the preamble of claim 1.

[0002] In the case of large battery modules consisting of multiple individual battery cells, repairs are often comparatively difficult because the individual cells are, for example, potted or glued within the battery module. DE 10 2020 003 870 A1 therefore describes a method and a device for repairing a battery. The idea is to electrically bridge a defective individual battery cell, thus electrically removing it from the battery module. Mechanically, the cell remains contained within the battery module because, as mentioned above, it is often glued or potted within the module and therefore cannot be removed, or only with considerable effort.The aforementioned document focuses on placing the electrical bridging of the defective individual battery cell as compactly as possible below the actual cell contact, in order not to impair the overall battery design.

[0003] The capacity and voltage of the overall battery change after bridging one or more individual battery cells. Typical high-voltage batteries, as defined by ECE 100R and used as traction batteries in vehicles, have a relatively high number of individual battery cells. Depending on the design, for example, 400 or 800 individual battery cells are used. The absence of one or a few individual battery cells does not cause a significant loss of capacity or voltage; rather, the changes fall within the tolerances that typically occur during manufacturing and affect the overall voltage or capacity of the battery.

[0004] From CN 109 698 311 A, a liquid-exchangeable lithium battery is known, comprising a discharge device, a seepage section, and a suction section. The side wall of a battery cell is sealed with a supporting seepage section of the discharge device. The liquid circulation path is formed by the supporting seepage section and the suction section, and the circulation path is effectively limited so that in the event of a defect, the liquid is directly extracted.

[0005] From DE 10 2014 221 300 A1, a device for removing particles from a battery cell is known, in which at least one battery winding is received in a housing and the housing comprises flow guidance elements along which a rinsing medium, in particular an electrolyte, flows through the housing during the filling process from at least one inlet opening of the housing to at least one outlet opening.

[0006] German patent DE 10 2009 047 057 A1 discloses a battery cell or a group of battery cells of an energy storage device with a dosing unit. The dosing unit enables a fast, safe, and efficient exchange of the electrolyte in a battery cell. This allows the depleted electrolyte, which still has a low content of free lithium ions and therefore poor conductivity, to be removed from the battery cell. Furthermore, the depleted electrolyte contains undesirable byproducts that can negatively affect the battery cell's capacity. By refilling electrolyte-depleted battery cells, their capacity can be increased and their internal resistance reduced.

[0007] An alternative method is proposed in DE 10 2023 100 047 A1. The structure described therein is repaired by separating the cell casing of a single battery cell and removing the jelly roll contained within. The term jelly roll refers to a coiled winding of electrodes and separators, which sits as a roll impregnated with electrolyte inside the cell casing. The casing is accordingly cup-shaped.

[0008] Essentially, this repair method is therefore limited in practical application to such individual battery cells, since only the coil of wound internal materials from a cell casing is sufficiently stable to be removed and replaced. A stack of electrodes and separators, as used in a prismatic battery cell, would not be mechanically stable enough for reinsertion. Furthermore, the method is extremely complex, especially when repairing only a single battery cell, and is therefore hardly feasible in practice outside of actual battery manufacturing.

[0009] The object of the present invention is to provide an improved method for repairing a battery module with several individual battery cells, which can be implemented simply and efficiently.

[0010] According to the invention, this problem is solved by a method with the features in claim 1, and in particular in the characterizing part of claim 1. Advantageous embodiments and further developments are described in the dependent claims.

[0011] The method according to the invention essentially adopts the basic idea described in the aforementioned DE 10 2020 003 870 A1 and electrically short-circuits the at least one defective battery cell in order to bypass it. Unlike in the aforementioned document, the at least one defective battery cell is brought into a safe state before the short-circuiting. Such a safe state is a state in which the battery cell no longer poses any danger, even in the event of thermal runaway of the battery module, and in particular of the neighboring cells of the defective battery cell. To achieve this, the electrolyte is extracted from the battery cell through an opening. The electrodes and separators within the cell housing are then at least largely dry, so that they completely lose their electrochemical effect and are thereby brought into a safe state.The defective battery cell can then simply be short-circuited. Disconnecting the electrodes is no longer strictly necessary, as they no longer function due to the lack of electrolyte. A relatively small opening or hole in the cell casing is sufficient for extraction. Such an opening can easily be made even in glued or potted battery cells.

[0012] A particularly advantageous embodiment of the method according to the invention can further provide that, during the electrolyte extraction, the system is rinsed at least once with a rinsing medium. Such a rinsing medium can ensure that not only the electrolyte that is easily accessible within the individual battery cell is reliably extracted, but also that it is reliably extracted from difficult-to-access areas such as corners, sections between the electrodes and separators, and from the area of ​​porous separators and the like.

[0013] A further highly advantageous embodiment of the method according to the invention can provide that, after the electrolyte has been extracted, the electrodes and separators are at least partially removed from the cell housing. Ideally, these materials are removed from the cell housing so that, after the repair, a completely empty cell housing remains within the battery module, which is electrically short-circuited and thus bypassed. With such an empty cell housing, the assembly has been repaired in an extremely safe manner.

[0014] In detail, according to a favorable embodiment of the inventive method, it can be provided that, for the purpose of extracting the electrolyte, the first of the electrolyte filling openings is reopened. Typically, the cell casing has one or more electrolyte openings, which were used for filling the battery cell with electrolyte during its manufacture. One or more of these electrolyte openings, which may have been welded shut, can then typically be reopened relatively easily to extract the electrolyte.

[0015] An advantageous further development of this provides that a second electrolyte opening is also opened to allow air to flow in. This setup with two electrolyte openings is the typically used configuration. During cell production, electrolyte is supplied through one of the electrolyte openings, while air is extracted through the other electrolyte opening during electrolyte filling or can escape automatically. In the inventive method, if both openings are reopened, electrolyte can be extracted through one opening, and air can flow in through the other.

[0016] A highly advantageous further development can also provide that, after the electrolyte has been aspirated, the rinsing medium is supplied through one of the openings and aspirated through the other. The rinsing medium can thus be supplied and aspirated simply and efficiently. After a single or multiple rinsing cycle, the cell housing is then filled with the rinsing medium, in particular an electrochemically neutral liquid or a liquid-gas mixture.

[0017] This can now be extracted again, with air flowing in through the other opening.

[0018] To drain the electrolyte, an overpressure relief vent in the cell casing can also be opened according to an alternative design. Typically, the cell casing has an overpressure relief vent to release unwanted overpressure in the event of a thermal event in the individual battery cell. These overpressure relief vents are often formed by predetermined breaking points within the cell casing. They can therefore be easily opened, for example, by inserting a tool through the predetermined breaking point to lift off the remaining material attached to the cell casing via the breaking point, similar to removing the lid of a tin can.This creates a relatively large opening compared to the electrolyte openings, which is suitable for suctioning the electrolyte, filling the rinsing medium and / or allowing air to flow in, especially when a suction nozzle is used whose outer diameter is smaller than the opening diameter of the overpressure relief opening.

[0019] Often, the pressure relief opening is so large that, according to a highly advantageous further development, it is relatively easy to grasp the individual electrodes and separators in the cell housing, once emptied of electrolyte, manually or automatically, for example with tweezers or a similar tool, and pull them out of the opening layer by layer. This makes it easy to remove the individual electrodes and separators from the cell housing, and it is sufficient to remove a large proportion of them, especially those that are easily accessible through the opening.

[0020] The entire process is exceptionally simple and efficient, and in particular, it can be carried out without a new additional opening if it utilizes the electrolyte openings originally used for filling and / or the pressure relief opening to remove the electrolyte and, if necessary, at least some of the separators and electrodes from the cell housing. The cell housing then remains completely or largely empty and without electrochemical activity, i.e., in a safe state. It therefore does not need to be resealed, which further simplifies the repair process. In principle, filling the cell housing with a potting compound or similar material would also be possible.

[0021] This repair method is particularly suitable for use with individual battery cells featuring a prismatic cell casing, especially since the pressure relief vent and / or the two filling ports are typically located on the same side of such cells, thus simplifying the process with regard to cell casing accessibility. While the method can, in principle, be used with any type of battery module, it is particularly advantageous when the cell casings are bonded and / or potted within the battery module.

[0022] Further advantageous embodiments of the method according to the invention can also be seen from the exemplary embodiment, which is described in more detail below with reference to the figures.

[0023] This shows: Fig. 1. A section of an exemplary battery module with a defective single battery cell; Fig. 2. A view of the defective single battery cell alone; and Fig. 3 a view of the already in Fig. 2 shows a section of the battery module after the repair.

[0024] In the presentation of the Fig. Figure 1 shows a section of a battery module 1, in the example shown here with five individual battery cells 2. The individual battery cells 2 are electrically connected in series, for which opposite adjacent poles are electrically connected via the cell connectors labeled 3.

[0025] One of the individual battery cells 2 in the battery module 1 or the section from the battery module 1 in Fig. Item 1 is now said to be defective. In the representation of the Fig. 1 This single battery cell 2 is marked with an “X”.

[0026] This defective single battery cell 2 is now shown in the representation of the Fig. 2 is shown again separately. It has two cell terminals, labeled 4, on its upper surface for electrically connecting the individual battery cell 2. Furthermore, a first electrolyte opening 5 and a second electrolyte opening 6, used as filling openings during the production of the individual battery cell 2, are visible, as well as a pressure relief element labeled 7 between them.

[0027] In the production of the battery cell 2, a stack of individual electrodes and separators is arranged in the cell housing designated 8. The electrodes of one pole are connected to one cell terminal 4, and the electrodes of the other pole are connected to the other cell terminal 4. The interior of the cell housing 8 is then filled with a suitable liquid or gel electrolyte. This is typically done via the first electrolyte inlet 5, through which the electrolyte is introduced into the interior of the cell housing 2. Air can escape through the second electrolyte inlet 6 or is actively extracted. After filling with electrolyte, the electrolyte inlets 5 and 6 are closed; in the case of a plastic cell housing 8, this is done, for example, by ultrasonically welding.

[0028] The cell housing 8 also features the known overpressure relief element 7. Typically, this is an oval section of the cell housing 8, which is connected to the rest of the cell housing 8 via a predetermined breaking point. The predetermined breaking point is dimensioned such that, at a critical overpressure within the cell housing 8, this breaking point tears open and an oval cover of the overpressure relief element 7 opens at least partially to release the so-called venting gases.

[0029] The defective single battery cell 2 also has this configuration, with electrolyte openings 5 ​​and 6 typically sealed during operation (e.g., welded shut) and a sealed overpressure relief element 7. To bring the defective single battery cell 2 into a safe condition, the liquid or gel-like electrolyte inside the cell housing 8 is now extracted. The first electrolyte opening 5 can be used for this purpose, through which the electrolyte is extracted, for example, via a nozzle, hose, or similar device inserted into the interior of the cell housing 8. Ideally, not only the first electrolyte opening 5 but also the second electrolyte opening 6 is reopened to allow air to flow in. A flushing process can also be performed to remove as much of the electrolyte as possible.In this case, a liquid rinsing medium could be introduced via the second electrolyte opening 6 instead of air until the electrolyte is completely or almost completely flushed out. This rinsing medium is then extracted, allowing air to enter the individual battery cell X. This cell is now in a safe state and can therefore remain within the battery module 1 being repaired without posing any danger.

[0030] As an alternative to opening one or both of the filling openings 5, 6, the overpressure relief element 7 can also be opened along its predetermined breaking point to aspirate the electrolyte, allow air to flow in or introduce the rinsing medium.

[0031] Furthermore, opening the overpressure relief element offers the advantage that the resulting opening in the cell housing 8 is comparatively large. This makes it possible to grasp individual layers of the electrodes and separators using a gripping tool such as tweezers and pull them out of the cell housing 8. Ideally, all separators and electrodes can be removed from the cell housing 8 in this way, one after the other. Since the electrodes are typically relatively thin films, they simply detach from their internal connection with the cell terminals 4. This setup is even safer than if only the electrolyte had been removed, and is therefore generally preferable.

[0032] In Fig. Figure 3 shows how the defective battery cell 2, designated X, is bridged via an electrical short-circuit connector 9 in order to restore the function of the battery module 1 and to bridge the defective or reduced-performance battery cell 2. By removing at least the electrolyte, ideally the electrolyte and at least some of the electrodes and separators from the cell housing 8 of the defective battery cell 2, a very safe setup is created.

[0033] Since such battery modules 1 typically have many more individual battery cells 2 than shown in the illustration of the Fig. 1 and Fig.As shown in Figure 3, bridging a single battery cell usually does not cause any significant loss in the total capacity and total voltage of such a battery module 1, as has already been addressed in the prior art mentioned at the beginning in the form of DE 10 2020 003 870 A1.

Claims

Method for repairing a battery module (1) with several individual battery cells (2) comprising electrodes, separators and electrolyte in a cell housing (8), and of which at least one is defective, wherein the at least one defective individual battery cell is electrically short-circuited, characterized in that the at least one defective individual battery cell (2) is brought into a safe state before short-circuiting, in which the electrolyte is drawn out of the cell housing (8) of the individual battery cell (2) through an opening (5, 6, 7) provided in its cell housing (8). Method according to claim 1, characterized in that the cell housing (8) of the defective battery single cell (2) is rinsed at least once with a rinsing medium during the extraction of the electrolyte. Method according to claim 1 or 2, characterized in that after the electrolyte has been aspirated, the electrodes and / or separators are at least partially removed from the cell housing (8). Method according to claim 1, 2 or 3, characterized in that, for the purpose of aspirating the electrolyte, a first electrolyte opening (5) originally intended for filling is reopened in order to aspirate the electrolyte. Method according to claim 4, characterized in that during the extraction of the electrolyte via the first electrolyte opening (5) a second electrolyte opening (6) is reopened to allow air to flow in. Method according to claim 4 or 5, characterized in that after the electrolyte has been aspirated, a rinsing medium is supplied through the first or second electrolyte opening (5, 6) and aspirated again through this electrolyte opening (5, 6) or the other electrolyte opening (6, 5). Method according to one of claims 1 to 6, characterized in that an overpressure relief element (7) of the cell housing (8) is opened for the purpose of aspirating the electrolyte. Method according to claim 7, characterized in that after the electrolyte has been aspirated, the electrodes and separators are at least partially removed from the cell housing (8) through the opening of the overpressure relief element (7). Method according to one of claims 1 to 6, characterized in that after the electrolyte has been aspirated, an overpressure relief element (7) of the cell housing (8) is opened in order to remove the electrodes and separators at least partially from the cell housing (8) through the opening of the overpressure relief element (7). Method according to one of claims 1 to 9, characterized in that the cell housings (8) of the battery individual cells (2) are designed as prismatic self-supporting cell housings (8). Method according to one of claims 1 to 10, characterized in that the cell housings (8) are glued and / or fixed within the battery module (1) using a potting compound.

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