Contacting system for individual battery cells of a battery module

Abstract

The invention relates to a contacting system (5) for individual battery cells (2) of a battery module (1), said contacting system comprising cell connectors (8, 10, 11) for contacting the cell poles (3, 4) of at least two of the individual battery cells (2) of the battery module (1). The contacting system according to the invention is characterized in that at least one of the cell connectors (8, 10, 11) has an internal cooling channel (9) for receiving a cooling medium.

Description

[0001] Mercedes-Benz Group AG

[0002] Contact system for individual battery cells of a battery module

[0003] The invention relates to a contacting system for individual battery cells of a battery module according to the type defined in more detail in the preamble of claim 1.

[0004] Battery modules with multiple individual battery cells are a well-established technology. These are often so-called high-voltage or HV batteries, which are used, for example, as traction batteries in vehicles. Crucially, such a battery must operate within a specific temperature range to achieve its ideal performance and maximum lifespan. Therefore, it is common knowledge that battery modules are cooled. For example, the

[0005] DE 10 2012 217267 A1 describes the integration of battery cooling into clamping elements of a battery module. In the illustrated embodiment, individual battery cells are clamped between clamping plates and side walls of the battery module. The clamping plates and side walls have cooling channels for a cooling medium through which they flow.

[0006] Further prior art is known from DE 10 2018216 713 A1. It addresses a different method of temperature control for battery modules, namely temperature control via so-called bottom coolers or cooled base plates. The aforementioned document describes a specific geometry for such a cooled base plate, in which raised sections are repeatedly arranged within the cooling channel to achieve the most turbulent flow possible of the cooling medium. This improves the heat transfer from the plate to the cooling medium.

[0007] A problem with these designs is that such additional cooling elements always require extra installation space, which is detrimental to the power density of the battery module. Furthermore, the bottom of the battery module is often cooled, for example, via the cooled base plate mentioned earlier. This can cause the cell connectors of the contacting system, typically located at the top of the individual battery cells at the opposite end, to heat up considerably, especially since they conduct the electrical current that flows during charging and discharging of the battery module.

[0008] The object of the present invention is therefore to create an improved cooling system for a battery module, which ensures efficient cooling in a space-saving design.

[0009] According to the invention, this problem is solved by a contacting system for the individual battery cells of a battery module, which is configured according to the features of claim 1. Advantageous embodiments and further developments are described in the dependent claims.

[0010] The contacting system according to the invention serves to electrically contact the cell terminals of at least two individual battery cells using cell connectors. The individual battery cells are connected, for example, in parallel and / or in series via the cell connectors of the contacting system, in order to draw energy from the battery module or to supply it during charging. The contacting system can also include lines for tapping individual voltages at the individual battery cells, which serve for control purposes.

[0011] The contacting system according to the invention is designed such that the cell connectors, i.e., those parts which are in contact with the cell terminals of the individual battery cells, have an internal cooling channel for receiving a cooling medium. Thus, in the contacting system according to the invention, the cell connectors themselves are provided with a cooling medium within their volume. This allows for direct cooling of the current-conducting cell connectors, which, through the current- and heat-conducting contact with the cell terminals, also cools the individual battery cells themselves and their internal electrodes. All in all, this creates a very efficient method of cooling that requires hardly any additional installation space and helps to increase the performance of the battery module.

[0012] In principle, such cooling can be used on its own. However, it would also be conceivable to combine it with a known cooling method between the individual battery cells, a cooled base plate, or so-called direct cooling of the individual battery cells via a dielectric cooling medium.

[0013] According to a particularly advantageous embodiment, the cell connectors can be designed to have an upper part and a lower part connected to it, with the cooling channel being arranged at least partially between the upper and lower parts. This design is particularly simple and efficient with regard to the production of the cell connectors of the contacting system according to the invention. These can, for example, be produced as formed parts by internal pressure forming, or they can also be designed as extruded or continuously cast profiles. Other manufacturing methods are also conceivable, such as deep drawing or similar processes.

[0014] According to a further, highly advantageous embodiment, the cell connector can also be provided with contact tabs that are either bonded to the connector material or integrally formed with it, remaining free of the cooling channel and thus made of solid material. These contact tabs can be manufactured integrally with the cell connector, for example, by stamping followed by deep drawing, bending, or forging, or attached by welding, riveting, or similar processes. The contact tabs themselves are then connected to the cell terminals of the individual battery cells. Various manufacturing processes are possible here as well, with a bonding process such as welding typically being used. In principle, however, riveting, screwing, or even bonding with a suitable electrically conductive adhesive would also be possible.

[0015] An alternative connection method using wire bonding is also conceivable in principle. According to a particularly advantageous refinement, the contact tabs of the two-part cell connector can be integrated with the lower part of the connector. The contact tabs and the lower part of the cell connector can then be manufactured from a material with good thermal and electrical conductivity, for example, by deep drawing, bending, or similar processes, and the cooling channels can be designed as open-topped recesses. A cover can then be easily placed on this lower part to close the cooling channels.

[0016] Such a cover can, for example, be made of the same material and joined to the base by welding or soldering. To prevent electrical contact between overlapping parts of the cell connector, if desired, the cover can also have an electrically insulating coating. In principle, it would also be conceivable to manufacture this cover directly from an electrically insulating material, such as a plastic, which would then be bonded to the electrically and thermally conductive base of the cell connector to close the cooling channels.

[0017] Regarding the cooling channels, various cooling media in different configurations are conceivable. One option, for example, could involve using a phase-change material as the cooling medium in the cooling channels. This material changes from its solid to its liquid phase at a specific, predetermined temperature and can absorb a particularly large amount of thermal energy in the process. Alternatively, a liquid cooling medium could also be used. In both cases, the cooling medium could be contained entirely within the cooling channels and circulated there as needed by thermal convection. Alternatively, the medium could be actively circulated, for example, by a pumping system that circulates the cooling medium within the cooling channels of the contacting system.In this particular case, a heat exchanger can be used to connect to an external cooling circuit, or external cooling air can be drawn across the heat exchanger to cool the cooling medium within the cooling channels. Another design option, whether using a phase-change material or, especially, a liquid cooling medium, involves drawing the coolant from an external cooling circuit and circulating it through the cooling channels of the contacting system to ensure cooling. Such an external cooling circuit might already be present in a vehicle application for cooling other power electronic components and can then also be used to cool the contacting system.As mentioned above, other cooling options for the battery module are also fundamentally conceivable as a supplement, so that the external cooling circuit could, for example, convey a liquid cooling medium partly through a bottom cooler on the one hand and the contacting system according to the invention on the other.

[0018] A further highly advantageous embodiment of the contacting system according to the invention can also provide that the contacting system is constructed from two superimposed layers which are electrically insulated from each other or are arranged in an insulated manner, i.e., have an air gap between them for electrical insulation. In this configuration, a particularly advantageous further development allows the contact tabs of an upper layer to project through recesses in the layer below in order to contact the cell poles. This creates a grid-like structure in which the grid elements or grid bars themselves contain the cooling channels, and in which several such grid elements can be used to implement the desired type of contacting.For example, a first layer can be positioned directly on the individual battery cells and contacted with the desired cell terminals to connect them in parallel. To further connect the individual battery cells, it would be conceivable to add one or more additional layers, or even to arrange two cell connector components within a single layer, spaced apart from each other. One cell connector could then collect the electrical potential of all positive cell terminals, and the other that of the negative terminals, thus enabling the entire battery module to be connected externally.

[0019] Optionally, a thermally conductive filler material can be placed between the cell connectors, and especially those of the lower layer, and the individual battery cells. Such a material, e.g., an electrically insulating thermal paste or a suitable potting compound, can be used to further improve the thermal connection. The corresponding cell connector can thus essentially take on the function of a (possibly additional) cooling plate for the battery module, without requiring a separate component and the associated space, weight, and cost.

[0020] Advantageous embodiments and further developments of the contacting system according to the invention also result from the exemplary embodiment, which is described in more detail below with reference to the figures.

[0021] This shows:

[0022] Fig. 1 shows a battery module and a contacting system in a three-dimensional exploded view;

[0023] Fig. 2 shows a schematic sectional view through part of a battery module and the contacting system; and

[0024] Fig. 3 shows an exploded view of a cell connector of the contacting system.

[0025] Figure 1 shows a battery module, designated 1 in its entirety. This module comprises individual battery cells 2, each of which has a cell housing 3 as one cell terminal and another cell terminal, designated 4, projecting vertically above it. The individual battery cells 2 are shown here as cylindrical cells for illustrative purposes only. A contact system 5 is visible above the battery module 1, through which the cell terminals 3 and 4 of the individual battery cells 2 will later be electrically contacted and connected in the desired electrical configuration.

[0026] In the embodiment shown here, the contacting system 5 comprises a lower layer 5A and an upper layer 5B. A cell connector 8 is visible in the lower layer 5A, which has contact tabs designated 6 only in the front row. These tabs each contact the cell terminals 4 of the individual battery cells 2 below. The cell connector 8 also has contact tabs 7 to contact the cell housings as the other cell terminal 3 of adjacent individual battery cells 2. Thus, several parallel individual battery cells 2 are connected in series above this lower layer 5A, or rather, above the cell connector 8 of the contacting system 5. Above this lower layer 5A with the cell connector 8, two further cell connectors 10 and 11 are arranged in the upper layer 5B.The contact tabs 12 of the cell connector 11 contact the cell housings 3 by protruding through recesses 13 of the cell connector 8. A similar process applies to the cell connector 10, whose contact tabs 14 also protrude through recesses 13 of the cell connector 8, but here they contact the cell poles 4. The cell connectors 10 of the upper layer 5B are electrically insulated from the cell connector 8 of the lower layer 5A, for example by an air gap between the cell connectors 8 and 10, 11, or by an electrically insulating coating, or the like.

[0027] In the described circuit, the negative battery terminal of the battery module would be formed via cell connector 11 and the positive battery terminal via cell connector 10.

[0028] Figure 2 shows the contact system 5 on the battery module 1 again in its assembled state in a section view, which is essentially based on line 11-11 in the contact system 5 in Figure 1. The lower layer 5A shows the cell connector 8. It comprises a total of four cooling channels 9, each of which is arranged adjacent to the contact tabs 6 or 7. Furthermore, another section of the cell connector 8 of the lower layer 5A can be seen on the far left of Figure 2, which also has a cooling channel 9. Above this, the two cell connectors 10 and 11 are arranged in the layer 5B above. The contact tabs 12 of the cell connector 11 contact the cell housings 3 by projecting through the recesses 13 of the cell connector 8. This cell connector 11 also comprises cooling channels 9.The same applies to the cell connector 10, whose contact tabs 14 also protrude through the recesses 13 of the cell connector 8, but here they contact the cell poles 4. The cell connector 10 also has the cooling channels 9.

[0029] Figure 3 shows an exploded view illustrating the possible configuration of the cell connector 10 within the contacting system 5. The other cell connectors 8 and 11 can be configured analogously. In the embodiment shown here, the cell connector 10 consists of a lower part 15, which has the contact tabs 14. Preferably, these are formed integrally with the lower part, for example, from an electrically and thermally conductive metal such as a copper or aluminum alloy. The lower part 15 also provides a free volume for the cooling channel 9. This assembly is then connected by a cover designated 16. In Figure 2, this cover, like the lower part 15, is only attached to the cell connector.

[0030] 10 is marked with a reference symbol. This structure can also be seen analogously in the other two cell connectors 8 and 11. The cover 16 can be made of the same material as the base 15. The parts can be joined, for example, by laser welding. However, the cover 16 can also be made of a different material, since its contribution to thermal and electrical conductivity is rather small. It could, for example, be made of a plastic in order to provide electrical insulation between the layers—at least in cell connector 8 of the lower layer 5A.

[0031] Within the resulting inner cooling channel 9 of the respective cell connector 8, 10,

[0032] A cooling medium can then either be passed through or contained within the cooling channel 11. For a passed-through cooling medium, a cooling fluid from an external cooling circuit flowing through the cooling channels 9 would typically be preferred. In this case, very low electrical conductivity of the cooling medium would be essential. For a cooling medium contained within the cooling channel 9, which is not exchanged during operation, a phase-change material would be preferable. Due to the phase change at a predetermined temperature, this material can absorb a very high amount of heat per unit volume. Since the cooling medium remains within the cooling channels 9 of its respective cell connector 8, 10, or 11, the requirements regarding electrical conductivity are considerably lower.

[0033] In addition to cooling the contacting system 5 via the cooling channels 9, a known bottom cooling system 17 can also be provided, which is indicated schematically and shown as a dashed line in Figure 2. Furthermore, although not shown here, corresponding channels for a cooling medium or a volume for a phase-change material could be provided between the individual battery cells 2. Direct cooling of the individual battery cells 2 via a dielectric would also be conceivable as an addition to the cooled contacting system 5.

[0034] To improve the thermal connection of the individual battery cells 2 to the cooled cell connectors 8, 10, 11, a thermal paste can also be applied to fill any gaps. This minimizes air gaps between the individual battery cells 2 and, in particular, the cell connector 8 of the lower layer 5A. This allows the connector to additionally perform the function of a cooling plate.

Claims

Mercedes-Benz Group AG Patent claims 1. Contacting system (5) for individual battery cells (2) of a battery module (1) with cell connectors (8, 10, 11) for contacting the cell poles (3, 4) of at least two of the individual battery cells (2) of the battery module (1), characterized in that at least one of the cell connectors (8, 10, 11) has an internal cooling channel (9) for receiving a cooling medium.

2. Contacting system (5) according to claim 1, characterized in that the cell connector (8, 10, 11) has a lower part (15) and a lid (16) connected thereto, wherein the cooling channel (9) is formed at least section by section between the lower part (15) and the lid (16).

3. Contacting system (5) according to claim 1 or 2, characterized in that the cell connector (8, 10, 11) has contacting tabs (6, 7, 12, 14) which are bonded to the respective cell connector (8, 10, 11) or are integrally formed with it, wherein the contacting tabs (6, 7, 12, 14) themselves are free from the cooling channel (9).

4. Contacting system (5) according to claims 2 and 3, characterized in that the contacting tabs (6, 7, 12, 14) are formed integrally with the lower part (15) of the cell connector (8, 10, 11).

5. Contacting system (5) according to claim 2, 3 or 4, characterized in that the cover (16) has an electrically insulating coating or is made of an electrically insulating material.

6. Contacting system (5) according to one of claims 1 to 5, characterized in that the cooling medium is designed as a phase change material or comprises such a material.

7. Contacting system (5) according to one of claims 1 to 5, characterized in that the cooling medium is designed as a cooling fluid, in particular as a liquid cooling medium.

8. Contacting system (5) according to one of claims 1 to 7, characterized in that a conveying device for circulating the cooling medium in at least one of the cell connectors (8, 10, 11) is provided.

9. Contacting system (5) according to one of claims 1 to 8, characterized in that a heat exchanger is provided through which the cooling medium is in contact with an external cooling circuit.

10. Contacting system (5) according to one of claims 1 to 8, characterized in that the cooling channels (9) are part of an external cooling circuit.

11. Contacting system (5) according to one of claims 1 to 10, characterized in that two or more superimposed layers (5A, 5B) are provided with at least one of the cell connectors (8, 10, 11) which are electrically insulated from each other or insulated from each other.

12. Contacting system (5) according to claim 11 , characterized in that the contacting tabs (12, 14) of an upper layer (5B) project through recesses (13) of the underlying layer (5A) to the cell poles (3, 4).

13. Contacting system (5) according to one of claims 1 to 12, characterized in that a thermally conductive filler material is arranged between the individual battery cells (2) and at least one of the cell connectors (8, 10, 11) and / or between the cell connectors (8, 10, 11).

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