Battery module, method for its manufacture and motor vehicle with a battery module

Abstract

Method for manufacturing a battery module (10) comprising several battery cells (4) grouped together to form a cell stack (1), characterized by the step: - Applying an electrically insulating thermal conductivity compound (2) to a base (1a) of the cell stack (1).

Description

[0001] The present invention relates to a method for manufacturing a battery module, a battery module and a motor vehicle comprising at least one battery module.

[0002] High-voltage storage systems utilize battery modules, each containing several battery cells grouped together to form a cell stack. During the manufacturing process, these cell stacks are typically pressed together, clamped by a surrounding frame, and held in shape. The battery modules are also equipped with a cooling system. To improve heat dissipation from the cell stack and thus enhance cooling efficiency, a heat-conducting plate is inserted between the cell stack and the cooling system. This plate is attached to the cell base using a thermally conductive compound. To prevent short circuits within a battery module, an additional electrically insulating layer is incorporated into the heat path between the cell stack and the cooler, as well as along the sides of the cell stack.The laterally positioned insulating layer is typically fixed between the base of the cell stack and the cooler by creating an overlap in the thermal interface material or between the thermal interface material and the cooler. Due to this multi-layered structure of the battery module, a high number of heat transfers occur, resulting in a large temperature difference between the layers. Heat generated within the battery module is poorly dissipated, thus reducing its lifespan. Furthermore, the layered structure is not very compressible, meaning that, once installed, there is no way to compensate for manufacturing tolerances and component tolerances of the individual layers and battery cells.

[0003] DE 10 2009 011 656 A1 discloses a method and a device for bonding battery cells to form a cell assembly. A fluid flowing through the spaces between the individual battery cells is used as the cooling medium. During the manufacturing process, the bottom and top of the cell packs are coated with an electrically insulating potting compound.

[0004] Based on this prior art, the object of the present invention is therefore to provide a simple and cost-effective method for manufacturing a battery module that uses a reduced number of layers for heat conduction and electrical insulation, provides good thermal contact between the cell stack, and compensates for manufacturing and component tolerances in the battery module. Furthermore, the object of the invention is to provide a cost-effective battery module of high quality and dimensional accuracy with very good electrical insulation and high heat dissipation from the battery cell stack, as well as a battery-powered vehicle characterized by high reliability and good driving range.

[0005] According to the invention, the problem of manufacturing a battery module with several battery cells grouped into a cell stack is solved by applying an electrically insulating thermally conductive compound, preferably an electrically insulating thermally conductive potting compound, to a base of the cell stack. A thermally conductive compound or a thermally conductive potting compound within the meaning of the invention is a plastic mass used for filling gaps, joints, and the like, wherein the mass, in its cured state, enables heat transfer through this mass and furthermore exhibits high electrical insulation resistance combined with good thermal conductivity. The thermally conductive compound or the thermally conductive potting compound can be processed by casting, injection molding, or similar methods, since the thermally conductive compound or the thermally conductive potting compound is at least partially flowable before curing.The inventive step enables the production of a battery module with excellent heat dissipation properties that simultaneously meets the stringent requirements for high electrical insulation. Due to the combination of thermal conductivity and electrical insulating properties in a single compound applied to the cell base of the battery cell stack, the addition of further separate layers is unnecessary. This reduces both the logistical and manufacturing effort involved in producing the battery module, as well as its material costs. Consequently, the number of heat transfer points between the battery module and any connected cooling device can be minimized while maintaining maximum thermal conductivity of both the battery module and the thermally conductive compound.Furthermore, to ensure electrical insulation, particularly regarding air and creepage distances, no overlap of an insulating layer between any cooling device and the thermal interface material is necessary, which would impair heat transfer between the cell stack and the cooling device. By using only an electrically insulating thermal interface material, and thus eliminating the need for conventional heat-conducting plates and other functional layers, especially insulating layers between a cooling device and the thermal interface material, a battery module with good dimensional accuracy is obtained, while manufacturing tolerances in the cell stack or in the individual battery cells can be more easily compensated for.The process is suitable for large-scale series production and also improves the quality of energy storage devices containing the battery module produced according to the invention: due to the omission of further layers before the connection of a cooling device, the thermally conductive material is exposed and can be subjected to non-destructive quality control without affecting the manufacturing process. The manufactured battery modules can be fed into further production without post-processing. The process according to the invention enables the cost-effective and simple production of high-quality and functional battery modules without significant technical effort.

[0006] The dependent claims include advantageous further developments and embodiments of the invention.

[0007] An advantageous further development of the method according to the invention is characterized by the step of curing the thermally conductive compound, in particular by heating the thermally conductive compound. Especially when using a thermally conductive compound that is designed as a thermally conductive potting compound and is therefore flowable at least during the application process, curing is advantageous for the final shaping and stabilization of the forming thermally conductive layer. Curing by heating the thermally conductive compound, for example for cross-linking it, can be carried out very uniformly without significant technical effort.

[0008] By distributing and shaping the thermally conductive compound applied to the base of the cell stack using a stamp, and especially under pressure, a particularly uniform distribution of the compound can be achieved very efficiently, preventing bubble formation and defects, particularly at the edge of the cell base. A uniform and flat electrically insulating thermally conductive layer with a high surface finish is formed, to which, for example, a cooling device can be easily connected with good contact. Applying pressure or vacuum allows for the particularly effective removal of air inclusions introduced during the application of the thermally conductive compound, creating a thermally conductive layer with the specified thickness and high density that compensates for unevenness on the battery module.

[0009] The thermally conductive compound is advantageously held in place by the stamp during curing. This prevents the thermally conductive compound from flowing or slipping after application, especially when using a thermally conductive potting compound. This eliminates the need for steps to dimensionally adjust the applied thermally conductive compound and allows for the production of high-quality battery modules with high dimensional accuracy, while compensating for manufacturing and component tolerances.

[0010] If the stamp can be heated, the distribution of the thermal conductivity can be simplified, and the thermal conductivity can also be cured without the aid of additional devices, even directly during or after application, which further simplifies the manufacturing process and reduces the cycle time of the process.

[0011] A further advantage is that the stamp is shaped in such a way that it covers the cell base and also has an excess on at least one side. This allows the thermal conductivity to be distributed precisely on the cell base. The excess material creates a buffer zone, for example at the edges or outside the flat surface of the thermal conductivity, providing a capacity to absorb excess material and thus making it easier to compensate for geometric component tolerances.

[0012] It is further advantageous that the thermally conductive compound is applied with a specific geometry, in particular meandering or labyrinthine. Applying the thermally conductive compound in these shapes, especially in combination with the use of a stamp, offers the advantage of effectively preventing bubble formation or overflow of material with air entrapment.

[0013] Applying the thermally conductive compound to the base of the cell stack under vacuum is advantageous, especially for complex geometries, to prevent blistering in the compound. Furthermore, the enclosed structure largely eliminates environmental influences such as temperature fluctuations, humidity, and contamination, thus improving the quality of the manufactured battery module. When using a thermally conductive potting compound, which is typically flowable during application, a vacuum potting process creates a particularly uniform and even material layer without inhomogeneities.

[0014] A further advantageous development is characterized by the step of applying a protective layer to the thermal interface material. This allows the battery module to be stored very effectively before final assembly, with the aid of a cooling device, without environmental influences impairing the quality of the thermal interface material and thus the battery module. Transport, storage, and handling of the battery module are simplified. A protective layer can, for example, be a film, such as a coated, adhesive, removable film (non-stick film), which is applied to the thermal interface material after application and distribution, either before or after the thermal interface material has cured.

[0015] Preferably, the stamp is designed to pick up the protective layer and apply it to the thermally conductive compound. This eliminates the need for separate feeding and arrangement of the protective layer. The protective layer can be applied by the stamp during the distribution of the thermally conductive compound, thus protecting it from environmental influences and, in particular, from the ingress of dirt or dust particles at this early stage. Furthermore, this simplifies the removal of the stamp from the thermally conductive compound.

[0016] The method advantageously includes the step of arranging a cooling device on the thermal interface material. The cooling device can be arranged before the thermal interface material has cured or after at least partial curing. Arranging it before curing offers the advantage that the curing process can contribute to the formation of a metallurgical bond between the thermal interface material and the cooling device. Bond defects between the cooling device and the thermal interface material are effectively prevented, thereby optimizing heat dissipation from the battery module to the cooling device. Arranging the cooling device after the thermal interface material has cured is also possible, for example, by clamping the cooling device to the cell stack containing the cured thermal interface material. This also avoids bond defects. Furthermore, the battery module is less sensitive to pressure at the time of clamping.It is less sensitive to mechanical impacts. The thermal compound can no longer slip or run, which simplifies handling the battery module.

[0017] If the thermally conductive compound has been provided with a protective layer, the procedure is advantageously carried out by the following steps: - Removal of the protective layer and - Arranging a cooling device on the thermal conductivity marked. This improves the thermal conductivity of the battery module. As previously explained, the thermal interface material may be uncured or at least partially cured when the cooling device is installed. It is advantageous if the thermal interface material is already cured in this case, as this facilitates the removal of the protective layer.

[0018] An alternative advantageous embodiment of the inventive method provides that the electrically insulating thermally conductive compound is cured and shaped before being applied to the base of the cell stack. By providing, shaping (using a forming process), and curing an electrically insulating thermally conductive compound, a molded part with the desired geometry and structure can be provided, which can then be applied to the base of the cell stack and, if necessary, assembled. In this case, the thermally conductive molded part, once installed, fulfills the same function as a thermally conductive compound that is cured only after application to the base of the cell stack. Likewise, the geometry of the thermally conductive molded part corresponds to that of the thermally conductive compound applied and subsequently cured.

[0019] The invention also describes a battery module comprising several battery cells grouped into a cell stack and a thermally conductive material arranged on a base of the cell stack, characterized in that the thermally conductive material is electrically insulating. This eliminates the need for a separate electrically insulating layer and conventional heat-conducting plates, simplifying the structure of the battery module while maintaining high functionality and reducing both material and manufacturing costs. Furthermore, by using only one material that serves simultaneously as a thermally conductive and electrically insulating material, the number of heat transfers is minimized while maximizing thermal conductivity.By applying the thermally conductive compound, and in particular by using a thermally conductive potting compound that is flowable, spreadable, or pasty during the application process and thus even easier to distribute, manufacturing and component tolerances in the battery module can be better compensated for, and surface defects can be avoided. This improves thermal conductivity and the dimensional accuracy of the battery module. The battery module according to the invention is characterized by high quality, excellent functionality, and a long service life.

[0020] The advantageous developments, effects and benefits set out for the method according to the invention are also applicable to the battery module according to the invention.

[0021] By attaching a cooling device in such a way that the thermal interface material connects the cell stack to the cooling device, very good contact between the thermal interface material and the cooling device is achieved, which improves heat dissipation from the battery module. Additional fastening elements can be provided.

[0022] The thermal conductivity is advantageously elastic and / or compressible, which minimizes the air gap between the cooling device and the thermal conductivity when a cooling device is installed, and compensates for geometric tolerances of the cooling device.

[0023] The battery module according to the invention can be manufactured according to the method disclosed above.

[0024] The invention also describes a motor vehicle comprising at least one battery module as described above. The motor vehicle is not limited in detail and can be battery-powered or designed as a hybrid using a battery module. The motor vehicle is characterized by high quality, high reliability, and a long driving range.

[0025] The advantageous developments, effects and benefits presented for the inventive method and the inventive battery module are also applicable to the inventive motor vehicle.

[0026] The following advantages result from the solutions according to the invention and their further developments: - A method for manufacturing a battery module is provided that is effective, easy to implement and therefore cost-effective. - The process does not require a high level of technical effort and can be carried out at high speeds. Surface defects, blistering and air inclusions in the thermal conductivity compound are avoided. - The thermal conductivity between the cell stack and a cooling device is increased. - The thermal conductivity compound can also be applied evenly with complex geometric shapes. - The thermal conductivity compound can be applied largely without exposure to environmental influences. - Protection of the battery module, which is coated with thermally conductive material, during transport, storage and handling can be provided more easily. - The process allows for 100% non-destructive inspection of all manufactured battery modules. - The battery module has a simple structure and requires a minimal number of functional layers. - Manufacturing tolerances of the battery cells, cell stack and cooling device are compensated for and air gaps between the components are eliminated. - The battery module is highly functional, in particular electrically insulating and thermally conductive, and is characterized by high quality and very good dimensional accuracy. - The vehicle is characterized by high reliability and long driving range.

[0027] Further details, features and advantages of the invention will become apparent from the following description and the figure. It shows: Fig. 1 A sectional view of a battery module according to an advantageous further development.

[0028] The present invention will be explained in detail with reference to an exemplary embodiment. Fig. Figure 1 shows only the parts of the battery module that are of interest here; all other elements have been omitted for the sake of clarity.

[0029] In detail, it shows Fig. 1. A battery module 10 comprising battery cells 4 grouped into a cell stack 1. The number of battery cells 4 is not limited and depends on the desired power output of the battery module 10. The cell stack 1 can be braced in the usual manner, for example by a frame surrounding the battery cells 4, thereby securing the geometric arrangement of the cell stack 1 and ensuring good contact between the battery cells 4.

[0030] A thermally conductive material 2 is provided on the bottom 1a of the cell stack 1 / on the cell bottom. The thermally conductive material 2 completely covers the cell bottom, thereby ensuring good heat conduction away from the cell stack 1, which contributes to a long service life of the battery module 10.

[0031] The thermal conductivity compound 2 also compensates for component tolerances and dimensional tolerances of the cell stack 1 and unevenness, prevents air inclusions and thus ensures good thermal conductivity.

[0032] The thermal conductivity 2 is also electrically insulating and thus also designed to prevent unwanted electrical contact between the battery cells 4.

[0033] The thermal conductivity 2 is not limited in its specific composition and is preferably designed as a thermally conductive potting compound. This means that the thermal conductivity 2 is flowable, spreadable, or pasty, at least during its application, e.g., on the cell floor, so that it can be distributed particularly well, preferably by means of a stamp, on the exposed surface of the cell floor.

[0034] The thermal conductivity compound 2 can be hardened by a curing step.

[0035] Alternatively, a heat-conducting molded part can be produced from the thermal conductivity compound 2 by a shaping process and subsequent hardening, which can then be applied to the base 1a of the cell stack 1.

[0036] Due to the high functionality of the thermally conductive material 2, in particular its good thermal conductivity and its electrically insulating properties, the application of additional insulating layers or layers that improve thermal conductivity can be dispensed with. The battery module 10 according to the invention has a simple but highly functional structure.

[0037] The battery module 10 further comprises a cooling device 3, which is designed to absorb and dissipate the heat dissipated from the cell stack 1 via the thermal interface material 2. The cooling device 3 is arranged on a lower surface 2a of the thermal interface material 2. Due to the high surface quality of the lower surface 2a of the thermal interface material 2, which is free of irregularities, optimal contact between the cooling device 3 and the cooling device is ensured without the formation of air gaps or inclusions, thus making heat dissipation from the cell stack 1 particularly effective. This effectively extends the service life of the battery module 10.

[0038] The preceding description of the present invention serves only for illustrative purposes and not to limit the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents. Reference symbol list: 1 cell stack 1a floor 2 Thermal conductivity 2a lower surface 3 Cooling device 4 battery cells 10 battery modules

Claims

Method for manufacturing a battery module (10) comprising several battery cells (4) grouped together to form a cell stack (1), characterized by the step: - applying an electrically insulating thermal conductivity material (2) to a base (1a) of the cell stack (1). Method according to claim 1, characterized by the further step of curing the thermal conductivity (2), in particular by heating the thermal conductivity (2). Method according to claim 1 or 2, characterized in that the thermal conductivity (2) is distributed by means of a stamp after being applied to the base (1a) of the cell stack (1) and is shaped, in particular under pressure. Method according to claim 3, characterized in that the thermal conductivity (2) is held by the stamp during curing. Method according to claim 3 or 4, characterized in that the stamp is heatable. Method according to one of claims 3 to 5, characterized in that the punch is shaped such that the bottom (1a) of the cell stack (1) is covered and the punch additionally has excess material on at least one side. Method according to one of the preceding claims, characterized in that the thermal conductivity material (2) is applied with a specific geometry, in particular meandering or labyrinthine. Method according to one of the preceding claims, characterized in that the application of the thermal conductivity material (2) to the base (1a) of the cell stack (1) is carried out under vacuum. Method according to one of the preceding claims, characterized by the step of applying a protective layer to the thermally conductive material (2). Method according to claim 9, characterized in that the stamp is configured to receive the protective layer and apply it to the thermally conductive material (2). Method according to any one of claims 1 to 8, characterized by the step of arranging a cooling device (3) on the thermally conductive material (2). Method according to claim 9 or 10, characterized by the steps: - removing the protective layer and - arranging a cooling device (3) on the thermally conductive material (2). Method according to claim 1, characterized in that the electrically insulating thermal conductivity material (2) is shaped and cured before being applied to the base (1a) of the cell stack (1). Battery module (10) comprising several battery cells (4) grouped together to form a cell stack (1) and a thermal conductivity material (2) arranged on a base (1a) of the cell stack (1), characterized in that the thermal conductivity material (2) is electrically insulating. Battery module (10) according to claim 14, characterized by a cooling device (3), wherein the thermal conductivity (2) connects the cell stack (1) to the cooling device (3). Battery module (10) according to claim 14 or 15, characterized in that the thermal conductivity material (2) is elastic and / or compressible. Battery module (10) according to one of claims 14 to 16, manufactured according to a method according to one of claims 1 to 13. Motor vehicle comprising at least one battery module (10) according to any one of claims 14 to 17.

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