High-voltage battery

Abstract

The invention relates to a high-voltage battery (1) acting as a traction battery for a motor vehicle, the high-voltage battery comprising a plurality of individual battery cells (2), the battery terminals (8, 10) of which are arranged on a first side of a cell housing (4) and are connected by cell connectors (16), wherein each of the individual battery cells (2) has an overpressure relief element (12) which opens the cell housing (4) when a predefined pressure is exceeded therein, wherein the overpressure relief element (12) is arranged together with the battery terminals (8, 10) of the individual battery cell (2) on a first side of the cell housing (4), wherein the battery terminals (8, 10), which are connected by the cell connectors (16), and the overpressure relief element (12) are covered with an electrically insulating potting compound (20) that is chemically, mechanically, and thermally resistant. The high-voltage battery according to the invention is characterised in that the potting compound (20) comprises a phase change material (18).

Description

[0001] High-voltage battery

[0002] The invention relates to a high-voltage battery as a traction battery for a motor vehicle, with a plurality of individual battery cells according to the type defined in more detail in the preamble of claim 1.

[0003] So-called high-voltage batteries according to ECE R100 are known from the state of the art and are used, for example, in motor vehicles as traction batteries. They typically consist of one or more modules, each of which contains a plurality of individual battery cells, which can be implemented in various mechanical designs, for example, as round cells with a cup-shaped housing, as prismatic cells with a solid housing, or the like.

[0004] Often, the battery terminals are located on one side of the housing of each individual battery cell, for example, to enable electrical contact of the fully assembled battery from above via cell connectors. Many currently common battery types, such as lithium-ion batteries, also feature an overpressure relief element that opens the cell housing in the event of thermal runaway of the individual battery cell, allowing the excess pressure to be released and hot gases to be released into the environment. This is typically referred to as cell venting.

[0005] To prevent flames or sparks from escaping from the battery housing along with the hot gases, DE 102021 000 029 A1 describes a multi-layer protective element for thermal insulation that filters the escaping gases through a fiber layer. This allows flames and sparks to be contained. The applicant's two non-German prior-published applications 102023 128 877.6 and 102023 128 879.2 also disclose the use of electrically insulating potting compounds to provide a protective cover for the cell connectors and the overpressure relief element.

[0006] In addition, the individual battery cells require temperature control, typically cooling during operation, and possibly preheating during commissioning at very low ambient temperatures. Heat exchangers are provided for this purpose, which are generally arranged between the individual battery cells to ensure temperature control without locally competing with the battery terminals or the overpressure relief element.

[0007] From DE 102021 005260 A1 it is further known to hold the cell connectors in an electrically insulating carrier, wherein this carrier, which holds and carries the cell connectors, has an embedded phase change material.

[0008] Based on this initial situation, the object of the present invention is to provide an improved high-voltage battery which enables simple and efficient cooling.

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

[0010] In the high-voltage battery according to the invention, the overpressure relief element is provided together with the battery terminals of the individual battery cell on a first side of the cell housing, wherein the battery terminals connected to the cell connectors and the overpressure relief element are covered with an electrically insulating, temperature-resistant potting compound. This can preferably be designed such that, if the overpressure relief element is activated, it ruptures in the area of ​​the affected individual battery cell, and only in this area. The high-voltage battery thus achieves a very compact design, in which both the cell venting via the overpressure relief element and the battery terminals, which are contacted by the cell connectors, are arranged on the same side.According to a very advantageous refinement, another side, especially the opposite side, can then be connected to a heat exchanger, for example, a cooled base plate. This eliminates the need for space for cooling between the individual battery cells.

[0011] For the high-voltage battery according to the invention, it is crucial that the potting compound contains a phase change material. The phase change material in the area of ​​the potting compound can be added very easily and efficiently as a filler to the potting compound. With minimal effort and without requiring additional installation space, this phase change material can now cool the cell connectors as well as the battery terminal connected to them and the top of the cell housing when required. Such a need arises predominantly when the individual battery cells are being charged at high power or when very high power is required, for example during acceleration while driving uphill. In such operating phases in which a large amount of waste heat is generated, the phase change material can then absorb heat by changing from a solid to a liquid phase.During subsequent normal operation, this heat can then be transferred back to the individual battery cell and dissipated by conventional cooling, so that the cooling capacity of the phase change material is restored for the next high-performance phase.

[0012] The phase change material can preferably be a microencapsulated phase change material. Such a microencapsulated phase change material offers the decisive advantage that the individual particles of the phase change material are comparatively small, so that they can be very easily introduced into the potting compound as fillers, where they are evenly distributed, for example through a mixing process, and thus are homogeneously distributed throughout the volume of the potting compound after curing, even with small layer thicknesses. Such microencapsulated phase change materials typically have a particle diameter on the order of a few pm and are therefore ideally suited. According to a very advantageous development, the phase change material can have polymer-coated cores with the phase change properties.This creates a simple and efficient microencapsulated phase-change material, which, thanks to the polymer coating of the cores, remains in the potting compound as a closed system without chemically interacting with the material of the potting compound. The phase-change material can be designed in such a way that it experiences virtually no change in volume during the phase change, so that the mechanical properties of the potting compound also remain virtually unchanged despite the phase change.

[0013] The potting compound can be polyurethane-based or, preferably, silicone-based. A silicone-based potting compound offers several key advantages for its application. It remains largely elastic at typical temperatures, allowing minimal volume changes in the phase-change material to be easily and efficiently absorbed. Furthermore, silicone is largely chemically resistant, meaning that even if one of the microcapsules were to burst, there is no risk of the phase-change material chemically affecting the potting compound. Furthermore, silicone offers excellent thermal protection properties for neighboring cells in the case of a thermally permeable single battery cell, as its surface tends to vitrify or ceramize, thus providing good thermal protection.Furthermore, silicone is so flexible that if an overpressure relief element in one of the individual battery cells is triggered, it simply ruptures, allowing the gases in the area of ​​the affected individual battery cell to escape as desired. However, this is comprehensively described in the two unpublished documents by the applicant mentioned above, so it need not be discussed further here.

[0014] A further very advantageous embodiment of the high-voltage battery according to the invention can further provide for a heat exchanger which is in heat-conducting contact with the cell housings of the individual battery cells on a second side opposite the first side. The individual battery cells can therefore, for example, in a design provided as round cells according to a very advantageous further development, be placed on such a heat exchanger, which is then designed as a cooled base plate. This cooled base plate enables the individual battery cells to be effectively cooled during normal operation by dissipating the waste heat in the lower area, which can be placed over the entire surface of the heat exchanger, since the functionalities of the overpressure relief element and the cell connector are arranged on the opposite side. In the case of high power storage orWhen the heat is removed from the individual battery cell, additional cooling can now be achieved on the opposite side via the phase-change material. During normal operation, the thermal energy absorbed by the phase-change material can then be released again through the individual battery cell itself to the heat exchanger on the opposite side, restoring the cooling capacity of the phase-change material in the encapsulation compound for the next high-performance phase.

[0015] The individual battery cells can be designed as round cells using lithium-ion technology.

[0016] Further advantageous embodiments of the high-voltage battery according to the invention also emerge from the exemplary embodiment, which is described in more detail below with reference to the figures.

[0017] Showing:

[0018] Fig. 1 is a three-dimensional representation of a section of a high-voltage battery to illustrate the cell connectors;

[0019] Fig. 2 is a three-dimensional view of a section of a possible embodiment of a high-voltage battery according to the invention;

[0020] Fig. 3 is an enlarged three-dimensional view of one of the recesses in a cover of the structure according to Fig. 2;

[0021] Fig. 4 is a sectional view along line IV-IV in Fig. 3;

[0022] Fig. 5 is a representation analogous to that in Fig. 2 with the potting compound introduced;

[0023] Fig. 6 shows the cooling system used for a single battery cell

[0024] mechanisms; and

[0025] Fig. 7 is a schematic, greatly enlarged view of the usable phase change material. The illustration in Figure 1 shows a section of a high-voltage battery, designated as a whole by 1. This comprises a plurality of individual battery cells 2, which are intended to be designed here as round cells using lithium-ion technology, without limiting the high-voltage battery 1 according to the invention to this. The individual individual battery cells 2 comprise a cell housing 4. The individual battery cell 2 or its cell housing 4 has a first pole, designated 8, which is electrically insulated from the rest of the cell housing 4 by an electrical insulation 9, which can be seen in Figures 3 and 4. This remainder of the cell housing 4 forms the second pole, designated 10 here.The illustration in Figure 1 also shows a predetermined breaking point designated 11, which largely or completely surrounds a circular section of the cell casing, which here carries one of the battery terminals 8. Due to the special properties of the material of the cell casing 4, such as low elongation at break, low tensile strength, and low tear strength, the predetermined breaking point 11 causes the part located centrally within the circumferential predetermined breaking point 11, which is additionally provided with the reference numeral 12 here, to serve as an overpressure relief element.If the pressure inside the cell casing 4 rises above a desired pressure because a thermal event has occurred inside the cell casing 4 of the single battery cell 2, the predetermined breaking point 11 ruptures, and the central part of the upper part of the cell casing 4, acting as an overpressure relief element 12, is blown off or torn open and folds upward like a lid. This separates the battery terminal 8 from its electrode inside the cell casing 4, and also allows the gases causing the overpressure to escape.

[0026] The part of the cell housing 4 surrounding the battery terminal 8 forms the other battery terminal 10, typically the negative terminal. Cell connectors 16 are provided for electrically contacting the individual battery cells 2. These each comprise two contacting regions 13, 14 connected via a connecting web 17. The first contacting region 13 is formed here as the end of the connecting web 17, the other is essentially C-shaped and partially encompasses the overpressure relief element 12 of the adjacent individual battery cell 2. It contacts the other battery terminal 10. It can therefore, for example, be welded to the cell housing 4. The cell connector 17 typically disappears under a cover 6, as can be seen in the following Figure 2. This shows a section of a possible embodiment of the high-voltage battery 1 according to the invention.Three round cells can be seen as individual battery cells 2, which are assembled as tightly as possible using spacers 3. The spacers 3 merely fill the unavoidable empty spaces. The cup-shaped cell housings 4 of the individual battery cells 2 stand with their bottoms on a very schematically indicated heat exchanger 5, which is intended to be designed as a cooling plate or cooled base plate. On the opposite side, in this case the top side of the cup-shaped cell housings 4, the cover designated 6 is arranged on the individual battery cells 2. This cover has at least one of the recesses designated 7 here for each of the individual battery cells 2.

[0027] Figure 3 shows an enlarged view of one of the recesses 7. The recess 7 is designed such that it has a basic shape analogous to the shape of the overpressure relief element 12—in this case, round. It also includes a further section, which lies above the ring of the cell housing 4 surrounding the overpressure relief element 12, outside the predetermined breaking point 11. The components described in Figure 1, such as the cell connectors 16 and their contact areas 13, 14, the battery terminals 8, 10, and the overpressure relief element 12, can be partially seen through the recess.

[0028] This is shown again in section in Figure 4. The predetermined breaking point 11 can be seen in the cell housing 4, the first battery terminal 8 is located centrally in the middle, and the rest of the cell housing 4 forms the other battery terminal 10. The recess 7 is surrounded by a circumferential collar 15 which projects upwards. The side of the cover 6 facing the cell housings 4 of the individual battery cells 2 rests on the edge of the cup-shaped cell housings 4 or the cell connectors 16 in such a way that a sealing effect is achieved here. The recess 7 can therefore be easily and efficiently filled with a potting compound 20 in order to protect the overpressure relief element 12 and the cell connectors 16. The collar 15 ensures that a certain variance in the applied quantities of the potting compound 20 is possible without the surface of the cover 6 being wetted by the potting compound 20.In the described high-voltage battery 1, the functionalities of the electrical contact via the cell connectors 16 and the functionality of the overpressure relief element 12 are all arranged on one upper side. This enables particularly good cooling of the high-voltage battery 1 via the aforementioned heat exchanger 5, since the base parts of the cup-shaped cell housings 4 can form a large-area heat-conducting contact.

[0029] The potting compound 20 is, in particular, an electrically insulating, chemically, mechanically and, above all, thermally stable potting compound 20. The potting compound 20 can, for example, be a silicone-based potting compound 20, although a potting compound 20 produced on the basis of a polyurethane would also be conceivable.

[0030] A phase change material, which is first visible in the illustration in Figure 4 and designated 18 on the basis of some examples, is embedded in the potting compound 20. This phase change material 18 can be added as a filler to the potting compound 20 and can be homogeneously distributed therein by appropriate mixing. After the potting compound 20 has hardened, the individual particles of the phase change material 18 then remain evenly distributed in the potting compound 20. Particularly preferably, the phase change material 18 can be a microencapsulated phase change material which has a particle diameter in the range of a few pm. The illustration in Figure 7 shows such a particle of the phase change material 18. It consists of a core, designated 19, which has the phase change properties.This core 19 is encased in a polymer shell 21 to encapsulate the phase change material 19 so that chemical interaction with the potting compound 20 is excluded both during potting and during subsequent operation within the cured potting compound 20.

[0031] In the illustration in Figure 5, the illustration in Figure 2 is taken up again, whereby the individual recesses 7 are filled with the casting compound 20 analogously to the illustration in Figure 4.

[0032] The schematic sectional view in Figure 6 shows one of the individual battery cells 2 with its cell housing 4, the battery terminal 8, and the corresponding contact areas 13, 14 of the cell connectors 16. The potting compound 20 with the phase-change material 18 is applied in the upper area. The heat exchanger 5 in the form of the cooled base plate is shown below, with several cooling channels 22 schematically indicated within the plate.

[0033] During normal operation, the cooling of the heat exchanger 15 is sufficient. However, during charging at high power, for example during rapid charging, or when very high power is drawn, the contact areas 13, 14 of the cell connectors and thus ultimately also the poles 8, 10 of the individual battery cell 2 heat up considerably. The individual battery cell 2 therefore has a high amount of waste heat in its upper area (shown in Figure 6), which cannot be dissipated as dynamically as would be sensible by the heat exchangers 5 arranged below. Especially during this phase, the phase change material 18 can absorb heat in order to cool the upper area of ​​the individual battery cell 2. When a regular operating phase then occurs again, the heat in the phase change material 18 can be conducted downwards through the individual battery cell 2 and through its cell housing 4 and dissipated via the heat exchanger s.The phase change material 18 then changes back into the other phase, for example a solid phase, and is thus again available for cooling in the high-performance case mentioned above.

[0034] A large amount of heat is then absorbed by a phase change from the solid state mentioned above to the liquid state.

Claims

Patent claims 1. A high-voltage battery (1) as a traction battery for a motor vehicle, comprising a plurality of individual battery cells (2), the battery poles (8, 10) of which are arranged on a first side of a cell housing (4) and connected by cell connectors (16), each of the individual battery cells (2) having an overpressure relief element (12) which opens the cell housing (4) when a predetermined pressure is reached, the overpressure relief element (12) being arranged together with the battery poles (8, 10) of the individual battery cell (2) on a first side of the cell housing (4), the battery poles (8, 10) connected to the cell connectors (16) and the overpressure relief element (12) being covered by an electrically insulating, chemically, mechanically and temperature-resistant potting compound (20), characterized in that the potting compound (20) comprises a phase change material (18).

2. High-voltage battery (1) according to claim 1, characterized in that the phase change material (18) is designed as a microencapsulated phase change material (18).

3. High-voltage battery (1) according to claim 1 or 2, characterized in that the phase change material (18) has polymer-coated cores (21) with phase change properties.

4. High-voltage battery (1) according to claim 1, 2 or 3, characterized in that the phase change material (18) is designed in such a way that almost no volume change occurs during the phase change.

5. High-voltage battery (1) according to one of claims 1 to 4, characterized in that the phase change material (18) has a particle size of a few pm.

6. High-voltage battery (1) according to one of claims 1 to 5, characterized in that the potting compound (20) is formed on the basis of polyurethane or on the basis of silicone.

7. High-voltage battery (1) according to one of claims 1 to 6, characterized by a heat exchanger (5) which is in heat-conducting contact with the cell housings (4) of the individual battery cells (2) on a second side opposite the first side.

8. High-voltage battery (1) according to one of claims 1 to 7, characterized in that the individual battery cells (2) are designed as round cells.

9. High-voltage battery (1) according to one of claims 1 to 8, characterized in that the individual battery cells (2) are designed using lithium-ion technology with a liquid electrolyte.

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