Battery module for a motor vehicle and motor vehicle with such a battery module

Abstract

Battery module (10) for a motor vehicle, wherein the battery module (10) comprises several battery cells (12), and wherein a separating element (20) is arranged between at least two of the several battery cells (12), wherein the separating element (20) comprises at least a first electrically and / or thermally insulating layer (22) and at least a second layer (24) arranged on the first layer (22), which is at least partially elastically compressible, characterized in that the separating element (20) is provided as a glass fiber fabric coated with an elastomer coating, wherein the first layer (22) represents the glass fiber fabric and the second layer (24) represents the elastomer coating.

Description

[0001] The invention relates to a battery module for a motor vehicle, wherein the battery module has several battery cells, and wherein a separating element is arranged between at least two of the several battery cells, according to the preamble of claim 1. The invention also includes a motor vehicle with such a battery module.

[0002] Separating elements can fulfill various functions in connection with batteries. For example, such a separating element can be provided in the form of a separator for a lead-acid battery, as described in DE 38 10 125 A1. This separator is provided by a glass fiber fleece which is additionally impregnated with a water-soluble adhesive.

[0003] Furthermore, DE 10 2015 210 515 A1 describes an energy storage device comprising an electrode assembly and a housing for receiving the electrode assembly. A separating element is arranged in a gap between the housing and the electrode assembly housed within the housing. This separating element divides the gap in the direction of the winding axis of the electrode assembly by surrounding the assembly in the winding direction of the electrode. An electrolyte solution filling opening in the housing is located closer to one end of the electrode assembly, i.e., closer to the separating element. This is intended to reduce the likelihood of uneven impregnation of the electrolyte solution into the interior of the electrode assembly.

[0004] The invention, however, does not deal with separating elements within a battery cell, but instead with separating elements that can be arranged, for example, between two battery cells. In this context, separating elements are known, for example, which are arranged as cooling plates between battery cells and which can be connected to an active cooling device to cool the battery cells.

[0005] It would nevertheless be desirable to be able to implement further functions, different from cooling the battery cells, through such a separating element between battery cells, which would have a positive effect on the properties of a battery module.

[0006] DE 10 2016 219 283 A1 describes an energy storage device with a plurality of electrical energy storage cells, between which cooling plates are arranged into which cooling or refrigerant can be introduced, wherein each cooling plate has a support frame that surrounds an elastic insert, the elastic insert forming a channel structure that guides the cooling or refrigerant through the elastic insert. An electrically insulating film is arranged between the elastic insert together with the support frame and the energy storage cells adjacent to the cooling plate.

[0007] DE 10 2015 202 149 B3 describes an energy storage device with prismatic storage cells, wherein a first and second layer made of a compressible, flexible and thermally conductive material is arranged between the interfaces of adjacent storage cells, which are under pressure against one of the two interfaces of the adjacent storage cells, wherein a thermally conductive device is arranged in the first layer and the second layer, and wherein a thermal insulation layer is arranged between the first layer and the second layer.

[0008] The object of the present invention is therefore to provide a battery module and a motor vehicle which enable an improvement with regard to at least one of the aspects of safety and lifespan of the battery module.

[0009] This problem is solved by a battery module and a motor vehicle with the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description, and the figures.

[0010] A battery module according to the invention for a motor vehicle comprises several battery cells, with a separating element arranged between at least two of the several battery cells. This separating element is also thus encompassed by the battery module. The separating element comprises at least a first electrically and / or thermally insulating layer and at least a second layer arranged on the first layer, which is at least partially elastically compressible. The separating element is provided as a glass fiber fabric coated with an elastomer coating, wherein the first layer is the glass fiber fabric and the second layer is the elastomer coating.

[0011] The first electrically and / or thermally insulating layer can increase the safety of the battery module. This is because, on the one hand, it advantageously provides electrical isolation between the individual cell casings of the battery cells, and on the other hand, it mitigates the effects of overheating in one battery cell on other battery cells through thermal insulation. Both properties—electrical and thermal insulation—can be easily combined in a single layer, since electrically insulating materials are not metals and non-metallic materials generally also have low thermal conductivity. Therefore, this first layer can simultaneously provide both electrical and thermal insulation between the individual battery cells.Overheating of one battery cell thus advantageously does not directly affect adjacent battery cells. A thermally insulating layer is generally understood to be a layer with a thermal conductivity of less than 1 watt per meter per Kelvin (W / (m·K)), preferably less than 0.1 watts per meter per Kelvin. However, it is particularly advantageous that a second layer, which is at least partially elastically compressible, is arranged on top of this first layer. This allows the service life of the battery cells to be increased in a particularly simple, compact, and cost-effective manner. The invention is based on the understanding that battery cells can grow, i.e., expand, over their service life. Without any means of relieving this expansion, the cells become mechanically overloaded over time, leading to accelerated aging or even cell failure.If, on the other hand, no force is applied to such a growing battery cell, this also leads to accelerated aging of the battery cell. By placing a separating element with an elastically compressible layer between at least two of the battery cells, a relief mechanism is advantageously provided as the battery cells swell, through the elastic compression of this second layer. Furthermore, the elastic properties of this second layer allow a tension or restoring force to be applied to the swelling battery cells.While additional tensioning elements, such as tension bands or similar devices, can be used to brace the battery cells, the invention nevertheless provides a particularly advantageous and, above all, cost-effective way to provide both tensioning and a relief option for the battery cells, thus counteracting the aging effects of the battery cells even without additional tension bands. These properties—namely, electrical insulation, elastic mounting or arrangement of the battery cell, and, in particular, thermal insulation of the battery cells from one another—can now advantageously be provided by the invention using a single separating element arranged between the battery cells in a multilayer structure.This requires correspondingly little installation space, because such a separating element can also be designed to be particularly light and compact, for example with a thickness in the range between 0.8 millimeters and 1.5 millimeters, which is already perfectly sufficient to provide the aforementioned advantageous properties of electrical and / or thermal insulation and elastic compressibility.

[0012] Furthermore, the separating element can be positioned between each pair of adjacent battery cells in the battery module, or it can be positioned only between some adjacent battery cells and not between all adjacent battery cells in the battery module. Between battery cells where such a separating element is not present, another separating layer can be arranged, for example, only the first electrically and / or thermally insulating layer, or any other element, or even no separating element at all. Since the side walls of the respective battery cells are still in direct contact, or at least in contact via such a differently designed separating element, tensile forces can also be transmitted through this contact.In other words, if, for example, a tensile force is applied to the first battery cell of a cell stack, this force can be transmitted through the battery cells, provided their side walls are in direct or indirect contact, all the way to the last cell in the stack, similar to the principle of a Newton's cradle, and thus distributed across the multiple side walls. Conversely, this also applies if, for example, one of the battery cells expands. This expansion can advantageously be cushioned by the described separating element, particularly due to its elastic properties, even if the battery cell in question is not in direct contact with this separating element. Accordingly, it can also be provided that such a separating element is located only between groups of several, for example, two, three, four, or even more, battery cells.

[0013] Furthermore, the battery cells, which are preferably designed as prismatic cells, can be provided in the form of a cell pack or cell stack, which can also be provided in the form of several of the aforementioned cell groups, wherein this cell stack is preferably supported at one end or at both ends, for example against a module housing or similar. Such support can be elastic or inelastic. This type of support prevents the cell stack from deflecting in one or two opposing directions, or at least prevents it from deflecting excessively, which further increases the efficiency of the elastically compressible second layer of the separating element.

[0014] In a further embodiment of the invention, the first layer is at least flame-retardant. Preferably, the first layer is non-combustible. This further increases the safety of the battery module, as it significantly hinders the spread of not only excessive heat in a battery cell, but also a fire in a battery cell or cell group.

[0015] In a further advantageous embodiment of the invention, each battery cell has two opposing first sides, which represent the largest sides of the respective battery cell in terms of their area, wherein the battery cells are arranged relative to each other such that their respective first sides face each other. The separating element is thus arranged between two such first sides, which represent the largest sides of a battery cell in terms of area. This allows a tension force to be exerted particularly efficiently against the expansion of the battery cells by means of the elastic properties of the separating element.Accordingly, it is advantageous if the separating element is further designed such that, in the event of expansion of at least one side of one of the two battery cells between which the separating element is arranged, in the direction of the first side of the other, adjacent battery cell, the separating element is at least partially compressed. This counteracts overloading of the battery cells in a particularly efficient manner, since the separating element compresses and, moreover, exerts a tension force on the battery cells, especially on their largest surfaces. Both of these factors have a positive effect on the service life of a battery cell, as already described at the outset.

[0016] The separating element can, for example, be designed to be compressible by 50 percent in terms of its thickness. In other words, the thickness of the separating element can be halved, for example, when a corresponding force is exerted on it by the battery cells due to their expansion. Generally, the maximum compressibility of the separating element in terms of its thickness can range between 40 and 60 percent. This allows for very efficient cushioning of the battery cells in the event of expansion, and also makes it easy to set a desired maximum deformation path or maximum expansion of a battery cell by appropriately dimensioning the thickness of the separating element or the thickness of at least one secondary layer.

[0017] In a further advantageous embodiment of the invention, the separating element directly contacts the facing first sides of the two battery cells. This allows for a very space-efficient and compact battery cell arrangement overall.

[0018] In a further advantageous embodiment of the invention, the separating element extends over at least a large part of the surface of the respective facing first sides, preferably over the entire surface of the respective facing first sides. However, the separating element does not need to directly contact these first sides, although this is still advantageous for the reasons mentioned above. The separating element is therefore at least as large as half the surface area of ​​each first side, preferably exactly as large as or larger than the surface area of ​​such a first side. This allows the pressure on these first sides of the battery cells to be distributed particularly evenly, and advantageously prevents any local stresses from being introduced into the cell or the cell casing from being damaged or locally deformed by uneven pressure distribution and locally high forces.

[0019] A further advantage is that the first layer is a fiberglass fabric. Such a fiberglass fabric advantageously provides both good electrical and thermal insulating properties. Furthermore, glass is a non-combustible material that only melts at very high temperatures, making the fiberglass fabric a particularly advantageous fire-resistant material for the electrical and thermal insulation of the battery cells. Another major advantage of such a fiberglass fabric is that, due to its high inherent stability, it can serve as a substrate for at least one second layer, which can then be applied as a coating onto the fiberglass fabric.

[0020] According to the invention, the second layer is an elastomer layer. Elastomers are particularly suitable for providing the desired elastically deformable properties of the second layer. This elastomer layer is designed as an elastomer coating on the glass fiber fabric, which thus acts as a carrier layer. Furthermore, there are numerous different elastomers available, so the ideal properties for the respective battery cells or cell types used can be easily achieved by selecting suitable elastomers. The material properties of this second layer can therefore be easily and optimally adapted to the specific requirements. For example, both softer and harder elastomers can be used, depending on the situation and the spring stiffness required by the second layer.Apart from the choice of material for the second layer, the elastically compressible properties of the second layer can be further varied, for example, by the thickness of the second layer and / or its pattern, and so on. This advantageously provides numerous customization options.

[0021] In a further advantageous embodiment of the invention, the at least one second layer has an elastic modulus in the range between 3 and 5 megapascals, for example, 4 megapascals. This elasticity range has proven particularly advantageous with regard to cushioning swelling or growing battery cells. Accordingly, the use of a layer with such an elastic modulus has a particularly positive effect on the service life of the battery cells.

[0022] In a further advantageous embodiment of the invention, the separating element comprises two second layers arranged on opposite sides of the first layer. For example, the separating element can be provided as a fiberglass fabric coated on both sides with an elastomer coating. These two second layers arranged on the central first layer provide the necessary stability for the two second elastic layers and increase the overall thickness of these two layers. The central first layer also allows it to function optimally as a support layer, and such a separating element can be manufactured simply by coating, in particular by coating, this support layer on both sides.

[0023] The invention also includes a motor vehicle with a battery module according to the invention or one of its embodiments. The advantages described with regard to the battery module according to the invention and its embodiments therefore also apply in the same way to the motor vehicle according to the invention.

[0024] The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.

[0025] Furthermore, the battery module preferably forms part of a high-voltage battery. In other words, a high-voltage battery with one or more battery modules according to the invention or its embodiments should also be considered to belong to the invention. Especially with high-voltage batteries, the reduction of aging effects in a cost-effective and space-efficient manner plays a particularly important role, which is why the application of the invention to a high-voltage battery offers significant advantages.

[0026] The invention also includes combinations of the features of the described embodiments.

[0027] The following are exemplary embodiments of the invention described. This is illustrated by: Fig. 1 a schematic cross-sectional view through a battery module, comprising several battery cells and separating elements arranged at least between some of the battery cells, according to an embodiment of the invention; and Fig. 2 A schematic cross-sectional representation through a separating element for a battery module according to an embodiment of the invention.

[0028] The exemplary embodiments described below are preferred embodiments of the invention. In these exemplary embodiments, the described components each represent individual features of the invention, which can be considered independently of one another and each further develops the invention independently. Therefore, the disclosure is intended to include combinations of features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0029] In the figures, identical reference symbols denote functionally equivalent elements.

[0030] Fig. Figure 1 shows a schematic representation of a battery module 10 according to an embodiment of the invention. The battery module 10 comprises several battery cells 12, of which eight are shown here by way of example. Each battery cell 12 has two first sides 12a, which represent the sides with the largest surface area of ​​the respective battery cells 12. The battery cells 12 are arranged relative to each other such that their respective first sides 12a face each other. Furthermore, the battery module 10 comprises a module housing 14 in which the battery cells 12 are arranged. This battery cell arrangement thus forms a cell stack that extends in the x-direction of the Fig. The cell stack extends along the coordinate system shown in Figure 1. In this x-direction, this cell stack is supported on both sides, so that expansion of the cell stack in the x-direction is only possible to a limited extent. Such support is provided here, for example, on one side by the housing wall 14a of the battery housing, and on the other side by a pressure plate 16, which in turn is resiliently attached, for example by a suitable spring element 18, to the Fig. The cell stack is supported by the housing wall 14b of the module housing 14 shown on the left. However, there are numerous other possibilities for supporting this cell stack on both sides, which can be combined in any way. Support on both sides by the respective walls 14a and 14b of the module housing 14 would also be conceivable, as would spring support on both sides, or similar solutions. Such support can also be provided indirectly, for example, by a tension band wrapped around this cell stack, by tie rods, or similar means.

[0031] Over the lifetime of battery cells 12, they typically swell, leading to a bulging of the respective cell casings, in particular a bulging of the described first sides 12a in or against the x-direction shown. If no counterforce were applied to this growth or expansion of the battery cells 12, and no relief mechanisms were provided, this could lead to faster aging of the battery cells. To counteract this, a separating element 20 is advantageously arranged at least between some of the battery cells 12. This separating element 20 has a multilayered structure. Firstly, this separating element comprises at least a first layer 22, which is provided by a glass fiber fabric and is both fire-resistant and electrically insulating.Furthermore, this first layer 22 is preferably also a very good thermal insulator and accordingly has a thermal conductivity that is lower, in particular orders of magnitude lower, than that of, for example, aluminum or iron. Such a first layer 22 can thus advantageously increase the safety of the battery module 10, since this first layer 22 allows the cells to be electrically insulated from one another, in particular their cell casings, and also, in the event of a fire in such a battery cell 12, the fire in this battery cell can be contained particularly well by this first layer 22 and its spread, in particular its rapid spread, can be prevented.

[0032] It is particularly advantageous if this separating element 20 not only comprises this first layer 22, but also if an additional second layer 24 is arranged on this first layer 22, which is elastically deformable, and in particular elastically compressible, at least in the x-direction shown. This second layer 24 allows the separating element 20 to be separated only, or at least in the direction of its thickness D (see figure). Fig. 2) is designed to be elastically compressible. This advantageously allows the separating element 20 to be at least partially compressed in the event of expansion of the battery cells 12 in the x-direction, thereby providing the battery cells 12 with a means of relieving stress while simultaneously counteracting it with a tension force due to the elastic properties of the second layer 24. This allows the service life of the battery cells 12 to be increased in a particularly simple and cost-effective manner. In particular, aging effects can be reduced very efficiently, since the arrangement of very thin separating layers between the battery cells 12 is sufficient for this purpose.In this case, such a described separating element 20 does not have to be arranged between all of the adjacent battery cells 12, but can also be arranged only after every second, third, or even only after every fourth, and so on, battery cell 12 and before the following adjacent battery cell 12. In the present example in . Fig. Figure 1 shows, by way of example, such a separating element 20 arranged between each pair of cell groups comprising only two battery cells 12. Alternatively, it is also possible that such a separating element 20 is arranged between each pair of battery cells 12.

[0033] Furthermore, in the present example, in Fig. 1. Between the remaining battery cells 12, between which no such multilayer separating element 20 is arranged, an element is nevertheless arranged which, for example, can only be designed as the described first layer 22 and provides electrical and thermal insulation between the battery cells 12, and which is ideally also flame-retardant or fire-resistant. Here, too, there are no limits to the possible uses and arrangements. Instead of the described first layer 22, another layer or even no layer at all can be used for this element located between the remaining battery cells 12. Then, accordingly, some first sides 12a of the battery cells 12 can also be in direct contact with each other.

[0034] The elastically compressible second layer 24 is provided as an elastomer coating of the first layer 22. Such elastic elastomers are particularly suitable for compensating for the cell growth of the battery cells 12. Furthermore, material properties, thickness, pattern, and so on can be easily and, in particular, independently selected to adjust the desired mechanical properties for the respective battery cells 12 with regard to their cushioning by this elastically compressible second layer 24.

[0035] Furthermore, such a separating element 20 can also be manufactured in a particularly cost-effective and simple manner, for example by coating a glass fiber fabric, which provides the first layer 22, on one or both sides with such an elastomer coating as the second layer 24. In the example in Fig. Figure 1 shows the separating element 20, in particular as an example, in the form of a two-layer structure, which thus comprises, for example, only a single first layer 22 and a single second layer 24. However, the separating element 20 can also comprise many more layers, for example three layers, as shown in Figure 1. Fig. 2 shown.

[0036] Fig. Figure 2 shows a schematic and cross-sectional view of such a separating element 20 for a battery module 10 in detail, in an enlarged representation. In particular, the separating element 20 is now rotated by 90 degrees relative to the representation of the separating element 20 in Fig.1. In this example, the separating element 20 again has the first layer 22 as a glass fiber fabric, which simultaneously acts as a carrier layer for the elastomer coating, which in this example is applied to both sides of the carrier layer. The total thickness of the two second layers 24 can advantageously be increased without impairing the stability of these layers 24. By coating the first layer 22 on both sides, the elastically compressible properties of the separating element 20 can therefore be optimized overall.

[0037] Furthermore, the separating element has a length L that preferably corresponds to, or coincides with, a length L of a respective battery cell 12, that is, a dimension of the first side 12a of the respective battery cell 12 in the y-direction shown here. A width of the separating element 20, which is not shown here and is perpendicular to the x- and y-directions shown here, also corresponds to a respective dimension of the battery cells 12 in this direction, perpendicular to the respective x- and y-directions. In other words, the separating element 20 preferably rests on the entire surface of the respective first sides 12a. This allows forces to be distributed particularly evenly on the first sides of the battery cells 12 and prevents local stresses.

[0038] Overall, the invention makes it possible to provide a battery module, for example with an elastomer-coated fiberglass fabric as a separating element between battery cells in the battery module, whereby such a separating element advantageously increases the safety of the battery module on the one hand and also the service life of the respective battery cells on the other.

Claims

[1] Battery module (10) for a motor vehicle, wherein the battery module (10) comprises several battery cells (12), and wherein a separating element (20) is arranged between at least two of the several battery cells (12), wherein the separating element (20) comprises at least a first electrically and / or thermally insulating layer (22) and at least a second layer (24) arranged on the first layer (22), which is at least partially elastically compressible, characterized by , that the separating element (20) is provided as a glass fiber fabric coated with an elastomer coating, wherein the first layer (22) represents the glass fiber fabric and the second layer (24) represents the elastomer coating. [2] Battery module (10) according to claim 1, characterized by , that the first layer (22) is flame-retardant, in particular non-combustible. [3] Battery module (10) according to any one of the preceding claims, characterized by, that each of the battery cells (12) has two opposite first sides (12a) which, with respect to their area, represent the largest sides (12a) of the respective battery cell (12), wherein the battery cells (12) are arranged to each other such that their respective first sides (12a) face each other, wherein the separating element (20) is designed such that, in the event of an expansion of at least one first side (12a) of one of the two battery cells (12), between which the separating element (20) is arranged, in the direction of the first side (12a) of the other, adjacently arranged of the two battery cells (12), the separating element (20) is compressed at least partially. [4] Battery module (10) according to claim 3, characterized by, that the separating element (20) directly contacts the mutually facing first sides (12a) of the two battery cells (12), wherein the separating element (20) extends over at least a large part of the area of ​​the respective mutually facing first sides (12a), preferably over the entire area of ​​the respective mutually facing first sides (12a). [5] Battery module (10) according to any one of the preceding claims, characterized by , that at least one second layer (24) has an elastic modulus in the range between 3 MPa and 5 MPa. [6] Battery module (10) according to any of the preceding claims, characterized by , that the separating element (20) has two second layers (24) arranged on opposite sides of the first layer (22). [7] Battery module (10) according to any of the preceding claims, characterized by, that the separating element (20) is provided as a fiberglass fabric coated on both sides with an elastomer coating. [8] Motor vehicle with a battery module (10) according to one of the preceding claims.

Images