Insert element for a battery module, and battery module

Abstract

The present invention relates to an insert element for insertion between two adjacent battery cells of a battery module, and to a battery module of this type. In order to improve insert elements of this type, in particular with regard to the flexibility of their use and their configuration, an insert element is proposed comprising two rigid cover plates and an intermediate layer which is arranged between the two cover plates, can be compressed elastically, and is constructed from a multiplicity of individual compression elements which are arranged distributed over the entire intermediate layer. The compression elements are each of at least partially hose-shaped or tubular configuration and have one or more predetermined bending points in a region between the cover plates which move, in the case of compression of the intermediate layer, by way of reduction of the spacing between the cover plates in a direction transversely with respect to a connecting line between the cover plates.

Description

Insert element for a battery module and battery module

[0001] The present invention relates to an insert element for insertion between two adjacent battery cells of a battery module and a corresponding battery module.

[0002] Solid-state battery cells change their volume / breathing capacity depending on the charge level. Therefore, solid-state battery cells are housed in so-called pouch cells (housings with a flexible structure). To prevent cracks in the battery's solid electrolyte due to volume changes, solid-state batteries must be kept under constant load. Non-solid-state battery cells can also expand due to temperature fluctuations or damage within the cell. For this reason, swelling pads in the form of deformable cushions are placed between the battery cells in a battery stack to compensate for volume changes and create a defined load on the battery cells.

[0003] Such a swelling cushion is known, for example, from US 2022 / 0037714 A1. It describes a battery module comprising a cell stack with a plurality of battery cells and at least one pad arranged between adjacent battery cells. The pad comprises a pair of expanding absorption pads that are compressed accordingly when the battery cell expands in volume. A heat protection pad is arranged between the pair of expanding absorption pads, which blocks heat transfer between the adjacent battery cells and is configured to expand at or above a preset reference temperature.

[0004] Against this background, the present invention is based on the object of improving the known solutions of swelling cushions or comparable means for insertion between adjacent battery cells of a battery module, in particular with regard to the flexibility of their use and their design, in order to enable, for example, an adjustment of the desired load profile during the expansion of the adjacent battery cells and thus to better protect the battery cell from damage.

[0005] According to one aspect of the present invention, an insert element is provided for insertion between two adjacent battery cells of a battery module, comprising: two rigid cover plates and an intermediate layer arranged between the two cover plates, which intermediate layer is elastically compressible and is constructed from a plurality of individual compression elements distributed over the entire intermediate layer, wherein the compression elements are each at least partially designed in the shape of a hose or tube and have one or more predetermined bending points in a region between the cover plates, which bending points move in a direction transverse to a connecting line between the cover plates when the intermediate layer is compressed by reducing the distance between the cover plates.

[0006] According to a further aspect of the present invention, a battery module is provided, comprising a cell stack with a plurality of battery cells; at least one An insert element according to any preceding claim, arranged between adjacent battery cells; and a module housing in which the cell stack is arranged.

[0007] Known swelling cushions are usually made of foam-like materials, with their behavior primarily depending on or being limited by the properties of the foam structure and the base material. There is usually no way to improve or change the properties of swelling cushions through design adaptations. The insert element according to the invention, which could also be referred to as an insert plate, swelling plate or swelling cushion, has a sandwich made of two cover plates (e.g. made of metal or plastic) for constant load distribution and compression elements (e.g. as elastomer structures) in an intermediate layer for load distribution. The compression elements have predetermined buckling points at which, when the respective insert element is loaded, the compression elements begin to buckle and thus change their shape.The predetermined bending points thus change their position under load and essentially move in a direction perpendicular to the connection between the cover plates. The position, number, location, and design of the predetermined bending points offer a wide range of options for adapting the behavior of the insert element to the requirements of the application or customer.

[0008] In particular, the insert elements with the sandwich solution according to the invention gain additional degrees of freedom in design and adaptation of properties depending on application requirements. For example, the structure, number, arrangement, and material of the compression elements can be varied and adapted to achieve the desired behavior. Furthermore, additional properties can be added through coating, e.g., of the cover plates, or other processes to improve, for example, thermal conductivity, flammability risk, or EMI shielding.

[0009] In a preferred embodiment, it is provided that the compression elements each have an even number of predetermined bending points, two of which are located opposite each other in a direction transverse to the connecting line between the cover plates. Such a symmetrical arrangement of the predetermined buckling points allows the behavior of the insert element under load and thus its load progression to be better predicted.

[0010] The predetermined bending points can be designed and arranged differently depending on the application of the insert element. In one embodiment, a predetermined bending point is formed by a notch on a surface and / or by local material thinning and / or by forming an angle of less than 180° between the adjacent regions of the respective compression element on either side of the predetermined bending point. Such predetermined bending points are easy to manufacture and effectively achieve the desired bending of the compression elements.

[0011] The cover plates are preferably arranged parallel to each other, and the predetermined buckling points are preferably arranged in a plane parallel to the cover plates, in particular, they are located in a plane centrally located between the cover plates. However, the predetermined buckling points can also be arranged in a different plane or in multiple planes, for example, if each buckling element has more than two predetermined buckling points. The preferably symmetrical arrangement makes it easier to predict the load distribution during operation.

[0012] The compression elements can be arranged separately or connected to one another. Both designs have advantages. Separate compression elements enable simple production (e.g. as a continuous extrusion) and do not interact (or only slightly) with the neighboring element, or enable a deliberately delayed interaction / support. This represents an additional degree of freedom in the design and enables simpler interpretation of the course of the force-displacement curve, which represents the force on the compression element versus the reduction in the thickness of the compression element. Connected compression elements enable easier assembly, as the elements can be manufactured and assembled in one piece. Furthermore, individual elements do not have to be used up separately (e.g. glued on) and aligned. Interaction with the secondary elements can also be used specifically to adjust the course of the force-displacement curve.

[0013] In principle, different compression elements can be used. However, the compression elements are preferably identically designed and / or aligned. This enables, in particular, simple and cost-effective production of the insert element.

[0014] In one embodiment, the compression elements have several continuous bores in the longitudinal direction, so that one compression element essentially comprises several sub-elements. This offers more options for adjusting the desired load distribution through the design and arrangement of the compression elements.

[0015] In such a configuration, the compression elements can, for example, each comprise a central, hose- or tubular element and two or more side elements adjoining it at the sides. The side elements can be connected to the central element or can come into contact with the central element and / or an adjacent compression element upon compression of the intermediate layer. This can, for example, limit the expansion of a compression element when the distance between the cover plates is reduced, and it can also provide support for adjacent compression elements. The load distribution can thus transition into a saturated region above a certain load, e.g. as a type of stop, or if a change in the force-displacement curve is desired or required above a certain compression.

[0016] Furthermore, the side elements can be designed as rod-shaped, hose-shaped, or tubular connecting elements between the cover plates, and the central element can be hose-shaped or tubular. Such a design offers advantages in manufacturing, for example, because these structures can be manufactured using a continuous process (e.g., with an extruder) and the parts do not have to be manufactured in a mold with individual cavities. Both processes are possible, although the extrusion process offers cost advantages.

[0017] In a further embodiment, it is provided that the predetermined bending points are each located on the surface of the connecting elements directed towards the central element and / or on the outer surface of the central element facing the connecting elements. In an alternative embodiment, the predetermined buckling points are each arranged on the surface of the connecting elements facing away from the central element and / or on the inner surface of the central element facing away from the connecting elements. In a further embodiment, predetermined buckling points can also be provided at both points. With these embodiments, it is possible to set whether the compression element bends inwards or outwards, and thus becomes wider or narrower in the direction parallel to the cover plates. Depending on the distance between the individual elements, the buckling of the structures can only be limited by inwards buckling, since the next element may be too far away. The stiffness can also vary inwards or outwards depending on the shape of the buckling structure.

[0018] In general, the predetermined bending points can be arranged and designed to move away from the center of the respective compression element or towards the center of the respective compression element upon compression of the intermediate layer by reducing the distance between the cover plates.

[0019] In principle, the compression elements can be shaped differently. One embodiment provides for the compression elements to have a round, oval, or polygonal cross-section, particularly rectangular or honeycomb. Each structure generally has a different force-displacement characteristic and can therefore be more or less suitable for the respective application.

[0020] In one design, the compression elements are flattened toward the cover plates and can rest flush against the cover plates. This prevents the compression elements from moving relative to the cover plates and slipping from their initial position as the load increases.

[0021] The compression elements are preferably made of plastic and / or rubber to ensure a certain elasticity, and the cover plates are preferably made of plastic. Fabric and / or metal to ensure a certain level of strength. Other materials that ensure the desired function can also be used.

[0022] The cover plates are preferably rectangular in shape, and the compression elements are preferably longitudinally shaped and arranged transversely to the longitudinal direction or in the longitudinal direction of the cover plates. This facilitates manufacture and assembly.

[0023] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0024] Embodiments of the invention are illustrated in the following drawings and explained in more detail in the following description. They show: Fig. 1 shows a perspective view of a first embodiment of an insert element according to the invention. Fig. 2 shows a plan view of an embodiment of a battery module according to the invention. Fig. 3 shows a diagram with the course of the surface pressure over the thickness of the insert element for different foldings of intermediate layers. Fig. 4 shows a first embodiment of a compression element in cross section. Fig. 5 shows a second embodiment of a compression element in cross section. Fig. 6 shows a third embodiment of a compression element in cross section. Fig. 7 shows a fourth embodiment of a compression element in cross section. Fig. 8 shows the compression element shown in Fig. 6 in a slightly compressed state and the course of the force on the compression element over the thickness. Fig. 9 shows the compression element shown in Fig. 6 in a highly compressed state and the force distribution on the compression element over the thickness.

[0025] Fig. 1 shows a perspective view of a first embodiment of an insert element 1 according to the invention for insertion between two adjacent battery cells of a battery module. The insert element 1 is designed as a sandwich of two rigid cover plates 2, 3 and an intermediate layer 4 arranged between the two cover plates 2, 3. The cover plates 2, 3 are preferably designed to be relatively rigid and stable, for example from a rigid material such as plastic or metal. The intermediate layer 4 is elastically compressible and constructed from a plurality of individual compression elements 5 distributed over the entire intermediate layer 4. The intermediate layer 4 is designed, for example, as an elastomer structure in which the compression elements 5 consist, for example, substantially or entirely of plastic and / or rubber.

[0026] The compression elements 5 are generally each at least partially tubular. In the illustrated embodiment, the compression elements 5 are configured as tubular elements that are arranged side by side along the longitudinal direction of the insert element 1 without touching each other (in the unpressurized state), and that each extend across the entire width of the insert element 1.

[0027] The compression elements 5 each have one or more (in the present embodiment two) predetermined bending points 6, 7, which are located in an area between the cover plates 2, 3 and extend over the entire length of the respective compression element. merits 5. When the intermediate layer 4 is compressed by reducing the distance between the cover plates 2, 3, in particular as a result of an expansion of one or more adjacent battery cells, the predetermined bending points 6, 7 of one or more (preferably all) compression elements 5 move in a direction transverse to a connecting line V between the cover plates 2, 3. In this way, the desired load profile can be achieved, as will be shown in more detail below.

[0028] It should be noted at this point that the size, number, arrangement, and design of the cover plates 2, 3, compression elements 5, and predetermined buckling points 6, 7 shown in Fig. 1 are merely examples. Various variations of these parameters are possible. In particular, the thickness of the cover plates 2, 3 and the size, number, design / shape, arrangement, and material of the compression elements 5 can be adapted to the requirements of a specific application of the insert element 1. This provides additional degrees of freedom, independent of the material properties, in order to enable, for example, a customer-specific and improved force-displacement design. In addition, further improvements, for example with regard to flammability, EMI shielding, and / or reducing thermal conductivity, can be achieved by applying a suitable coating(s) to the cover plates 1, 2 and / or the compression elements 5.

[0029] Fig. 2 shows a plan view of an embodiment of a battery module 10 according to the invention. This has a cell stack with a plurality of battery cells 11 (often a two- or three-digit number), with an insert element 12, for example of the type shown in Fig. 1, arranged between adjacent battery cells. The cell stack is usually arranged in a module housing 13. The battery cells 11 are preferably housed as solid-state battery cells in so-called pouch cells. The insert elements 12 between adjacent battery cells 11 serve in particular to keep the battery cells under constant load during operation in order to prevent cracks in the solid electrolyte of the battery due to volume changes. The insert elements 12 compensate for volume changes from the battery cells 11 and generate a defined load on the battery cells 11.

[0030] Fig. 3 shows a diagram with the surface pressure curve (in MPa) versus the thickness of the insert element (in mm) for various designs of intermediate layers 4. It can be seen that the curve for each design has a linear range, starting with the greatest thickness (in the pressure-free state) up to a specific (smaller) limiting thickness at a limiting pressure. This illustrates that, using the present invention, it is possible to change / adapt the gradient and shape of the curve as needed, up to a curve with one or more steps, where in the plateau region there is no or only a slight increase in force, even though the compression of the pad increases.

[0031] As mentioned above, the compression elements 5 can be designed in different ways. Figures 4 to 7 show four different configurations in cross-section, each in a depressurized (unassembled or assembled) initial state (Figures 4A, 5A, 6A, 7A), in an assembled, slightly compressed state (Figures 4B, 5B, 6B, 7B), and in a (nearly or fully) compressed state (Figures 4C, 5C, 6C, 7C).

[0032] The compression element 20 shown in Fig. 4 corresponds in its cross-section approximately to the compression element 5 shown in Fig. 1. It has a hexagonal (honeycomb-shaped) cross-section and is hollow on the inside. Towards the cover plates 2, 3, the compression element 20 is flattened in contact areas 21, 22 and, in the unpressurized state, lies flat against the cover plates 2, 3. The predetermined bending points 22, 24 lie in a central plane E, which runs approximately midway between and parallel to the cover plates 2, 3, and are formed as corner areas at which the adjacent areas 25, 26 and 27, 28 run at an angle to one another, for example in the range of 60° to 120°. The further the cover plates 2, 3 are pressed together, the further the predetermined bending points 23, 24 are pressed apart along the center plane E, so that the angle between the adjacent regions 25, 26 and 27, 28 is increasingly reduced, as can be seen in Figures 4B and 4C.The contact areas 21, 22 then no longer lie completely flat against the cover plates 2, 3, but only in certain areas or even at certain points. This is due to the interplay of stresses that arise in the individual areas of the molds during pressing. Individual areas are stretched or compressed and are then damaged by contact with other elements. are hindered or can move freely if there is no contact. This interaction then results in the desired load distribution.

[0033] The compression element 30 shown in Fig. 5 has a hose- or tubular-shaped central element 31 and two side elements 32, 33 adjoining it laterally (on opposite sides). In this exemplary embodiment, the side elements 32, 33 are designed - in cross-section - as rod-shaped connecting elements, but can also be hose- or tubular. Both the side elements 32, 33 and the central element 31 rest partially against the pressure plates 2, 3. The side elements 32, 33 are connected to the central element 31 at protruding connection points 34, 35, which simultaneously also represent predetermined bending points. The predetermined bending points 34, 35 are thus arranged in the center plane E on a surface 36, 37 of the rod-shaped side elements 32, 33 oriented towards the central element 31.The further the cover plates 2, 3 are pressed together, the further the predetermined bending points 34, 35 (and also the adjacent point of the central element 31) are moved apart within the center plane E, until the inner surfaces 36, 37 of the side elements 32, 33 and the opposite outer surfaces 38, 39 of the central element 31 abut against each other, as can be seen in Fig. 5C.

[0034] Fig. 6 shows a further embodiment of a compression element 40, which also has a central element 41 and two side elements 42, 43. In this embodiment, the central element 41 has a central connecting web 44 running parallel to the cover plates 2, 3 between the webs 45, 46 of the central element 41 running between the cover plates 2, 3. The side elements 42, 43 are connected along the cover plates 2, 3 to the webs 45, 46 of the central element 41. On the surface 47, 48 opposite the central element 41, a predetermined bending point 49, 50 is arranged approximately in the region of the center plane E in the form of a groove running in the longitudinal direction of the compression element 40 (or material constriction of the respective side element 42, 43). At this predetermined bending point, the side elements 42, 43 bend when pressure is applied to the compression element 40, so that the predetermined bending points 49a, 49b move apart.When greater pressure is applied, the central element 41 is completely compressed, as shown in Fig. 6C.

[0035] Fig. 7 shows a further embodiment of a compression element 50 which, similar to the compression element 20 shown in Fig. 4, is tubular with a hexagonal cross-section. A continuous bore 51 runs in the longitudinal direction and, in this embodiment, is slot-shaped, with the slot running parallel to the cover plates 2, 3. Thin webs 52, 53 laterally along the slot-shaped bore 51 form the predetermined bending points. With increasing pressure application, the slot-shaped bore 51 initially narrows and the predetermined bending points 52, 53 move apart in a direction parallel to the cover plates 2, 3. Finally, only two small lateral bores 54, 55 remain of the slot-shaped bore 51.

[0036] At this point it should be mentioned that in the embodiments shown in Figures 5 and 6, when the intermediate layer is compressed, the side elements may come into contact with the central element and / or an adjacent compression element (for example with one of its side elements), so that the elements that come into contact can then support one another. In principle, in these embodiments the predetermined bending points can each be arranged on the surface of the connecting elements oriented towards the central element and / or on the outer surface of the central element oriented towards the connecting elements. Furthermore, the predetermined bending points can each be arranged on the surface of the connecting elements facing away from the central element and / or on the inner surface of the central element facing away from the connecting elements.

[0037] Furthermore, it should be noted that in the embodiments shown in Figures 4 to 7, adjacent compression elements may come into contact upon compression of the intermediate layer, thereby supporting each other and increasing stability. The predetermined bending points can generally be arranged and designed such that, upon compression of the intermediate layer, they move away from the center of the respective compression element (i.e., away from each other) or toward the center of the respective compression element (i.e., toward each other) by reducing the distance between the cover plates.

[0038] In summary, Fig. 4 shows a variant with a slight increase in force over a wide range (flat curve) of compression and a strong / exponential increase in force from a certain compression (i.e. with a sudden, strong increase). Fig. 5 shows a variant with a flat curve with an adjacent small plateau region over a large compression range with a late, significant (exponential) increase in force. Fig. 6 shows a rapid increase in force up to a desired target value, followed by a large plateau phase with approximately constant force with increasing compression, followed by an exponential increase in force when a defined compression limit is reached. Fig. 7 shows a variant with a short range in which the force increases slowly with compression, but a large increase in force is achieved relatively quickly with increasing compression.

[0039] The cross-section of the compression elements is preferably symmetrical, and the compression elements preferably each have an even number of predetermined bending points, two of which are located opposite each other in a direction transverse to the connecting line between the cover plates. The cover plates are preferably arranged parallel to one another, and the predetermined bending points lie in a plane parallel to the cover plates, in particular in a plane arranged centrally between the cover plates. However, they can also lie in another plane or in several planes that run parallel to one or both cover plates.

[0040] Different configurations are possible for the design of the predetermined bending points. For example, a predetermined bending point can be formed by a notch on a surface and / or by locally reducing the material thickness and / or by creating an angle of less than 180° between the adjacent regions of the respective compression element on either side of the predetermined bending point.

[0041] The compression elements can be arranged separately or connected to one another. Preferably, identically designed and / or arranged compression elements are used, which allows for easier manufacture and assembly. Furthermore, the compression elements can have one or more through-bores in the longitudinal direction. Different configurations are also possible for the cross-section of the compression elements, such as a round, oval, or multi- Angular, especially rectangular or honeycomb, cross-section. There are also different design options for the cross-section of one or more holes.

[0042] Fig. 8 shows the compression element 40 shown in Fig. 6 in the slightly compressed state shown in Fig. 6B, as well as the course ("force-displacement curve") of the force on the compression element (in Newtons x 1000) versus the reduction in the thickness of the compression element (in mm; starting at 0, corresponding to the initial state, to -2, corresponding to a reduction in thickness of 2 mm). The linear course of the curve is evident when the compression element 40 is compressed to this extent.

[0043] Fig. 9 shows the compression element 40 shown in Fig. 6 in the more strongly compressed state shown in Fig. 6C, as well as the progression ("force-displacement curve") of the force on the compression element over the reduction in the thickness of the compression element (in mm; starting at 0, corresponding to the initial state, to -6.8, corresponding to a reduction in thickness of 6.8 mm). When compressing the compression element 40 to this extent, the step or plateau phase can be seen, in which the force remains at a nearly constant level, even though the compression increases.

[0044] In principle, different curve profiles for the force-displacement curve and corresponding designs of the insert element can be used according to the invention. For example, the curve can have a gentle initial rise followed by a sharp rise, or the curve can have one or more steps and / or plateau areas, or a sharp initial rise can be followed by a phased, slower rise in the curve. If necessary, a phased, declining curve with a linear progression over long stretches can also be used.

[0045] The insert element according to the invention offers a number of advantages over known swelling cushions. These include, in particular, easier handling and production and greater flexibility with regard to the structure and desired properties. shafts that do not only depend on the material properties of the materials used.

Claims

Patent claims Insert element for insertion between two adjacent battery cells of a battery module, comprising: two rigid cover plates and an intermediate layer arranged between the two cover plates, which intermediate layer is elastically compressible and is constructed from a plurality of individual compression elements distributed over the entire intermediate layer, wherein the compression elements are each at least partially hose- or tubular-shaped and have one or more predetermined bending points in a region between the cover plates, which bending points move in a direction transverse to a connecting line between the cover plates when the intermediate layer is compressed by reducing the distance between the cover plates. Insert element according to claim 1, wherein the compression elements each have an even number of predetermined bending points, two of which are located opposite one another in a direction transverse to the connecting line between the cover plates.Insert element according to one of the preceding claims, wherein a predetermined bending point is formed by: a notch on a surface, and / or local material slimming, and / or. Formation of an angle of less than 180° between the adjacent regions of the respective compression element on both sides of the predetermined bending point. Insert element according to one of the preceding claims, wherein the cover plates are arranged parallel to one another and the predetermined bending points are arranged in a plane parallel to the cover plates, in particular in a plane arranged centrally between the cover plates. Insert element according to one of the preceding claims, wherein the compression elements are arranged separately from one another or connected to one another. Insert element according to one of the preceding claims, wherein the compression elements are identically designed and / or identically aligned. Insert element according to one of the preceding claims, wherein the compression elements have a plurality of through-bores in the longitudinal direction. Insert element according to one of the preceding claims, wherein the compression elements each have a central, hose- or tubular central element and two or more side elements laterally adjoining it. Insert element according to claim 8, wherein the side elements are connected to the central element or come into contact with the central element and / or an adjacent compression element upon compression of the intermediate layer.Insert element according to claim 8, wherein the side elements are configured as rod-shaped, hose-shaped, or tubular connecting elements between the cover plates, and the central element is configured as a hose or tubular element. Insert element according to claim 10, wherein the predetermined bending points are each arranged on the surface of the connecting elements oriented toward the central element and / or on the outer surface of the central element oriented toward the connecting elements. Insert element according to claim 10 or 11. wherein the predetermined bending points are each arranged on the surface of the connecting elements facing away from the central element and / or on the inner surface of the central element facing away from the connecting elements. Insert element according to one of the preceding claims, wherein the predetermined bending points are arranged and designed to move away from the center of the respective compression element or towards the center of the respective compression element upon compression of the intermediate layer by reducing the distance between the cover plates. Insert element according to one of the preceding claims, wherein the compression elements have a round, oval or polygonal, in particular rectangular or honeycomb-shaped, cross-section. Insert element according to one of the preceding claims, wherein the compression elements are flattened towards the cover plates and lie flat against the cover plates.Insert element according to one of the preceding claims, wherein the compression elements are made of plastic and / or rubber. Insert element according to one of the preceding claims, wherein the cover plates are made of plastic and / or metal. Insert element according to one of the preceding claims, wherein the cover plates are rectangular and the compression elements are longitudinal and arranged transversely to the longitudinal direction or in the longitudinal direction of the cover plates. Battery module comprising: a cell stack with a plurality of battery cells;. at least one insert element according to one of the preceding claims, which is arranged between adjacent battery cells; and a module housing in which the cell stack is arranged.

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