BATTERY MODULE WITH AN INWARD-DEFORMING COVER

Abstract

A battery module comprises a container, a multitude of battery cells within the container, and a cover attached to the sides of the container that extends in one plane over the multitude of battery cells, the cover comprising an inner layer and an outer layer. In the event of a thermal event in one of the cells, the battery cover can flex inwards towards the cells.

Description

INTRODUCTION

[0001] This disclosure concerns battery modules and, in particular, battery modules used in vehicles.

[0002] Rechargeable battery cells can be useful in a variety of modern technical applications, such as electronic devices, e-bikes, hybrid vehicles, electric cars, and so on. In certain applications, the battery cells are contained within one or more battery modules, which in turn comprise a multitude of battery cells. Accordingly, the term "battery module" as used here refers to multiple battery cells connected in series and / or parallel, housed within a mechanical assembly. Optionally, the battery module may also include thermal management devices such as cooling plates, voltage, temperature, or pressure sensors, and / or similar components. The battery module may include a cover for protection. Battery cells occasionally experience adverse thermal runaway, in which the heat generated by a source (e.g., a battery cell) exceeds the module's capacity to dissipate the heat to the surroundings.Thermal runaway can occur, for example, if the battery is short-circuited or damaged. This can lead to an unfavorable temperature increase within the battery module and undesirable deformation of the module cover. In particular, the battery cover can expand thermally, which, in combination with the ejected mass of a damaged cell, can cause the cover to bulge outwards from the module. As in... Fig. As shown in Figure 1, for example, during a thermal event in a prior art module with a single-layer cover 20 attached at points 24, the cover 20 bulges outwards away from the cells 41 and the thermal barrier 42. This outward deformation enlarges the gaps 60 and 61 and can cause adjacent cells 41 to be exposed to heat, including the ejected hot particle mass, which can promote thermal runaway. BRIEF SUMMARY OF THE INVENTION

[0003] In one embodiment, a battery module is disclosed comprising a container, a plurality of battery cells within the container, and a cover attached to sides of the container and extending in one plane over the plurality of battery cells, the cover comprising an inner layer and an outer layer.

[0004] Furthermore, the battery module may have one or more of the following features.

[0005] The battery module may include a thermal barrier that separates a first group of battery cells from a second group. The battery module may have a gap between the cover and the top edge of the battery cells, and the thermal barrier extends upwards into the gap towards the cover.

[0006] When a thermal event occurs in one or more of the multitude of battery cells, the cover deforms inwards in the direction of the multitude of cells.

[0007] The inner layer of the battery module can be connected to the outer layer at a minimum of two attachment points. These two attachment points can be located on two opposite edges of the cover. In addition to the attachment points on opposite edges, the inner layer can be connected to the outer layer at one or more additional points within the perimeter of the cover. Attachment at one or more additional points within the perimeter of the cover can be achieved by spot welding. The inner layer can be connected to the outer layer by means of a laminating material located between the inner and outer layers. The laminating material can comprise an adhesive, an insulating material, or both. The inner layer can also be connected to the outer layer by a roll-bonding process.

[0008] The inner and outer layers can be made of the same material, or the inner layer can be made of one material and the outer layer of a different material. Both the inner and outer layers can be metals. The metal for the inner and outer layers can be selected independently from carbon steel, alloy steel, copper, aluminum, and zinc.

[0009] The coefficient of thermal expansion of the inner layer can be greater than the coefficient of thermal expansion of the outer layer.

[0010] The cover can have a thickness of 0.4 to 5 mm. The inner layer can have a thickness of 0.2 to 2.5 mm, and the outer layer can have a thickness of 0.1 to 2.5 mm. The thickness of the inner layer can be greater than the thickness of the outer layer.

[0011] The battery cover may have one or more vents to allow gas to escape from the module.

[0012] In a further embodiment, a battery module is disclosed comprising a container, a plurality of battery cells within the container, a thermal barrier separating a first group of the plurality of battery cells from a second group of the plurality of battery cells, and a cover attached to the sides of the container and extending in one plane over the plurality of battery cells, wherein the cover comprises an inner layer and an outer layer, the inner layer being connected to the outer layer at at least two attachment points, wherein a gap is present between the cover and an upper edge of the plurality of battery cells, and the thermal barrier extends upward into the gap towards the cover, wherein, upon the occurrence of a thermal event in one or more of the plurality of battery cells, the cover deforms inwards towards the plurality of battery cells.and wherein the battery cover has one or more vents to allow gas to escape from the module.

[0013] The aforementioned features and advantages, as well as other features and advantages of the disclosure, will become apparent from the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Further features, advantages, and details are listed only as examples in the following detailed description, which refers to the drawings. These show: Fig. 1 a schematic cross-section of a prior art module cover for a module exposed to a thermal event; Fig. 2 a schematic perspective view of a battery module; Fig. 3 a schematic partial cross-section of a battery module made of AA' Fig. 2; Fig. 4 a schematic partial cross-section of a battery module exposed to a thermal event, represented by AA' Fig. 2; Fig. 5A a schematic cross-section of an exemplary module cover disclosed herein; and Fig. 5B-D Schematic cross-sections of exemplary module covers disclosed herein, which are subject to a thermal event. DETAILED DESCRIPTION

[0015] The following description is merely exemplary and is not intended to limit the present disclosure, its application, or its use. It should be noted that in the drawings, corresponding reference numerals denote identical or corresponding parts and features.

[0016] According to one embodiment, as in Fig. As shown in Figure 2, a battery module 10 comprises a container 30 and a cover 20. The cover may include optional ventilation openings 22. As shown in Figure 2. Fig. As shown in Figure 3, the container 30 comprises several groups 40 of cells 41, each group 40 being separated from an adjacent group 40 by a thermal barrier 42. The thermal barrier extends over a top edge 45 of the cells 41 into a gap 60. The cover 20 is located over the cells 41 and the thermal barrier 42, with a small gap 61 between the top of the thermal barrier 42 and the cover 20. The cover 20 may optionally include one or more vents 22. The vents 22 may optionally include a vent cover 23, which is ruptured or removed by a thermal event occurring beneath the vent cover 23. The vent cover 23 may, for example, comprise a thin, flexible film of a material such as mica. The cover 20 comprises an outer layer 25 and an inner layer 26.

[0017] As in Fig. As shown in Figure 4, the two-layer structure of the cover 20 ensures that, in the event of a thermal event in one of the groups 43 of cells 41, the cover deforms inwards. This inward deformation can shrink or close the gap 61 above the thermal barrier 42, thus preventing the propagation of the thermal event to other cell groups 40.

[0018] The inward deformation can be attributed to the fact that the inner layer 26 is closer to the thermal event than the outer layer 25 and therefore heats up and expands more rapidly than the outer layer 25, leading to inward deformation. Additionally or alternatively, the inner layer 26 may have a higher coefficient of thermal expansion than the outer layer 25, resulting in greater or faster expansion of the inner layer and thus inward deformation.

[0019] An example of such a structure is in Fig. Figure 5A shows a cover 20 with an inner layer 26 and an outer layer 25, which are physically connected at two or more attachment points 24. The connection of the inner layer 26 and the outer layer 25 at the attachment points 24 is necessary to cause the cover 20 to deform inwards when the inner layer 26 expands during a thermal event.

[0020] As in Fig. As shown in Figure 5B, the inner layer 26 and the outer layer 25 can be physically connected via a continuous section of the cover 20. This continuous section can be the entire cover 20. As shown in Fig. 5C and Fig. As shown in 5D, the inner layer 26 and the outer layer 25 can be physically connected at isolated connection points 27 distributed across the cover 20. These isolated connection points can be, for example, welds (e.g., spot welds or weld lines).

[0021] The physical bond between the inner layer 26 and the outer layer 25 can be achieved by adhesive bonding (e.g., roll bonding), plating (e.g., zinc plating), mechanical fastening (e.g., welding), or laminating using an intermediate material between the inner layer 26 and the outer layer 25, or by a combination thereof. The intermediate material can be, for example, an adhesive or an insulating material. It can also be a sacrificial material that decomposes under thermal stress. The intermediate material should be able to withstand the normal operating temperatures of the battery module (e.g., -50 °C to 120 °C or -40 °C to 90 °C).

[0022] The inner layer 26 and the outer layer 25 can be made of the same material. In this case, the inward deformation is caused by the inner layer 26 heating up and expanding more rapidly due to its proximity to the thermal event. The inner layer 26 and the outer layer 25 can also be made of different materials. If different materials are used, the inner layer 26 can be made of a material with a higher coefficient of thermal expansion than the outer layer 25. The material selected for the inner layer 26 and the outer layer 25 must withstand both the normal operating temperatures of the battery module and at least the initial temperatures during a thermal event. For example, the materials used for the inner layer 26 and the outer layer 25 can have a melting point of more than 500 °C or at least 600, 700, 800, 900, 1000, or 1100 °C.

[0023] Examples of materials that can be used to form the inner layer 26 and the outer layer 25 are steel (e.g., stainless steel, such as ferritic or austenitic stainless steel; carbon steel; galvanized steel and aluminized steel), zinc, copper, and copper-based alloys. For example, the combination of inner layer 26 and outer layer 25 can be a coated steel (e.g., carbon steel), where the coating can be zinc-based, e.g., pure Zn, Zn-Fe, Zn-Ni, Zn-Mg, Zn-Mg-Al, or aluminum-based, e.g., Al-Si or Al-Zn. For example, the outer layer 25 can also be carbon steel and the inner layer stainless steel. Alternatively, both the inner layer 26 and the outer layer 25 can be carbon steel.

[0024] The thickness of the cover can be, for example, more than 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8, at least 0.9, or at least 1 to 5, up to 4, up to 3, up to 2, or up to 1.5 millimeters (mm). The inner layer 26 and the outer layer 25 can have the same thickness or different thicknesses. According to one embodiment, the inner layer 26 is thicker than the outer layer 25. This construction can lead to greater inward deflection of the cover. According to another embodiment, the inner layer 26 is thinner than the outer layer 25. The thickness of the inner layer 26 and the outer layer 25 can be individually greater than 0.1, greater than 0.15, greater than 0.2, greater than 0.25, at least 0.3, at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8 up to 4, up to 3.5, up to 3 mm.

[0025] The terms "a" and "an" do not represent a quantity limitation, but rather indicate that at least one of the mentioned items is present. Unless the context clearly indicates otherwise, the term "or" means "and / or." When the description refers to "an aspect," this means that a specific element described in connection with the aspect (e.g., a characteristic, a structure, a step, or a property) is contained in at least one of the aspects described here and may, but does not necessarily, also occur in other aspects. Furthermore, it should be noted that the described elements can be combined in any suitable way across the various aspects.

[0026] When an element such as a layer, film, area, or substrate is described as being "on" another element, it may be located directly on top of the other element, or there may be intermediate elements. Conversely, when an element is described as being "directly on" another element, there are no intermediate elements.

[0027] Unless otherwise stated herein, all testing standards are the most recent standards in force on the filing date of this application or, if priority is claimed, on the filing date of the earliest priority application in which the testing standard appears.

[0028] Unless otherwise specified, all technical and scientific terms used herein have the meanings that a person skilled in the field to which this disclosure relates would normally associate with such terms.

[0029] Although the above disclosure has been described with reference to exemplary embodiments, the person skilled in the art knows that various modifications can be made and equivalent elements substituted without altering its scope. Furthermore, many modifications can be made to adapt a particular situation or material to the teachings of the disclosure without deviating from its essential scope. Therefore, the present disclosure is not intended to be limited to the specific embodiments disclosed, but rather to encompass all embodiments that fall within its scope.

Claims

[1] Battery module comprising: a container, a plurality of battery cells within the container, and a cover attached to sides of the container and extending in a plane over the plurality of battery cells, the cover comprising an inner layer and an outer layer. [2] The battery module of claim 1, further comprising a thermal barrier separating a first group of the plurality of battery cells from a second group of the plurality of battery cells, wherein a gap is present between the cover and a top edge of the plurality of battery cells, the thermal barrier extending upward into the gap toward the cover. [3] The battery module of claim 1, wherein the cover deforms inwardly toward the plurality of cells upon the occurrence of a thermal event in one or more of the plurality of battery cells. [4] Battery module according to claim 1, wherein the inner layer is connected to the outer layer at at least two attachment points on two opposite edges of the cover. [5] A battery module according to claim 4, wherein the inner layer is connected to the outer layer at one or more additional points within the perimeter of the cover. [6] The battery module of claim 5, wherein the connection of the inner layer to the outer layer at the one or more additional points within the perimeter of the covers comprises welding points, via a laminating material located between the inner layer and the outer layer, or by means of a roll bonding process. [7] The battery module of claim 1, wherein the inner layer comprises a first material and the outer layer comprises a second material, wherein the first material and the second material are metals independently selected from steel, copper, and zinc for the inner layer and the outer layer. [8] The battery module according to claim 7, wherein a thermal expansion coefficient of the inner layer is greater than a thermal expansion coefficient of the outer layer. [9] The battery module according to claim 1, wherein the cover has a thickness of 0.4 to 5 mm, the inner layer has a thickness of 0.2 to 2.5 mm, and the outer layer has a thickness of 0.1 to 2.5 mm, provided that the thickness of the inner layer is greater than the thickness of the outer layer. [10] The battery module of claim 1, wherein the battery cover includes one or more vents to allow gas to escape from the module.

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