Battery module for a vehicle

Abstract

The invention relates to a battery module (1), in particular for a vehicle, in particular an electric vehicle. The battery module (1) has a housing (3) and at least one battery cell (2) arranged in the housing (3), wherein the battery cell (2) has an electric positive pole (5) and an electric negative pole (8) which are electrically insulated from one another by an insulating material (9). A functional element (4) is provided, which is arranged between the battery cell (2) and the housing (3) of the battery module (1) and is designed to act on the battery cell (2) in such a way that the insulating material (9) is at least partially displaced when heat is generated above a specified threshold value, in order to thereby establish an electric connection between the electric positive pole (5) and the electric negative pole (8) of the battery cell (2).

Description

[0001] BATTERY MODULE FOR A VEHICLE

[0002] The present invention relates to the field of batteries for electric vehicles. In particular, the invention is directed to a battery module for a vehicle, in particular an electric vehicle, and to a vehicle having at least one such battery module.

[0003] A key focus in the development of electric or hybrid vehicles, i.e., vehicles that are at least partially powered by electric motors, is the battery that powers the electric motor (hence also called "drive battery" or "traction battery"). Various battery cells have been developed for this purpose, for example, lithium-ion cells. Several battery cells are typically arranged as a "battery pack" and, through appropriate wiring, form a "battery module" or simply a "battery." It is understood that the term "battery" hereinafter refers in particular to a rechargeable battery ("accumulator" or "battery").

[0004] A battery module can contain multiple battery cells. For example, a battery module for a 12 V starter battery for a motor vehicle can have four battery cells, each with 4 V, whereas a high-voltage storage device that can provide 400 V or even 800 V as an output voltage can have multiple battery modules. In the battery cells, an energy storage device and associated electrodes can be arranged within a cell housing. Electrical power can be tapped from outside the cell housing via provided electrical connections to the electrodes. The connection between the individual battery cells in a battery module is also called the cell contact system.

[0005] Battery modules can experience what is known as thermal runaway. Thermal runaway in an electric vehicle battery is caused by a combination of physical and chemical processes that lead to increased heat generation. This can be caused by a number of factors, including overload, temperature, voltage or current, and the condition of the battery. When the temperature in the battery rises, chemical reactions can begin that lead to uncontrolled heat generation. This, in turn, can cause a further increase in temperature and thus the formation of explosive gases. It is therefore important to detect thermal runaway early and take appropriate measures to avoid a serious accident.

[0006] A thermal runway can occur, in particular, due to a short circuit in a battery cell, which can trigger the processes described above, leading to uncontrolled heat buildup and spread to neighboring cells. A short circuit can occur between the layers of a battery cell. Each cell comprises several layers: an electrode known as the "anode," an electrode known as the "cathode," and a separator located between the two electrodes to electrically separate them (i.e., impermeable to electrons) and conduct ions. For example, a defect in the separator layer can lead to an internal cell short circuit.

[0007] Depending on the type of short circuit in the cell in question, escalation and thus, in particular, spread to neighboring battery cells can possibly be prevented. In particular, a fuse, such as a melting fuse, can be used in the cell contact system to interrupt the power source if the temperature exceeds a certain threshold. This is particularly effective if a low-resistance short circuit with a correspondingly high current has occurred in the battery cell, which then connects to the melting fuse and triggers it. If, on the other hand, a high-resistance short circuit exists in the battery cell, the relatively low current allows the neighboring cells to be safely discharged without the melting fuse triggering.

[0008] However, if there is a medium-resistance short circuit, the neighboring cells cannot be safely discharged. At the same time, separation cannot be achieved even with a fuse because the current is still too low. A fuse could indeed be dimensioned accordingly to ensure safe separation even at lower currents. However, this would impair the current-carrying capacity of the cell contact system, i.e. the fuse would not be able to withstand high currents, for example during rapid charging. The fuse can, if necessary, be designed such that it is triggered not only by its own heat due to an overcurrent, but also by external heat, for example the heat generated by a short-circuited battery cell. It is an object of the present invention to provide a battery module in which thermal runaway can be prevented in an improved manner.In particular, this should also apply to situations in which a medium-resistance short circuit occurs in a battery cell.

[0009] This object is achieved according to the teaching of the independent claims. Various embodiments and further developments of the invention are the subject of the dependent claims.

[0010] A first aspect of the invention relates to a battery module, in particular for a vehicle, in particular an electric vehicle. The battery module has a housing and at least one battery cell arranged in the housing, wherein the battery cell has a positive electrical pole and a negative electrical pole, which are electrically insulated from one another by an insulating material. A functional element is provided in the battery module, which functional element is arranged between the battery cell and the housing of the battery module and is designed to act on the battery cell in such a way that the insulating material is at least partially displaced when heat is generated above a predetermined threshold value, in order to thereby establish an electrical connection between the positive electrical pole and the negative electrical pole of the battery cell.

[0011] The invention is therefore based on deliberately establishing an electrical connection (i.e., a short circuit) between the positive electrical pole and the negative electrical pole of the battery cell in the event of heat development above a predetermined threshold value, e.g., above approximately 400 or 450°C, which may in particular be heat development in a battery cell that may lead to thermal runaway. The direct (metallic) contact between the two poles of the battery cell creates, in particular, a low-resistance short circuit in the battery cell, so that reliable disconnection can be achieved, in particular by means of a fuse. The resulting short-circuit current should preferably be higher than the operating current of the battery cell.

[0012] Without the functional element, the insulating material would possibly also be damaged, but would most likely maintain the electrical separation between the two poles of the battery cell, as this is actually the primary function of the insulating material. However, the functional element acts on the battery cell, i.e. a force is exerted on the battery cell which can displace the insulating material, for example by squeezing it out between the two poles. In this way, in the event of heat generation, the described low-resistance short circuit in the battery cell can be promoted in order to prevent thermal runaway. In particular, this can also achieve safe shutdown in the event of a medium-resistance short circuit, which previously led to heat generation.

[0013] The term "vehicle" used here refers in particular to a passenger car, including all types of motor vehicles, hybrid and battery-powered electric vehicles, as well as vehicles such as sedans, vans, buses, trucks, delivery vans, and the like. The term "electric vehicle" then refers in particular to electric or hybrid vehicles, in particular vehicles that are at least partially powered by an electric motor. An electric vehicle can in particular be a passenger car, but also a vehicle such as a van, bus, truck, delivery van, and the like, or a two-wheeler such as an (electric) motorcycle, (electric) scooter, e-bike, e-scooter, and the like. The battery module can in particular be a battery or part of a battery, in particular a drive battery of an electric vehicle.

[0014] The term "functional element" used here refers in particular to a (mechanical) element that is arranged between the housing of the battery module and a battery cell. The functional element can be designed as a "support element" and can be supported between the housing of the battery module and a battery cell. It can then also be referred to as a "pressure element." This can occur (in a normal state or during regular operation) with or without a preload force. In particular, it is provided that it is "supported" therebetween, i.e., mechanically rests on opposite sides. It is understood that support can be understood as "direct" support, i.e., with direct contact, or "indirect support," i.e., via another element, another structure, an intermediate material, and the like.In a reverse mode of operation, the functional element can also be designed as a “tensile element” which is arranged between the housing of the battery module and a battery cell and is connected accordingly in order to be able to exert a tensile force.

[0015] The term "pole" or "electrical pole" of a battery cell used here refers in particular to the terminals of an individual cell that make the electrodes inside the battery cell—in the case of a round cell, in particular an electrode coil—accessible from outside the cell, i.e., electrically contactable. The poles of battery cells in a battery module can be interconnected, in particular by means of a connecting element, such as a cell contact system.

[0016] As used herein, the terms "comprises," "includes," "includes," "has," "has," "with," or any other variation thereof are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or has a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or that are inherent in such a method or apparatus.

[0017] Furthermore, unless explicitly stated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, a condition A or B is satisfied by one of the following conditions: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present).

[0018] The terms "a" or "an" as used herein are defined as "one or more." The terms "another" and "another," and any other variations thereof, are defined as "at least one other."

[0019] The term “plurality” as used here shall mean “two or more”.

[0020] The term “configured” or “set up” to fulfil a specific function (and respective modifications thereof) is to be understood within the meaning of the invention that the corresponding device is already in a design or setting in which it can carry out the function or is at least adjustable - i.e. configurable - so that it can carry out the function after being set accordingly. The configuration can be carried out, for example, by appropriately setting parameters of a process sequence or of switches or the like for activating or deactivating functionalities or settings. In particular, the device can have a plurality of predetermined configurations or operating modes, so that the configuration can be carried out by selecting one of these configurations or operating modes.Preferred embodiments of the battery module according to the first aspect are described below, which can each be combined with one another as desired, unless this is expressly excluded or is technically impossible.

[0021] In some embodiments, the functional element is configured to act on one of the poles of the battery cell in such a way as to establish the electrical connection between the electrical positive pole and the electrical negative pole of the battery cell when heat is generated above the predetermined threshold value. In particular, the functional element can be supported on one of the poles as a support element. While it is in principle possible for the functional element to be supported at any point on the battery cell, as long as it can act on the battery cell in this way, i.e. in particular can exert a force that can bring the two poles of the battery cell into contact, it is advantageous if the functional element is supported on one of the poles. This pole, i.e. the one on which the functional element is supported, can then be moved towards the other pole by the action of the functional element (when heat is generated).This allows the insulating material to be displaced. The force exerted by the functional element can then be applied more precisely to the battery cell to achieve the desired effect.

[0022] In some embodiments, the battery cell has a cylindrical cell housing, wherein the electrical positive pole is formed by a terminal connection on one end face of the cell housing and the electrical negative pole is formed by the cell housing. A sealing ring made of the insulating material is provided, which electrically insulates the terminal connection from the cell housing. This shape of battery cell, also called a round cell, is a well-known type of battery cell. The cylindrical cell housing allows the functional element to act on the battery cell as described.

[0023] In cylindrical battery cells, electrode ends of like-polarized electrodes, in particular cathodes, which are electrically positively polarized, can be electrically connected to a so-called terminal connection. The terminal connection can be formed on an end face of the cell housing, wherein the terminal connection is electrically insulated from the cell housing. Through the terminal connection, an electrically positive pole of the battery cell can be contacted from outside the battery cell. Likewise, electrode ends of anodes, which are electrically negatively polarized, can be electrically connected to the cell housing, which is also electrically conductive, so that the electrically negative pole of the battery cell can be contacted via the cell housing.

[0024] In the case of cylindrical battery cells, the functional element can be supported in particular on the terminal connection in order to be able to exert a compressive force on the terminal connection, or alternatively can be connected to the terminal connection in order to be able to exert a tensile force on the terminal connection. This connection, which is usually arranged centrally on one end face of the cylindrical cell housing, forms the positive electrical pole and can in particular also form a closure of the cylindrical cell housing, which is seated in the cell housing with a sealing ring made of the insulating material, with the cell housing forming the negative electrical pole. The terminal connection can, for example, have at least one flange which displaces the sealing ring, i.e. the insulating material, when the functional element is applied, in order to thereby establish direct (metallic) contact between the terminal connection and the building.This allows the desired short circuit described above to be effectively achieved.

[0025] In some embodiments, the insulating material is designed such that it at least partially softens upon heat development above the predetermined threshold, so that it can be displaced in the softened state by the action of the functional element. Softening means, in particular, that the insulating material melts due to the heat development. It can therefore be provided that the insulating material, which in conventional battery cells may be rather robust and have a high melting point, is made from a material with a somewhat lower melting point. This can promote the displacement caused by the force applied by the functional element.

[0026] In some embodiments, the functional element, in particular as a support element, has at least one spring element which is pre-tensioned between the housing of the battery module and the battery cell. A spring element offers a simple element which can be supported by a certain pre-tensioning force between the housing of the battery module and the battery cell. When heat is generated and in particular when the insulating material softens, this pre-tensioning force then brings the two poles of the battery cell together by displacing the insulating material. The spring element can be designed as desired, for example as a simple spiral spring or another (metallic) spring element. However, an element made of a non-metallic compressible material can also be used as the functional element (orA "spring element" may be provided, which, in its compressed form, rests between the battery module housing and the battery cell in the normal state and is thus "preloaded." This can be, for example, a compressible pad made of a foam material, a rubber material, or another (compressible) plastic material, such as a thermoplastic elastomer (TPE) or a thermoplastic polyurethane (TPU).

[0027] In some embodiments, the functional element is configured to expand upon heat development above the predetermined threshold, thereby acting on the battery cell. Instead of providing a functional element, such as a spring element, which is already inserted with a preload force, an element can also be used which, in the normal state, is supported between the housing of the battery module and the battery cell with little or no force. Only upon heat development, in particular above the predetermined threshold, does the functional element expand, thereby exerting the force on the battery cell to cause the short circuit. It is understood that a previously described spring element can also be configured such that it expands upon heat development.

[0028] In some embodiments, the battery module comprises a plurality of battery cells, wherein the battery cells are electrically connected via a connecting element to establish electrical contact between the battery cells and to an electrical terminal of the battery module. This so-called cell contact system establishes, in particular, electrical contact between the electrical positive terminal of one battery cell and the electrical negative terminal of another (particularly adjacent) battery cell. In this way, the battery cells of the battery module are interconnected.

[0029] In some embodiments, the functional element rests on the connecting element, in particular as a support element. The connecting element (ZKS) can, for example in the case of round cells, rest on the end faces of the battery cells (and be welded, for example) in order to effect the described interconnection of the battery cells. The functional element can then be provided between the connecting element and the housing of the battery module. The support is then thus "indirect", with the force being transmitted via the connecting element. In this way, too, the functional element can effectively act on the battery cell(s) in the manner described. The short circuit can then be brought about, in particular in a battery cell in which heat is generated.

[0030] In some embodiments, a functional element is provided for each of the battery cells. This advantageously allows for targeted action on each battery cell to cause a short circuit in a damaged battery cell. However, fewer functional elements can also be provided, which can, for example, be spatially distributed and exert the desired force on the battery cells via the connecting element.

[0031] In some embodiments, the connecting element has at least one fuse. The fuse can, in particular, be configured to trigger when the electrical connection is established between the positive electrical pole and the negative electrical pole of the battery cell. In a battery module for a vehicle, for example, a current of approximately 1000 A can then be generated. The fuse reliably triggers in the event of such a high overcurrent. This high current is achieved, as described, by the deliberately induced low-resistance short circuit between the two poles, whereas a medium-resistance short circuit in the battery cell itself, in particular between the two electrodes, for example in the event of defects in the separator layer, does not ensure reliable triggering of the fuse.

[0032] In some embodiments, the functional element or elements are supported on the housing of the battery module via a load distribution structure, such as a load distribution plate. A functional element can exert a relatively point-like force. This is advantageous on the battery cell side, as the short circuit can then be effectively caused by displacing the insulating material. On the other hand, however, the point-like force also acts on the housing. Therefore, it can be advantageous to provide a load distribution element, particularly in plate form, so that the housing does not need to be additionally reinforced.

[0033] A second aspect of the invention relates to a vehicle, in particular an electric vehicle, which has at least one battery module according to the first aspect of the invention, in particular as a drive battery for an electric motor of the electric vehicle.

[0034] The features and advantages explained with reference to the first aspect of the invention also apply accordingly to the other aspects of the invention. Further advantages, features, and possible applications of the present invention will become apparent from the following detailed description in conjunction with the drawings.

[0035] It shows:

[0036] Fig. 1 schematically shows a section of a battery module according to an embodiment;

[0037] Fig. 2 schematically shows a section of a battery module according to another embodiment;

[0038] Fig. 3 shows a schematic section through a terminal connection of a battery cell in normal operation; and

[0039] Fig. 4 shows a schematic section through a terminal connection of a battery cell with heat development above a predetermined threshold value.

[0040] Throughout the figures, the same reference numerals are used for the same or corresponding elements of the invention.

[0041] Fig. 1 schematically shows a section of a battery module 1 in a partial sectional view. By way of example, two battery cells 2 of the battery module 1 are shown in a housing 3 of the battery module 1. It is understood that the battery module 1 can have a plurality of battery cells 2 in order to achieve a desired voltage. For example, the battery module 1 can serve as a drive battery for the electric motor of an electric vehicle (not shown). In the illustrated embodiment, the battery cells 2 are designed as cylindrical battery cells (round cells). A battery cell 2 can, for example, have a diameter of 46 mm and a length of 95 mm and can be, for example, a lithium-ion cell.

[0042] The battery cells 2 each have a housing in the form of a hollow cylinder made of an electrically conductive material. An electrode coil is arranged in the housing, which can be formed by winding a layer structure around a winding core. An anode of the electrode coil is connected to the cell housing 8 (see Figs. 3 and 4) via a current collector, which thereby forms a negative pole of the battery cell 2. A cathode of the electrode coil is connected to a terminal connection 5 of the battery cell 2 via a current collector, which thereby forms a positive pole of the battery cell 2. The battery cells 2 of the battery module 1 are interconnected via connecting elements 6, a so-called cell contact system, by corresponding electrical connections of the positive and negative poles of the battery cells 2.Fuses 7 are provided in the connecting elements 6, in particular by means of a cross-sectional taper, which are dimensioned such that a fuse 7 is triggered in the event of a certain overcurrent and the resulting heat development and separates the electrical connection.

[0043] If a short circuit occurs in one of the battery cells 2, for example due to a defect within the battery cell 2, the fuse 7 can only reliably trigger if it is a low-resistance short circuit, since the overcurrent is then sufficiently high. In the case of a high-resistance short circuit in a battery cell 2, however, the neighboring cells can be safely discharged. This is important in order to prevent thermal runaway, which can be triggered by heat development from the internal cell short circuit. However, if a medium-resistance short circuit should occur in a battery cell 2, neither safe discharge nor triggering of the fuse 7 is guaranteed.

[0044] Therefore, a functional element 4 is provided between each battery cell 2 and the housing 3 of the battery module 1, in particular as a support element. It is supported between the housing 3 and the respective battery cell 2 in such a way that a force acts in particular on the terminal connection 5 (i.e. the positive pole). For example, the functional element 4 can be designed as a spring element which is inserted with a prestressing force. In Fig. 1, the functional element 4 is not supported directly on the battery cell 2 or the terminal connection 5, but via the connecting element 6. However, this has no influence on the effect of the functional element 4 on the battery cell, which will be explained in more detail below with reference to Fig. 3 and Fig. 4.

[0045] The functional element 4 can also have a different shape than the spiral spring shown. For example, an element such as a pad made of a foam, rubber, or plastic material (e.g., TPE or TPU) can be provided, which is compressed and supported between the housing 3 and the respective battery cell 2. A functional element 4 can also be provided which, in the normal state, does not exert any force on the battery cell 2, but only expands when heat is generated. The effect in the scenario shown in particular in Fig. 4 is then essentially the same. It is also conceivable to design the functional element as a tension element, which is connected to the housing 3 and the terminal connection 5 in order to be able to exert a corresponding tensile force.

[0046] Fig. 3 and Fig. 4 each show the upper end of a battery cell 2 with the terminal connection 5 in a sectional view. For reasons of clarity, the connecting element 6 and the housing 3 are not shown in Fig. 3 and 4. A sealing ring made of an insulating material 9 is provided between the terminal connection 5, i.e., the positive pole, and the housing 8 of the battery cell 2, i.e., the negative pole. During normal operation, this sealing ring electrically insulates the two electrical poles of the battery cell 2 from each other to prevent a short circuit. This is shown in Fig. 3.

[0047] If heat is generated in the battery cell 2, as illustrated in Fig. 4, in particular due to a medium-resistance short circuit within the cell, the insulating material 9 of the sealing ring softens or melts. Due to the action of the functional element 4 (arrow in Fig. 4), the terminal connection 5 is pressed towards the cell housing 8, thereby displacing the insulating material 9 of the sealing ring. In particular, the terminal connection 5 has a flange so that the insulating material 9 is pushed out laterally (9' in Fig. 4). It is understood that if a tension element were used as the functional element 4, the insulating material 9 on the inside of the cell housing 8 would be pushed out (not shown). In this way, a short circuit 10 can be deliberately created in the battery cell 2. This is caused by the direct metallic contact between the terminal connection 5 and the cell housing.This short circuit 10 will be a low-resistance short circuit, so that the resulting high overcurrent reliably triggers the fuse 7, thus preventing thermal runaway. In other words, the resulting electrical connection is so low-resistance and current-carrying that the resulting short-circuit currents melt the fuse 7. The resulting short-circuit currents should, in particular, be higher than the operating currents of the battery cells 2.

[0048] Fig. 2 shows an embodiment of a battery module 1, which is essentially similar to the embodiment of Fig. 1. In this respect, reference is made to the above description. The only difference is that the functional elements 4 are not supported directly on the inside of the housing 3 of the battery module 1, but via a load distribution structure 11, here in the form of a load distribution plate. This is supported at several points on the inside of the housing 3 of the battery module 1 in order to avoid high point loads on the housing 3 from the functional elements 4. While at least one exemplary embodiment has been described above, it should be noted that a large number of variations exist.It should also be noted that the described exemplary embodiments are merely non-limiting examples and are not intended to limit the scope, applicability, or configuration of the devices and methods described herein. Rather, the foregoing description will provide a guide to implementing at least one exemplary embodiment, with the understanding that various changes in the operation and arrangement of the elements described in an exemplary embodiment may be made without departing from the subject matter defined in the appended claims, as well as their legal equivalents.

[0049] LIST OF REFERENCE SYMBOLS

[0050] 1 battery module

[0051] 2 battery cells

[0052] 3 Housing of the battery module 4 Functional element

[0053] 5 Terminal connection (positive pole)

[0054] 6 Connecting element

[0055] 7 Fuse

[0056] 8 Cell casing (negative pole) 9 Insulating material

[0057] 9' displaced insulation material

[0058] 10 Short circuit

[0059] 11 Load distribution structure

Claims

CLAIMS 1. Battery module (1), in particular for a vehicle, comprising a housing (3) and at least one battery cell (2) arranged in the housing (3), wherein the battery cell (2) has an electrical positive pole (5) and an electrical negative pole (8) which are electrically insulated from one another by an insulating material (9), wherein a functional element (4) is provided which is arranged between the battery cell (2) and the housing (3) of the battery module (1) and is designed to act on the battery cell (2) in such a way that the insulating material (9) is at least partially displaced when heat is generated above a predetermined threshold value, in order to thereby establish an electrical connection between the electrical positive pole (5) and the electrical negative pole (8) of the battery cell (2).

2. Battery module according to claim 1, wherein the functional element (4) is designed to act on one of the poles of the battery cell (2) in such a way as to establish the electrical connection between the electrical positive pole (5) and the electrical negative pole of the battery cell (2) when heat is generated above the predetermined threshold value.

3. Battery module according to claim 1 or 2, wherein the battery cell (2) has a cylindrical cell housing, wherein the electrical positive pole (5) is formed by a terminal connection on an end face of the cell housing and the electrical negative pole (8) is formed by the cell housing, wherein a sealing ring made of the insulating material (9) is provided, which electrically insulates the terminal connection from the cell housing.

4. Battery module according to claim 3, wherein the functional element (4) is supported on the terminal connection (5).

5. Battery module according to one of the preceding claims, wherein the insulating material (9) is designed such that it at least partially softens when heat is generated above the predetermined threshold value, so that it can be displaced in the softened state by the action of the functional element (4).

6. Battery module according to one of the preceding claims, wherein the functional element (4) has at least one spring element which is prestressed between the housing (3) of the battery module (1) and the battery cell (2).

7. Battery module according to one of the preceding claims, wherein the functional element (4) is configured to expand upon heat development above the predetermined threshold value in order to thereby act on the battery cell (2).

8. Battery module according to one of the preceding claims, wherein the battery module (1) has a plurality of battery cells (2), wherein the battery cells (2) are electrically connected via a connecting element (6) in order to establish an electrical contact between the battery cells (2) and to an electrical connection of the battery module (1).

9. Battery module according to claim 8, wherein the functional element (4) is supported on the connecting element (6).

10. Battery module according to claim 8 or 9, wherein a functional element (4) is provided for each of the battery cells (2).

11. Battery module according to one of claims 8 to 10, wherein the connecting element (6) has at least one fuse (7).

12. Battery module according to one of the preceding claims, wherein the functional element (4) or the functional elements (4) are supported on the housing (3) of the battery module (1) via a load distribution structure (11).

13. Vehicle comprising at least one battery module according to one of the preceding claims.

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