BATTERY MODULE WITH MULTIPLE BATTERY CELLS

Description

[0001] The invention relates to a battery module with a plurality of individual battery cells according to the type defined in more detail in the preamble of claim 1.

[0002] Batteries constructed from battery modules with multiple individual battery cells are known from the prior art. A typical design for the individual battery cells is the so-called round cell configuration. This allows for various arrangements. DE 10 2009 000 673 A1, for example, describes a battery module in which a plurality of round cells are grouped around a free space. This can preferably be done in a hexagonal arrangement, wherein the free space can be filled with a material with good thermal conductivity or can also be designed as a channel for the flow of a cooling medium. Another design in which several of the individual battery cells are arranged one behind the other in the form of round cells and are thus electrically interconnected is also known, for example, from DE 10 2016 103 667 A1.

[0003] If such battery modules are used to provide electric drive power in a vehicle, they typically have a relatively high energy density. Lithium-ion cells are often used for this purpose according to the current state of the art. If a thermal problem occurs within one of the cells, excess pressure builds up and can lead to a so-called thermal runaway, i.e. thermal failure of the entire battery module. To counteract this, the housings of the individual battery cells have bursting elements which, in the event of excess pressure within the individual battery cell, open the housing to relieve the excess pressure and remove the electrolyte from the individual battery cell. This means that thermal runaway can ideally be limited to one or a few cells, which is a decisive advantage with regard to the safety of a battery constructed from such battery modules.

[0004] The hot gases released during this process, also known as venting gases, can be flammable or even explosive. Therefore, ignition of these gases, for example, through a short circuit or an arc, should be prevented if possible.

[0005] EP 2 557 615 A1 describes a battery for a motor vehicle consisting of several individual modules. Individual battery cells are arranged within the modules. Each of these cells has a current interruption device (CID) to interrupt the current flow from the respective individual battery cell in the event of a pressure increase due to thermal runaway of the battery.

[0006] Something similar is also described in JP 2011-135657 A. In a further embodiment, this also involves connecting several individual cells together and providing each of these series of interconnected individual cells with a common CID.

[0007] JP 2019-145490 A describes a battery in which several round individual battery cells are arranged in a common sealed tube.

[0008] For further prior art, reference can also be made to DE 10 2019 216 606 A1, US 2013 / 0280559 A1, DE 10 2017 212 223 A1, and DE 10 2008 013 188 A1. These essentially show devices for pressure reduction in individual battery cells, which ensure the discharge of excess pressure by means of bursting elements or the like that rupture in the event of a pressure increase.

[0009] The object of the present invention is to provide an improved battery module with a plurality of individual battery cells designed as round cells, which enables safe operation of such a battery module.

[0010] According to the invention, this object is achieved by a battery module having the features in claim 1, and here in particular in the characterizing part of claim 1.

[0011] Advantageous embodiments and further developments result from the dependent claims.

[0012] The battery module according to the invention comprises a plurality of individual battery cells designed as round cells, which are arranged one behind the other in several strings. The round cells of each individual string are electrically connected in series, which can be achieved, for example, by designing the cup-shaped housing of each of the individual battery cells as a negative pole and forward-projecting positive poles, so that they can be placed one behind the other and thus connected in series - similar to batteries for use in small appliances. According to the invention, each of the strings is arranged in a closed tubular volume. A device for severing the electrical contact of at least one string in the event of an unauthorized pressure increase in at least one of the individual battery cells is provided in the tubular volume of the string.If thermal propagation or thermal runaway occurs in one of the individual battery cells, a pressure increase typically occurs within that cell. A burst element in the cell's can will then rupture at a critical pressure limit, and the venting gases will flow out of the individual battery cell. These then enter the tubular volume of the affected string, causing a pressure increase there.

[0013] In the battery module according to the invention, the device for severing the electrical contact of the strand electrically separates this strand from the other strands of the battery module and, if applicable, other battery modules forming the battery in the event of such an unauthorized pressure increase. This interrupts the current path at a relatively low voltage level, which is defined solely by the number of individual battery cells within the strand. This significantly reduces the potential ignition voltage available to ignite the venting gases, which represents a decisive safety advantage.

[0014] The battery module according to the invention features at least one electrical contact plate that electrically contacts at least two of the strings. The strings can be interconnected differently within the module depending on the number of strings. For example, they can all be interconnected in parallel or in series, or they can be interconnected in parallel or in series in groups, with these groups then in turn being interconnected in series or in parallel. All of this can be accomplished via one or more electrical contact plates, which are preferably arranged at the end and beginning of the corresponding tubular volumes and the strings of the individual battery cells arranged therein.

[0015] It is further provided that at least one flow channel is formed between the individual battery cells of the row and the wall of the tubular volume. Such a flow channel ensures that gases escaping from one of the individual battery cells are safely and reliably guided within the tubular volume and, for example, reach a bursting element arranged at the beginning or end of the tubular volume without first deforming the tubular volume. Such channels can be created, for example, by a ribbed surface of the wall of the tubular volume.

[0016] According to the invention, this contact plate is designed as a bursting element. The electrical contact plate is connected to a housing of the battery module in such a way that it is blown off in the event of excess pressure. This enables pressure relief within the tubular volume and, on the other hand, disconnects the electrical connections of all strands within the battery module that are in contact with the respective plate. Additionally or alternatively, an actuator can also be provided to remove the contact plate, for example, to blow it off via a pyrotechnic charge if a pressure increase has been detected directly or indirectly by a sensor.

[0017] In an advantageous embodiment of the invention, the device can comprise a detection device for at least indirectly detecting the pressure increase and at least one actuator triggered thereby. The pressure can thus be detected directly or indirectly, which can trigger an actuator. This can, for example, trigger a pyroelectric fuse to break the electrical contact or to blow off a contact element from the string of individual battery cells.

[0018] This variant, with a direct or indirect pressure sensor, offers the additional advantage of allowing the current paths to open before the pressure has risen to the point where venting gases are released, which could then potentially ignite. This further reduces the risk of ignition of the venting gases.

[0019] According to a further very advantageous embodiment of the battery module according to the invention, it can further be provided that the device has a bursting element, wherein this forms the electrical contact or a conductor forming this contact runs over the bursting element. This bursting element for the tubular volume of the affected strand will therefore rupture automatically in the event of a critical overpressure in order to release the overpressure into the environment, preferably along a predetermined safe venting path. With this embodiment of the device, when the bursting element ruptures, the electrical contact is simultaneously destroyed, either by being formed by the bursting element itself or by a conductor running over the predetermined breaking point of the bursting element, which is destroyed when the bursting element is triggered in order to interrupt the current path.

[0020] According to an exceptionally advantageous development of the battery module according to the invention, it can also be provided that the flow channel is created by spirally wrapping the individual battery cells with a flexible material such as a wire or stranded wire, or even an elastic round material or band made of elastomer, plastic, or the like. When these are then introduced together into the tubular volume, a spiral-shaped channel is formed. With a sufficiently flexible material, such as a rubber strand with an oval or round cross-section, a secure fixation of the individual battery cells within the tubular volume can be ensured at the same time, without hindering their potential movement during charging and discharging, during which the individual battery cells become somewhat larger and somewhat smaller in terms of their diameter.

[0021] According to an exceptionally advantageous development of the battery module according to the invention, the at least one tubular volume can be arranged adjacent to a channel through which a cooling medium flows. In particular, this can be a fully or partially hexagonal arrangement of several such tubular volumes around the cooling medium channel.

[0022] The cooling medium channel can be connected to the cooling channel via a pressure and / or fusible link made of a material that breaks and / or melts in the event of thermal runaway. This would allow venting gases to be diverted not (only) into the housing surrounding several such battery modules, for example, but into the cooling medium channel, allowing the venting gases to be specifically cooled and dissipated with the cooling medium.

[0023] In addition to such a defined venting path via the cooling medium, a venting channel can also be created from the battery module into a battery housing surrounding the battery module according to a very advantageous embodiment by specifically arranging the bursting point / predetermined breaking point at one end of the tubular volume, from which the gases can then be diverted in a manner known per se, typically via a further bursting element and a venting channel, in a very targeted manner into a non-critical area outside the battery.

[0024] Further advantageous embodiments of the battery module according to the invention also emerge from the further dependent subclaims and become clear from the exemplary embodiment which is described in more detail below with reference to the figures.

[0025] Showing: Fig. 1 shows a schematic arrangement of a part of a battery module according to the invention in regular operation; Fig. 2 shows a representation analogous to that in Fig. 1 in the case of a thermal event in a first embodiment; Fig. 3 a representation analogous to that in Fig. 1 in the event of a thermal event in a second embodiment; Fig. 4 a schematic representation of a bursting element in the battery module according to the invention in regular operation; Fig. 5 a representation analogous to that in Fig. 4 in the event of a thermal event; and Fig. 6 shows a plan view of a battery with several battery modules according to the invention.

[0026] In the presentation of the Figure 1A tubular volume 1 of a battery module 2 is schematically indicated. In this tubular volume 1, four individual battery cells 3 are arranged one behind the other in the exemplary embodiment shown here. They are electrically connected in series with one another, for example, by their cup-shaped housings forming the negative battery terminal and a positive battery terminal 4 in the illustration of the Figure 1 the individual battery cells 3 are formed on their left side. If the individual battery cells 3 are now inserted one after the other into the tubular volume 1 and pressed together, for example by a negative contact plate 5 and a spring 6 on the right side and a positive contact plate 7 on the left side, the individual battery cells 3 are then connected in series with one another and a voltage corresponding to their number is applied between the two contact plates 5, 7.

[0027] In the event that one of the individual battery cells 3 of this string of individual battery cells 3 thermally breaks down and venting gases escape into the area of the tubular volume 1, the individual battery cells 3 in the embodiment shown here are spirally wound with a cord-shaped element 8 in order to create a spiral path for any venting gases. The cord 8, which can be designed, for example, as a rubber cord, a wire, a stranded wire or the like, also holds the individual battery cells 3 securely in position in the tubular volume 1 and at the same time allows a certain amount of breathing of the individual battery cells 3, which refers to the increase and decrease in volume during charging and discharging. Adjacent to the tubular volume 1 in the illustration of the Figure 1also indicated is a cooling medium channel 9, through which, as indicated by the arrows, a liquid or possibly also gaseous cooling medium flows in order to reliably dissipate waste heat generated in the area of the individual battery cells 3.

[0028] If the aforementioned thermal event occurs in one of the individual battery cells 3 within the tubular volume 1, the resulting overpressure of the venting gases will spread within the volume 1. The tubular volume 1 now has, for example, predetermined breaking points or bursting elements in the area of its positive contact plate 7, which rupture in such a case and release a venting path for the gases. This is shown in the illustration of the Figure 2indicated by the contact plate 7, which is connected to a housing 12 of the battery module 2 by means of a predetermined breaking point. This can, for example, be glued to the housing 12 in such a way that it detaches in the event of a critical overpressure in the volume 1. The venting gases symbolized by the arrows 10 are then released, for example, into a battery housing (not shown here) and from there diverted specifically into a non-critical area.

[0029] By breaking off the positive contact plate 7, pressure is released. At the same time, however, the electrical contact between the string of individual battery cells 3 in the tubular volume 1 is interrupted. The voltage is interrupted at a relatively low level, since only the voltage of the individual battery cells 3 located within the volume 1 is present. This reduces the potential ignition voltage available to ignite the venting gases, which increases safety.

[0030] In principle, it is sufficient to remove the affected string of individual battery cells 3 with the thermally continuous cell 3 from the current path. However, it is preferable to separate all current paths within the battery module 2 if multiple strings of individual battery cells 3 are present. This can ideally be achieved by detaching the entire contact plate 7.

[0031] In Figure 3is analogous to the representation in Figure 2 An alternative embodiment is shown. Instead of detaching the contact plate 7, on the one hand to relieve pressure in the tubular volume 1 and, on the other hand, to disconnect the electrical contact of the individual battery cells 3 of the string, a pressure sensor 14 can be seen here, which is connected to an actuator 15, for example a pyroelectric charge, in order to detach the contact plate 7 in the event of a pressure increase or to assist its detachment through the forces of the pressure increase.

[0032] Another passive option essentially analogous to that in Figure 2 The variant described, in which the contact plate 7 is completely blasted off, is shown in the illustrations of the Figures 4 and 5 to recognize. In Figure 4 The undamaged state can be seen. In place of the electrical contact plate 7 in the illustration of the Figure 2An electrically non-conductive closure plate 17 is used here, which closes the tubular volume 1. This electrically non-conductive closure plate 17 has a bursting element designated 18, which is designed here as a disc connected via a predetermined breaking point 19. An electrical conductor 20 runs over the bursting element 18, via which the corresponding assigned string of the individual battery cells 3 is electrically contacted. In the illustration of the Figure 5The case is now shown in which the pressure increase within the tubular volume 1 has already occurred. The disc of the bursting element 18 has torn open along the predetermined breaking point 19. As indicated by the two arrows, again labeled 10, venting gas flows out of the opening created by the bursting element 18 tearing open. Simultaneously with the tearing open of the bursting element 18, the electrical conductor 20 is also destroyed, so that the electrical contact previously established via it between the individual battery cells 3 of the string is interrupted. In contrast to the use of a sensor, this structure is similar to that in Figure 2 The structure described has a purely passive effect.

[0033] In the presentation of the Figure 6an overall battery 11 can now be seen, which is made up of several such battery modules 2. Each of the battery modules 2 comprises the cooling channel 9, which here is arranged centrally within a hexagonal arrangement of six of the tubular volumes 1, which are then correspondingly equipped with the individual battery cells 3. Alternatively, seven volumes 1 with individual battery cells 3 would also be conceivable if the cooling channel can be dispensed with because cooling is unnecessary, is arranged between the volumes 1 or, for example, takes place via one of the head plates 5, 7. Each of the battery modules 2 can have a single positive contact plate 7 on one side and a negative contact plate on the other side, which offers the possibility of being blown off in the event of thermal propagation, i.e. thermal runaway of the battery cells 3 in one of the volumes 1, in order toto electrically separate the individual battery cells 3 installed therein at a relatively low voltage level of the series connection within each of the tubular volumes 1.

[0034] In the battery module 2 shown on the far left, a ring-shaped contact plate 7 is shown purely as an example, via which an electrical parallel connection of all strings of individual battery cells 3 in the tubular volumes 1 can be established. If this contact plate is blown off in the event of overpressure in one or more of the tubular volumes 1, all strings of individual battery cells 3 are electrically disconnected, so that the entire battery module 2 is electrically switched off.

[0035] In order to adapt the structure to a battery housing (not shown here) surrounding the individual battery modules 2, cavities can be provided which can be filled, for example, by half battery modules (not shown) with only three of the volumes 1 and half a cooling channel 9, or which can have, for example, as indicated here by the space designated 13, electronic components such as a battery management system or electrical components such as electrical connections for the entire battery 11.

Claims

1. Battery module (2) comprising a plurality of individual battery cells (3) designed as round cells, which individual battery cells are arranged one behind the other in a plurality of branches and are electrically connected in series within the relevant branch, characterized in that each of the branches is arranged in a closed tubular volume (1), wherein an apparatus is provided for severing the electrical contact of at least one branch in the event of an unauthorized increase in pressure in at least one of the individual battery cells (3) within the tubular volume (1) of this branch, for which purpose at least one electrical contact plate (5, 7) is formed, which electrically contacts at least two of the branches, wherein the electrical contact plate (7) is designed as a rupture element, or an actuator (15) is provided which is designed to separate the electrical contact plate (7) from the branches in the event of an actuation, and wherein at least one flow channel is formed between the individual battery cells (3) of the relevant branch and the material (12) surrounding the tubular volume (1).

2. Battery module (2) according to claim 1, characterized in that the apparatus has a detection device (14) for at least indirectly detecting the pressure increase, and at least one actuator (15) which is triggered thereby.

3. Battery module (2) according to claim 1 or claim 2, characterized in that the apparatus has a rupture element (18), wherein this forms the electrical contact, or a conductor (20) forming this electrical contact extends across the rupture element (18).

4. Battery module (2) according to any of claims 1 to 3, characterized in that the flow channel is provided by helically wrapping the individual battery cells (3) with a flexible material (8) before introduction into the tubular volume (1).

5. Battery module (2) according to any of claims 1 to 4, characterized in that the tubular volumes (1) are arranged adjacent to a cooling media channel (9), wherein preferably a plurality of the tubular volumes (1) are grouped around a cooling media channel (9).

6. Battery module (2) according to claim 5, characterized in that the tubular volumes (1) are grouped in a completely or partially hexagonal arrangement around the cooling media channel (9).

7. Battery module (2) according to either claim 5 or claim 6, characterized in that the cooling media channel (9) is connected to at least one of the tubular volumes (1) via a pressure release device and / or a fuse.

8. Battery module (2) according to any of claims 3 to 7, characterized in that a path for escaping gases (10) can be opened into a housing of a battery (11) surrounding the battery module (2) by means of the rupture element.