Battery module with multiple individual battery cells

Abstract

The invention relates to a battery module (2) with a number of individual battery cells (3) formed as circular cells, which are arranged one behind the other in a number of rows and are electrically connected in series in each row, characterized in that each row is arranged in a closed tubular volume (1) and in that the tubular volume (1) of the row is provided with a device for disconnecting the electrical contacts of at least one row in the event of an impermissible pressure buildup in at least one of the individual battery cells (3).

Description

[Technical Field]

[0001] The present invention relates to a battery module comprising a plurality of individual battery cells as defined in more detail in the preamble of claim 1. [Background technology]

[0002] Batteries consisting of battery modules with several individual battery cells are known in the prior art. A typical construction of the individual battery cells is a so-called circular cell configuration. This allows for various arrangements. For example, Patent Document 1 describes a battery module in which several circular cells are grouped around a free space. Preferably, this grouping is carried out in a hexagonal arrangement, where the free space can be filled with a material with good thermal conductivity or can be formed as a channel for the flow of a cooling medium. Another construction in which several individual battery cells are arranged in series as circular cells and are therefore electrically connected to each other is also known, for example, from Patent Document 2.

[0003] When battery modules of this type are used in vehicles to provide electrical drive power, they typically have a relatively high energy density. According to the prior art, lithium-ion cells are often used for this purpose. If a thermal problem occurs in one of the cells and an overpressure subsequently develops, this can lead to so-called thermal runaway, i.e., uncontrollable heat generation throughout the battery module. To counter this, the housings of the individual battery cells have rupture elements that, if an overpressure develops in an individual battery cell, open the housing, thereby relieving the overpressure and removing the electrolyte from the individual battery cell. Ideally, this allows thermal runaway to be limited to one or a few cells, which is highly advantageous in terms of the safety of batteries constructed from such battery modules.

[0004] The resulting hot gases, also known as vent gases, can be flammable or explosive, so ignition of the gases, for example by a short circuit or an electric arc, should be prevented as much as possible.

[0005] Patent Document 3 describes a vehicle battery that is composed of multiple individual modules. Each module contains individual battery cells, each of which has a current interruption device (CID) to interrupt the flow of current from the individual battery cells when a pressure rise occurs during thermal runaway of the battery.

[0006] A similar concept is also described in Patent Document 4. This publication also describes, in another embodiment, connecting a plurality of individual cells together and providing a common CID for each of the connected series of individual cells.

[0007] Patent document 5 describes a battery in which a number of individual circular battery cells are arranged within a common closed tube. For further prior art, see also U.S. Patent Nos. 5,299,999, 6,399,049, 6,399,052, and 6,399,052, which essentially describe devices for reducing pressure in individual battery cells, such as by means of a rupture member that opens when a pressure increase occurs, thereby relieving excess pressure. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] DE102009000673A1 [Patent Document 2] DE102016103667A1 [Patent Document 3] EP2557615A1 [Patent Document 4] JP2011-135657A [Patent Document 5] JP2019-145490A [Patent Document 6] US2013 / 0280559A1 [Patent Document 7] DE102017212223A1 [Patent Document 8] DE102008013188A1 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to provide an improved battery module with a plurality of individual battery cells formed as circular cells, and to ensure a safe operation of such a battery module. [Means for solving the problem]

[0010] According to the invention, this problem is solved by a battery module having the features of claim 1, and here in particular the features recited in the characterizing part of claim 1. Advantageous configurations and developments emerge from the claims dependent on the independent claims.

[0011] The battery module according to the present invention includes a plurality of individual battery cells formed as circular cells, which are arranged one after the other in a plurality of rows. The circular cells in each row are electrically connected in series with one another, for example, by forming the cup-shaped housing of each individual battery cell as a negative electrode and a forward-projecting positive electrode, and arranging the individual battery cells one after the other and thereby connecting them in series, similar to batteries for use in small devices. According to the present invention, each row is arranged in a closed tubular volume. Here, a device is provided for disconnecting the electrical contact of at least one row in the event of an unacceptable pressure buildup in at least one of the individual battery cells in the tubular volume of the row. That is, when heat propagation or thermal runaway occurs in one of the individual battery cells, a pressure buildup typically occurs in that cell. Subsequently, a rupture element in the cell's cup ruptures when a critical pressure limit is exceeded, allowing vent gas to escape from the individual battery cell. This vent gas reaches the tubular volume of the corresponding row and causes a pressure buildup there.

[0012] In the battery module according to the present invention, if such an unacceptable pressure rise occurs, the string is electrically disconnected from the other strings of battery modules via a device for disconnecting the electrical contacts of the string, and, if necessary, further disconnects the battery modules forming the battery. This interrupts the current path at a relatively low voltage level determined only by the number of individual battery cells in the string. This significantly reduces the potential ignition voltage that could ignite the vent gas, which is a decisive advantage in terms of safety.

[0013] The battery module according to the invention is formed with at least one electrical contact plate that is in electrical contact with at least two of the rows. These rows can then be connected in various ways within the module depending on the number of rows. That is, the rows can be connected, for example, all in parallel, all in series, or in groups connected in parallel or series, with the groups themselves being connected in series or parallel to one another. All of this can be achieved via one or more electrical contact plates, which are preferably arranged at the end or beginning of the corresponding tubular volumes and the rows of individual battery cells arranged therein.

[0014] According to the invention, the contact plate is configured as a rupture element. The electrical contact plate is connected to the housing of the battery module in such a way that it bursts open in the event of an overpressure. This, on the one hand, reduces the pressure load in the tubular volume, and, on the other hand, disconnects the electrical contacts of all rows in contact with each plate in the battery module. Additionally or alternatively, an actuator can be provided to burst the contact plate, for example via a pyrotechnical charge, in order to remove the contact plate when a pressure increase is detected directly or indirectly via a sensor.

[0015] In an advantageous configuration of the invention, the device can have a detection device for at least indirectly detecting the pressure increase and at least one actuator that is triggered thereby, i.e., the pressure can be detected directly or indirectly and thereby trigger an actuator, which can be, for example, the triggering of a pyro-fuse for breaking an electrical contact or for rupturing contact members in a row of individual battery cells.

[0016] This variation, using a direct or indirect pressure sensor, has the additional advantage that the current path can already be opened before the pressure rises enough to release vent gas, which may potentially ignite after release. Thus, the risk of vent gas ignition is further reduced.

[0017] According to another highly preferred configuration of the battery module according to the invention, the device can furthermore have a rupture element which forms an electrical contact or on which a conductor forming this electrical contact extends, i.e., this rupture element for the tubular volume of the corresponding row automatically ruptures in the event of a critical overpressure, thereby releasing the overpressure to the surroundings, preferably along a predetermined safe vent path. In this configuration of the device, the rupture element ruptures and simultaneously breaks the electrical contact, either by being formed by the rupture element itself or by a conductor extending over the target rupture point of the rupture element, which breaks when the rupture element ruptures, thereby interrupting the current path.

[0018] In a highly preferred development of the battery module according to the invention, at least one flow channel is formed between a row of individual battery cells and the wall of the tubular volume. Such a flow channel allows gas escaping from one of the individual battery cells to be safely and reliably guided within the tubular volume, for example, to reach a rupture element arranged at the beginning or end of the tubular volume without the need to previously deform the tubular volume. Such a channel can be provided, for example, by a ribbed surface of the wall of the tubular volume.

[0019] According to a highly preferred development of the battery module of the present invention, the flow paths can be realized by spirally winding a flexible material, such as a wire or strand or a resilient circular material, or a band made of elastomer, plastic, etc., around the individual battery cells. When these are introduced together into the tubular volume, a spiral channel is formed. A sufficiently flexible material, such as a rubber strand with an oval or circular cross section, can ensure a secure fixation of the individual battery cells in the tubular volume without at the same time preventing potential movements of the individual battery cells during charging and discharging, which would cause them to slightly increase or decrease in diameter.

[0020] According to a highly preferred development of the battery module according to the invention, at least one tubular volume can be arranged adjacent to a channel through which a coolant flows, in particular in the form of a complete or partial hexagonal arrangement of a plurality of such tubular volumes around the coolant channel.

[0021] The cooling medium channels can be connected to the cooling medium channels via pressure protection and / or fuses made of a material that ruptures and / or melts in the event of thermal runaway, thereby allowing vent gas to be discharged not only into a housing around, for example, a plurality of such battery modules, but also into the cooling medium channels, so that the vent gas can be cooled in a desired manner and discharged together with the cooling medium.

[0022] In addition to the vent path thus defined via the cooling medium, the intentional positioning of rupture points / target rupture points at each end of the tubular volume also allows the vent channel to exit the battery module and reach a battery housing that surrounds the battery module in a very advantageous configuration, from which the gas can then be discharged in a known manner, typically via a separate rupture member and via the vent channel, in a completely intentional manner, to a non-critical area outside the battery.

[0023] Further advantageous configurations of the battery module according to the invention emerge from the further dependent claims and from the detailed description of the exemplary embodiments which follow with reference to the drawings. [Brief explanation of the drawings]

[0024] [Figure 1] 2 shows a schematic layout of a portion of a battery module according to the invention during normal operation; [Figure 2] 2 shows a view similar to FIG. 1 when a thermal event occurs in the first embodiment; [Figure 3] 1 during the occurrence of a thermal event in a second embodiment; [Figure 4] 1 shows a schematic diagram of a rupture member in a battery module according to the invention during normal operation. [Figure 5] 5 shows a view similar to FIG. 4 during the occurrence of a thermal event. [Figure 6] 1 shows a plan view of a battery with multiple battery modules according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0025] FIG. 1 shows a diagrammatically indicated tubular volume 1 of a battery module 2. In the illustrated embodiment, four individual battery cells 3 are arranged in series, one behind the other, in this tubular volume 1. The individual battery cells 3 are electrically connected in series, for example, by the cup-shaped housing of each individual battery cell 3 forming the negative battery pole and the individual battery cells 3 forming the positive battery pole 4 on their left side in FIG. 1. When the individual battery cells 3 are inserted one behind the other into the tubular volume 1 and pressed against each other, for example, by a negative contact plate 5 and a spring 6 on the right side and by a positive contact plate 7 on the left side, the individual battery cells 3 are connected in series, and a voltage corresponding to their number is applied between the two contact plates 5, 7.

[0026] In the illustrated embodiment, if one individual battery cell 3 of the array of individual battery cells 3 experiences thermal runaway and vent gas migrates into the region of the annular volume 1, a string-like member 8 is spirally wound around the individual battery cell 3 to create a spiral path for the resulting vent gas. The string 8 can be formed, for example, as a rubber band, wire, or twisted wire, and securely holds the individual battery cell 3 in place while at the same time allowing the individual battery cell 3 to breathe to some extent, exhibiting volumetric expansion and contraction during charging and discharging. Adjacent to the tubular volume 1, FIG. 1 also suggests a cooling medium channel 9 through which a fluid cooling medium, or possibly a gaseous cooling medium, flows according to the arrows, thereby ensuring that waste heat generated in the region of the individual battery cell 3 is removed.

[0027] If a thermal event occurs in one of the individual battery cells 3 in the tubular volume 1, an overpressure of vent gas is generated and spreads within the volume 1. The tubular volume 1 has, for example, a target rupture point or rupture element in the region of its positive contact plate 7, which in such a case tears and opens a ventilation path for the gas. This is indicated in FIG. 2 by the contact plate 7 being connected to the housing 12 of the battery module 2 by a target rupture point. This contact plate 7 can, for example, be glued to the housing 12 so that it detaches in the event of a critical overpressure occurring within the volume 1. The vent gas, symbolically represented by arrow 10, is then released, for example, into a battery housing (not shown) from which it is vented in a targeted manner to a non-critical area.

[0028] The splitting of the positive contact plate 7 reduces the pressure load, but at the same time also interrupts the electrical contact of the row of individual battery cells 3 within the tubular volume 1. In this case, 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 that could ignite the vent gas, which increases safety.

[0029] In principle, it is sufficient to remove from the current path the relevant string of individual battery cells, including the cell 3 experiencing thermal runaway. However, if there are several strings of individual battery cells 3, it is preferable to cut all current paths within the battery module 2. This can ideally be achieved by tearing off all contact plates 7.

[0030] In Figure 3, an alternative variant embodiment is shown in a view similar to Figure 2. Instead of the contact plates 7 splitting open, on the one hand to reduce the pressure load in the tubular volume 1 and, on the other hand, to break the electrical contacts of the individual battery cells 3 of the string, a pressure sensor 14 can now be seen, which is connected to an actuator 15, for example a pyroelectric charge, in order to split the contact plates in the event of a pressure increase or to assist this splitting by the force of the pressure increase.

[0031] Another passive possibility, substantially similar to the variant described in FIG. 2 , in which the contact plate 7 is completely torn open can be seen in FIGS. 4 and 5 . FIG. 4 shows the unbroken state. Here, a non-conductive closing plate 17, which closes the tubular volume 1, replaces the electrical contact plate 7 shown in FIG. 2 . This non-conductive closing plate 17 has a rupture element, designated 18, which is configured as a disk connected across a target rupture point 19. Electrical conductors 20 extend over the rupture element 18, via which a correspondingly associated row of individual battery cells 3 is electrically contacted. FIG. 5 shows the case where a pressure buildup has already occurred in the tubular volume 1. The disk of the rupture element 18 has torn along the target rupture point 19. As again indicated by the arrow designated 10, vent gas escapes through the opening created by the rupture element 18. At the same time that the rupture member 18 ruptures, the electrical conductor 20 is also destroyed, resulting in the interruption of the electrical contact of the individual battery cells 3 of the string that was previously established via this conductor 20. Unlike the use of a sensor, this structure acts purely passively, similar to the structure described in FIG.

[0032] FIG. 6 shows an entire battery 11 made up of a number of such battery modules 2. Each battery module 2 includes a cooling channel 9, which is arranged in the center of a hexagonal arrangement of six tubular volumes 1 in which individual battery cells 3 are correspondingly installed. Alternatively, it is also conceivable to provide seven volumes 1 with individual battery cells 3, in which case such cooling is not necessary and the cooling channel can be omitted because cooling is arranged between the volumes 1 or occurs, for example, via one of the head plates 5, 7. Each battery module 2 can have an individual positive contact plate 7 on one side and a negative contact plate on the other side, which can be split open in the event of heat transfer to the battery cells 3 in one of the tubular volumes 1, i.e., in the event of thermal runaway, so that the battery module 2, or the individual battery cells 3 installed therein, are electrically disconnected at a relatively low voltage level in the series circuit inside each of the tubular volumes 1.

[0033] In the battery module 2 shown at the far left here, a ring-shaped contact plate 7 is shown by way of example only, via which all rows of individual battery cells 3 in the tubular volumes 1 can be electrically connected in parallel. If this contact plate is torn open in the event of overpressure in one or more of the tubular volumes 1, all rows of individual battery cells 3 are electrically disconnected, and as a result the entire battery module 2 is electrically isolated.

[0034] To adapt this structure to a battery housing enclosing individual battery modules 2, not shown here, it can be filled, for example, with half a battery module with only three volumes 1 and half a cooling channel 9, not shown, or a hollow portion can be provided, such as suggested here by the space 13, which can have electrical terminals for electronic components, such as a battery management system, or electrical components, such as the entire battery 11.

Claims

1. A battery module (2) comprising a plurality of individual battery cells (3) formed as circular cells, the individual battery cells (3) being arranged one after the other in a plurality of rows and electrically connected in series within each of the rows, The battery module (2) is characterized in that each of the rows is arranged in a closed tubular volume (1), and a device for disconnecting the electrical contact of the plurality of rows in the event of an unacceptable pressure increase in at least one of the individual battery cells (3) is provided in the tubular volume (1) of the plurality of rows, wherein for this purpose an electrical contact plate (7) is formed in electrical contact with the plurality of rows, the electrical contact plate (7) being configured as a rupture member that, when ruptured, electrically disconnects all of the rows, or an actuator (15) is provided that, when activated, electrically disconnects the electrical contact plate (7) from all of the rows.

2. 2. The battery module (2) according to claim 1, characterized in that the device comprises a detection device (14) for at least indirectly detecting a pressure increase and at least one actuator (15) triggered by said detection.

3. 3. The battery module (2) according to claim 1 or 2, characterized in that the device has a rupture member (18), the rupture member (18) forming the electrical contact, or the conductor (20) forming the electrical contact extending on the rupture member (18).

4. 3. The battery module (2) according to claim 1 or 2, characterized in that at least one flow path is formed between the individual battery cells (3) of each row and the material (12) surrounding the tubular volume (1), the flow path being provided by spirally wrapping a flexible material (8) around the individual battery cells (3) before introducing them into the tubular volume (1).

5. 3. The battery module (2) according to claim 1 or 2, characterized in that the tubular volumes (1) are arranged adjacent to a cooling medium channel (9), and a plurality of the tubular volumes (1) are grouped around the cooling medium channel (9).

6. 6. Battery module (2) according to claim 5, characterized in that the tubular volumes (1) are grouped in a complete or partial hexagonal arrangement around the cooling medium channels (9).

7. 6. The battery module (2) according to claim 5, characterized in that the cooling medium channel (9) is connected to at least one of the tubular volumes (1) via a pressure protection and / or a fuse.

8. 4. The battery module (2) according to claim 3, characterized in that a path for the escape of gas (10) into a housing of a battery (11) surrounding the battery module (2) can be opened through the rupture member.

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