Prismatic battery cell and battery

Abstract

The invention relates to a prismatic battery cell (1), in particular for a battery (100) of a motor vehicle, having at least one electrode stack (10), a rectangular tubular housing body (4), in which the electrode stack (10) is accommodated and which has four wall surfaces (20, 22, 24), and two housing covers (8), by means of which opposite housing openings of the housing body (4) are closed in order to close off a housing interior. The battery cell (1) additionally has a bursting membrane (30) that is incorporated into one of the four wall surfaces (20, 22, 24) for irreversibly opening the housing interior when a specified internal pressure value is exceeded, and a unidirectional degassing element (42) that comprises a gas-permeable membrane arranged on a degassing opening (40) formed in one of the housing covers (8) so as to cover same.

Description

[0001] Description

[0002] Prismatic battery cell and battery

[0003] The invention relates to a prismatic battery cell, in particular for a battery, preferably for a motor vehicle. The invention also relates to such a battery.

[0004] With the increasing electrification of motor vehicles, as well as buildings and similar structures, energy storage devices, specifically rechargeable batteries, are being used more frequently. Particularly in (land-based) vehicles, these batteries serve to provide energy for electric motor drives, such as traction motors, and are also referred to as "traction batteries." Such batteries are typically composed of multiple individual battery cells (secondary cells). Each battery cell has at least one pair of opposing electrodes (anode and cathode), which are usually galvanically separated by a separator. Liquid electrolytes are most commonly used, in which the electrodes are arranged and which enable charge transport—usually in the form of ions—between the electrodes (and especially through the separator).A battery cell typically contains several pairs of electrodes, which together form an electrode stack. This electrode stack is enclosed in a (cell) casing, from which connection contacts lead to the electrodes. Several of these battery cells are then connected together to form the battery and usually housed in a larger casing.

[0005] Battery cells are generally available in three cell shapes: prismatic (i.e., box- or cage-like), cylindrical (usually in the form of a circular cylindrical rod), and pouch cells. In pouch cells, the electrodes and electrolytes are stacked flat and layered, sealed fluid-tight in a flexible, usually rectangular, pouch. Prismatic cells typically have a relatively rigid housing, often deep-drawn from a sheet of metal.

[0006] Depending on the cell chemistry (i.e., especially the composition of the electrodes and the electrolyte), but also due to operating influences, gas formation can occur within the battery cells. Such gas formation leads to increased internal pressure in the battery cell. This increased internal pressure can, in turn, compress the layers, especially the electrodes, so that contact occurs and consequently a short circuit. The latter can then trigger a thermal reaction with the release of extreme heat. Such an exothermic reaction can spread to other battery cells and thereby cause a so-called "thermal runaway," a chain reaction in which many battery cells overheat and consequently also undergo an exothermic reaction in these battery cells, which further fuels heat generation and the spread to other battery cells.

[0007] Such situations are known to be avoided. To this end, control-related measures (e.g., temperature monitoring, selective shutdown of individual battery cells or at least groups of cells) and preventive measures (e.g., cooling of the battery cells) are known. For example, US 2021 / 0320375 A1 discloses a degassing unit with a semipermeable membrane that allows continuous gas release from the housing while preventing the ingress of moisture and other contaminants. DE 10 2022 205 365 A1 also discloses a gas-permeable membrane that seals a housing opening, in particular one that is liquid- and / or gas-tight around the housing opening. The membrane is covered on the outside of the housing by a cover element to limit the ingress of substances into the housing.Optionally, a valve is arranged in the cover element, which serves to influence the gas outlet from the housing, e.g. depending on a pressure difference between the housing's internal pressure and the ambient pressure.

[0008] The invention is based on the objective of enabling a further improvement in the safety of a battery cell.

[0009] This problem is solved according to the invention by a prismatic battery cell having the features of claim 1. Furthermore, this problem is solved according to the invention by a battery having the features of claim 10. Further advantageous and partly inventive embodiments and developments of the inventions are set out in the dependent claims and the following description.

[0010] The battery cell according to the invention is a prismatic battery cell. It is specifically designed and intended for use in a battery (traction battery) of a motor vehicle. The battery cell comprises at least one electrode stack, a rectangular tubular housing body in which the electrode stack is received and which has four wall surfaces, and two housing covers by means of which opposing housing openings of the housing body are closed to seal off an interior space. The battery cell has a burst membrane integrated into one of the four wall surfaces for the irreversible opening of the interior space when a predetermined internal pressure value (also: burst pressure value) is exceeded. Furthermore, the battery cell has a unidirectional degassing element comprising a gas-permeable membrane that is arranged to cover a degassing opening formed in one of the housing covers.In other words, at least one of the two housing covers has a degassing opening which is sealed (especially fluid-tight) by means of the degassing element.

[0011] Preferably, the membrane is permeable to gases, e.g., CO, CO2, H2, and / or CH4, but impermeable to moisture (vapor and / or liquid) or at least exhibits increased resistance to permeation. This prevents moisture from entering the housing interior. This membrane thus advantageously allows gas exchange, at least from the housing interior to the environment. In particular, since such gas exchange is usually driven by a pressure differential, the ingress of gases into the housing interior is prevented or minimized, as there is typically a pressure gradient between the housing interior and the environment. The membrane also allows for continuous degassing of the housing interior. Optionally, the degassing element can also have a cover that protects the membrane from damage and / or contact with environmental media (moisture, contaminants, etc.).) protects. Optionally, this cover can also incorporate a valve function that can influence the pressure differential between the housing interior and the environment, thus controlling the gas passage through the membrane. Preferably, the degassing element is designed to be comparable to or in accordance with DE 102022 205 365 A1, the contents of which are incorporated herein.

[0012] Arranging the burst diaphragm and the degassing element at different locations within the housing has the advantage that both "release devices" (i.e., the irreversibly opening burst diaphragm and the degassing element) can be exposed to different pressure values, at least for a short period. This allows for a delayed opening of the burst diaphragm compared to gas release via the degassing element. If, however, the two release devices are located next to each other or even integrated within one another, the same pressure value is applied to both devices almost simultaneously. At sufficiently high pressure values, this can cause the burst diaphragm to open (break) undesirably (or even unnecessarily), especially with rapidly increasing pressure (since the gas may not be able to escape through the diaphragm quickly enough in this case).If, on the other hand, the burst diaphragm is located on one of the four wall surfaces of the housing and the degassing element is located on one of the housing covers perpendicular to it, any time delay that occurs until increased internal pressure has spread throughout the entire housing can be used to reduce the increased internal pressure via the degassing element (e.g., by using the degassing element's valve function, if present, to increase gas passage through the diaphragm). This allows the degassing element to "intercept" a pressure increase that would (especially if it were just barely) trigger the burst diaphragm, thus keeping the internal pressure in the area of ​​the burst diaphragm low enough to prevent it from triggering. If the internal pressure continues to rise despite the degassing element (or remains at a level high enough to trigger the burst diaphragm), it can still trigger.

[0013] The burst diaphragm thus represents a safety mechanism that triggers particularly when the internal pressure at the burst diaphragm exceeds the burst pressure limit. The degassing element, on the other hand, can compensate for smaller and only short-term pressure increases, so that triggering the burst diaphragm is not yet necessary.

[0014] According to a preferred embodiment, the electrode stack comprises two mirror-image electrodes (i.e., an anode and a cathode), each connected to a terminal located in one of the two housing covers. Preferably, the electrode stack comprises several such electrode pairs. The one anode or all anodes are connected to a terminal on one housing cover, and the one cathode or all cathodes are connected to a terminal on the other housing cover.

[0015] Preferably, the electrode stack is cuboid-shaped and encased in a separator material casing that follows the wall surfaces of the housing. The cuboid shape of the electrode stack is preferably, in cross-section (especially parallel to the housing covers), modeled as an elongated rectangle. The rectangle is therefore preferably significantly longer than it is wide, e.g., at least twice as long, but expediently no more than ten to twenty times longer. For automotive applications, the length of the rectangle (which corresponds to the height of the battery cell in its usual installation state) is, for example, in the range of 110 to 150 mm (usually no more than 200 mm), and the width of the rectangle is 20 to 50 mm (optionally around or below 10 mm). The battery cell length is between 200 and 400 mm, but can also be up to 1000 mm. For stationary applications (e.g.,In building energy storage systems, the dimensions can also be larger, as the available installation space in the vehicle is not a limiting factor. In particular, the end faces of the (cuboidal) electrode stack facing the two housing covers are free of the casing. Roughly speaking, the electrode stack is rolled up in the casing without its end faces being covered. The arrangement of the burst membrane and the degassing element described above is particularly advantageous for this design, because if the electrolyte gases, this gas is first channeled outwards between the electrodes and can only escape from the casing at the edges of the electrodes on the exposed end faces of the electrode stack. Adjacent to, specifically opposite, these end faces, the two housing covers are located in the battery cell's intended state.As a result, escaping gas first (or especially "first") hits the respective housing cover and thus also the degassing element. The burst membrane is, as can be seen, "shielded" by the separator material lining.

[0016] According to a practical design, the burst membrane is arranged in a wall surface that, in the intended operating state of the battery cell, faces the underside of the battery. This has the advantage that gases – usually hot – which, in the event of a fault, lead to the burst membrane rupturing and escape through it, are relatively easily vented away from the passenger compartment of the vehicle in which the battery is used.

[0017] According to another advantageous embodiment, the degassing opening and (therefore also) the degassing element are arranged in an area (hereinafter referred to as the "lid area") of the respective housing lid that faces away from (or, in other words, is turned away from) the wall surface supporting the burst membrane. For example, the lid area comprises half or one-third of the surface of the housing lid, with the degassing element not being located in the half or third that borders the wall surface containing the burst membrane. This increases the distance between the degassing element and the burst membrane, which in turn can have a beneficial effect on the time delay between the occurrence of the increased pressure at the degassing element and at the burst membrane.Particularly in combination with the burst membrane facing downwards, the degassing opening located in this "upper" cover area has the advantage that, with typically liquid electrolytes, the gas formed rises to the top of the battery cell housing. Thus, in this case, the degassing opening is advantageously positioned where gas and increased pressure can be present particularly quickly.

[0018] In particular, the respective connection contact is arranged in a central area of ​​the associated housing cover, preferably in relation to a housing cover that has the shape of an elongated rectangle. In this case, the degassing opening and the degassing element are arranged in the cover area that is spaced apart from the wall surface supporting the burst membrane across the central area.

[0019] According to another advantageous embodiment, the degassing opening and the degassing element (optionally also independently of whether the burst membrane is located in one of the housing wall surfaces) are arranged in a cover area of ​​the respective housing cover that, in its intended operating state, faces the top of the battery. In principle, the burst membrane can therefore be located laterally or on top (relative to the intended arrangement of the battery cell within the battery), and yet the degassing opening can still be located in the upward-facing cover area of ​​the corresponding housing cover.

[0020] For example, an alternative design is also provided, according to which the degassing opening and the degassing element are arranged in a cover area of ​​the respective housing cover that faces the wall surface supporting the burst membrane, in particular between the corresponding wall surface and the central area. In this case, however, the degassing element can also be arranged laterally or, in particular, in the downward-facing cover area.

[0021] Optionally, a degassing opening and a degassing element are arranged in each of the two housing covers.

[0022] The battery according to the invention preferably forms a (traction) battery for a motor vehicle. However, the battery can also be used as a stationary energy storage device. The battery comprises the battery cells described above, specifically a plurality (i.e., at least two) of these (prismatic) battery cells. Preferably, the battery also has a housing in which the battery cells are arranged. Optionally, the battery also has so-called module housings in which the battery cells are grouped into modules and which are arranged within the battery housing. An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows:

[0023] Fig. 1 schematically shows a perspective view of a battery cell in a partially assembled state, and

[0024] Fig. 2 shows a schematic representation of a battery with several battery cells according to Fig. 1.

[0025] Corresponding parts in all figures are always marked with the same reference symbols.

[0026] Figure 1 schematically depicts a prismatic battery cell 1 in a partially assembled state (comparable to an exploded view). The battery cell 1 has a housing 2, which comprises a rectangular tube body 4 ("tube can") with an opening 6 at each of its opposite ends (comparable to the opposite ends of a short, straight tube). The housing 2 also has two covers 8, one of which, in the intended final assembly state (not shown), closes one of the openings 6. The battery cell 1 further comprises an electrode stack 10, which includes a plurality of electrodes 12 – in particular, pairs of identical electrodes 12 (i.e., anodes and cathodes).

[0027] The electrode stack 10 is wrapped with a cover 14 made of separator material, whereby the end faces of the electrodes 12 facing the openings 6 remain free of the cover 14. In addition to the cover 14, a cover made of a plastic film, e.g., a biaxially oriented polyester film (BO-PET, also known under the brand name Mylar), may also be present (not shown separately), with this cover also leaving the end faces of the electrodes 12 facing the openings 6 free. This cover can facilitate the insertion of the electrode stack 10 into the housing body 4. This allows the anodes to be contacted on one of the housing covers 8 via a connection contact 16 integrated into the housing cover 8, and the cathodes to be contacted on the other housing cover 8 via the connection contact there.

[0028] The tubular housing body 4 has four wall surfaces (or walls), of which two opposing wall surfaces facing one side in the intended operating state of the battery cell 1 (see Fig. 2) are designated as side walls 20, one wall surface facing upwards is designated as the top wall 22, and one wall surface facing downwards is designated as the bottom wall 24. A burst membrane 30 is inserted into the bottom wall 24, which seals a bottom opening. The burst membrane 30 serves as an emergency pressure relief device and can only open the bottom opening irreversibly in the event of damage to the battery cell 1.

[0029] The battery cell 1 also has a degassing opening 40 with a degassing element 42 inserted therein. The degassing element 42 has a gas-permeable membrane (not shown) which seals the degassing opening 40 all around. The degassing element 42 also has a cover to protect the membrane. The membrane serves to allow gas to escape – particularly continuously – from an interior space surrounded by the housing 2 into the environment of the battery cell 1. Optionally, a valve is integrated into the cover, by means of which the amount of gas flowing through the membrane can be controlled. This valve can be adjusted reversibly, for example, to accelerate or reduce pressure relief.

[0030] The burst membrane 30 is designed and specifically configured – particularly with regard to its surface area and / or material thickness – to rupture at a predetermined internal pressure (burst pressure). The rupture of the burst membrane 30 allows the internal pressure to be reduced quickly, but only irreversibly, i.e., resulting in the permanent failure of battery cell 1.

[0031] The burst pressure value is selected between 5 and 15 bar (0.5 to 1.5 MPa). If the degassing element includes a valve, it can be configured – for example, via a control system in the case of an actively actuated valve or by means of appropriate spring preload – to increase the gas flow through the diaphragm below (e.g., approximately 1.5–3 bar below) or at or near (especially, for example, 0.5 bar below) the burst pressure value.

[0032] The degassing element 42 is arranged in an "upper" cover area 44, which corresponds to approximately one-third of the area of ​​the rectangular housing cover 8. The connection contact 16 is located in the middle third (also: "central area"). The upper cover area 44 faces away from the bottom wall 24 and is separated from it at least by the central area (as well as by a lower cover area).

[0033] Due to this arrangement, in the event of gas formation, particularly in the electrolyte introduced between the electrodes 12, which can occur under unfavorable operating conditions, the gas can flow along the electrodes 12 towards the housing covers 8. Gas escape perpendicular to this direction (and particularly downwards) is prevented or at least reduced by the band 14 (and any additional band that may be present). The gas can then escape from the electrode stack 10 at the end faces of the electrodes 12 and enter the area of ​​the degassing element 42, through which it can be vented from the interior. If the cross-section of the degassing element 42 (and / or the gas flow through its membrane) is insufficient and / or the internal pressure continues to rise, the increased internal pressure also reaches the burst membrane 30, causing it to trigger if its burst pressure limit is exceeded.

[0034] In an embodiment not shown in detail, the degassing element 42 is arranged only in one of the two housing covers 8.

[0035] Figure 2 schematically shows a battery 100, which is used as a traction battery in a motor vehicle. The motor vehicle with this battery 100 also represents an invention, but is not shown in detail.

[0036] In the present embodiment, the battery 100 comprises a plurality of the battery cells 1 described above, which are grouped into so-called battery modules 102 and mounted in a module housing 104. The burst membrane 30 is oriented towards the underside of the battery 100. These battery modules 102 are in turn arranged in a battery housing 110.

[0037] The subject matter of the invention is not limited to the embodiment described above. Rather, further embodiments of the invention can be derived by a person skilled in the art from the above description.

[0038] Reference symbol list

[0039] Battery cell

[0040] Housing

[0041] Housing body

[0042] opening

[0043] Housing cover

[0044] Electrode stack

[0045] Electrodes

[0046] cover

[0047] Connection contact

[0048] side wall

[0049] ceiling wall

[0050] floor wall

[0051] Burst membrane

[0052] Degassing opening

[0053] Degassing element

[0054] Cover area

[0055] battery

[0056] Battery module

[0057] Module housing

[0058] Battery housing

Claims

Patent claims 1. Prismatic battery cell (1), in particular for a battery (100) of a motor vehicle, comprising - at least one electrode stack (10), - a rectangular tubular housing body (4) in which the electrode stack (10) is accommodated and which has four wall surfaces (20, 22, 24), - two housing covers (8) by means of which opposing housing openings of the housing body (4) are closed to close off an interior housing space, - a burst membrane (30) incorporated into one of the four wall surfaces (20, 22, 24) for the irreversible opening of the housing interior when a predetermined internal pressure value is exceeded, and - a unidirectional degassing element (42) comprising a gas-permeable membrane which is arranged covering a degassing opening (40) formed in one of the housing covers (8).

2. Prismatic battery cell (1) according to claim 1, wherein the electrode stack (10) has two opposite electrodes (12) which are contacted by a terminal contact (16) which is arranged in one of the two housing covers (8) that is assigned to each.

3. Prismatic battery cell (1) according to claim 2, wherein the electrode stack (10) is cuboid in shape and is wrapped in a cover (14) made of separator material following the wall surfaces (20, 22, 24) of the housing body (4).

4. Prismatic battery cell (1) according to claim 3, wherein the end faces of the electrode stack facing the two housing covers (8) (10) are free from the binding (14).

5. Prismatic battery cell (1) according to one of claims 1 to 4, wherein the burst membrane (30) is arranged in a wall surface (24) facing a bottom of the battery (100) in a battery (100) in a state of intended use of the battery cell (1).

6. Prismatic battery cell (1) according to one of claims 1 to 5, wherein the degassing opening (40) and the degassing element (42) are arranged in a cover area (44) of the respective housing cover (8) which points away from the wall surface (24) supporting the burst membrane (30).

7. Prismatic battery cell (1) according to claim 6, wherein the respective terminal contact (16) is arranged in a central region of the associated housing cover (8) and wherein the degassing opening (40) and the degassing element (42) are arranged in the cover region (44) which is spaced apart from the wall surface (24) supporting the burst membrane (30) over the central region.

8. Prismatic battery cell (1) according to one of claims 1 to 7, wherein the degassing opening (40) and the degassing element (42) are arranged in a cover area (44) of the respective housing cover (8) which, in the intended operating state, faces a top side of the battery (100).

9. Prismatic battery cell (1) according to one of claims 1 to 5, wherein the degassing opening (40) and the degassing element (42) are arranged in a cover area of ​​the respective housing cover (8) which faces the wall surface (24) supporting the burst membrane (30), in particular between the wall surface (24) and the central area.

10. Battery (100), in particular for a motor vehicle, comprising a plurality of prismatic battery cells (1) according to any one of claims 1 to 9.

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