Battery cell

Abstract

The invention relates to a battery cell (14) having a cell casing (28) in which a number of electrodes (20) are arranged. The cell casing (28) has a rupture region (30), said rupture region (30) having an opening (36). The opening (36) is covered by a gas-permeable membrane (38).

Description

[0001] Description

[0002] Battery cell

[0003] The invention relates to a battery cell. The battery cell has a cell housing in which several electrodes are arranged.

[0004] Motor vehicles are increasingly being powered at least partially by an electric motor, so that they are designed as electric vehicles or hybrid vehicles. A high-voltage battery comprising several individual battery modules is usually used to power the electric motor. The battery modules are usually identical in construction and are electrically connected in series and / or parallel, so that the electrical voltage applied to the high-voltage battery corresponds to a multiple of the electrical voltage provided by each of the battery modules. Each battery module, in turn, comprises several battery cells, which are usually arranged in a common module housing and are electrically connected in series and / or parallel.

[0005] Each of the battery cells, in turn, usually comprises several galvanic elements. These each have two electrodes, namely an anode and a cathode, as well as a separator arranged between them and an electrolyte with freely moving charge carriers. A liquid, for example, is used as such an electrolyte. In an alternative, the battery cell is designed as a solid-state battery, and the electrolyte is in the form of a solid. The anode and the cathode, which form the electrodes of the battery cell, usually comprise a carrier that acts as a current collector. An active material is usually attached to this carrier, which is a component of a layer applied to the carrier, which is also referred to as a collector. In this case, the electrolyte may already be present in the layer, or it may be added subsequently. At the very least, however, the active material is designed to absorb the working ions, e.g.Lithium-ion batteries are suitable. Depending on whether they are used as an anode or cathode, a different material is used for the carrier and a different type of layer material.

[0006] To protect the galvanic elements, they are usually arranged in a cell housing of the battery cell, which is also referred to as a cell cup. The cell housing also protects the electrolyte from environmental influences. In order to provide a comparatively large capacity from each battery cell, several such galvanic elements, usually up to 100, are usually arranged in the common cell housing. In order to use the available space comparatively efficiently and to simplify production, the individual components of the galvanic elements are designed to be flat and stacked on top of one another in a stacking direction, forming an essentially cuboid-shaped cell stack. In an alternative embodiment, for example, the separator is designed in a strip-shaped manner and is provided with several electrodes on opposite sides.The strip is wound into a roll, specifically a so-called "jelly roll." Thus, the galvanic elements are rolled into a cylindrical shape.

[0007] The cell housing is shaped depending on the arrangement of the galvanic elements used. It can be rigid and made of aluminum, for example. The cell housing's shape is, for example, cuboidal. Such a battery cell is also called a prismatic cell. In an alternative embodiment, the cell housing is constructed using a foil wrapped around the galvanic elements. Such a battery cell is also called a pouch cell.

[0008] During operation of the battery cell, i.e. during charging and discharging, it is possible that gases are released due to unwanted chemical reactions. This increases the pressure within the cell casing, which can lead to the de-contacting of individual electrodes and a loss of performance of the battery cell. On the other hand, it is possible that the cell casing is deformed due to the increased pressure, which in particular has a mechanical impact on the area surrounding the battery cell. At a comparatively high pressure, the cell casing bursts, allowing the electrolyte to leak out and making the entire battery cell unusable. It is also possible that unwanted chemical reactions occur between the individual components of the battery cell and the environment.

[0009] To avoid such gas formation, a special selection of the individual electrode materials is necessary, which on the one hand increases manufacturing costs. On the other hand, such materials reduce the capacity of the battery cell. Alternatively, for example, additional elements are present in the cell housing by means of which the resulting gases are bound and / or converted. In a further variant, the cell housing is designed to be comparatively robust, so that the pressure that leads to rupture of the cell housing is never reached during operation of the battery cell. However, due to the additional elements and the robust design of the cell housing, the installation space and the weight of the battery cell are increased, which therefore reduces the energy density. The object of the invention is to provide a particularly suitable battery cell, wherein operational reliability and / or energy density are advantageously increased.

[0010] According to the invention, this object is achieved by the features of claim 1. Advantageous further developments and refinements are the subject of the subclaims.

[0011] The battery cell is in particular designed to be rechargeable and is expediently a secondary battery. Preferably, in its intended state, the battery cell is a component of a motor vehicle. The battery cell is suitable, in particular provided and configured for this purpose. In its intended state, the battery cell is, for example, a component of an energy storage device of the motor vehicle which has a plurality of such battery cells. Preferably, the battery cells are divided into a plurality of battery modules which are in turn structurally identical to one another. The battery cells are in particular arranged in a housing of the energy storage device or the respective battery module and are electrically connected to one another in parallel and / or in series. Thus, the electrical voltage applied to the energy storage device / battery module is a multiple of the electrical voltage provided by each of the battery cells.Conveniently, all battery cells are identical to each other, which simplifies production.

[0012] The housing of the energy storage device or the respective battery module, which thus in particular forms a composite of such battery cells, is preferably made of a metal, for example a steel such as stainless steel, or an aluminum alloy. For production, for example, a die-casting process, deep-drawing process, casting molding, or extrusion molding is used. In particular, the housing of the energy storage device or the respective battery module is designed to be closed. An interface is expediently incorporated into the housing of the energy storage device or the respective battery module, which forms a connection of the energy storage device / battery module. The interface is electrically connected to the battery cells, so that electrical energy can be fed in and / or withdrawn from the battery cells from outside the energy storage device, provided a corresponding plug is plugged into the connection.

[0013] The motor vehicle is preferably land-based and preferably has a number of wheels, of which at least one, suitably several or all, are driven by a drive. In particular, one, preferably several, of the wheels is designed to be steerable. This makes it possible to move the motor vehicle independently of a specific roadway, for example rails or the like. In this case, it is expediently possible to position the motor vehicle essentially arbitrarily on a roadway, which is made in particular of asphalt, tar, or concrete. The motor vehicle is, for example, a commercial vehicle, such as a lorry (truck) or a bus. However, the motor vehicle is particularly preferably a passenger car (car).

[0014] The motor vehicle is expediently moved by means of the drive. For example, the drive, in particular the main drive, is at least partially electric, and the motor vehicle is, for example, an electric vehicle. The electric motor is operated, for example, by means of the energy storage device, which is suitably designed as a high-voltage battery. A direct electrical voltage is expediently provided by the high-voltage battery, wherein the electrical voltage is, for example, between 200 V and 800 V and, for example, substantially 400 V. Preferably, an electrical converter is arranged between the energy storage device and the electric motor, by means of which the current supply to the electric motor is adjusted. In an alternative, the drive additionally has an internal combustion engine, so that the motor vehicle is designed as a hybrid motor vehicle.In an alternative, the energy storage device is used to feed a low-voltage electrical system of the motor vehicle, and the energy storage device is used to provide, in particular, an electrical direct voltage of 12 V, 24 V or 48 V.

[0015] In another alternative, the battery cell is a component of an industrial truck, an industrial plant, or a handheld device, such as a tool, in particular a cordless screwdriver. In another alternative, the battery cell is a component of a power supply and is used there, for example, as a so-called buffer battery. In another alternative, the battery cell is a component of a portable device, such as a portable mobile phone or other wearable. It is also possible to use such a battery cell in camping, model making, or other outdoor activities.

[0016] The battery cell has a plurality of electrodes, for example two or preferably more. In particular, the electrodes are divided into anodes and cathodes, with expediently half of the electrodes forming the anodes and the other half the cathodes. Preferably, however, there is one more anode than cathode. Particularly preferably, all anodes and all cathodes are structurally identical to one another, which simplifies production. The electrodes are, for example, flat in design and in particular have a carrier, which is also referred to as a conductor. In particular, the respective carrier is formed by means of a metal foil which is coated on one or both sides with a layer, at least in sections. Aluminum, for example, is used as the metal of the carrier / conductor of the cathodes, and copper is used as the metal of the conductor of the anodes.

[0017] The layer has a thickness of less than 1 mm. The supports expediently have a thickness of less than 0.1 mm. Preferably, each layer comprises an active material, a binder, and / or a conductive additive, such as conductive carbon black. The active material serves to absorb working ions, such as lithium ions, and is suitable, intended, and configured for this purpose. The active material used for the cathode is, for example, a lithium metal oxide, such as lithium cobalt(III) oxide (LiCoO2), NMC, for example NMC622 or NMC811, NCA, LMNO, or LFP, and / or for the anode, LTO or Si-based graphite.

[0018] In particular, the electrodes are essentially rectangular. The electrodes are, for example, stacked one above the other to form a cell stack, wherein the stacking direction is perpendicular to the direction of extension of the electrodes, which are arranged parallel to one another. The anodes and cathodes preferably alternate in the stacking direction of the cell stack. Advantageously, a separator of the cell stack is arranged between adjacent electrodes, i.e. in particular between one of the anodes and one of the cathodes, which separator is preferably also designed to be flat. For example, all of the separators are structurally identical to one another. In particular, the electrodes are stacked essentially flush one above the other, wherein, for example, all of the anodes protrude at least slightly beyond the cathodes. Particularly preferably, the protrusion on one of the sides is increased.Preferably, the cathodes also protrude beyond the anodes on one side, with the (enlarged) projections located on opposite sides of the cell stack. This simplifies contacting the anodes and cathodes with other components. Due to the stacking of the electrodes, the cell stack is also essentially cuboid-shaped.

[0019] In an alternative embodiment, for example, all anodes, all cathodes, or the separator are formed by means of a common band, or they are attached to a common band. The band itself is rolled into a cylindrical shape or the like, forming a so-called "jelly roll."

[0020] The battery cell has a cell housing, within which the electrodes are arranged, for example the cell stack or the "jelly roll". Suitably, the cell housing has a base body, within which the electrodes are arranged. The base body is, for example, pot-shaped and closed by a cover of the cell housing. This simplifies the arrangement of the electrodes. In particular, a volume between 0.1 dm3 and 10 dm3 is enclosed by the cell housing, preferably the base body. For example, the cell housing is additionally at least partially filled with an electrolyte, or the electrolyte is, for example, already partially formed by the respective active material. The cell housing, in particular any base body, is preferably rigid. In other words, the battery cell is a prismatic cell.In particular, the cell housing, preferably the base body and / or any cover, is made of a metal such as aluminum, i.e., pure aluminum or an aluminum alloy. The cell housing, in particular the base body, has, for example, a cuboid shape. Alternatively, the cell housing, and preferably the base body, is designed to be flexible and, for example, formed at least partially by a metal foil, which is coated on one or both sides. The electrodes are folded over by means of the metal foil, and the metal foil is expediently sealed at the ends, thus preventing the electrolyte from escaping and / or ambient air from entering the cell housing.

[0021] The electrodes are in particular arranged directly in the cell housing, so that the electrodes rest, for example, directly or via a further component against an inner wall of the cell housing and are thus stabilized by the latter. At least the cell housing directly serves to protect the electrodes and / or prevent contact of the electrodes / electrolytes with ambient air or other particles. In other words, the electrodes within the cell housing are preferably not, or at least not completely, surrounded by a further component, so that the weight of the battery cell and material costs are reduced. In particular, there is no further housing in the cell housing by which the electrodes are surrounded. Consequently, it is possible to fill the cell housing essentially completely with the electrodes and any separator(s).

[0022] The cell housing suitably has at least one or two openings, through each of which a connection is led. By means of the connection(s), at least some of the electrodes arranged in the cell housing are electrically contacted, such that electrical energy can be fed in and / or drawn from outside the cell housing to or from the galvanic elements formed by the electrodes via the connection(s). If only a single connection is present, at least some of the electrodes are electrically contacted with the cell housing, such that an electrical potential of the cell housing is predetermined by means of these electrodes. In particular, the connection(s) are electrically insulated from the cell housing, wherein the connections are connected to the cell housing in a fluid-tight manner, such that leakage of the electrolyte in the region of the connections is prevented.

[0023] The cell housing, in particular the base body, has a predetermined breaking area.

[0024] The predetermined breaking zone thus covers a specific area of ​​the cell housing, in particular the base body. The predetermined breaking zone is designed such that it breaks at a specific pressure difference between the interior and exterior of the cell housing, thus enabling, in particular, a material exchange between the interior of the cell housing and the environment. The breaking of the predetermined breaking zone is irreversible. For example, if the pressure difference, which is also referred to below as burst pressure, is exceeded, the predetermined breaking zone breaks completely or only partially. In particular, the area of ​​the predetermined breaking zone that breaks and is thus opened depends on the actual pressure difference.

[0025] The cell housing is particularly designed such that, when the bursting pressure is exceeded, the cell housing initially only breaks in the predetermined breaking area, whereas the remaining components of the cell housing, in particular the base body, remain undamaged. These are only damaged if the pressure difference increases further and, in this case, break in an uncontrolled manner. The bursting pressure is preferably selected such that it is lower than the pressure difference between a pressure inside the cell housing and a pressure outside the cell housing that would lead to destruction of the cell housing, for example, a complete bursting or rupture. The bursting pressure is preferably between 70% and 90%, between 75% and 85%, or 80% of this pressure difference.

[0026] The predetermined breaking area has an opening, which is arranged in particular in a central region, i.e., offset inward from an edge of the predetermined breaking area. Suitably, the distance of the opening to an edge of the predetermined breaking area is greater than a quarter of the extent of the predetermined breaking area in the respective direction. In particular, the opening is located exactly in the center of the predetermined breaking area. The area of ​​the opening is smaller than the area of ​​the predetermined breaking area and in particular smaller than 50%, 20%, 10%, 5%, 1%, or 0.1% thereof.

[0027] The opening is covered by a gas-permeable membrane. In particular, the membrane is rigidly, i.e. immobilely, connected to the cell housing, preferably the base body and / or the predetermined breaking area, so that movement of the membrane relative to the cell housing / base body is prevented. The area of ​​the membrane is at least equal to the area of ​​the opening or preferably larger, so that the membrane completely overlaps the opening. In particular, the area of ​​the membrane is smaller than the area of ​​the entire predetermined breaking area. This reduces material costs. The membrane area can also be optimized independently of the area of ​​the predetermined breaking area with regard to the necessary active area and its connection to the predetermined breaking area / cell housing. Alternatively, the area is larger than the area of ​​the predetermined breaking area, and the membrane overlaps the predetermined breaking area.In this way, the predetermined breaking area is not influenced when the membrane is attached to the cell housing, particularly at the edge.

[0028] The membrane is preferably arranged in such a way that the passage of liquids and / or gas between the membrane and the predetermined breaking area is prevented. In other words, the membrane is connected to the cell housing in a gas-tight and fluid-tight manner, for example directly or via further components. For this purpose, the membrane is particularly preferably welded to the cell housing, e.g. the predetermined breaking area, suitably with a circumferential weld seam. For this purpose, an ultrasonic, laser or temperature welding process is used, for example. Alternatively, the membrane is connected to the cell housing in a form-fitting and / or material-fitting manner, in particular by adhesive bonding. In this case, the opening is expediently completely surrounded by the adhesive or the weld seam. For example, the connection is made directly adjacent to the opening, or between the opening and the connection of the membrane to the cell housing, for example the adhesive orA gap is formed between the weld seam and the cell housing. Consequently, gas can only escape from or into the cell housing through the opening, with the gas also being conducted through the membrane.

[0029] In particular, the membrane is selected such that it is permeable to CO, CO2, H2 and / or CH4. For example, the membrane does not impede the passage of such gases, or only impedes it to a comparatively small extent. However, the membrane's permeability to moisture, in particular to water vapor, is preferably significantly lower. In particular, the membrane has a ratio of CO2 permeability to moisture permeability of at least 0.5, of at least 1, or at least 1.5. Preferably, the ratio is more than 0.5 and less than 3. In particular, the membrane acts as a barrier to the penetration of moisture, in particular water vapor, into the cell housing. In summary, the membrane is designed such that gases generated in the cell housing can pass through it and out of the cell housing through the opening, for which purpose the opening is used.The membrane makes it difficult or significantly reduces the ingress of liquids, particularly water, into the cell casing. The gas-permeable membrane essentially enables continuous degassing of the cell casing, so that the formation of a pressure difference between the pressure outside the cell casing and the pressure inside the cell casing, particularly due to the unwanted formation of gases in the cell casing during operation of the battery cell, is avoided or slowed down. Due to the comparatively small area of ​​the opening, the mechanical integrity of the cell casing is only slightly reduced. On the other hand, the penetration of foreign substances, such as moisture or liquids, into the cell casing is only fundamentally possible in this area, which is comparatively unlikely.This allows for comparatively safe operation of the battery cell over a comparatively long period of time, thus increasing operational reliability. In other words, during uninterrupted operation of the battery cell, the essentially continuous release through the membrane prevents excessive accumulation of gases within the cell casing, so the pressure difference between the surroundings of the cell casing and the interior of the cell casing remains comparatively low.

[0030] However, if the pressure difference increases comparatively sharply and rapidly due to unwanted chemical reactions in the cell casing, for example, due to overloading, so that the resulting gases cannot be adequately discharged through the opening and the membrane, the predetermined breaking point breaks, and the cell casing is opened at a defined location, namely the predetermined breaking point. Consequently, uncontrolled damage to the cell casing and uncontrolled impact on the environment are avoided. Rather, this only occurs in the predetermined breaking point, making it possible to adapt the installation situation of the battery cell accordingly. This increases operational reliability.

[0031] The membrane is made in particular from a polymer, for example a film, for example a polymer film. Suitably, the membrane is made from or consists of PTFE, i.e., polytetrafluoroethylene. The membrane expediently has a crystallinity between 85% and 100% and a density between 0.2 g / cm3 and 2 g / cm3. With such a choice of material, gas permeability is ensured, whereby the membrane prevents or at least impedes the penetration of moisture, in particular water vapor, into the cell housing. A membrane suitable for battery applications is described in WO 2021 / 079163 A1. For example, the membrane is designed to be flat. This simplifies production and reduces weight. For example, the predetermined breaking area / opening can be positioned arbitrarily on the cell housing.However, if the battery cell is designed as a pouch cell, it is particularly preferably located in the region of one of the ends of the cylindrical shape near the conductor, in which the foil, if any, is sealed (e.g., on the so-called gas pocket). In this case, the predetermined breaking area / opening is expediently offset inward from the respective ends up to a maximum of one-third of the maximum length of the cell housing.

[0032] If the battery cell is a prismatic cell, the predetermined breaking region / opening is preferably located in the region of the end faces and / or narrow sides, which in particular are not parallel to the electrodes layered to form the cell stack, if any. Alternatively, the opening is located in one of the sides of the cell housing that is parallel to the electrodes, but preferably in an edge region, i.e. offset inwards from the edge up to a maximum of one-third of the width of the side. Due to this position of the opening, construction is simplified, and it is not necessary to modify an existing design of the cell stack. Furthermore, the predetermined breaking region / opening is arranged in an area where gases collect, thus enabling comparatively efficient removal of the gases through the opening. For example, the predetermined breaking region has only the single opening, which is covered by the membrane.Alternatively, the predetermined breaking area comprises several such openings, each of which is covered by the membrane. In this case, the membrane is, for example, continuous, or each of the openings is assigned a corresponding (separate) membrane.

[0033] The predetermined breaking area is, for example, stadium-shaped, round, or rectangular. In particular, the area of ​​the predetermined breaking area is between 0.01 cm2 and 20 cm2, and preferably between 0.1 cm2 and 10 cm2. Suitably, the predetermined breaking area has a size of 0.01% and 50% of the area of ​​the cell housing. Preferably, the predetermined breaking area has a size of between 0.1% and 40%, and in particular between 0.3% and 30%, of the area of ​​the complete cell housing. For example, the membrane has an area 50% larger than the opening. Suitably, the opening has an area of ​​50 μm2 to 15 mm2, preferably of 0.2 mm2 to 3 mm2.

[0034] Preferably, the opening is covered with a gas-permeable, hydrophobic, i.e., at least water-repellent, additional membrane. Preferably, the contact angle of the material of the additional membrane to water is greater than 80°, 90°, or 100°, especially if the material is also exposed to air or is in ambient air. The additional membrane thus keeps moisture away from the membrane, further impeding the penetration of moisture into the cell housing. At the very least, however, the additional membrane keeps moisture from penetrating from the outside out.

[0035] In particular, the two membranes are arranged in parallel, and the further membrane expediently covers the membrane completely. Preferably, the further membrane is fastened in a fluid-tight manner to the cell housing, for example the predetermined breaking area. For example, the opening is directly covered with the further membrane, and the further membrane is fastened directly to the cell housing. In this case, the membrane is offset inwards, in particular with respect to the predetermined breaking area or at least the further membrane, so that the opening is covered on both sides by the two membranes. Thus, the membrane is also protected by the membrane, and impingement of water (vapor) on it is prevented. Furthermore, due to the arrangement of the two membranes on both sides of the predetermined breaking area, construction is simplified, and the two membranes are expediently fastened to the cell housing in a fluid-tight manner.Alternatively, for example, the position of the additional membrane and the membrane is swapped. In a further alternative, the additional membrane and the membrane are on the same side with respect to the cell housing / predetermined breaking area, and the additional membrane in particular covers the membrane so that the opening is also covered. In particular, the additional membrane is offset outwards with respect to the membrane so that the membrane is protected by the additional membrane. In this way, it is also possible to select a comparatively large area of ​​the additional membrane used for gas passage. For example, the additional membrane is attached to the membrane, and this in particular provides a type of laminate or sandwich. This simplifies production.

[0036] For example, the membrane is designed to be tear-resistant. However, the membrane is particularly preferably designed such that it tears when the pressure difference between a pressure outside the cell housing and a pressure inside the cell housing exceeds a first limit value. Due to the tearing, gas passage through the membrane or at least the opening is accelerated, so that the pressure inside the cell housing dissipates relatively quickly. In this way, damage to the cell housing is avoided. For example, if the first limit value is exceeded, the membrane tears completely and is thus destroyed, i.e. breaks. Thus, the entire area of ​​the opening is effectively used for gas passage, so that the pressure difference can be dissipated relatively quickly.Alternatively, or in combination with the membrane rupture, the fluid-tight connection between the membrane and the cell housing is at least partially broken if, for example, the first or a further limit is exceeded. This allows gases to escape there as well, leading to a reduction in the pressure difference.

[0037] The first limit value is expediently lower than the burst pressure, which represents a second limit value. The predetermined breaking range is thus designed such that it breaks when the pressure difference between the pressure outside the cell housing and the pressure inside the cell housing exceeds the second limit value, which is higher than the first limit value. The first limit value is, for example, between 90% and 50% of the second limit value (burst pressure), between 80% and 60% of the second limit value (burst pressure), and, for example, substantially equal to 70% of the second limit value (burst pressure). Thus, in the event of an excessive pressure increase, the membrane is initially at least partially destroyed, whereas the predetermined breaking range remains intact. This means that continued operation of the battery cell is subsequently possible.If, however, the pressure difference does not remain below the bursting pressure despite the membrane tearing, the predetermined breaking point bursts, preventing the cell casing from tearing open at another location.

[0038] For example, the membrane is attached to an outer surface of the cell housing, for example, to an outer surface of the predetermined breaking area or any base body. In this way, the membrane does not fill the interior of the cell housing, leaving a comparatively large volume available for the electrodes. This increases the capacity of the battery cell. This also makes it possible to select a membrane surface larger than the area of ​​the opening. After the gases pass through the opening, an enlarged surface is available for them to pass through the membrane.

[0039] Preferably, the membrane rests on the side facing away from the cell housing against a stabilizing element having a plurality of additional openings. By means of the stabilizing element, in particular, the spatial degrees of freedom for the membrane are limited and thus the membrane is additionally stabilized under increased pressure. In other words, a maximum deformation of the membrane is predetermined by the stabilizing element and the membrane is thus stabilized. Thus, stability of the membrane itself is not required, or at least the requirements for this are reduced, which is why there are no restrictions on the choice of material for the membrane in this regard. Expediently, the stabilizing element completely covers the membrane. The stabilizing element is preferably rigid and made, for example, from a metal.In particular, the stabilizing element is designed in the manner of a grid, by means of which the additional openings are formed. These additional openings allow unhindered gas passage through the stabilizing element.

[0040] For example, the stabilizing element is designed to rupture at an increased pressure difference between the pressure inside the cell housing and the pressure outside the cell housing. The pressure difference at which this occurs can be adjusted relatively precisely. Due to the rupture, the membrane is no longer stabilized and thus also overloaded, causing it to rupture. As a result, a comparatively large volume of gas can pass through the additional opening. The pressure difference advantageously corresponds to the first limit value, if any.

[0041] For example, the stabilizing element is attached to the cell casing at a distance from the predetermined breaking area. This prevents damage to the predetermined breaking area during production due to the stabilizing element's connection to it, thus reducing scrap and manufacturing costs. Furthermore, the predetermined breaking area is at least partially stabilized by the stabilizing element, thus reducing restrictions on the material selection or geometry of the predetermined breaking area. Alternatively, the stabilizing element is attached to the predetermined breaking area. This reduces space requirements.

[0042] In an alternative, the membrane is arranged on an inward-facing side of the predetermined breaking area. In other words, the membrane is offset from the predetermined breaking area into the interior of the cell housing. In this way, even at a comparatively high pressure within the cell housing, the membrane does not bulge excessively outwards if the design of the membrane does not allow immediate passage of gases. In this case, the membrane is at least partially pressed against the inward-facing side of the predetermined breaking area. Consequently, the membrane is stabilized by the predetermined breaking area, which increases robustness. In the event of excess pressure, the membrane is pressed against the predetermined breaking area, and the passage of gas between the predetermined breaking area and the membrane is thus prevented, which increases tightness in this area.Consequently, the gas can only escape through the membrane, which is controlled.

[0043] For example, the membrane is attached directly to the inward-facing side of the predetermined breaking area. This also allows a comparatively large-area connection of the membrane to the predetermined breaking area, thus increasing tightness in this area. However, it is particularly preferred that the membrane is partially supported on the predetermined breaking area by spacers. Thus, the membrane does not contact the predetermined breaking area, or only contacts it at the edges, and is spaced from the predetermined breaking area in other areas by the spacers. As a result, an enlarged surface of the membrane is provided for the passage of gas, thus increasing the volume of gases that can be guided through the membrane.For example, it is possible for some of the gases to enter the space formed between the membrane and the predetermined breaking point, which is defined by the spacers, through the membrane and only then pass through the opening into the environment of the battery cell. In summary, the spacers do not support the membrane over its entire surface, but rather only partially, for example, at specific points or in specific areas, creating a comparatively large space between the membrane and the predetermined breaking point.

[0044] The spacers are, for example, at least partially mandrel- or web-like, so that they also stabilize the membrane, which is therefore not excessively deformed even in the case of a comparatively large pressure difference. In this case, for example, the membrane is directly attached to the cell housing at the edge, or the membrane is supported on the cell housing at the edge via another, circumferentially designed spacer, for example the predetermined breaking area. The spacers are, for example, attached to the predetermined breaking area. Particularly preferably, however, the spacers are attached to the membrane and in particular molded onto it. This creates a fluid-tight connection between the membrane and the spacers. This also simplifies production.In particular, the spacers are made of the same material as the membrane and are produced, for example, in an injection molding or lamination process in a single production step. In another alternative, the spacers and the membrane are separate components that are joined together during assembly. Preferably, the membrane is fluid-tightly attached to the predetermined breaking area by means of a portion of the spacers, particularly the edge portion. Alternatively, the membrane is attached directly to the predetermined breaking area at the edge, with the membrane being spaced from the predetermined breaking area in the other portions by means of the spacers.

[0045] For example, the base body may have a further opening. The base body is, for example, rigid, so that the battery cell is a prismatic cell. Alternatively, the base body is at least partially elastic, and the battery cell is a pouch cell. A rupture disc is inserted into the further opening so that the opening is closed with the rupture disc. The rupture disc is made, for example, of a metal such as aluminum or a plastic. The rupture disc is a separate component from the base body that is joined to the cell housing during assembly. In particular, the rupture disc is connected to the cell housing in a gas-tight and fluid-tight manner, preferably fastened, for example by welding and / or gluing. The rupture disc is, for example, round and, in particular, essentially flat. In this case, the rupture disc is expediently arranged parallel to a possible side of the cell housing that has the further opening.Alternatively, the rupture disc is at least partially concave or convex, thereby increasing its compressive strength. The predetermined rupture area expediently comprises the rupture disc. For example, the predetermined rupture area is formed by the rupture disc, or the predetermined rupture area comprises further components. At least, however, the rupture disc preferably comprises the opening. In particular, the rupture disc ruptures when the bursting pressure is exceeded, and the rupture disc is selected accordingly. The rupture disc thus provides a prefabricated component that is inserted into the further opening during assembly to provide the predetermined rupture point. This simplifies assembly. It is also possible to adapt the bursting pressure to the respective application by selecting the appropriate rupture disc.

[0046] The membrane is expediently attached to the rupture disc, for example by gluing and / or welding. For this purpose, an ultrasonic, laser or thermal welding process is used, for example. Because the membrane is attached to the rupture disc, it is possible to manufacture this composite separately and then insert the rupture disc with the membrane into the further opening. This simplifies assembly and essentially eliminates subsequent damage to the rupture disc. It also enables a comparatively cost-effective fluidic connection of the membrane to the rupture disc. Furthermore, it is possible to manufacture the rupture disc with the attached membrane as a module, whereby the material properties of the membrane are already matched to the rupture disc. For example, one of several modules is used for the specific application.

[0047] Alternatively or in combination with this, a wall thickness of the cell housing, preferably of any base body, is reduced in the predetermined breaking area. In other words, the cell housing has a wall that encloses the predetermined breaking area. The wall is, for example, flat or rounded. Adjacent to the predetermined breaking area, the thickness of the wall is increased. In particular, the thickness of the or all walls of the cell housing, with the exception of the predetermined breaking area, is constant, and the predetermined breaking area is surrounded at the edge, in particular by a step. The wall thickness of the cell housing in the predetermined breaking area is, in particular, adapted to the bursting pressure. For example, the cell housing is already pre-formed with the reduced wall thickness in the predetermined breaking area. Alternatively, to produce the predetermined breaking area, material is removed from one of the walls of the cell housing, for example by milling or a laser. For example, the wall thickness in the predetermined breaking area is constant.Alternatively, the predetermined breaking point varies, so that when the bursting pressure is exceeded, a specific type of rupture occurs in the predetermined breaking point. For example, the predetermined breaking point is formed solely by reducing the wall thickness. Alternatively, the predetermined breaking point comprises additional components, such as the rupture disc. At least, however, the opening is preferably located in the area of ​​the reduced wall thickness of the cell casing.

[0048] Alternatively, the cell casing has one or more notches in the predetermined breaking area. The notch(s) are used to at least partially remove material from the cell casing, preferably the base body, so that the notch represents a desired structural weakening of the cell casing, for example, the base body. If the bursting pressure is exceeded, the cell casing ruptures in the area of ​​the notch(s), allowing material to escape from the cell casing.

[0049] The notch(s) is / are introduced, for example, after the cell housing, in particular the base body, has been formed. This facilitates production. For example, the notch is designed to be closed and thus shaped, in particular, in the manner of a ring. Alternatively, the notch is designed to be elongated and has two ends that are spaced apart from one another. In a further alternative, the notches, or at least some of the notches, are point-shaped and designed in the manner of a perforation. For example, the predetermined breaking region comprises several notches designed as rings or circles. These are arranged, for example, concentrically to the opening, which is thus surrounded by the notches. For example, in addition to the notch(s), the wall thickness of the cell housing is reduced across the surface in the predetermined breaking region. This enables a comparatively precise setting of the bursting pressure, while simplifying production.

[0050] In particular, the outer contour of the predetermined breaking area is defined by the notch(s). In other words, all or at least some of the notches run along the outer contour, i.e., the boundary of the predetermined breaking area. Thus, when the burst pressure is exceeded, the predetermined breaking area ruptures along its outer contour, releasing, in particular, the entire predetermined breaking area. This results in a comparatively rapid equalization of the pressure difference. For example, additional notches are present in the predetermined breaking area, so that only comparatively small fragments are created upon tearing / breaking. Consequently, damage to other components due to the fragments is ruled out.

[0051] The battery cell particularly preferably comprises a drying element. The drying element serves in particular to reduce moisture penetrating through the further opening into the cell housing. The drying element is suitable, in particular provided and configured, for this purpose. Due to the drying element, penetrating moisture, such as water (vapor), is bound, so that an unwanted reaction with the electrodes arranged in the cell housing and / or any electrolytes is prevented. Operational reliability is thus further increased. In particular, the drying element is designed such that it binds water, in particular absorbs water molecules. Suitably, the drying element comprises silicate or is formed thereof. In this way, a drying effect is further improved.

[0052] The drying element preferably surrounds the opening. This improves the drying effect in the area of ​​the fluidic connection between the interior and exterior of the cell housing. The drying element is thus preferably designed in the manner of a hollow cylinder, which facilitates manufacturing. For example, the drying element is located on the outside or inside of the predetermined breaking area. The drying element is preferably offset from the membrane to the interior of the cell housing, so that any moisture penetrating the cell housing despite the membrane is bound by the drying element.

[0053] The invention further relates to a battery cell assembly of such cells, wherein the assembly is preferably a battery module or a high-voltage battery. Furthermore, the invention relates to a motor vehicle, such as a passenger car (PV), having such a battery cell, in particular such an assembly. The battery cell is used in particular to supply power to a main drive of the motor vehicle.

[0054] The advantages and further developments described in connection with the battery cell are also to be transferred analogously to the combination / motor vehicle and to each other and vice versa.

[0055] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In the drawing: Fig. 1 shows a simplified schematic of a motor vehicle having several identical battery cells,

[0056] Fig. 2 shows a schematic sectional view of one of the battery cells having a cell housing with a predetermined breaking area,

[0057] Fig. 3 shows a perspective section of the cell housing, wherein the predetermined breaking area comprises a rupture disc,

[0058] Fig. 4 - 7 each show schematically fragmentary sectional views of variants of the cell housing, wherein the predetermined breaking area has an opening covered with a gas-permeable membrane, and

[0059] Fig. 8, 9 each show schematically in perspective detail in a sectional view further variants of the cell housing.

[0060] Corresponding parts are provided with the same reference numerals in all figures.

[0061] Corresponding parts are provided with the same reference numerals in all figures.

[0062] Figure 1 shows a simplified schematic representation of a motor vehicle 2 in the form of a passenger car (car). The motor vehicle 2 has a number of wheels 4, at least some of which are driven by a drive 6 comprising an electric motor. Thus, the motor vehicle 2 is an electric vehicle or a hybrid vehicle. The drive 6 has an inverter by means of which the electric motor is powered. The inverter of the drive 6, in turn, is powered by an energy storage device 8 in the form of a high-voltage battery. For this purpose, the drive 6 is connected to an interface 10 of the energy storage device 8, which is incorporated into an energy storage housing 12 of the energy storage device 8, which is made of stainless steel.

[0063] Arranged within the energy storage housing 12 of the energy storage device 8 are a plurality of identical battery modules (not shown in detail), each comprising a plurality of battery cells 14. The battery cells 14 of each battery module are partly electrically connected in series with one another and partly electrically connected in parallel with one another. Some of the battery modules are in turn electrically connected in series with one another, and these in turn are electrically connected in parallel with one another. The electrical connection of the battery modules is electrically contacted with the interface 10, so that when the drive 6 is in operation, the battery modules and thus also the battery cells 14 are discharged or charged (recuperated). Due to the electrical wiring, the electrical voltage provided at the interface 10, which is 400 V, is a multiple of the electrical voltage provided by each of the battery modules and also by each of the battery cells 14.

[0064] Figure 2 shows a sectional view of one of the identical battery cells 14. The battery cell 14 has a plurality of anodes 16 and cathodes 18, of which only two are shown at a time. The anodes 16 and the cathodes 18, which form the electrodes 20 of the battery cell 14, are each flat and are alternately layered on top of one another to form a cell stack, with a separator (not shown in detail) being arranged between adjacent anodes 16 and cathodes 18. The anodes 16 protrude beyond the cathodes 18 on a common side, namely a respective conductor, which is formed by means of a respective metal foil. In the region of the projection, the respective conductor is free of further components, but in the other regions, a layer comprising an active material is applied to the respective conductor, which is also referred to as a carrier.The cathodes 18 also protrude beyond the anodes 16 in the same way, with the projections being located on opposite sides of the stack formed by the anode 16 and cathodes 18.

[0065] The projections of the anodes 16 and the cathodes 18 are each welded to an associated busbar 22 made of copper. One of the busbars 22 is assigned to each of the anodes 16 and the cathodes 18. The busbars 22 each have a connection 24 that extends through a base body 26 of a cell housing 28, within which the anodes 16 and the cathodes 18 are arranged. Thus, the electrodes 20 are arranged within the cell housing 28. The base body 26 is rigid and made of aluminum. Thus, the battery cell 14 is a prismatic cell. The base body 26, and thus the cell housing 28, is filled with a liquid electrolyte (not shown in detail).

[0066] The cell housing 28 comprises a predetermined breaking area 30 with an area of ​​5 cm². The predetermined breaking area 30 is designed such that, if the pressure difference between the pressure outside the cell housing 28, namely the base body 26, and the pressure inside the cell housing 28, namely the base body 26, exceeds a bursting pressure of 1 bar, the predetermined breaking area 30 ruptures, so that the cell housing 28 is opened and pressure equalization can occur. The bursting pressure is 90% of the maximum pressure load on the base body 26, i.e., the pressure difference at which irreversible and uncontrolled destruction of the base body 26 occurs. The bursting pressure represents a second limit value.

[0067] Figure 3 shows a perspective view of a section of the cell housing 28 with the cuboid-shaped base body 26. A stadium-shaped further opening 32 is introduced into the base body 26 and is closed by a rupture disc 34 of the cell housing 28. In other words, the rupture disc 34 is inserted into the further opening 32, with the edge of the rupture disc 34 overlapping the edge of the further opening 32 and being fastened thereto in a fluid-tight and gas-tight manner by welding. The cell housing 28 is designed such that the base body 26 and the rupture disc 34 are flush with one another on the outside. The rupture disc 34 defines the predetermined rupture area 30, so that the predetermined rupture area 30 encompasses the rupture disc 34. The size of the further opening 32 is equal to the size of the predetermined breaking area 30. If the bursting pressure is exceeded, the bursting disc 34 tears or breaks completely, so that the further opening 32 is released.

[0068] The rupture disc 30 is made of aluminum and has a reduced thickness compared to the wall thickness of the cell housing 26. The additional opening 32 is located in the same wall of the base body 26 as the opening for one of the connections 24. With the exception of the additional opening 28, the base body 26 is designed to be fluid-tight and gas-tight. Thus, the areas between the connections 24 and the associated openings in the base body 26 are filled with a plastic (not shown in detail).

[0069] Figure 4 shows a schematic section of the battery cell 14. The rupture disk 34, and thus also the predetermined rupture area 30, have a circular opening 36 in their center. The opening 36 has a smaller area of ​​1 mm2 than the other opening 32. The opening 36 is covered with a gas-permeable membrane 38, which is made at least partially of PTFE and has a crystallinity between 85% and 100% and a density between 0.2 g / cm3 and 2 g / cm3. Thus, the passage of H2 and CO2 through the membrane 38 is comparatively easy, whereas the passage of moisture, namely water vapor in particular, is comparatively more difficult. The area of ​​the membrane 38, which is arranged concentrically to the opening 36 and is also circular, is three times the area of ​​the opening 36 in this embodiment.

[0070] The membrane 38 is arranged on an inward-facing side 40 of the rupture disc 34 and thus of the predetermined rupture area 30. In other words, the membrane 38 is offset into the interior of the base body 26 and therefore also of the cell housing 28 with respect to the rupture disc 30 and the other predetermined rupture area 30. Between the membrane 38 and the rupture disc 34, web-shaped spacers 42 are arranged, by means of which the membrane 38 is partially supported on the rupture disc 34 and thus also on the predetermined rupture area 30. In other words, the membrane 34 is spaced from the predetermined rupture area 30 by the thickness of the spacers 42.

[0071] One of the spacers 42 is arranged at the edge of the membrane 38 and is designed to be circular or annular. This spacer 42 is attached to the rupture disc 34 in a gas- and liquid-tight manner, i.e., fluid-tight, by laser welding. The other spacers 42, however, only rest loosely on the rupture disc 34 and, unlike the annular spacer 42, do not completely enclose a spatial area circumferentially. All spacers 42 are molded onto the membrane 38 and are made of the same material and manufactured in the same production step.

[0072] The membrane 38 is designed such that it ruptures when the pressure difference between the pressure outside the cell housing 28 and the pressure inside the cell housing 28 exceeds a first threshold. The first threshold is 50% lower than the burst pressure, i.e., the second threshold. Once rupture has begun, it continues until the pressure difference drops below the first threshold. When this occurs, the rupture stops.

[0073] The opening 36 is covered by an additional membrane 44, which is arranged on the outside of the rupture disc 34 and thus also of the predetermined rupture area 30. Thus, the additional membrane 44 is offset outwardly with respect to the rupture disc 34 / the predetermined rupture area 30, and the opening 36 is covered on each side by one of the membranes 38, 44. The additional membrane 44 is gas-permeable but also hydrophobic. In other words, water is repelled by the additional membrane 44. The additional membrane 44 is also attached to the rupture disc 34 in a fluid-tight manner.

[0074] During operation of the battery cell 14, it is possible that gases such as H2 and / or CO2 form in the cell housing 28 due to unwanted chemical reactions, for example due to a comparatively high load or due to unwanted foreign particles. The gases 36 require a larger volume than the reactants, so that the pressure inside the cell housing 28 increases. Thus, the pressure inside the cell housing 28 is higher than outside the cell housing 28. In other words, the ambient pressure around the cell housing 28 is lower than the pressure inside the cell housing 28. As a result, the gases, or at least some of the gases, escape through the membrane 38 and through the opening 36 and the further membrane 44 into the environment of the battery cell 14, so that pressure equalization occurs. Since the surface area of ​​the membrane 38 is comparatively large, it is possible to discharge a comparatively large volume of gases.A portion of this gas passes through the area of ​​the membrane 38 that is covered by the rupture disc 34. Subsequently, there is no further fluidic resistance for this portion to pass through the opening 36, since, with the exception of the outermost spacer 42, no space is completely enclosed. In other words, the spacers 42 do not impede the further flow of gases. The outermost spacer 42 prevents the gases or any other fluid from flowing out of or into the cell housing 28 between the rupture disc 34 and the membrane 38 without passing through the membrane 38.

[0075] The gases flowing out through the opening 36 pass through the additional membrane 44 and thus escape. The membrane 44 prevents water in liquid or gaseous form, as well as water vapor, from penetrating the opening 36 and thus also into the interior of the cell housing 28. Should moisture nevertheless reach the membrane 38, it is retained by the membrane 38, which has a comparatively high impermeability to moisture. This prevents moisture from outside the cell housing 28 from entering it and causing undesired reactions with the electrodes 20.

[0076] If, due to special circumstances, such as excessive loading, the volume of gases allowed to pass through the membrane 38 is insufficient to limit the pressure difference to below 0.5 bar, i.e., the first limit value, the membrane 38 begins to tear. As a result, an increased volume of gases can pass through, limiting or at least slowing the pressure increase. If this is sufficient to eliminate the pressure difference, further operation of the battery cell 14 is subsequently possible, with the membrane 38 only partially preventing the penetration of moisture from the outside into the cell housing 28.Alternatively, or in combination with the rupture of the membrane 38, the fluid-tight connection of the outermost spacer 42 to the rupture disc 34 also begins to dissolve at a pressure difference that is greater than the first limit value, so that gases can escape there as far as the opening 36 and from there into the environment. If, even with a completely ruptured / detached membrane 38, i.e., when the opening 36 is completely exposed with the exception of the further membrane 44, the pressure increase is not limited and exceeds the bursting pressure, i.e., the second limit value, the rupture disc 34 ruptures, opening the further opening 32. Thus, the volume of gases that can escape from the cell housing 28 is further increased, with essentially no fluidic resistance being present.Thus, the pressure difference is reduced comparatively quickly, preventing uncontrolled destruction of the base body 26, which could lead to damage to objects located in the vicinity of the battery cell 14. However, it is also possible that the electrolyte could leak from the additional opening 32, rendering the battery cell 14 unusable.

[0077] Figure 5 shows a modification of the battery cell 14, wherein the additional opening 32 as well as the position of the rupture disc 34 and its attachment to the base body 26 have not been changed. The rupture disc 34, i.e., the predetermined breaking area 30, also still has the opening 36, which is also not modified. In this embodiment, however, the rupture disc 34 is made of a polymer, and the thickness of the rupture disc 34 is adjusted such that it also breaks at a burst pressure of 1 bar. The opening 36 is also still completely covered by the membrane 38, which is arranged offset from the rupture disc 34 into the interior of the base body 26. The material of the membrane 38 has also not been changed. However, the surface area of ​​the membrane 38 is slightly reduced, and it lies mechanically directly against the rupture disc 34, i.e., the predetermined breaking area 30, and is attached to it, namely by ultrasonic welding.Thus, a fluid-tight connection is directly realized between the membrane 38 and the predetermined breaking area 30.

[0078] In comparison to the previous embodiment, the additional membrane 44 is omitted, and the opening 36 is surrounded by an annular or hollow-cylindrical drying element 46, which is hydrophilic and made of a silicate. With the exception of the membrane 38, the opening 36 is thus not covered. The drying element 46 absorbs water, and therefore also water vapor, that strikes the predetermined breaking area 30 in the region of the opening 36 from the outside, so that it does not reach the opening 36. Thus, the drying element 46 prevents or at least reduces the penetration of moisture into the cell housing 28. During operation of the battery cell 14, the drying element 46 is at least partially heated due to heat loss, so that any absorbed moisture is released back into the environment and transported away. The drying element 46 is thus ready for use for a comparatively long period of time.The functionality of the membrane 38 and the rupture disc 34 is unchanged compared to the previous embodiment. However, in this variant, the effective area provided for the passage of gases through the opening 36 by the membrane 38 is equal to the area of ​​the opening 36. In other words, the volume of gases that can pass through the membrane 36 is reduced. Therefore, in this variant of the battery cell 14, the pressure increase in the cell housing 28 until the membrane 38 ruptures or the rupture disc 34 bursts is only slightly reduced or limited.

[0079] Figure 6 shows a further modification of the battery cell 14, wherein the cell housing 26 and the further opening 32, which is closed by the rupture disk 34, have not been changed. Thus, the rupture disk 34, and therefore also the predetermined rupture region 30, still has the opening 36. The membrane 38 is again present, with the extension of the membrane 38 essentially corresponding to the variant shown in Figure 3. However, the membrane 38 is now attached to the edge of the opposite side of the rupture disk 30, i.e., to an outer side 48 of the cell housing 28, namely on the outward-facing side of the predetermined rupture region 30, namely by means of thermal welding. Otherwise, the membrane 38 is not attached to the rupture disk 34 and in the other areas merely rests loosely on the rupture disk 34.

[0080] The battery cell 14 further comprises a stabilizing element 50, by means of which the membrane 38 is completely covered and which protrudes slightly beyond the membrane 38 at the edge. Thus, the membrane 38 bears against the outside of the stabilizing element 50, which is made of a metal. In the edge region of the stabilizing element 50, the element is continuous and welded to the predetermined breaking area 30, namely the rupture disk 34, thus forming a fluid-tight connection thereto. With the exception of the edge, the stabilizing element 50 is designed in the manner of a grid and thus has a plurality of additional openings 52.

[0081] During operation of the battery cell 14, any gases that may be produced first escape through the opening 36 and then through the membrane 38 and the additional openings 52 into the environment. Because the membrane 38 only loosely fits against the rupture disc 34, with the exception of the edge attachment, an accumulation of the gases is possible in the area formed between the membrane 38 and the rupture disc 34, so that a comparatively large surface area of ​​the membrane 38 is available for the passage of the gases. In this case, the membrane 38 is partially bulged / bulged outwards, with excessive bulging being prevented by the stabilizing element 50. Thus, a corresponding bulge of the membrane 38 results in each of the additional openings 52. Due to the bulge or bulge, the surface area of ​​the membrane 38 available for the passage of the gases is further increased.However, excessive deformation of the membrane 38 is prevented by the stabilizing element 50, thus avoiding damage to the membrane 38. The stabilizing element 50 also stabilizes the mechanical connection between the membrane 38 and the rupture disc 34, thus preventing the membrane 38 from tearing off the rupture disc 34.

[0082] If the pressure difference between the pressure inside the cell housing 28 and the pressure outside the cell housing 28 exceeds the first limit value, the stabilizing element 50 ruptures at least partially, thereby eliminating the stabilizing function of the membrane 38. As a result, the membrane 38 ruptures, allowing an increased volume of gases to continue to escape.

[0083] Figure 7 shows a further modification of the battery cell 14. This variant essentially corresponds to the previous embodiment, except that the stabilizing element 50 is covered on the outside with the additional membrane 44. Thus, the stabilizing element 50 is located between the two membranes 38, 44. The additional membrane 44 prevents moisture from penetrating the additional openings 52 and thus up to the membrane 38, while still allowing gases to escape from the cell housing 28.

[0084] In a variant not shown in detail, instead of the further membrane 44 or in addition there is the drying element 46, by means of which the stabilizing element 50 is surrounded, or which rests on the edge of the stabilizing element 50, so that the opening 36 is surrounded thereby.

[0085] In variants not shown in detail, either in the embodiment according to Figure 6 or in the embodiment according to Figure 7, the stabilizing element 50 is omitted, and the membrane 38 is designed to be more stable. When gases accumulate between the membrane 38 and the rupture disc 34, the membrane 38 thus bulges comparatively far, preventing tearing. This only occurs when the first limit value is exceeded.

[0086] Figures 8 and 9 show variants of the battery cell 14, each of which has a modified predetermined breaking region 30. This still has the opening 36, which is covered by the membrane 38. In the variants shown, the membrane 38 is fastened to the outer side 48 of the cell housing 28, namely by welding. In the two variants shown, neither the additional membrane 44 nor the drying element 46 or the stabilizing element 50 is present. However, in modifications not shown in detail, the battery cell 14 is further developed according to the variants shown in Figures 4-7, the predetermined breaking region 30 being designed according to the embodiment shown in Figures 8 and 9.

[0087] In the variant shown in Figure 8, a wall thickness of the cell housing 28, namely of the base body 26, is reduced in the predetermined breaking region 30. The predetermined breaking region 30 is molded onto the base body 26 and is integral with it. Compared to the base body 26, however, the wall thickness in the predetermined breaking region 30 is reduced to 25%, so that the predetermined breaking region 30 is separated from the base body 46 by a circumferential step 54. In other words, the step 54 forms the transition from the predetermined breaking region 30 to the base body 26. The wall thickness in the predetermined breaking region 30 is constant. The predetermined breaking region 30 is round and arranged concentrically to the opening 36.

[0088] To produce the predetermined breaking area 30, material is removed from the created base body 26, which has a continuous wall thickness, for example, by milling or using a laser. In the illustrated variant, the material is removed from the inside, so that the outside of the cell housing 28 is flat. This facilitates attachment of the membrane 38.

[0089] In the variant shown in Figure 9, the predetermined breaking region 30 has essentially the same wall thickness as the base body 26, and the predetermined breaking region 30 is also integral with the base body 26. The predetermined breaking region 30 is separated from the base body 26 by means of a circumferential notch 56, which is also introduced into the base body 28 after completion of the latter to create the predetermined breaking region 30. Consequently, the outer contour of the predetermined breaking region is delimited by the notch 56. The notch 56 is annular and arranged concentrically to the opening 36. In addition, the predetermined breaking region 30 has another such notch 56, which is also annular but has a reduced diameter. The predetermined breaking region 30 thus comprises the two notches 56 arranged concentrically to the opening 36, which represent a structural weakening of the cell housing 26.

[0090] In the variants of the predetermined breaking area 30 shown in Figures 8 and 9, the weakening of the cell housing 28 by reducing the wall thickness or the notches 56 is such that the predetermined breaking area 30 breaks when the bursting pressure is exceeded, allowing an increased volume of gas to escape from the cell housing 26. This also prevents uncontrolled damage to the base body 26 in the event of a pressure increase.

[0091] The invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived therefrom by those skilled in the art without departing from the scope of the invention. In particular, all individual features described in connection with the individual exemplary embodiments can also be combined with one another in other ways without departing from the scope of the invention.

[0092] List of reference symbols

[0093] Motor vehicle

[0094] wheel

[0095] drive

[0096] Energy storage

[0097] interface

[0098] Energy storage housing

[0099] Battery cell

[0100] anode

[0101] cathode

[0102] electrode

[0103] Busbar

[0104] Connection

[0105] Basic body

[0106] Cell housing

[0107] Predetermined breaking area further opening

[0108] rupture disc

[0109] opening

[0110] Membrane facing inwards

[0111] Spacer additional membrane

[0112] Drying element

[0113] Outside stabilizing element additional opening step notch

Claims

Claims: A battery cell (14) with a cell housing (28) in which several electrodes (20) are arranged and which has a predetermined breaking point (30), wherein the predetermined breaking point (30) has an opening (36) which is covered by a gas-permeable membrane (38). A battery cell (14) according to claim 1, characterized in that the membrane (38) is configured such that it tears when a pressure difference between a pressure outside the cell housing (28) and a pressure inside the cell housing (28) exceeds a first limit value. A battery cell (14) according to claim 2, characterized in that the predetermined breaking point (30) is configured such that it breaks when the pressure difference between the pressure outside the cell housing (28) and the pressure inside the cell housing (28) exceeds a second limit value that is greater than the first limit value.A battery cell (14) according to any one of claims 1 to 3, characterized in that the membrane (38) is attached to an outer surface (48) of the cell housing (28). A battery cell (14) according to claim 4, characterized in that the membrane (38) rests on a stabilizing element (50) on the side facing away from the cell housing (26), the stabilizing element having several additional openings (52). A battery cell (14) according to any one of claims 1 to 3, characterized in that the membrane (38) is arranged on an inwardly facing side (40) of the predetermined breaking point (30), wherein the membrane (38) is partially supported on the predetermined breaking point (30) by spacers (42). Battery cell (14) according to one of claims 1 to 6, characterized in that the cell housing (28) comprises a base body (26) with a further opening (32) into which a burst disc (34) is inserted, wherein the predetermined breaking area (30) comprises the burst disc (34). A battery cell (14) according to any one of claims 1 to 7, characterized in that the wall thickness of the cell housing (28) is reduced in the predetermined breaking point (30). A battery cell (14) according to any one of claims 1 to 8, characterized in that the cell housing (28) has a notch (56) in the predetermined breaking point (30), by means of which, in particular, an outer contour of the predetermined breaking point (30) is defined. A battery cell (14) according to any one of claims 1 to 9, characterized in that the opening (36) is surrounded by a drying element (46).

Images