Battery cell

Abstract

The present invention relates to a battery cell (14) comprising a cell casing (28) within which a plurality of electrodes (20) are arranged. The cell casing (28) has a target break region (30) which has an opening (36). This opening (36) is covered by a gas-permeable diaphragm (38).

Description

Technical Field

[0001] The present invention relates to battery cells. A battery cell has a cell casing in which a plurality of electrodes are arranged.

[0002] Automobiles are increasingly being driven at least partially by electric motors, and thus such automobiles are configured as electric vehicles or hybrid vehicles. For power supply to the electric motor, a high-voltage battery including a plurality of individual battery modules is usually considered. The battery modules often have the same structure as each other and are electrically connected in series and / or in parallel with each other. As a result, the voltage applied to the high-voltage battery corresponds to several times the voltage provided by each battery module. Each battery module itself often has a plurality of battery cells arranged in a common module casing, and these battery cells are electrically connected in series and / or in parallel with each other.

[0003] Each battery cell also usually has a plurality of galvanic elements. These galvanic elements each have two electrodes, namely an anode and a cathode, a separator arranged therebetween, and an electrolyte having freely movable charge carriers. For example, a liquid is used as such an electrolyte. Alternatively, the battery cell is formed as a solid battery, and the electrolyte exists as a solid. The anode and cathode forming the electrodes of the battery cell usually include a support that functions as a conductor. On this conductor, an active material, which is a component of a layer deposited on the support, also usually called a conductor, is attached. In this case, an electrolyte already exists in this layer or it is possible to introduce the electrolyte later. However, at least the active material is suitable for absorbing working ions, such as lithium ions. Depending on the use as an anode or a cathode, different materials are used for the support, and various types of layer materials are used.

[0004] To protect the galvanic element, the galvanic element is usually arranged within the cell casing of a battery cell, which is also commonly referred to as a cell cup. Also, the cell casing protects the electrolyte from the influence of the environment. To enable each battery cell to provide a relatively large capacity, usually a plurality of, typically up to 100, such galvanic elements are arranged within one common cell casing. To utilize the existing space relatively efficiently and to simplify manufacturing, the individual components of the galvanic element are configured in a planar manner and stacked on top of each other in the stacking direction, thereby forming a substantially cuboid cell stack. In an alternative embodiment, for example, the separator is configured in a strip shape and a plurality of electrodes are provided on opposite surfaces respectively. This strip is wound up to form a roll, in particular a so-called "Jelly Roll". Accordingly, the galvanic element is wound up in a cylindrical shape.

[0005] Depending on the use and arrangement of the galvanic element, the cell casing is shaped. In this case, the cell casing can be configured to be rigid and can be manufactured, for example, from aluminum. In this case, the shape of the cell casing is, for example, a cuboid shape. A battery cell of such a type is also referred to as a prismatic cell. In an alternative embodiment, the cell casing is made of a film coated around the galvanic element. A battery cell of such a type is also referred to as a so-called pouch cell.

[0006] During operation of the battery cell, i.e., during charging and discharging, there is a risk of gas generation based on undesirable chemical reactions. Based on this, the pressure inside the cell casing increases, and as a result, on the one hand, non-contact connection of the individual electrodes may occur, resulting in output loss of the battery cell. On the other hand, the increased pressure may cause the cell casing to deform, which may mechanically affect especially the surroundings of the battery cell. When the pressure is relatively high, the cell casing may rupture, which may cause the electrolyte to leak out and the entire battery cell to become unusable. There is also a risk of undesirable chemical reactions between the individual components of the battery cell and the surroundings.

[0007] To avoid such gas formation, a special selection of the individual materials of the electrodes is necessary, which on the one hand increases the manufacturing cost. On the other hand, in the case of such materials, the capacity of the battery cell decreases. Alternatively, for example, additional elements for binding and / or reacting the generated gas are provided inside the cell casing. In another variant, the cell casing is configured to be relatively robust, so that the pressure leading to damage of the cell casing does not occur during operation of the battery cell. However, the additional elements or the robust configuration of the cell casing also increase the construction space and the weight of the battery cell, so that the energy density is reduced.

[0008] The underlying problem of the present invention is to provide a particularly suitable battery cell with advantageously improved operational reliability and / or energy density.

[0009] According to the present invention, this problem is solved by the characterizing part of claim 1. Advantageous developments and configurations are the subject of the dependent claims.

[0010] The battery cell is configured to be rechargeable in particular and is preferably a secondary battery. Preferably, the battery cell is a component of a motor vehicle in a predetermined state. The battery cell is suitable therefor, in particular provided and adjusted. In the predetermined state, the battery cell is, for example, a component of the energy accumulator of a motor vehicle, and this energy accumulator has a plurality of battery cells of such a type. Preferably, in this case, these battery cells are also divided into a plurality of battery modules of the same structure as each other. The battery cells are arranged in particular within the casing of the energy accumulator or each battery module and are electrically connected to each other in parallel and / or in series. Thus, the voltage applied to the energy accumulator / battery module is several times the voltage provided by each of the battery cells. Preferably, in this case, all the battery cells have the same structure as each other, which facilitates manufacture.

[0011] Thus, in particular, the casing of the energy accumulator or each battery module forming such a composite of battery cells is preferably manufactured from metal, for example steel such as special steel, or an aluminum alloy. For manufacture, for example, die-casting, deep drawing, casting press or extrusion press is used. In particular, the casing of the energy accumulator or each battery module is configured to be closed. Preferably, an interface forming the terminals of the energy accumulator / battery module is attached within the casing of the energy accumulator or each battery module. In this case, since the interface is in electrical contact with the battery cells, the supply of electrical energy and / or the extraction of electrical energy from the battery cells is possible from the outside of the energy accumulator if a corresponding connector is inserted into the terminals.

[0012] The motor vehicle is preferably a land vehicle, preferably having a specific number of wheels, and at least one of these wheels, in a suitable form a plurality or all of the wheels, is driven by one drive device. In particular, one of the wheels, preferably a plurality, is configured to be controllable. Thus, the motor vehicle is movable without depending on a specific travel path, such as a rail or the like. In this case, preferably, the motor vehicle can be positioned substantially arbitrarily on a travel path, in particular made of asphalt, bitumen or concrete. The motor vehicle is, for example, a commercial vehicle such as a goods vehicle (Lkw: Lastkraftwagen) or a bus. However, particularly preferably, this motor vehicle is a passenger car (Pkw: Personenkraftwagen).

[0013] By means of the drive device, preferably, the motor vehicle is caused to move forward. For example, the drive device, in particular the main drive device, is at least partially electrically configured, and the motor vehicle is, for example, an electric vehicle. The electric motor is driven, for example, by an energy accumulator configured as a high-voltage battery in a suitable form. By means of the high-voltage battery, preferably a DC voltage is supplied, and this voltage is, for example, between 200 V and 800 V, for example substantially 400 V. Preferably, an electric converter for regulating the power supply to the electric motor is arranged between the energy accumulator and the electric motor. Alternatively, the drive device has an additional internal combustion engine, whereby the motor vehicle is configured as a hybrid motor vehicle. Alternatively, the low-voltage on-board power supply network of the motor vehicle is supplied with power by the energy accumulator, and the energy accumulator provides, in particular, a DC voltage of 12 V, 24 V or 48 V.

[0014] In a further alternative form, the battery cell is a component of an industrial vehicle, industrial equipment, such as tools, in particular a handheld device such as a rechargeable driver. In a further alternative form, the battery cell is a component of an energy supply unit, where, for example, it is used as a so-called buffer battery. In a further alternative form, the battery cell is a component of a portable device, such as a mobile phone, or other wearable devices. Such battery cells can also be used in the camping field, in the model making field, or for other outdoor activities.

[0015] The battery cell has a plurality of electrodes, i.e., for example, two or preferably more electrodes. In particular, these electrodes are divided into an anode and a cathode, in which case preferably half of these electrodes form the anode and the other half form the cathode. However, preferably, there is one more anode than cathode. Particularly preferably, all the anodes and all the cathodes have the same structure as each other, which simplifies manufacturing. The electrodes are, for example, configured in a planar shape and in particular have a support, also called a conductor. In particular, each support is formed by a metal foil that is at least partially coated on one or both sides by a layer. As the metal of the support / conductor of the cathode, for example, aluminum is used, and as the metal of the conductor of the anode, copper is used.

[0016] In this case, the layer has a thickness of less than 1 mm. Preferably, the thickness of the support is less than 0.1 mm. Preferably, each layer has an active material, a binder, and / or a conductive additive such as conductive carbon black. The active material is used to absorb working ions such as lithium ions, is suitable for this purpose, and is provided and adjusted. As the active material, for the cathode, for example, lithium metal oxides such as lithium cobalt(III) oxide (LiCoO2), NMC, such as NMC622 or NMC811, NCA, LMNO, or LFP are used, and / or for the anode, LTO, or graphite based on Si is used.

[0017] In particular, the electrodes are substantially rectangular. The electrodes are, for example, stacked on top of each other to form a cell stack, in which case the stacking direction is perpendicular to the extending direction of the electrodes arranged parallel to each other. In this case, the anode and the cathode preferably appear alternately in the stacking direction of the cell stack. Preferably, one separator of the cell stack is arranged between adjacent electrodes, that is, in particular between one anode and one cathode, and this separator is preferably also configured in a planar manner. For example, all the separators have the same structure as each other. In particular, these electrodes are stacked substantially flush with each other, in which case, for example, all the anodes protrude at least slightly beyond the cathode. Particularly preferably, in this case, the protrusion is enlarged on one of the two sides. Preferably, the cathode also protrudes beyond the anode on one side, in which case the (enlarged) protrusions are located on opposite sides of the cell stack. In this way, contact with other components of the anode and the cathode is facilitated. Therefore, based on the fact that the electrodes are stacked, the cell stack is also substantially rectangular.

[0018] In an alternative embodiment, for example, all the anodes, all the cathodes, or the separators are formed by one common strip, or they are attached to one common strip. Since the strip itself is rolled up into a cylindrical shape or the like, a so-called "jelly roll" is formed.

[0019] The battery cell has a cell casing inside which the electrodes are arranged, that is, for example, a cell stack or a "jelly roll" is arranged. In a suitable form, the cell casing has a substrate, and the electrodes are arranged inside this substrate. The substrate is, in this case, configured, for example, in a pot shape and is closed by a lid of the cell casing. Therefore, the arrangement of the electrodes is made easy. In particular, the cell casing, preferably the substrate, is from 0.1 dm 3 to 10 dm 3The volume is enclosed. For example, additionally, the cell casing is at least partially filled with an electrolyte, or the electrolyte is, for example, already partially formed by each active material. The cell casing, in particular, the substrate which may be present in some cases, is preferably configured to be rigid. In other words, the battery cell is a prismatic cell. In particular, the cell casing, preferably the substrate and / or the lid which may be present in some cases, is manufactured from a metal, for example aluminum, that is, pure aluminum or an aluminum alloy. The cell casing, in particular the substrate, has, for example, a cuboid shape. Alternatively, the cell casing, preferably the substrate, is configured to be flexible and is formed, for example, at least partially, in particular on one or both sides, by a metal foil that is coated. A metal foil is wound around the electrodes and the ends of the metal foil are preferably sealed, so that the outflow of the electrolyte and / or the inflow of ambient air into the cell casing are avoided.

[0020] The electrodes are arranged directly in the cell casing in particular, whereby the electrodes are applied, for example directly or via another component, against the inner wall of the cell casing and are thus stabilized by the inner wall. At least, the cell casing serves for the direct protection of the electrodes and / or for preventing contact between the electrodes / electrolyte and the ambient air or other particles. In other words, the electrodes inside the cell casing are preferably not at least completely surrounded by another component, so that the weight and material costs of the battery cell are reduced. In particular, there is no separate casing surrounding the electrodes inside the cell casing. Thus, it is possible to fill the cell casing substantially completely with the electrodes and, in some cases, the separator provided.

[0021] In a suitable form, the cell casing has at least one or two through-holes, through which one terminal is guided respectively. By means of one or more terminals, at least some of the electrodes arranged on the cell casing are electrically contact-connected, whereby electrical energy can be supplied to the galvanic element formed by the electrodes and / or electrical energy can be taken out from the galvanic element from the outside of the cell casing via the one or more terminals. If only one terminal is provided, at least some of the electrodes are electrically contacted with the cell casing, whereby the potential of the cell casing is preset by this electrode. In particular, one or more terminals are electrically insulated from the cell casing, and these terminals are fluid-tightly connected to the cell casing, so that the outflow of the electrolyte is avoided in the region of the terminals.

[0022] The cell casing, in particular the substrate that may be present in some cases, has a target breaking region. Thus, the target breaking region covers a predetermined area of the cell casing, in particular of the substrate. The target breaking region is configured to break when there is a predetermined differential pressure between the inside and the outside of the cell casing, so that, in particular, the exchange of substances between the inside of the cell casing and the surroundings becomes possible. The breaking of the target breaking region is irreversible in this case. For example, when the differential pressure, which is also particularly described as the bursting pressure below, is exceeded, the entire such target breaking region or simply a part thereof breaks. In particular, in this case, the area of the target breaking region that breaks and thus opens depends on the actually existing differential pressure.

[0023] In this case, the cell casing is formed such that, particularly when the burst pressure is exceeded, the cell casing first breaks only in the region of the target fracture region, while the remaining components of the cell casing, particularly the substrate, are maintained without damage. The remaining components break only when a greater differential pressure occurs, and in this case, they break in an uncontrolled manner. The burst pressure is preferably selected to be less than the differential pressure between the pressure inside the cell casing and the pressure outside the cell casing that causes, for example, complete rupture or breakage of the cell casing. Preferably, the burst pressure is 70% - 90%, 75% - 85% or 80% of this differential pressure.

[0024] The target fracture region has an opening that is particularly located in the central region, i.e., shifted inward from the edge of the target fracture region. In a suitable form, the spacing of this opening from the edge of the target fracture region is greater than 1 / 4 of the extent of the target fracture region in each direction. In particular, this opening is exactly centered in the target fracture region. The area of this opening is smaller than the area of the target fracture region, particularly less than 50%, 20%, 10%, 5%, 1% or 0.1% of the area of the target fracture region.

[0025] The opening is covered by a gas-permeable diaphragm. In particular, the diaphragm is firmly, i.e., immovably, connected to the cell casing, preferably to the substrate and / or the target breaking region, so that movement of the diaphragm relative to the cell casing / substrate is avoided. The area of the diaphragm is at least as large as the area of the opening or, preferably, larger than the area of the opening, whereby the diaphragm completely overlaps the opening. In particular, the area of the diaphragm is smaller than the area of the entire target breaking region. Thereby, the material cost is reduced. Also, the diaphragm area may be optimized with respect to the required working surface and the connection to the target breaking region / cell casing, regardless of the area of the target breaking region. Alternatively, this area is larger than the area of the target breaking region and the diaphragm overlaps the target breaking region. Thereby, when the diaphragm is attached to the cell casing especially on the edge side, it does not affect the target breaking region.

[0026] Preferably, the diaphragm is arranged such that liquid and / or gas is prevented from passing through between the diaphragm and the target breaking region. In other words, the diaphragm is gas-tightly and fluid-tightly connected to the cell casing, for example directly or via another component. For this purpose, particularly preferably, the diaphragm is welded to the cell casing, for example to the target breaking region, in a suitable manner with a circumferential weld seam. For this purpose, for example, ultrasonic welding, laser welding, or thermal welding methods are used. Alternatively, for example, the diaphragm is form-fittingly and / or materially connected, in particular adhesively bonded, to the cell casing. In this case, the opening is preferably completely surrounded by an adhesive or a weld seam. For example, the connection is made directly adjacent to the opening or a gap is formed between the opening and the connection of the diaphragm to the cell casing, for example an adhesive or a weld seam. Thus, outflow of gas from the cell casing or inflow of gas into the cell casing is only possible through the opening, and the gas is guided through the diaphragm.

[0027] In particular, the diaphragm is selected to be permeable to CO, CO2, H2 and / or CH4. For example, with the diaphragm, the passage of such gases is either not blocked at all or only blocked to a relatively small extent. However, the permeability of the diaphragm is preferably significantly lower with respect to moisture, particularly water vapor. In particular, the ratio of the CO2 permeability to the moisture permeability of the diaphragm is at least 0.5, at least 1 or at least 1.5. Preferably, this ratio is greater than 0.5 and less than 3. In particular, the diaphragm functions as a barrier against the intrusion of moisture, particularly water vapor, into the cell casing. In short, the diaphragm is configured such that such gases generated within the cell casing can pass through the diaphragm and reach outside the cell casing through the opening, and for this purpose the opening is utilized. In this case, the intrusion of liquids, particularly water, into the cell casing is made difficult or is clearly reduced by the diaphragm.

[0028] Based on the gas-permeable diaphragm, substantially continuous degassing of the cell casing is possible, thereby avoiding or delaying the formation of a differential pressure between the pressure outside the cell casing and the pressure inside the cell casing, particularly based on the undesired generation of gas in the cell casing during the operation of the battery cell. In this case, based on the relatively small area of the opening, on the one hand, the mechanical integrity of the cell casing is only slightly reduced. On the other hand, only in this area is it basically possible for foreign substances, such as moisture or liquid, to enter the cell casing, and such a situation is relatively unlikely to occur. Therefore, a relatively safe operation of the battery cell is possible over a relatively long period, thereby improving the operational reliability. In other words, when there is no hindrance to the operation of the battery cell based on substantially continuous discharge through the diaphragm, no excessive gas is collected in the cell casing, so the differential pressure between the periphery of the cell casing and the inside of the cell casing remains relatively small.

[0029] However, based on unwanted chemical reactions within the cell casing, for example during overload, the differential pressure rises relatively significantly and rapidly, and as a result, the generated gas cannot be sufficiently discharged through the openings and the diaphragm. In this case, the target rupture area ruptures, and the cell casing opens at a defined location, i.e., the target rupture area. Thus, uncontrolled damage to the cell casing and uncontrolled effects on the surroundings are avoided. Rather, this occurs only in the area of the target rupture area, and thus the built-in state of the battery cell can be adapted thereto. Therefore, the operating reliability is improved.

[0030] The diaphragm is made especially from a polymer, for example a film, for example a polymer film. In a suitable form, the diaphragm is made of or consists of PTFE, i.e., polytetrafluoroethylene. Preferably, the diaphragm has a crystallinity of 85% - 100% and a density of 0.2 g / cm 3 ~2 g / cm 3 In such a material selection, gas permeability is provided, and in this case, the diaphragm prevents or at least makes it difficult for moisture, especially water vapor, to penetrate into the cell casing. Diaphragms suitable for battery applications are described in WO 2021 / 079163. For example, the diaphragm is formed flat. In this way, the manufacturing is simplified and the weight is reduced.

[0031] For example, the target rupture area / openings are arbitrarily positioned in the cell casing. However, particularly preferably, when the battery cell is configured as a pouch cell, the target rupture area / openings are located in the area near the conductor at one of the cylindrical ends, in the area where the foil that may exist is particularly sealed (for example, on the so-called gas pocket). In this case, the target rupture area / openings are preferably shifted inward from each end by up to 1 / 3 of the maximum length of the cell casing.

[0032] When the battery cell is a rectangular cell, preferably, the target breaking region / aperture is present in particular in regions of end faces and / or narrow-width faces that are not parallel to the electrodes that are stacked in some cases to form a cell stack. Alternatively, the aperture is located on the side face of the cell casing that is parallel to the electrodes, but preferably in the edge region, i.e., shifted inward from the edge by up to 1 / 3 of the width of this side face at most. Such a position of the aperture simplifies the structure and does not require changing the existing design of the cell stack. Thus, further, the target breaking region / aperture is arranged in a region where the generated gas accumulates, whereby relatively efficient discharge of the gas through the aperture is possible. For example, the target breaking region has only one aperture covered by a diaphragm. Alternatively, the target breaking region has a plurality of such apertures each covered by a diaphragm. In this case, the diaphragm is, for example, continuously configured, or a corresponding (separate) diaphragm is arranged corresponding to each of the apertures.

[0033] The target breaking region is configured, for example, in a stadium shape, circular or rectangular. In particular, the area of the target breaking region is 0.01 cm 2 ~20 cm 2 , preferably 0.1 cm 2 ~10 cm 2 . In a suitable form, the target breaking region has a size of 0.01% to 50% of the area of the cell casing. Preferably, the target breaking region has a size of 0.1% to 40%, particularly 0.3% to 30% of the area of the complete cell casing. For example, the diaphragm has an area 50% larger than the aperture. In a suitable form, the aperture has an area of 50 μm 2 ~15 mm 2 , preferably 0.2 mm 2 ~3 mm 2 .

[0034] Preferably, the opening is covered by another diaphragm that is gas permeable and hydrophobic, i.e., repels at least water. Preferably, the contact angle of the material of the other diaphragm with respect to water is greater than 80°, 90° or greater than 100°, especially when this material is also exposed to air in the same way or is present in the ambient air. Thus, this other diaphragm separates the moisture from the diaphragm, making it even more difficult for moisture to penetrate into the cell casing. However, at least with some other diaphragms, the moisture entering from the outside is separated.

[0035] In particular, the two diaphragms are arranged in parallel, and the other diaphragm preferably completely covers the diaphragm. Preferably, the other diaphragm is fluid-tightly attached to the cell casing, for example in the target break region. For example, the opening is directly covered by the other diaphragm, and the other diaphragm is directly attached to the cell casing. In this case, the diaphragm is particularly shifted and positioned inwardly with respect to the target break region or at least the other diaphragm, so that the opening is covered on both sides by the two diaphragms. Thus, the diaphragm is also protected by the diaphragm, and the impact of water (vapor) on the diaphragm is prevented. By arranging the two diaphragms on both sides of the target break region, the structure is simplified, and the two diaphragms are preferably fluid-tightly attached to the cell casing. Alternatively, for example, the positions of the other diaphragm and the diaphragm are interchanged. In a further alternative embodiment, the other diaphragm and the diaphragm are located on the same side with respect to the cell casing / target break region, and since the other diaphragm particularly covers the diaphragm, the opening is also covered. In particular in this case, the other diaphragm is shifted outwardly with respect to the diaphragm, whereby this diaphragm is protected by the other diaphragm. This also makes it possible to relatively largely select the area of the other diaphragm used for gas passage. For example, the other diaphragm is attached to the diaphragm, and this diaphragm particularly provides a kind of laminate or sandwich body. This simplifies the manufacturing process.

[0036] For example, the diaphragm is formed to have crack resistance. However, particularly preferably, the diaphragm is configured to rupture when the differential pressure between the pressure outside the cell casing and the pressure inside the cell casing exceeds a first threshold value. Due to the rupture, the flow of gas through the diaphragm or at least the opening is accelerated, so the pressure inside the cell casing drops relatively quickly. Thereby, damage to the cell casing is avoided. For example, when the first threshold value is exceeded, the diaphragm ruptures completely and thus is destroyed, i.e., breaks. Therefore, the full area of the opening is effectively used for the gas flow, whereby the differential pressure can be dropped relatively quickly. Alternatively to or in combination with the rupture of the diaphragm, for example, when the first threshold value or another threshold value is exceeded, the fluid-tight connection of the diaphragm to the cell casing is at least partially released. Therefore, gas outflow is also possible here, which leads to a reduction in the differential pressure.

[0037] The first threshold value is preferably smaller than the rupture pressure forming the second threshold value. Therefore, the target rupture region is configured to rupture when the differential pressure between the pressure outside the cell casing and the pressure inside the cell casing exceeds a second threshold value that is greater than the first threshold value. The first threshold value is, for example, 90% - 50% of the second threshold value (rupture pressure), 80% - 60% of the second threshold value (rupture pressure), or, for example, substantially 70% of the second threshold value (rupture pressure). Therefore, during excessive pressure increase, first the diaphragm is at least partially destroyed, while the target rupture region remains undamaged. Therefore, the operation of the battery cell can continue thereafter. In contrast, if the differential pressure does not fall below the rupture pressure despite the rupture of the diaphragm, the target rupture region ruptures, thereby preventing the rupture of the cell casing at another location.

[0038] For example, the diaphragm is attached to the outer surface of the cell casing, for example, to the outer surface of the target breaking region or, in some cases, the existing substrate. As a result, the inner space of the cell casing is not filled with the diaphragm, so a relatively large volume is provided here for the electrodes. Therefore, the capacity of the battery cell increases. Also, thereby, the area of the diaphragm can be selected to be larger than the area of the opening. Therefore, after the gas passes through the opening, an enlarged surface area is provided for the gas for the flow through the diaphragm.

[0039] Preferably, the diaphragm is applied against the stabilizing element on the side opposite to the cell casing, and the stabilizing element has a plurality of additional openings. By the stabilizing element, in particular, the spatial freedom for the diaphragm is restricted, and thus the diaphragm is additionally stabilized under higher pressure. In other words, the stabilizing element defines the maximum deformation of the diaphragm, whereby the diaphragm is stabilized. Therefore, the stability of the diaphragm itself is not required or at least the requirements for it are reduced, so there are no restrictions in the material selection of the diaphragm from this perspective. Preferably, the stabilizing element completely covers the diaphragm. The stabilizing element is preferably configured to be rigid and is made of, for example, metal. In particular, the stabilizing element is configured in the form of a grid, and thus additional openings are formed by the grid. Based on the additional openings, an unobstructed gas flow through the stabilizing element is enabled.

[0040] For example, the stabilizing element is configured to break when the differential pressure between the pressure inside the cell casing and the pressure outside the cell casing is increased. The differential pressure at which this occurs can be adjusted relatively accurately. Based on the breakage, the diaphragm is no longer stabilized and thus is overloaded as well, so the diaphragm tears. As a result, a relatively large volume of gas flow through another opening is possible. Preferably, in this case, the differential pressure corresponds to a first boundary value that may exist in some cases.

[0041] For example, the stabilizing element is attached to the cell casing spaced apart from the target breaking region. Thereby, during manufacturing, attaching the stabilizing element to the target breaking region avoids damage to the target breaking region, so that defective products and manufacturing costs are reduced. Also, thereby, since the target breaking region is at least partially stabilized by the stabilizing element, restrictions in the material selection and geometry of the target breaking region are reduced. Alternatively, the stabilizing element is attached to the target breaking region. Thereby, the required space is reduced.

[0042] In an alternative embodiment, the diaphragm is disposed on the inwardly facing surface of the target breaking region. In other words, the diaphragm is shifted and positioned inside the cell casing relative to the target breaking region. Thereby, even when the pressure inside the cell casing is relatively high, based on the configuration of the diaphragm, when rapid gas flow-through is not possible, the diaphragm does not bulge excessively outward. In this case, the diaphragm is at least partially pressed against the inwardly facing surface of the target breaking region. Thus, the diaphragm is stabilized by the target breaking region, thereby enhancing robustness. Further, the diaphragm is pressed against the target breaking region under excessive pressure, and thus the gas flow between the target breaking region and the diaphragm is blocked, thereby enhancing the sealing performance of this region. As a result, only the outflow of gas through the diaphragm is possible, and thus this is carried out in a controlled manner.

[0043] For example, the diaphragm is directly attached to the surface of the target breaking region facing inward. Thereby, a relatively large area of the diaphragm can be coupled to the target breaking region, so the sealing performance in this region is enhanced. However, particularly preferably, the diaphragm is supported on a partial surface of the target breaking region via a spacer. Therefore, the diaphragm does not contact the target breaking region or only contacts it on the edge side, and in other regions, it is separated from the target breaking region by the spacer. Therefore, a larger diaphragm area is provided for gas flow-through, so the volume of gas that can be guided through the diaphragm is increased. Therefore, for example, a part of the gas can flow through the diaphragm into the space defined by the spacer formed between the diaphragm and the target breaking region, and then only through the opening to reach around the battery cell. In short, the spacer causes the diaphragm to be supported not on the entire surface but only on a partial surface, that is, for example, pointwise or in a predetermined region, thereby forming a relatively large space between the diaphragm and the target breaking region.

[0044] The spacer is, for example, at least partially pin-shaped or web-shaped, whereby the diaphragm is also stabilized by the spacer, so that the diaphragm will not be excessively deformed even under a relatively large differential pressure. In this case, for example, the diaphragm is directly attached to the cell casing at the edge side, or the diaphragm is supported at the edge side on the cell casing, for example in the target rupture area, via another spacer configured in an annular shape. The spacer is, for example, attached in the target rupture area. However, particularly preferably, the spacer is attached to the diaphragm, especially integrally formed with the diaphragm. Thus, a fluid-tight connection between the diaphragm and the spacer is obtained. This also simplifies the manufacturing. In particular, the spacer is made of the same material as the diaphragm, and these are produced, for example, by injection molding or lamination in one common working step. In another alternative embodiment, the spacer and the diaphragm are separate components that are joined to each other during installation. Preferably, a fluid-tight attachment of the diaphragm in the target rupture area, especially on the edge side, is achieved by a part of the spacer. Alternatively, the diaphragm is directly attached to the target rupture area at the edge side, and the diaphragm is spaced from the target rupture area by the spacer in another area.

[0045] For example, in some cases, the existing substrate has another opening. In this case, since the substrate is, for example, rigid, the battery cell is a prismatic cell. Alternatively, the substrate is at least partially elastically configured, and the battery cell is a pouch cell. A rupture disk is inserted into the other opening, whereby the opening is closed by the rupture disk. The rupture disk is made of, for example, a metal such as aluminum or a plastic. The rupture disk is a separate component from the substrate and is joined to the cell casing during assembly. In particular, the rupture disk is gas-tightly and fluid-tightly coupled to the cell casing, preferably attached by, for example, welding and / or adhesion. The rupture disk is, for example, circular and particularly substantially flat. In this case, the rupture disk is preferably arranged parallel to the side of the cell casing that has the other opening, if any. Alternatively, the rupture disk is at least partially concave or convex, so that the pressure resistance is enhanced by such a rupture disk. The target rupture region preferably includes the rupture disk. For example, the target rupture region is formed by the rupture disk or the target rupture region has yet another component. However, at least the rupture disk preferably has an opening. In particular, the rupture disk breaks when the rupture pressure is exceeded, and the rupture disk is particularly suitably selected. Thus, based on the rupture disk, a pre-manufactured component is provided and inserted into the other opening to provide the target rupture location during assembly. Thus, the assembly is made easy. By selecting a suitable rupture disk, it is also possible to adapt the rupture pressure to each application.

[0046] Advantageously, the diaphragm is attached to the rupture disk and fixed, for example, by adhesion and / or welding. For this purpose, for example, ultrasonic welding, laser welding, or thermal welding is used. Based on the fixing of the diaphragm in the rupture disk, this composite can be manufactured separately and then the rupture disk with the diaphragm can be inserted into another opening. This simplifies assembly and substantially eliminates subsequent damage to the rupture disk. This also enables a relatively inexpensive fluid-technical connection of the diaphragm in the rupture disk. Furthermore, in this way, it is possible to manufacture the rupture disk as a module together with the diaphragm fixed to the rupture disk, in which case the material properties of the diaphragm are already adapted to the rupture disk. For a specific use example, for example, one of a plurality of modules is used.

[0047] Alternatively or in combination therewith, the cell casing, preferably the wall thickness of the substrate provided in some cases, is reduced in the target fracture region. In other words, the cell casing has a wall including the target fracture region. In this case, the wall is, for example, flat or rounded. In this case, adjacent to the target fracture region, the wall thickness is enlarged. In particular, the thickness of this wall or all walls of the cell casing is constant except for the target fracture region, and the target fracture region is surrounded on the edge side, in particular by a step. The wall thickness of the cell casing in the target fracture region is adapted, in particular, to the bursting pressure. For example, the cell casing is injection-molded so as to have a wall thickness already reduced in the target fracture region. Alternatively, in order to produce the target fracture region, material is removed from one of the walls of the cell casing, for example by milling or laser. For example, the wall thickness in the target fracture region is constant. Alternatively, the wall thickness varies in the target fracture region, so that when the bursting pressure is exceeded, a predetermined type of fracture of the target fracture region occurs. For example, the target fracture region is formed only by a reduction in wall thickness. Alternatively, the target fracture region has yet another component, such as a rupture disk. However, at least preferably, there is an opening in the region of the reduced wall thickness of the cell casing.

[0048] Alternatively, the cell casing has one or more notches in the target fracture region. Since the notch removes the material of the cell casing, preferably the substrate, at least partially, the notch forms a desired structural weakness of the cell casing, for example the substrate. When the bursting pressure is exceeded, the cell casing fractures in the region of the notch, thereby enabling the outflow of material from the cell casing there.

[0049] The notch is machined, for example, on the cell casing, in particular after the primary shaping of the substrate. This facilitates production. For example, in this case, the notch is configured to be closed and is thus particularly shaped in the form of a ring. Alternatively, the notch is configured to be elongated and has two ends spaced apart from each other. In another alternative embodiment, the notch or at least a part of the notch is formed in a punctiform manner and in the form of a perforation. For example, the target breaking region includes a plurality of notches configured as a ring or a circle. These notches are arranged, for example, concentrically with respect to the opening, and thus the opening is surrounded by the notches. For example, in addition to the notches, the wall thickness of the cell casing in the target breaking region is reduced planarly. This enables a relatively accurate adjustment of the bursting pressure, and at the same time, the production is simplified.

[0050] In particular, the notch defines the outer contour of the target breaking region. In other words, all or at least some of the notches extend along the outer contour, i.e., the boundary, of the target breaking region. Thereby, when the bursting pressure is exceeded, the target breaking region tears along its outer contour, thereby particularly releasing the entire target breaking region. Thus, a relatively rapid compensation of the differential pressure is carried out. For example, additionally, there is another notch within the target breaking range, whereby only relatively small fragments are produced during tearing / breaking. Thus, damage to other components by the fragments is eliminated.

[0051] Particularly preferably, the battery cell includes a drying element. The drying element functions, in this case, in particular to reduce moisture entering the cell casing from another opening. For this purpose, the drying element is suitable, particularly provided and adjusted. Thus, based on the drying element, the entering moisture such as water (vapor) is bound, preventing an undesirable reaction with the electrodes and / or possibly the electrolyte arranged in the cell casing. Thereby, the operating reliability is further improved. In particular, the drying element is configured such that the drying element binds water, in particular absorbs water molecules. In a suitable form, the drying element has or is formed from a silicate. Thereby, the drying effect is further improved.

[0052] Preferably, the drying element surrounds the opening. Thereby, the drying effect in the region of the fluid-technical connection between the inside and the outside of the cell casing is improved. Thus preferably, the drying element is formed in the form of a hollow cylinder, which facilitates manufacture. In this case, for example, the drying element is located on the outer or inner surface of the target breaking region. Preferably, the drying element is offset inside the cell casing compared to the diaphragm, so that, despite the presence of the diaphragm, the moisture entering the cell casing is bound by the drying element.

[0053] The invention further relates to a composite of such battery cells, which is preferably a battery module or a high-voltage battery. Furthermore, the invention relates to a motor vehicle such as a passenger car (PKW) equipped with a battery cell of such a type, in particular a composite of such a type. The battery cell is used, in particular, for supplying power to the main drive unit of the motor vehicle.

[0054] The advantages and developments described with respect to the battery cell are transferred, as appropriate, to the composite / motor vehicle, and also to each other, and vice versa.

[0055] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Brief Description of the Drawings

[0056]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

[0057] Parts corresponding to each other are denoted by the same reference numerals in all the drawings.

[0058] Parts corresponding to each other are denoted by the same reference numerals in all the drawings.

[0059] Figure 1 schematically shows a motor vehicle 2 in the form of a passenger car (Pkw). The motor vehicle 2 has a plurality of wheels 4, at least some of which are driven by a drive device 6 including an electric motor. Thus, the motor vehicle 2 is an electric vehicle or a hybrid vehicle. The drive device 6 has a converter for supplying power to the electric motor. The converter of the drive device 6 is also supplied with power by an energy accumulator 8 in the form of a high-voltage battery. For this purpose, the drive device 6 is connected to an interface 10 of the energy accumulator 8, which is inserted into an energy accumulator casing 12 of the energy accumulator 8 made of special steel.

[0060] Inside the energy accumulator casing 12 of the energy accumulator 8, a plurality of battery modules (not shown in detail), which have the same structure as each other, are arranged. These battery modules each include a plurality of battery cells 14. In this case, the battery cells 14 of each battery module are partly electrically connected in series with each other and partly electrically connected in parallel with each other. A part of the battery modules is also electrically connected in series with each other and also electrically connected in parallel with each other. The electrical composite of the battery modules is brought into electrical contact with the interface 10, whereby during operation of the drive device 6, the battery modules, and thus the battery cells 14, are discharged or charged (regenerated). In this case, based on the electrical connection, the 400 V voltage provided at the interface 10 is several times the voltage provided by each battery module and also by each battery cell 14.

[0061] FIG. 2 shows a cross-sectional view of one of the battery cells 14 having the same structure as each other. The battery cell 14 has a plurality of anodes 16 and cathodes 18, only two of each of which are shown. The anode 16 and the cathode 18 forming the electrode 20 of the battery cell 14 are each configured in a planar shape and are alternately stacked on each other to form a cell stack. In this case, a separator (not shown in detail) is disposed between each adjacent anode 16 and cathode 18. The anode 16 protrudes beyond the cathode 18 on a common one side, that is, each conductor formed by each metal sheet is not provided. In this case, in the region of the protrusion, each conductor is released from other components, but in other regions, a layer containing an active material is adhered to each conductor, also called a support. The cathode 18 also protrudes beyond the anode 16. In this case, there are protrusions on the opposite sides of the stack formed by the anode 16 and the cathode 18.

[0062] The protrusions of the anode 16 and the cathode 18 are each welded to correspondingly arranged bus bars 22 made of copper. In this case, one of the bus bars 22 is assigned to each of the anode 16 and the cathode 18. Each bus bar 22 has one terminal 24, and this terminal is guided through the base 26 of the cell casing 28 in which the anode 16 and the cathode 18 are disposed. Therefore, the electrode 20 is disposed inside the cell casing 28. The base 26 is configured to be rigid and is made of aluminum. Therefore, the battery cell 14 is a square cell. The base 26, and thus the cell casing 28, is filled with a liquid electrolyte (not shown in detail).

[0063] The cell casing 28 is 5 cm 2It includes a target breaking region 30 having an area. The target breaking region 30 breaks when the differential pressure between the pressure outside the cell casing 28, i.e., the pressure outside the base body 26, and the pressure inside the cell casing 28, i.e., the pressure inside the base body 26, exceeds the rupture pressure of 1 bar, whereby the cell casing 28 is opened and pressure compensation can be performed. The rupture pressure is, in this case, 90% of the maximum pressure load on the base body 26, i.e., the differential pressure at which irreversible and uncontrolled destruction of the base body 26 occurs. The rupture pressure is, in this case, the second boundary value.

[0064] Figure 3 partially shows a perspective view of a cell casing 28 provided with a rectangular parallelepiped-shaped base body 26. Another stadium-shaped opening 32 is provided in the base body 26, and this opening is closed by a rupture disk 34 of the cell casing 28. In other words, the rupture disk 34 is inserted into another opening 32, and the edge of the rupture disk 34 overlaps the edge of another opening 32 and is fixed to this edge in a fluid-tight and gas-tight manner by welding. The cell casing 28 is configured such that the base body 26 and the rupture disk 34 are coplanar with each other on the outer surface. Since the target breaking region 30 is defined by the rupture disk 34, the target breaking region 30 includes the rupture disk 34. In this case, the size of another opening 32 is the same as the size of the target breaking region 30. When the rupture pressure is exceeded, the rupture disk 34 completely ruptures or breaks, whereby another opening 32 is released.

[0065] The rupture disk 34 is made of aluminum and has a thickness slightly smaller than the wall thickness of the cell casing 28. Another opening 32 is located in the same wall of the base body 26 where a through-hole for one of the terminals 24 is also provided. Except for another opening 32, the base body 26 is configured to be liquid-tight and gas-tight. Therefore, the region between the terminal 24 and the through-hole in the base body 26 corresponding to this terminal is filled with plastic, not shown in detail.

[0066] Figure 4 schematically shows a partial cross-section of the battery cell 14. The rupture disk 34 and thus the target rupture region 30 also have a circular opening 36 in their center. The opening 36 has a reduced area of 1 mm compared to another opening 32. 2 The opening 36 is covered by a gas-permeable diaphragm 38, which is at least partially made of PTFE and has a crystallinity of 85% - 100% and a density of 0.2 g / cm 3 to 2 g / cm 3 Thus, the gas passage of the diaphragm 38 by H2 and CO2 is relatively easy, while the passage of moisture, i.e., especially water vapor, is made difficult compared to this. The area of the diaphragm 38, which is arranged concentrically with respect to the opening 36 and is also circularly formed, is three times the area of the opening 36 in this embodiment.

[0067] The diaphragm 38 is arranged on the inward-facing surface 40 of the rupture disk 34 and thus of the target rupture region 30. In other words, the diaphragm 38 is shifted relative to the rupture disk 34 and the other target rupture region 30 into the interior of the substrate 26 and thus of the cell casing 28. A web-like spacer 42 is arranged between the diaphragm 38 and the rupture disk 34, and by means of these spacers, the diaphragm 38 is supported on the rupture disk 34 and thus also on the target rupture region 30 in a partial area. In other words, the diaphragm 38 is spaced apart from the target rupture region 30, i.e., by the thickness of the spacer 42.

[0068] One of the spacers 42 is arranged at the edge of the diaphragm 38 and is configured to extend over the entire circumference, whereby this spacer is circular or ring-shaped. This spacer 42 is fixed to the rupture disk 34 in a gas-tight and liquid-tight, i.e., fluid-tight manner, specifically by laser welding. In contrast, the other spacers 42 only contact the rupture disk 34 loosely, and unlike this ring-shaped spacer 42, this other spacer does not surround a complete spatial region all around. All spacers 42 are integrally formed with the diaphragm 38 and are manufactured from the same material and in the same working step.

[0069] The diaphragm 38 is configured such that when the differential pressure between the pressure outside the cell casing 28 and the pressure inside the cell casing 28 exceeds a first threshold value, the diaphragm tears. The first threshold value is the rupture pressure, i.e., 50% lower than the second threshold value. When the tearing starts, this tearing continues until the differential pressure drops below the first threshold value. When the differential pressure drops below the first threshold value, the tearing stops.

[0070] The opening 36 is covered by another diaphragm 44 arranged on the outer surface of the rupture disk 34 and thus of the target rupture region 30. Thus, the other diaphragm 44 is shifted outward with respect to the rupture disk 34 / target rupture region 30, and the opening 36 is covered on each side by one of the diaphragms 38, 44, respectively. The other diaphragm 44 is formed to be gas-permeable but additionally hydrophobic. In other words, water is pushed back by the other diaphragm 44. The other diaphragm 44 is also attached to the rupture disk 34 in a fluid-tight manner.

[0071] During operation of the battery cell 14, for example, due to a relatively high load or an undesirable chemical reaction based on undesirable foreign particles, gases such as H2 and / or CO2 may be formed within the cell casing 28. Since the gas 36 requires a larger volume than the reaction materials, the pressure inside the cell casing 28 increases. Therefore, a high pressure is formed inside the cell casing 28 as compared to the outside of the cell casing 28. In other words, the ambient pressure around the cell casing 28 is lower than the pressure inside the cell casing 28.

[0072] As a result, the gas or at least a part of the gas flows out around the battery cell 14 through the diaphragm 38 as well as the opening 36 and another diaphragm 44, so that pressure compensation is performed. Since the area of the diaphragm 38 is relatively large, a relatively large volume of gas can be discharged. That is, a part of the gas passes through the area of the diaphragm 38 covered by the rupture disk 34. Then, since there is no space completely surrounded except for the outermost spacer 42, there is no further fluid-technical resistance to the flow through the opening 36 for this part of the gas. In other words, the spacer 42 does not prevent further flow of the gas. In this case, the outermost spacer 42 prevents the gas or other fluid between the rupture disk 34 and the diaphragm 38 from flowing out of the cell casing 28 or flowing into this cell casing without passing through the diaphragm 38.

[0073] The gas flowing out to the outside through the opening 36 passes through another diaphragm 44 and thus escapes. At this time, the diaphragm 44 prevents liquid or gaseous water from entering, and further prevents water vapor from entering the opening 36 and thus also into the interior of the cell casing 28. Even if moisture reaches the diaphragm 38, this moisture is retained by the diaphragm 38 which has a relatively high impermeability to moisture. Therefore, it is prevented that moisture enters the cell casing 28 from the outside of the cell casing 28 and causes an undesirable reaction with the electrodes 20 there.

[0074] Based on special situations such as excessive load, if the volume of gas transmitted by the diaphragm 38 is not sufficient to limit the differential pressure to 0.5 bar, i.e., below the first boundary value, the diaphragm 38 will begin to rupture. As a result, a larger volume of gas can pass through, thus limiting the pressure increase or at least slowing it down. If this is sufficient to eliminate the differential pressure, further operation of the battery cell 14 is still possible. In this case, the ingress of moisture from the outside into the cell casing 28 is only partially blocked by the diaphragm 38. Instead of or in combination with the rupture of the diaphragm 38, even if a differential pressure greater than the first boundary value occurs, the fluid-tight connection of the outermost spacer 42 to the rupture disk 34 begins to release, so that here too, gas can escape to the opening 36 and from there to the surroundings.

[0075] Even if the diaphragm 38 is completely ruptured / detached, i.e., the opening 36 is completely released except for another diaphragm 44, if the pressure increase is not limited and the rupture pressure, i.e., the second boundary value, is exceeded, the rupture disk 34 breaks, thereby releasing another opening 32. Therefore, the volume of gas that can flow out of the cell casing 28 further increases. In this case, the fluid-technical resistance no longer substantially exists. Therefore, the differential pressure disappears relatively quickly, and as a result, uncontrolled destruction of the substrate 26, which could cause damage to the articles arranged around the battery cell 14, is prevented. However, in this case, it is also possible that the electrolyte flows out through another opening 32, thereby rendering the battery cell 14 no longer usable.

[0076] FIG. 5 shows a variant of the battery cell 14, in which case another opening 32, as well as the position and fixation of the rupture disk 34 in the substrate 26, remain unchanged. Also, the rupture disk 34, i.e., the target rupture region 30, still has the same unchanged opening 36. However, in this embodiment, the rupture disk 34 is made of polymer, and the thickness of the rupture disk 34 is adapted to break even at a rupture pressure of 1 bar. The opening 36 is still completely covered by a diaphragm 38 that is offset and arranged inside the substrate 26 with respect to the rupture disk 34. The material of the diaphragm 38 also remains unchanged. However, the area of the diaphragm 38 is slightly reduced, and this diaphragm is in mechanical direct contact with the rupture disk 34, i.e., the target rupture region 30, and is fixed there, specifically by ultrasonic welding. Thus, a direct liquid-tight connection is achieved between the diaphragm 38 and the target rupture region 30.

[0077] Compared with the above-described embodiment, furthermore, another diaphragm 44 is omitted, and the opening 36 is surrounded by a ring-shaped or hollow cylindrical drying element 46 made of hydrophilic and silicate. Thus, except for the diaphragm 38, the opening 36 is not covered. Water colliding with the target rupture region 30 in the region of the opening 36 from the outside, and thus also water vapor, is absorbed by the drying element 46, and thus does not reach the opening 36. Thus, the drying element 46 prevents or at least reduces the ingress of moisture into the cell casing 28. During operation of the battery cell 14, the drying element 46 is at least partially heated by the heat loss, so that in some cases the absorbed moisture is released again to the surroundings and carried out. Thus, the drying element 46 can be used for a relatively long period of time.

[0078] The functional forms of the diaphragm 38 and the rupture disk 34 are unchanged compared to the above-described embodiments. However, in this variant, the effective area provided by the diaphragm 38 for the flow-through of the gas through the opening 36 is equal to the area of the opening 36. In other words, the volume of gas that can flow through the diaphragm 38 is reduced. Thus, in such an embodiment of the battery cell 14, the pressure increase within the cell casing 28 until the diaphragm 38 tears or the rupture disk 34 ruptures is slightly reduced or limited.

[0079] FIG. 6 shows a further variant of the battery cell 14, in which case the cell casing 28 and another opening 32 which is closed by the rupture disk 34 are unchanged. Thus, the rupture disk 34 and thus also the target rupture region 30 continue to have the opening 36. The diaphragm 38 also continues to be present, and the extent of the diaphragm 38 corresponds substantially to the embodiment shown in FIG. 3. However, the diaphragm 38 is fixed on the side of the edge to the side opposite the rupture disk 34, i.e., to the outer surface 48 of the cell casing 28, i.e., to the surface directed outside the target rupture region 30, specifically by thermal welding. In other parts, the diaphragm 38 is not fixed to the rupture disk 34 and in other regions it is merely loosely placed on the rupture disk 34.

[0080] The battery cell 14 further has a stabilizing element 50, by which the diaphragm 38 is completely covered, and this stabilizing element projects slightly beyond the diaphragm 38 on the edge side. Thus, the diaphragm 38 is applied on the outside to the stabilizing element 50 made of metal. In the edge region of the stabilizing element 50, the stabilizing element is continuously configured and is welded to the target rupture region 30, i.e., to the rupture disk 34, and thus is fluid-tightly connected to the rupture disk. The stabilizing element 50 is configured in the form of a grid except for the edge and thus has a plurality of additional openings 52.

[0081] When the battery cell 14 is operating, any gas that may be generated first flows out to the surroundings through the opening 36 and then through the diaphragm 38 and the additional opening 52. Except for the fixing part on the edge side, the diaphragm 38 only loosely contacts the rupture disk 34, so that gas can accumulate in the area formed between the diaphragm 38 and the rupture disk 34, whereby a relatively large area of the diaphragm 38 is provided for the gas flow. In this case, the diaphragm 38 is partially bulged / inflated outward, and in this case, excessive bulging is blocked by the stabilizing element 50. Therefore, at each of the additional openings 52, a corresponding bulge of the diaphragm 38 occurs. Due to the inflation or bulge, the area of the diaphragm 38 provided for the gas flow further increases. However, since excessive deformation of the diaphragm 38 is blocked by the stabilizing element 50, damage to the diaphragm 38 is prevented. Depending on the stabilizing element 50, the mechanical connection between the diaphragm 38 and the rupture disk 34 is also stabilized, so that detachment of the diaphragm 38 from the rupture disk 34 is blocked.

[0082] When the differential pressure between the pressure inside the cell casing 28 and the pressure outside the cell casing 28 exceeds a first threshold value, the stabilizing element 50 is at least partially broken, whereby the stabilizing function of the diaphragm 38 is eliminated. As a result, the diaphragm 38 is torn, so that the outflow volume of the gas can also be further increased.

[0083] FIG. 7 shows a further variant of the battery cell 14. This embodiment substantially corresponds to the above-described embodiment, but the stabilizing element 50 is covered from the outside by another diaphragm 44. Therefore, the stabilizing element 50 is located between the two diaphragms 38, 44. The other diaphragm 44 prevents the intrusion of moisture into the additional opening 52 and thus up to the diaphragm 38, but the escape of gas from the cell casing 28 is still possible.

[0084] In an embodiment not shown in detail, instead of or additionally to another diaphragm 44, a drying element 46 is provided that surrounds the stabilizing element 50 or is placed on the edge of the stabilizing element 50, thereby surrounding the opening 36.

[0085] In an embodiment not shown in detail, in the embodiment according to FIG. 6 or the embodiment according to FIG. 7, the stabilizing element 50 is not provided, and the diaphragm 38 is formed more stably. Therefore, when gas accumulates between the diaphragm 38 and the rupture disk 34, a relatively large bulge of the diaphragm 38 occurs, and in this case, rupture is avoided. Rupture is only carried out for the first time when the first boundary value is exceeded.

[0086] FIGS. 8 and 9 show embodiments of the battery cell 14, in which the target rupture regions 30 are each changed. This target rupture region also continues to have an opening 36 each covered by a diaphragm 38. In the illustrated embodiments, each diaphragm 38 is fixed to the outer surface 48 of the cell casing 28, specifically by welding. In both illustrated embodiments, neither another diaphragm 44 and a drying element 46 nor a stabilizing element 50 is present. However, in a variant not shown in detail, the battery cell 14 is correspondingly configured in the manner shown in FIGS. 4 to 7, and the target rupture region 30 is correspondingly configured in the configuration shown in FIGS. 8 and 9.

[0087] In the embodiment shown in FIG. 8, in the target breaking region 30, the wall thickness of the cell casing 28, i.e., the base body 26, is reduced. The target breaking region 30 is integrally formed with the base body 26 and is one-piece with the base body. However, compared with the base body 26, the wall thickness in the target breaking region 30 is reduced by up to 25%, so the target breaking region 30 is separated from the base body 26 via an annular step portion 54. In other words, the step portion 54 forms a transition portion from the target breaking region 30 to the base body 26. The wall thickness in the target breaking region 30 is constant in this case. The target breaking region 30 is formed in a circular shape and is concentrically arranged with respect to the opening 36.

[0088] To manufacture the target breaking region 30, material is removed from the base body 26 formed with a continuous wall thickness to form the target breaking region 30, for example, by milling or by using a laser. The material removal is performed from the inner surface in the illustrated embodiment, and thus, the outer surface of the cell casing 28 is flat. This facilitates the attachment of the diaphragm 38.

[0089] In the embodiment shown in FIG. 9, the target breaking region 30 has substantially the same wall thickness as the base body 26, and the target breaking region 30 is also formed integrally with the base body 26. The target breaking region 30 is similarly separated from the base body 26 by an annular notch 56 machined in the base body to form the target breaking region 30 after the completion of the base body 26. Therefore, the outer contour of the target breaking region is defined by the notch 56. The notch 56 is arranged in a ring shape and is concentric with respect to the opening 36. Further, the target breaking region 30 also has another notch 56 of such a form that is ring-shaped but has a reduced diameter. Therefore, the target breaking region 30 has both notches 56 arranged concentrically with respect to the opening 36, and these notches form a structural weak part of the cell casing 28.

[0090] Even in the embodiments shown in FIGS. 8 and 9 of the target breaking region 30, the vulnerable part of the cell casing 28 is configured such that when the rupture pressure is exceeded, the target breaking region 30 breaks due to a decrease in wall thickness or a notch 56, thereby increasing the volume of the gas flowing out from the cell casing 28. Therefore, also in this case, uncontrolled damage to the base body 26 during pressure increase is avoided.

[0091] The present invention is not limited to the above-described embodiments. Rather, those skilled in the art can also derive other aspects of the present invention without departing from the subject matter of the present invention. Furthermore, all the individual features described in particular in connection with the individual embodiments can be combined with each other in other forms without departing from the subject matter of the present invention.

Explanation of Reference Numerals

[0092] 2 Automobile 4 Wheel 6 Drive device 8 Energy accumulator 10 Interface 12 Energy accumulator casing 14 Battery cell 16 Anode 18 Cathode 20 Electrode 22 Bus bar 24 Terminal 26 Base body 28 Cell casing 30 Target breaking region 32 Another opening 34 Rupture disk 36 Opening 38 Diaphragm 40 Inner-facing surface 42 Spacer 44 Another diaphragm 46 Dry element 48 Outer surface 50 Stabilizing element 52 Additional opening 54 Step 56 Notches

Claims

1. A battery cell (14), comprising a cell casing (28) in which a plurality of electrodes (20) are arranged, the cell casing having a target breaking region (30), the target breaking region (30) having an opening (36) covered by a gas-permeable diaphragm (38).

2. The battery cell (14) according to claim 1, wherein the diaphragm (38) is configured to rupture when a differential pressure between a pressure outside the cell casing (28) and a pressure inside the cell casing (28) exceeds a first boundary value.

3. The battery cell (14) according to claim 2, wherein the target breaking region (30) is configured to break when the differential pressure between the pressure outside the cell casing (28) and the pressure inside the cell casing (28) exceeds a second boundary value greater than the first boundary value.

4. The battery cell (14) according to any one of claims 1 to 3, wherein the diaphragm (38) is attached to an outer surface (48) of the cell casing (28).

5. The battery cell (14) according to claim 4, wherein the diaphragm (38) is applied against a stabilizing element (50) on a side opposite to the cell casing (28), the stabilizing element having a plurality of additional openings (52).

6. The battery cell (14) according to any one of claims 1 to 3, wherein the diaphragm (38) is arranged on a surface (40) facing the inside of the target breaking region (30), and the diaphragm (38) is partially supported by the target breaking region (30) via a spacer (42).

7. The battery cell (14) according to any one of claims 1 to 6, wherein the cell casing (28) includes a substrate (26) having another opening (32), a rupture disk (34) is inserted into the another opening, and the target breaking region (30) includes the rupture disk (34).

8. The battery cell (14) according to any one of claims 1 to 7, wherein a wall thickness of the cell casing (28) is reduced in the target breaking region (30).

9. The cell casing (28) has a notch (56) in the target break region (30), and the outer contour of the target break region (30) is defined in particular by the notch, the battery cell (14) according to any one of claims 1 to 8.

10. The opening (36) is surrounded by a drying element (46), the battery cell (14) according to any one of claims 1 to 9.

Images