CN116937065A

CN116937065A - Battery core

Info

Publication number: CN116937065A
Application number: CN202310283609.3A
Authority: CN
Inventors: 张闻博; B·兹拉特科夫; P·武祖茨扎克
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2022-04-22
Filing date: 2023-03-22
Publication date: 2023-10-24
Also published as: DE102022203932A1

Abstract

The application relates to a battery cell (14) having an electrode arrangement (18) in a cell housing (16). An overpressure equalization element (26) connected to the electrode arrangement (18) in a gas-tight manner is inserted into a wall (24) of the cell housing (16). A cover device (30) is arranged in the cell housing (16), and the overpressure equalization element (26) is separated from the electrolyte (36) present in the cell housing (16) by the cover device (26) against the electrolyte. The application also relates to a method (38) for producing a battery cell (14).

Description

Battery core

Technical Field

The present application relates to a battery cell (or referred to as a cell, a battery cell) and a method of manufacturing the same. The battery cell has an electrode assembly disposed within a cell housing.

Background

More and more vehicles are driven at least in part by electric motors, and therefore they are designed as electric vehicles or hybrid vehicles. For the energization of the electric motor, a high-voltage battery is generally used, which comprises a plurality of individual battery modules. The battery modules are generally identical in structure to each other and are connected in series and/or parallel to each other, so that the voltage applied to the high-voltage battery corresponds to a multiple of the voltage supplied through each battery module. Each battery module in turn comprises a plurality of battery cells, which are usually arranged in a common module housing and are electrically connected in series and/or parallel to each other.

Each cell typically includes several plated elements. They each have two electrodes, an anode and a cathode, with a separator therebetween and an electrolyte with freely moving carriers. For example, a liquid is used as such an electrolyte. In another alternative, the battery cell is designed as a solid-state battery, the electrolyte being present in solid-state form. The anode and cathode, which constitute the cell electrodes, typically include a carrier as current conductors. In this case, an active material is generally used, which is a component of a layer coated on a carrier, also called a conductor. In this case, the electrolyte may already be present in the layer, or the electrolyte is subsequently introduced. At least the active material is however adapted to absorb working ions, such as lithium ions. Depending on the use as anode or cathode, different materials of the support and different types of layer materials are used.

In order to protect the plated components, they are usually placed in the cell housing of the cell, through which the electrolyte is also protected from the environment. Chemical reactions that occur when the cell is operated can also lead to unnecessary slight decomposition or other degradation of the electrolyte. These components of the electrolyte are no longer available for operation. In other words, in these chemicals, the working ions are bound in other ways, so they cannot be absorbed by the electrode. In order to provide sufficient electrolyte over a relatively long period of time, the cell housing is typically filled with a larger volume of electrolyte than is required at the beginning of the operation. In other words, a reserve of electrolyte is available.

In undesired chemical reactions, it is possible to generate gases, wherein the required volume is larger than the volume of the raw material. Thus, the pressure in the cell housing increases. In order to avoid uncontrolled bursting of the cell housing due to the additional volume, which would lead to damage to the components located around the cell housing, the cell housing is often provided with an overpressure balancing element, by means of which the overpressure present in the cell housing is released. In this way, the gases present in the cell housing are typically vented to the environment in a controlled manner. However, due to the excess electrolyte in the cell housing, the gas may not reach the overpressure balance element. In other words, the gas is intercepted by the electrolyte and/or the function of the overpressure balance element is impaired by the additional electrolyte. As a result, the pressure in the cell housing may increase and cause uncontrolled bursting of the cell housing.

The object of the present application is to provide a particularly suitable battery cell and a particularly suitable method for producing a battery cell, in which the material costs and/or the production costs are advantageously reduced and the service time and/or the operational reliability are appropriately increased.

With respect to the battery cell, this problem is solved by a battery cell, with respect to the method, according to a method for manufacturing the battery cell described above. Advantageous developments and designs are also the subject matter of the application.

The battery cells, which are also referred to hereinafter in particular only as batteries, are preferably designed to be rechargeable and suitably designed as secondary batteries. Preferably, the battery cell is a component of the vehicle in its predetermined state. For this purpose, the battery cells are suitable, in particular provided and arranged. In a predetermined state, the battery cell is part of an energy store of a motor vehicle, for example, having a plurality of such battery cells. Preferably, the battery cells are divided into a plurality of battery modules, which are identical in structure to each other. The battery cells are arranged in particular in the housing of the energy store of the respective battery module and are electrically connected in parallel and/or in series with one another. Thus, the voltage applied to the accumulator/battery module is a multiple of the voltage provided by each cell. Therefore, the structure of all the battery cells is the same, which simplifies production.

The housing of the energy store or of the respective battery module (in particular of the assembly constituting such a battery cell) is preferably made of metal, for example steel, such as stainless steel or an aluminum alloy. For example, a die casting process, a deep drawing process, a cast extrusion or an extrusion process is used for production. The housing of the energy store or of the individual battery modules is in particular designed to be sealed. It is expedient to insert an interface into the housing of the energy store or of the respective battery module, which interface forms, for example, a plug of the energy store/battery module. The interface is in electrical contact with the battery cell, so that electrical energy can be input from outside the energy store and/or extracted from the battery cell as long as a corresponding plug is plugged into the plug.

For example, the vehicle is a ship or a vessel. Preferably, however, the vehicle is land-based and preferably has a plurality of wheels, at least one, suitably a plurality or all of which are driven by one drive. In particular, one of the wheels, preferably a plurality of wheels, is controllable. Thus, the vehicle can move independent of a particular road, such as a track or similar road. In this case, the vehicle can be suitably positioned substantially on a road made in particular of asphalt, tar or concrete. For example, the vehicle is a commercial vehicle, such as a truck or bus. However, a particularly preferred vehicle is a personal car (sedan).

The appropriate movement of the vehicle is by means of a drive. For example, the drive, in particular the main drive, is at least partially electric, and the vehicle is for example an electric car. For example, the electric motor is operated by means of an energy store, suitably designed as a high-voltage battery. The direct voltage is expediently provided by a high-voltage battery, for example between 200V and 800V, and for example substantially 400V. Preferably, an electrical inverter is arranged between the energy store and the electric motor, by means of which inverter the power of the electric motor is regulated. In another option, the drive also has an internal combustion engine, so the vehicle is designed as a hybrid vehicle. In an alternative, the low-voltage on-board power supply of the vehicle is supplied via the energy store, and in particular a direct voltage of 12V, 24V or 48V is provided via the energy store.

In another alternative, the battery cell is part of an industrial truck, an industrial device, a handheld device, such as a tool, in particular a battery-driven screwdriver. In another alternative, the battery cell is part of a power supply, for example, used as a so-called buffer battery. In this case, for example, the battery cells are used in power plants or life/industrial factories. In another alternative, the battery cell is an integral part of a portable device, such as a portable mobile phone or a wearable device or computer. Such cells may also be used in camping areas, model building areas, or other outdoor activities.

The battery cell has an electrode assembly with a plurality of electrodes. The electrodes are particularly divided into anodes and cathodes, wherein for example the number of anodes is the same as the number of cathodes, or preferably there is one additional anode. It is particularly preferred that all anodes and all cathodes have the same structure, which simplifies the manufacture. For example, the electrodes, i.e. the anode and the cathode, are planar, in particular substantially rectangular. The anode and cathode each have a carrier, also known as a conductor. In particular, the respective support is formed by a metal foil at least partially coated with a layer on one or both sides. For example, aluminum is used as the metal of the cathode carrier/conductor and copper is used as the metal of the anode conductor.

The thickness of this layer is less than 1mm. Suitably, the thickness of the carrier is less than 0.1mm. Preferably, the respective 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 and is suitable for this purpose as well as for provision and arrangement. As active materials, for example lithium metal oxides, such as lithium cobalt (III) oxide (LiCoO 2), NMCs, such as NMC622 or NMC811, NCA or LFP for the cathode and/or LTO or silicon-based graphite for the anode.

For example, electrodes, i.e., an anode and a cathode, are stacked on each other to form a cell stack, wherein the stacking direction is perpendicular to the expansion direction of the electrodes arranged parallel to each other. The anode and the cathode alternate in the stacking direction of the cell stack. Between adjacent electrodes, i.e. between one of the cathodes and one of the anodes, a membrane of the stack is provided, which membrane is preferably also planar. For example, the structure of all the diaphragms is the same. In particular, the electrodes are stacked substantially flush with each other, wherein, for example, all anodes protrude at least slightly from the cathode. Thus, unwanted material deposition in the anode edge region is avoided during operation. The cell stack is also substantially rectangular parallelepiped due to the stacking of the electrodes. In particular, the stack forms an electrode arrangement. For example, in alternative designs, all anodes, all cathodes, or separators are formed by or connected to a common strip. The strip itself is rolled into a cylinder or the like, thus forming a so-called "jelly roll", which in particular forms the electrode device. In another embodiment, the membrane is formed by a band, a so-called membrane band, which is Z-folded a plurality of times. The individual electrodes are inserted into grooves formed in this way, which grooves are designed in particular as sheets.

The battery cell further has a cell housing in which the electrode device is disposed entirely. For example, the cell housing is made of aluminum and is preferably rigid. The cell housing has, in particular, a battery cup which is closed by a cover. In particular, the cell housing is cylindrical or square, and the cell is designed in particular as a so-called prismatic cell. Alternatively, the cell housing is created, for example, by a foil (e.g., a coated aluminum foil). In other words, the battery cells are designed as pouch-type cells. However, the cell housing is at least preferably fluid-tight, in particular electrolyte-tight. Thus, the electrode device is protected by the cell housing and intrusion of foreign particles is avoided.

Suitably, the cell housing has one or more perforations through which each connector is guided. For example, in this case, the battery cell includes one, two or more corresponding tabs, each tab corresponding to one of the perforations. In this case, too, the area between the tabs and the edge of the perforation is fluid-tight and each tab is in electrical contact with at least one electrode of the electrode arrangement. Thus, electrical energy can be injected and/or extracted from outside the cell housing to the electrode device through the connector.

In particular, the cell housing is partially filled with electrolyte after production, wherein the electrolyte is matched to the electrode arrangement, in particular to the active material used in each case. The particular working ions are provided by the electrolyte. The electrolyte is in particular liquid, i.e. liquid. Preferably, a larger volume of electrolyte is present in the cell housing than is initially required for operation of the electrode assembly.

In the wall of the cell housing (e.g. rigid or flexible and suitably designed to be essentially flat, i.e. planar) an overpressure balancing element is mounted. In particular, the overpressure balancing element is not part of the wall, but is independent with respect to the wall. For example, the overvoltage equalization element is made of a material different from the cell housing wall. Preferably, a fluid-tight connection is formed between the overpressure balance element and the wall, so that leakage of electrolyte between the overpressure balance element and the wall is avoided. Foreign particles are also prevented from entering the cell housing. In summary, the overvoltage-balancing component is therefore not in particular a component of any cell cup or lid made of a rigid metal (for example aluminum), nor of any membrane. Furthermore, they do not form in any way an overpressure balance element. In contrast, the overpressure balancing unit is a separate component from the battery cup/lid/membrane. By means of the overpressure balancing element, the overpressure in the cell housing can be reduced and preferably compensated for with respect to the ambient pressure of the cell housing, at least depending on the particular state/condition, so that no pressure difference exists anymore. For this purpose, gases from the interior of the cell housing (formed during operation as a result of undesired chemical reactions, such as H ₂ CO or CO ₂ ) Discharged from the cell housing into the environment.

The overpressure balance element is connected to the electrode arrangement in a ventilated manner. In other words, when the battery cell is in operation, the same pressure is generated at the overpressure compensating element and the electrode arrangement, and the flow of gas between the electrode arrangement and the overpressure compensating element may in particular not be disturbed, or only a relatively low, preferably negligible, flow resistance exists.

A covering device is also arranged in the cell housing, by means of which the overvoltage compensating element is separated from the electrolyte present in the cell housing in an electrolyte-tight manner (or in an electrolyte-tight manner). In other words, the electrolyte is prevented from entering the overpressure balance element by means of the covering means, and the overpressure balance element is blocked from the electrolyte by means of the covering means. In any case, the overpressure compensating element is covered by the covering device relative to the electrolyte, but a pressure difference between the electrode device and the overpressure compensating element is avoided.

Any excess pressure generated in the cell housing during operation can be released by the excess pressure equalization element, since the covering device ensures that the function of the excess pressure equalization element is not affected by the electrolyte. This increases operational reliability. The cell housing may be filled with a greater volume of electrolyte than is required for initial operation. Therefore, even if the aging effect of the electrolyte occurs, the battery cell can be used for a long period of time. In other words, the use time of the battery cell is increased. Furthermore, the overpressure balance element is separated from the electrolyte by the covering means, so that the overpressure balance element does not have to withstand the electrolyte. In this way, the material requirements for the overpressure balance element are reduced, thereby reducing the material costs and the manufacturing costs. Furthermore, the covering means ensure that no electrolyte escapes from the cell housing when gas is conducted from the cell housing to the surroundings via the overpressure equalization element, so that the environment is protected from the electrolyte, which further improves the operational safety and expands the range of application of the battery cell.

It is expedient if the electrode arrangement is at least partially electrically insulated by means of the covering device, in particular with respect to the overvoltage protection assembly and/or other components of the cell housing. For this purpose, the covering device is designed in particular to be electrically insulating. Thus, the functional range is further increased without requiring additional components. Therefore, the manufacturing cost is reduced and the energy density is improved. Preferably, at least a portion of the cell housing is also shielded by the electrolyte by the covering means, so that interactions with the electrolyte, such as corrosion, are avoided here. In other words, the electrolyte and at least a part of the cell housing are separated, in particular by means of a covering device. Thus, the service time of the battery cell is further increased, and relatively long cycle stability is provided.

For example, an overvoltage equalization element is inserted into the edge region of the cell housing. However, it is particularly preferred that the overvoltage balance element is inserted into the bottom of the cell housing. In other words, the bottom forms a wall of the cell housing into which the overpressure balance element is inserted. Particularly in the conventional arrangement of the battery cells, the bottom is the lower part of the battery cell housing in the vertical direction. If the battery cells are used in a vehicle, they are typically located below the passenger compartment. Since the overpressure equalization element is located at the bottom of the cell housing facing away from the passenger cabin, the gas is blocked out of the passenger cabin of the vehicle. Furthermore, in particular, any connectors or circuit elements in electrical contact therewith (suitably located at the upper end of the cell housing in the vertical direction) are not blocked by the overpressure balance element, in particular in the cover.

If the cell housing has a battery cup and a cover, the overpressure compensating element is in particular inserted into one of the walls of the battery cup, preferably into the bottom. In this way, the cap can be manufactured without overpressure balancing elements, thereby simplifying the manufacturing costs of the cap for a suitable guide joint. In this way, functional separation is also achieved and assembly is simplified. In this case, the electrolyte is blocked out of the overpressure equalization element by the covering device, so that leakage of electrolyte from the cell housing is avoided, although the overpressure equalization element is located in the lower part of the cell housing, wherein the electrolyte is collected during operation.

For example, the overpressure balance element comprises a rupture disc. For example, the overpressure balancing element is formed by means of a rupture disc, or the overpressure balancing element has, for example, one or more other components. For example, they are secured to the rupture disc or are disposed separately therefrom. In this case, the wall has in particular several openings, one of which is inserted into the rupture disc and in the other of which is inserted the or any other component. The rupture disk is designed in such a way that it tears, in particular breaks, when the pressure in the cell housing exceeds a threshold value relative to the pressure surrounding the cell housing. In particular, the tearing/rupture process is irreversible. The electrolyte is prevented from leaking by the cover means despite rupture of the rupture disc. For example, if the pressure differential is greater than a threshold value, the rupture disc may rupture completely or may first partially tear. Specifically, the rupture disc is designed such that tearing ceases when the pressure differential is reduced. Thus, firstly, complete failure of the battery cells is avoided and at least slightly further use is possible. Alternatively, when the limit is exceeded, the rupture disc ruptures completely, thereby reducing the pressure differential relatively quickly, thereby improving safety. In summary, if too much gas is formed in the cell housing due to undesired chemical reactions, rupture of the cell housing is avoided due to the rupture disc.

In another alternative, the overpressure balance element comprises an overpressure valve. For example, the overpressure balance element is formed by an overpressure valve, or the overpressure valve forms an additional component of the rupture disc. In a further alternative, the overpressure balancing element comprises an overpressure valve and other components. In particular, the overpressure valve is reversible and is designed in particular in such a way that it opens by a pressure difference between the pressure in the cell housing and the pressure surrounding the cell housing when a further limit value is exceeded, so that the pressure difference is reduced to at least the further limit value or to a further limit value below the further limit value. In particular, the overpressure valve closes after another/further limit value is exceeded. Preferably, it is designed as an overpressure valve of the check valve type. Thus, robustness is increased and foreign particles are avoided from entering the cell housing. In particular during operation of the battery cell, the overpressure valve serves for continuous degassing, so that gas which is unintentionally generated during normal operation of the battery cell is always or at least at a specific time discharged to the surroundings of the battery cell. Thus, continuous operation of the battery cells is possible, avoiding excessive accumulation of gas in the battery cells in the cell housing. Thanks to the covering means, the escape of electrolyte from the safety valve is avoided and the function of the overpressure valve is not affected.

For example, the covering means is by means of a labyrinth seal or some siphon. However, it is particularly preferred that the covering means comprises a membrane and is suitably formed by a membrane. The membrane is arranged between the overpressure balance element and the electrode arrangement and is thus mechanically located between the electrode arrangement and the overpressure balance element. Due to the use of the film, the required installation space is reduced, and thus the energy density of the battery cell is increased. In particular, the membrane is designed such that it is permeable to gases but impermeable to the electrolyte. In other words, the membrane is gas permeable and electrolyte tight. For example, the membrane is made of a polymer or a polymer matrix. In particular, the membrane is made of an elastomer (e.g. of thermoplastic elastomer), said material being chosen in particular to avoid damage due to the electrolyte or to interactions with the electrolyte. In other words, the material is particularly inert to the electrolyte used. For example, polypropylene is used as the material. Particularly preferred are membranes having a multilayer structure, wherein the individual layers are adapted to the respective use, so that the electrolyte sealing and gas permeation functions of the membrane can be assigned to the different layers. This increases the choice of available materials and thus reduces production costs.

For example, one or more of the possible joints may be arranged in such a way that they are spaced apart from the membrane. Alternatively, at least one tab is directed through the membrane. This increases the freedom of design. In particular, the membrane is at least partially fixed to the respective joint, for example directly or by other means. It is expedient here to provide a fluid-tight or electrolyte-tight connection of the membrane to the joint. For example, the connection here is such that it may also be impermeable to air. This increases the tightness. In this case, thanks to the other parts of the membrane, it is still possible to achieve that the gas reaches the overpressure balance element, so that the functionality is not limited by the joint.

For example, the overpressure balance element is covered by means of the membrane, which is (also) attached to the wall, preferably fluid-tight. However, it is particularly preferred that the entire wall is covered by the membrane and that the membrane is suitably fluid-tightly fixed to the other inner wall of the cell housing. For example, the film is bonded or welded by an additional inner wall. A spacing is preferably formed between the membrane and the wall. In this way, a region is formed in which gas can collect. In addition, due to the relatively large area of the membrane, gas can pass through even though the structure of the membrane is relatively dense. For example, there is an additional film by which, for example, the wall of the cell housing opposite the wall is also covered. Thus, there is more space to collect the gas, and the electrolyte is particularly free of gas that may be generated. Alternatively, for example, the membrane is designed as a hollow cylinder and is connected to two of the inner walls, whereas the remaining part of the cell housing is spaced apart from the membrane. In other words, the membrane and thus the electrode assembly is circumferentially surrounded by a space formed between the membrane and the cell housing, and the space remains free of electrolyte. Thus, there is a relatively large spatial area in which gas can accumulate and the area available for gas permeation is increased.

For example, the film is flat or planar. For example, if the membrane is hollow cylindrical, the membrane is continuously curved. Particularly preferably, the membrane is corrugated or pleated. In this way, the area of the membrane is further enlarged, thereby facilitating the passage of gas through the membrane. Therefore, the membrane can be sealed relatively, thereby further improving the sealability of the electrolyte.

In another design, the pouch is formed, for example, by a membrane, and the electrode device is disposed within the pouch. For example, the bag is fixed to the inner wall of the cell housing and thus also to the wall of the cell housing, which increases the robustness. Alternatively, the bag is only loosely inserted into the cell housing, which makes manufacturing easier. For example, in other cases, the pouch is closed and the electrode device is completely surrounded by a membrane on the outside. This increases the tightness. Preferably, the bag is arranged such that the bag is open on one side, preferably at the upper end in the vertical direction. In this way, on the one hand, filling of the electrolyte becomes easy. Alternatively, the membrane may be fabricated from an electrolyte-tight and gas-tight material, thereby reducing material matter. The venting connection of the electrolyte assembly to the gas of the overpressure balance element is made through the open part of the bag.

In this case, it is expedient for the membrane to be mechanically located between the electrode arrangements and thus also between the electrolyte and the overpressure balancing element, and for the electrolyte to be held in place in the pouch. It is particularly preferred that the pouch protrudes upward in the vertical direction with respect to the level of electrolyte, so that the electrolyte is prevented from reaching the overpressure balance element even in case of tilting or vibration of the battery cell. In particular, the membrane is located between the electrolyte and the overpressure balance element, so that the electrolyte is prevented from reaching the overpressure balance element by the membrane even in case of ejection of the electrolyte or possibly ejection of air bubbles.

A method for producing a battery cell having an electrode arrangement, which is arranged in a cell housing, an overpressure compensating element connected to the electrode arrangement in a gas-tight manner being inserted into a wall of the cell housing, and a cover device being arranged in the cell housing, by means of which the overpressure compensating element is separated from an electrolyte-protective electrolyte present in the cell housing, provides that the electrode arrangement, the cover device and the cell housing are provided first, wherein a separate overpressure compensating element is inserted into the wall of the cell housing. Preferably, the cell housing has several individual components which are not fixed to one another in particular. At least the cell housing is however open.

In a subsequent working step, the electrode arrangement and the cover arrangement are arranged in the cell housing in such a way that the overvoltage equalization element is connected to the electrode arrangement in a ventilated manner, wherein the overvoltage equalization element is separated from the electrolyte present in the cell housing by the cover arrangement from the electrolyte. For example, the electrolyte is then filled into the cell housing, unless this has been done when the covering means and/or the electrode means are arranged in the cell housing. Alternatively, for example, the cell housing is first closed and filled with electrolyte through the further opening.

For example, in one embodiment, first, the electrode means and the covering means are suitably positioned with respect to each other and, for example, fixed together. The assembly is then positioned in a cell housing. In an alternative, the covering device is first arranged within the cell housing, in particular by means of which the walls or other walls of the cell housing are covered. The electrode device is then positioned in the cell housing and/or the covering device.

The application also relates to a combination of such battery cells, preferably a battery module or a high voltage battery. The application further relates to a vehicle, for example a passenger car (PKW), having such a battery cell, in particular such a combination. The battery cell is preferably used to power a main drive of the vehicle.

The advantages and the extended design described in connection with the battery cells should also be correspondingly applicable to the method/combination/vehicle and vice versa.

Drawings

Embodiments of the present application are further described below with reference to the accompanying drawings. In the drawings:

fig. 1 schematically and simplified shows a vehicle with a plurality of identical battery cells.

Figure 2 shows schematically one of the battery cells in a cross-section,

figure 3 shows a method of manufacturing a battery cell,

fig. 4, 5 show in a flow chart a variant of the production of a battery cell, and

fig. 6 to 8 show further variants of the battery cell according to fig. 2.

Detailed Description

In all the figures, corresponding parts are provided with the same reference numerals.

In fig. 1, a vehicle 2 in the form of a car (Pkw) is schematically simplified. The vehicle 2 has a plurality of wheels 4, at least some of which are driven by a drive 6 comprising an electric motor. Therefore, the vehicle 2 is an electric vehicle or a hybrid vehicle. The drive 6 has an inverter through which the motor is supplied. The inverter of the drive 6 is in turn energized by means of an energy store 8 in the form of a high-voltage battery. For this purpose, the drive 6 is connected to an interface 10 of the energy store 8, which interface 10 is inserted into an energy store housing 12 of the energy store 8 made of stainless steel.

Within the accumulator housing 12 of the accumulator 8, a plurality of battery modules, which are not described in more detail, are provided, each of which comprises a plurality of battery cells 14, which are identical in structure to one another. Here, the battery cells 14 of each battery module are partially electrically connected to each other in series, and partially electrically connected to each other in parallel. A portion of the battery modules are electrically connected in series with each other, which modules are in turn electrically connected in parallel with each other. The electrical connection of the battery module is in electrical contact with the interface 10, so that when the drive 6 is running, discharging or charging (recycling) of the battery module and the battery cells 14 takes place. Thus, due to the circuitry, the voltage of 400V provided at interface 10 is multiple times the voltage provided by each battery module and each battery cell 14.

In fig. 2, one of the battery cells 14 of identical construction is schematically simplified in a cross-sectional view. The battery cell 14 has a rigid, substantially rectangular parallelepiped-shaped cell housing 16 made of aluminum. Thus, the battery cells 14 are prismatic cells. An electrode arrangement 18, indicated by dashed lines, is arranged in the cell housing 16, which electrode arrangement comprises a plurality of electrodes, not shown further. The electrodes are divided into an anode and a cathode, which are stacked on each other with a separator interposed therebetween. Here, the anode, cathode and separator are first separated from each other and connected together by suitable fasteners. Alternatively, for example, the anode, one of the cathodes and the two separators have been connected together, so that a so-called cell is formed. The cells are stacked on top of each other, in particular forming an electrode arrangement 18. In another alternative, the electrode arrangement 18 is formed by a so-called "Jelly Roll", or comprises a multi-Z folded separator strip into which the anode/cathode is inserted.

The electrode arrangement 18 is in electrical contact with two connectors 20, e.g. one connector 20 of the connectors 20 is in electrical contact with all anodes of the electrode arrangement 18 and the other connector 20 is in electrical contact with all cathodes of the electrode arrangement 18. The two connections 20 pass through a boundary wall 22 which delimits the cell housing 16 in the vertical direction upwards, for which purpose the boundary wall 22 has a through-hole which is not shown further. The region between the edge of the through-hole and the joint 20 is designed to be fluid-tight, for which purpose the joint 20 is correspondingly constructed. During operation, a voltage is applied at the junction 20 and by means of this voltage electrical energy can be extracted and supplied to the electrode arrangement 18 during operation.

The boundary wall 22 is formed by means of a cap, not shown in detail, of the cell housing 16, which is fastened to the cup-shaped cell cup. In the conventional use of the battery cells 14, an overpressure compensating element 26 is introduced in the wall 24 (forming the bottom of the cell housing 16 opposite the boundary wall 22). For this purpose, the wall 24 has an opening 28 completely filled with the overpressure compensating element 26, wherein the overpressure compensating element 26 is fixed to the wall 24 in a fluid-tight manner. In this embodiment, the overpressure compensating element 26 is a rupture disc, so that the overpressure compensating element 26 is formed by means of the rupture disc. The rupture disc is designed to rupture when the pressure difference between the pressure inside the cell housing 16 and the pressure surrounding the cell housing 16 exceeds a certain limit value. In the process, rupture disc 26 ruptures first until the pressure differential drops. If this does not occur, rupture disc 26 ruptures completely and thus ruptures.

Further provided within the cell housing 16 is a covering means 30 which is designed as a vertically upwardly opening pocket and is constituted by a suitably folded membrane 32. The membrane 32 is here embodied as electrolyte-tight and gas-tight. In this case, the pouch is fluid tight and is only loosely inserted into the cell housing 16 so that gas can pass between the cell housing 16 and the membrane 32. In an undescribed variant, the pouch is secured to the cell housing 16 in sections. An electrode device 18 is inserted in the pocket formed by the covering device 30, which extends in the vertical direction above the pocket. Thus, the material requirements for the membrane 32 are reduced and assembly and manufacture are facilitated. Also in this way, the electrode arrangement 18 is connected to the overpressure balance element 26 in a ventilated manner, the boundary wall 22 not impeding the permeation of gas from the electrode arrangement 18 to the overpressure balance element 26. In summary, therefore, the covering device 30 has a membrane 32 which is mechanically arranged between the overpressure balance element 26 and the electrode arrangement 18.

The covering device 30, i.e. the bag, is filled to a filling level 34 with an electrolyte 36. In this case, the liquid level 34 is located below the upper end of the bag constituted by the membrane 32 in the vertical direction, and thus leakage of the electrolyte 36 from the bag is avoided even in the case where the battery chamber 16 is inclined. Thus, the overpressure compensating element 26 is separated from the electrolyte 36 present in the cell housing 16 by means of the covering device 30 in an electrolyte-tight manner.

When the electrolyte 36 undergoes an undesired chemical reaction with the electrode arrangement 18 during operation, a gas may be formed and the volume of the electrolyte 36 in the cell housing 16 decreases, and thus the liquid level 34 decreases. However, due to the relatively high presence of electrolyte 36 in the cell housing 16, unimpeded continued operation of the battery cells 14, i.e., input/extraction of electrical energy, is still permitted. However, due to the gas, an overpressure is created in the cell housing 16. The gas thus produced can reach the pressure compensation element 26 undisturbed and in particular collect at the bottom of the cell housing 16. In the event that the overpressure exceeds a limit value, the overpressure compensating element 26, which is designed as a rupture disk, breaks open, so that gas can escape from the cell housing 16. The battery cell 14 may still continue to be used due to the covering device 30, preventing the electrolyte 36 from escaping from the cell housing 16.

Fig. 3 illustrates a method 38 of manufacturing a battery cell 14 of identical construction. In a first working step 40, the electrode arrangement 18, the covering arrangement 30 and the cell housing 16 are first provided. In this case, the cell housing 16 already has an opening 28 in the wall 24, into which the overpressure balance element 26 is inserted. In other words, an overpressure balance element 26 is inserted in the wall 24 of the cell housing 16, which overpressure balance element 26 is a separate component from the wall 24.

In a subsequent second working step 42, the electrode arrangement 18 and the covering arrangement 30 are arranged in the cell housing 16 such that the overpressure balance assembly 26 is connected to the electrode arrangement 18 in a ventilated manner, the overpressure balance assembly 26 being separated from the electrolyte 36 in the cell housing 16 by means of the covering arrangement 30. For this purpose, the pockets are positioned in particular in the cell housing 16 accordingly. Preferably, the electrolyte 36 is then filled into the pouch and the cell housing 16 is fluid-tightly closed.

In fig. 4, a first variant of the method 38, namely a second working step 42, is shown in the flowchart. In this case, the electrode device 18 (to which the connection 20 has been fixed) is first inserted into the covering device 30 of pocket-like design. Subsequently, the combination of the electrode assembly 18 and the cover assembly 30 (where they are loose from each other) is inserted into the cell housing 16. In particular, in this case, the boundary wall 22 is formed by a first separate cover, which is fastened to the other components of the cell housing 16 after the positioning of the covering device 30 into the cell housing 16, wherein the connector 20 is guided through the boundary wall 22.

Fig. 5 shows a variant of the method 38. In a second step 45, the covering device 30 is first positioned in the cell housing 16. Subsequently, the electrode arrangement 18 is inserted into the covering device 30 of pocket-like design and thus also into the cell housing 16. After this, the electrolyte 36 is filled and the boundary wall 22 is properly positioned and secured to the other components of the cell housing 16.

In fig. 6, a variant of the battery cell 14 is shown from the view of fig. 2. In this variation, the boundary wall 22 has no opening (with the tab 20 inserted therein) but rather the tab 20 protrudes through an opening in the opposite side wall 44 of the cell housing 16. Furthermore, in this variant, the electrode arrangement 18 is formed, for example, by a "jelly roll", wherein the electrode arrangement 18 is also in further electrical contact with the joint 20. The connector 20 passes through a covering device 30, also designed as a bag, wherein the membrane 32 is opened in sections for the connector 20 to pass through. In this case, the membrane 32 is fluid tightly secured to the junction 20, thereby preventing the electrolyte 36 from escaping from the pouch.

The wall 24 also has an opening 28 into which the overpressure balance element 26 is inserted in a fluid-tight manner. Here too, the wall 24 is formed by the bottom of the cell housing 16. However, in contrast to the former design, the overpressure equalization element 26 is formed by an overpressure valve. The overpressure valve is designed such that it opens already at a low pressure difference (i.e. another limit value) between the pressure in the cell housing 16 and the pressure around the cell housing 16, so that the gas generated in the cell housing 16 can escape from the cell housing 16 via the overpressure compensating element 26. Once the pressure differential falls below another limit, the overpressure valve of the check valve is designed to close, thereby preventing foreign particles from entering the cell housing 16. In this variant of the battery cell 14, due to the design of the element 26, such as an overpressure balance, a substantially continuous venting takes place during operation.

Fig. 7 shows a further variant of the battery cell 14, in which the cell housing 16 and the electrode arrangement 18 and the connector 20 are unchanged. Furthermore, the overpressure balance element 26 is unchanged. Only the covering means 30 is changed, wherein the covering means still comprises the membrane 32. The material of the membrane 32 is changed and the membrane is now gas permeable and the membrane 32 is still electrolyte tight. To provide these functions, the membrane 32 has different layers formed of different materials.

The membrane 32 is hollow-cylindrical and completely surrounds the electrode arrangement 18 on the circumferential side. The opposite ends of the hollow cylinder formed in this way are fluid-tight, i.e. fixed by means of adhesive or welding, to the further inner walls 46 of the cell housing 16 provided by the two opposite side walls 44. The membrane 32 is spaced from the wall 24. Thus, a surrounding space 48 is formed between the cell housing 16 and the membrane 32. Electrolyte 36 is disposed within membrane 32 such that space 48 is free of electrolyte 36. In summary, by means of the membrane 32, the complete wall 24 is covered and a portion of the cell housing 16 is not in contact with the electrolyte 36. Thus, corrosion is avoided and the service life of the battery cells 14 is increased. In this variant, the electrolyte 36 is completely excluded from reaching the overpressure balance element 26 even in the event of relatively large vibrations or tilting of the battery cell 14.

The gas that is unintentionally generated during operation passes through the membrane 32 into the space 48, wherein the passage of the gas is substantially unobstructed due to the relatively large surface area of the membrane 32, and thus has substantially the same pressure inside the membrane 32, i.e. inside the space 48, as outside the membrane 32. If the pressure difference between the pressure inside the cell housing 16 and the pressure outside the cell housing 16 exceeds a further limit value again, gas is released through the overpressure equalization element 26 to the surroundings of the cell housing 16, wherein the electrolyte 36 does not leak.

Fig. 8 shows a further variant of the battery cell 14, in which only the covering device 30 is changed compared to the previous design. The covering device 30 again has a membrane 32 made of the same material as the previous variant. However, the membrane 32 is disposed substantially in a plane and is not curved. In this case, the membrane 32 is not completely aligned on one plane due to the corrugation introduced into the membrane 32. Thus, the membrane 32 has an increased surface area compared to a fully planar design. The wall 24 and the overpressure balance element 26 are further completely covered by the membrane 32, wherein the membrane 32 is spaced apart from each other in a vertical direction above the wall 24. The membrane 32 is again attached in a fluid-tight manner to the further inner wall 46 and to further inner walls not further shown by welding or bonding, wherein the respective weld or bonding lines are rectilinear, which facilitates manufacturing. Thus, the electrolyte 36 is held above the wall 24 by the membrane 32.

A further membrane 50 is arranged in the vertical direction above the electrode arrangement 18, which membrane 50 is identical to the membrane 32, and which membrane 50 is also in fluid-tight connection with the further inner wall 46. Thus, an additional space 52 is created, which space 52 is also free of electrolyte 36 and in which gas can accumulate. The additional space 52 is in fluid connection with the overpressure equalization element 26 by means of the device shown in the figure, so that gas can also be discharged therefrom. The area available for gas permeation is enlarged due to the corrugated design of the membrane 32 and the additional membrane 50.

The present application is not limited to the above-described embodiments. On the contrary, other variants of the application can also be deduced therefrom by a person skilled in the art without departing from the subject matter of the application. More specifically, all of the individual features associated with the various embodiments may also be combined with each other in different ways without departing from the subject matter of the present application.

List of reference numerals

2 vehicle

4 wheel

6 driver

8 energy accumulator

10 interface

12 energy accumulator shell

14 cell core

16 electric core shell

18 electrode device

20 joint

22 boundary wall

24 wall

26 overpressure balance element

28 openings

30 cover device

32 film

34 level of liquid

36 electrolyte

38 method of

40 first working procedure

42 second working procedure

44 side wall

46 further inner walls

48 spaces

50 additional film

52, additional space.

Claims

1. A battery cell (14) having an electrode arrangement (18) located within a cell housing (16), wherein an overpressure compensating element (26) connected in a gas-tight manner to the electrode arrangement (18) is inserted into a wall (24) of the cell housing (16), and wherein a covering device (30) is provided in the cell housing (16), the overpressure compensating element (26) being separated from an electrolyte (36) present in the cell housing (16) by the covering device (26).

2. The battery cell (14) according to claim 1, wherein an overpressure balance element (26) is inserted into the bottom of the cell housing (16).

3. The cell (14) according to claim 1 or 2, wherein the overpressure balance element (26) comprises a rupture disc.

4. A battery cell (14) according to any of claims 1 to 3, characterized in that the overpressure balance element (26) comprises an overpressure valve.

5. The battery cell (14) according to any one of claims 1 to 4, wherein the covering means (30) comprises a membrane (32) arranged between the overpressure balancing or the like element (26) and the electrode means (18).

6. The battery cell (14) according to claim 5, wherein the complete wall (24) is covered by a membrane (32), wherein the membrane (32) is fixed in a fluid-tight manner to a further inner wall (46) of the cell housing (16).

7. The battery cell (14) of claim 6, wherein the membrane (32) is corrugated.

8. The battery cell (14) according to claim 5, wherein the pouch is formed by a membrane (32), and the electrode device (18) is disposed within the pouch.

9. A method (38) for manufacturing a battery cell (14) according to any one of claims 1 to 8, wherein

Providing an electrode arrangement (18), a covering arrangement (30) and a cell housing (16), wherein an overpressure balancing element (26) is inserted in a wall (24) of the cell housing (16),

-the electrode means (18) and the covering means (30) are arranged in the cell housing (16) such that the overpressure balance element (26) is connected to the electrode means (18) in a ventilated manner, wherein the overpressure balance element (26) is separated from the electrolyte (36) present in the cell housing (16) by the covering means (26) against the electrolyte texture.