DE102022203932A1 - Battery cell - Google Patents

Abstract

The invention relates to a battery cell (14) with an electrode arrangement (18) which is arranged within a cell housing (16). An overpressure compensation element (26) is inserted into a wall (24) of the cell housing (16), which is connected to the electrode arrangement (18) in a gas-open manner. A cover arrangement (30) is arranged in the cell housing (16), by means of which the overpressure compensation element (26) is separated in an electrolyte-tight manner from an electrolyte (36) present in the cell housing (16). The invention further relates to a method (38) for producing a battery cell (14).

Description

The invention relates to a battery cell and a method for producing a battery cell. The battery cell has an electrode arrangement which is arranged within a cell housing.

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

Each of the battery cells in turn usually includes several galvanic elements. These each have two electrodes, namely an anode and a cathode, as well as a separator arranged between them and an electrolyte with freely movable charge carriers. A liquid, for example, is used as such an electrolyte. In an alternative, the battery cell is designed as a solid-state battery and the electrolyte is in the form of a solid. The anode and cathode, which form the electrodes of the battery cell, usually include a carrier that acts as a current collector. An active material is usually attached to this, which is part of a layer applied to the carrier, which is also referred to as an arrester. It is possible that the electrolyte is already present in the layer, or it is introduced later. However, at least the active material is suitable for absorbing the working ions, e.g. lithium ions. Depending on the use as an anode or cathode, a different material is used for the carrier and a different type of material of the layer.

To protect the galvanic elements, they are usually arranged in a cell housing of the battery cell, which also protects the electrolyte from environmental influences.

The chemical reactions that occur during operation of the battery cell also lead to undesirable minor decomposition of the electrolyte or other aging. These components of the electrolyte can no longer be used for operation. In other words, with these chemical substances the working ions are bound elsewhere so that they cannot be absorbed by the electrodes. To ensure that sufficient electrolyte is available over a comparatively long period of time, the cell housing is usually filled with a larger volume of electrolyte than is required at the start of operation. In other words, a reserve of electrolyte is available.

In the event of unwanted chemical reactions, it is possible that gases are formed, with the required volume being larger than the volume of the starting materials. As a result, the pressure prevailing in the cell housing increases. To ensure that the cell housing does not burst uncontrollably due to the additional volume required, which would lead to damage to the components arranged in the vicinity of the battery cell, the cell housing usually has an overpressure compensation element, by means of which the excess pressure prevailing in the cell housing is reduced. By means of this, the gases present in the cell housing are usually discharged into the environment in a controlled manner. However, due to the excess electrolyte in the cell housing, it is possible that the gases do not reach the overpressure compensation element. In other words, the gases are retained due to the electrolyte, and/or the functioning of the overpressure compensation element is impaired due to the additional electrolyte present. It is therefore possible that the pressure in the cell housing increases and leads to an uncontrolled rupture of the cell housing.

The invention is based on the object of specifying a particularly suitable battery cell and a particularly suitable method for producing a battery cell, with material and/or manufacturing costs advantageously being reduced, and a period of use and/or operational reliability being suitably increased.

With regard to the battery cell, this task is solved according to the invention by the features of claim 1 and with regard to the method by the features of claim 9. Advantageous further developments and refinements are the subject of the respective subclaims.

The battery cell, which is hereinafter referred to in particular simply as a battery, is preferably designed to be rechargeable and is expediently a secondary battery. Preferably, the battery cell is a component of a motor vehicle in its intended condition. The battery cell is suitable for this, in particular intended and set up. In its intended condition, the battery cell is, for example, a component of an energy storage unit chers of the motor vehicle, which has several such battery cells. The battery cells are preferably divided into several battery modules, which in turn are structurally identical to one another. The battery cells are arranged in particular in a housing of the energy storage or the respective battery module and are electrically connected in parallel and/or in series with one another. The electrical voltage applied to the energy storage/battery module is therefore a multiple of the electrical voltage provided by each of the battery cells. All battery cells are expediently identical in construction, which simplifies production.

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

The motor vehicle is, for example, a ship or boat. Preferably, however, the motor vehicle is land-based and preferably has a number of wheels, at least one of which, suitably several or all of them, are driven by means of a drive. In particular, one, preferably several, of the wheels is designed to be controllable. This makes it possible to move the motor vehicle independently of a specific roadway, for example rails or the like. It is expediently possible to position the motor vehicle essentially anywhere on a road that is made in particular from asphalt, tar or concrete. The motor vehicle is, for example, a commercial vehicle, such as a truck or a bus. However, the motor vehicle is particularly preferably a passenger car (car).

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

In a further alternative, the battery cell is a component of an industrial truck, an industrial plant, a hand-held device, such as a tool, in particular a cordless screwdriver. In a further alternative, the battery cell is a component of an energy supply and is used there, for example, as a so-called buffer battery. Here, the battery cell is used, for example, within a power plant or a household/industrial facility. In a further alternative, the battery cell is a component of a portable device, for example a portable cell phone or a wearable, or a computer. It is also possible to use such a battery cell in camping, model building or other outdoor activities.

The battery cell has an electrode arrangement with several electrodes. The electrodes are divided in particular into anodes and cathodes, with, for example, as many anodes as cathodes, or preferably an additional anode. It is particularly preferred that all anodes and all cathodes are identical in construction, which simplifies production. The electrodes, i.e. the anodes and the cathodes, are, for example, flat and in particular essentially rectangular. The anodes and cathodes each expediently have a carrier, which is also referred to as an arrester. In particular, the respective carrier is formed by means of a metal foil which is coated at least in sections with a layer on one or both sides. For example, aluminum is used as the metal of the carrier/arrestor of the cathodes and copper is used as the metal of the arrester of the anodes.

The layer has a thickness of less than 1 mm. The carriers expediently have a thickness of less than 0.1 mm. The respective layer preferably 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, intended and set up for this purpose. The active material used for the cathode is, for example, a lithium metal oxide, such as lithium cobalt (III) oxide (LiCoO2), NMC, for example NMC622 or NMC811, NCA or LFP, and/or LTO or graphite, Si for the anode. based, used.

The electrodes, i.e. the anodes and cathodes, are stacked one above the other to form a cell stack, for example, the stacking direction being perpendicular to the direction of expansion of the electrodes, which are arranged parallel to one another. The anodes and cathodes alternate in the stacking direction of the cell stack. A separator of the cell stack is arranged between adjacent electrodes, that is to say between one of the anodes and one of the cathodes, which is preferably also designed to be flat. For example, all separators are identical to one another. In particular, the electrodes are stacked essentially flush one above the other, with all anodes, for example, protruding at least slightly beyond the cathodes. This avoids undesirable material accumulation on the edge regions of the anodes during operation. Due to the stacking of the electrodes, the cell stack is also essentially cuboid-shaped. In particular, the cell stack forms the electrode arrangement. In an alternative embodiment, for example, all anodes, all cathodes or the separator are formed by means of a common band, or these are attached to a common band. The band itself is rolled up into a cylindrical shape or the like, so that a so-called “jelly roll” is formed, which in particular forms the electrode arrangement. In a further embodiment, the separator is formed by means of a band, a so-called separator band, which is folded several times in a Z shape. The individual electrodes, which are in particular leaf-shaped, are inserted into the pockets formed in this way.

The battery cell also has a cell housing within which the electrode arrangement is completely arranged. The cell housing is made, for example, from aluminum and is preferably designed to be rigid. The cell housing in particular has a cell cup which is closed by a lid. In particular, the cell housing is cylindrical or cuboid-shaped, and the battery cell is designed in particular as a so-called prismatic cell. Alternatively, the cell housing is created, for example, using a film, which is, for example, a coated aluminum foil. In other words, the battery cell is designed as a pouch cell. At least, however, the cell housing is preferably designed to be fluid-tight, in particular electrolyte-tight. The electrode arrangement is therefore protected by the cell housing and penetration of foreign particles is avoided.

The cell housing expediently has one or more openings through which a connection is guided. For example, the battery cell includes one, two or more corresponding connections, each of which is assigned one of the openings. The area between the connections and the edge of the openings is also designed to be fluid-tight, and each connection is electrically contacted with at least one of the electrodes of the electrode arrangement. It is therefore possible to feed and/or remove electrical energy into the electrode arrangement from outside the cell housing via the connections.

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

An overpressure compensation element is introduced into a wall of the cell housing, which is, for example, rigid or flexible and which is expediently essentially flat, i.e. flat. In particular, the overpressure compensation element is not part of the wall, but is separate from it. The overpressure compensation element is, for example, made of a different material than the wall of the cell housing. Preferably, there is a fluid-tight connection between the overpressure compensation element and the wall, so that leakage of the electrolyte between the overpressure compensation element and the wall is avoided. Penetration of foreign particles into the cell housing is also avoided. In summary, the overpressure compensation element is therefore not a component of any cell cup or lid made of a rigid metal, such as aluminum, nor is it a component of any film. The overpressure compensation element is also not partially formed with any of them. Rather, the overpressure compensation element is a separate component from the cell cup/lid/film ment. By means of the overpressure compensation element, it is possible, at least depending on certain states/conditions, to reduce and preferably compensate for an overpressure within the cell housing compared to an ambient pressure of the cell housing, so that there is no longer a pressure difference. For this purpose, in particular gases from the interior of the cell housing, which occur during operation due to unwanted chemical reactions, such as H2, CO or CO2, are passed out of the cell housing into the environment.

The overpressure compensation element is connected to the electrode arrangement in a gas-open manner. In other words, the same pressure prevails in the overpressure compensation element and the electrode arrangement during operation of the battery cell, and a flow of gas between the electrode arrangement and the overpressure compensation element is possible in particular undisturbed, or there is only a comparatively low, preferably negligible, flow resistance.

A cover arrangement is also arranged in the cell housing, by means of which the overpressure compensation element is separated from the electrolyte present in the cell housing in an electrolyte-tight manner. In other words, the electrolyte is prevented from reaching the overpressure compensation element by means of the cover arrangement, and the electrolyte is kept away from the overpressure compensation element by means of the cover arrangement. In summary, the overpressure compensation element is covered from the electrolyte by means of the cover arrangement, but a pressure difference between the electrode arrangement and the overpressure compensation element is avoided.

The cover arrangement ensures that the functionality of the overpressure compensation element is not impaired by the electrolyte, so that any excess pressure in the cell housing that arises during operation can be reduced by means of the overpressure compensation element. This increases operational reliability. The cell housing can be filled with a larger volume of electrolytes than is initially required for operation. Therefore, it is possible to use the battery cell for an extended period of time even if aging effects of the electrolyte occur. In other words, a service life of the battery cell is increased. The overpressure compensation element is also separated from the electrolyte by means of the cover arrangement, so that resistance of the overpressure compensation element to the electrolyte is not necessary. In this way, material requirements for the overpressure compensation element are reduced, which is why material and manufacturing costs are reduced. In addition, the cover arrangement ensures that when gases are passed from the cell housing into the environment via the overpressure compensation element, no electrolyte escapes from the cell housing, so that the environment is protected from the electrolyte, which further increases operational safety and increases the range of use of the battery cell.

Advantageously, the electrode arrangement is additionally at least partially electrically insulated by means of the cover arrangement, in particular from the overpressure compensation element and/or other components of the cell housing. For this purpose, the cover arrangement is designed to be in particular electrically insulated. The range of functions is thus further increased, with no additional component being required. Consequently, manufacturing costs are reduced and energy density is increased. Preferably, at least part of the cell housing is shielded from the electrolyte by means of the cover arrangement, so that interaction with the electrolyte, for example corrosion, is avoided there. In other words, the electrolyte and at least part of the cell housing are separated, in particular by means of the cover arrangement. This further increases the service life of the battery cell and provides comparatively long cycle stability.

For example, the overpressure compensation element is introduced into an edge region of the cell housing. However, the overpressure compensation element is particularly preferably introduced into a bottom of the cell housing. In other words, the base forms the wall of the cell housing into which the overpressure compensation element is inserted. The bottom is the lower part of the cell housing in the vertical direction, particularly when the battery cell is arranged as intended. If the battery cell is used in a motor vehicle, it is usually located below a passenger compartment. Since the overpressure compensation element is located on the bottom of the cell housing facing away from the passenger compartment, the gases are kept away from the passenger compartment of the motor vehicle. In particular, any connections or interconnection elements electrically contacted with them, which are expediently located in the vertical direction at the upper end of the cell housing, in particular in a cover, are not hindered by means of the overpressure compensation element.

If the cell housing has the cell cup and the lid, the overpressure compensation element is introduced in particular into one of the walls of the cell cup, preferably the bottom. In this way it is possible to remove the lid without that To produce an overpressure compensation element, which is why the manufacturing costs of the cover, through which any connections are expediently guided, are simplified. In this way, a separation of functions is also achieved and assembly is simplified. Here, although the overpressure compensation element is located in the lower part of the cell housing in which the electrolyte collects during operation, the electrolyte is kept away from the overpressure compensation element by means of the cover arrangement, so that the electrolyte escapes from the cell housing.

For example, the overpressure compensation element comprises a rupture disk. For example, the overpressure compensation element is formed by means of the rupture disk, or the overpressure compensation element has, for example, one or more further components. These are, for example, attached to the rupture disk or arranged separately from it. In particular, the wall has several openings, with the rupture disk being inserted into one of the openings and the or one of the possible further components being inserted into the other. The rupture disk is designed in such a way that it ruptures, in particular breaks, when a pressure prevailing in the cell housing is greater than the pressure prevailing in the area surrounding the cell housing by a limit value. In particular, the tearing/breaking process is irreversible. Despite the broken rupture disk, the electrolyte is prevented from escaping by means of the cover arrangement. For example, if the pressure difference is greater than the limit value, the rupture disk breaks completely or, for example, initially partially tears. In particular, the rupture disk is designed in such a way that the rupture stops when the pressure difference decreases. This initially prevents a complete failure of the battery cell, and it can continue to be used at least to a limited extent. Alternatively, the rupture disk breaks open completely when the limit value is exceeded, so that the pressure difference is reduced comparatively quickly, which increases safety. In summary, the rupture disk prevents the cell housing from bursting if excessive gases form in the cell housing due to an unwanted chemical reaction during operation of the battery cell.

In a further alternative, the overpressure compensation element comprises an overpressure valve. For example, the overpressure compensation element is formed by means of the overpressure valve, or the overpressure valve represents, for example, the further component to the rupture disk. In a further alternative, the overpressure compensation element comprises the overpressure valve and other components. The pressure relief valve is in particular reversibly operable and is in particular designed in such a way that it opens when a further limit value is exceeded by the pressure difference between the pressure in the cell housing and the environment of the cell housing, so that the pressure difference at least up to the further limit value or another limit value below it is dismantled. In particular, the pressure relief valve closes after falling below the further/other limit value. It is preferably designed as a pressure relief valve in the manner of a check valve. This increases robustness and prevents foreign particles from entering the cell housing. By means of the pressure relief valve, a continuous degassing takes place, particularly when the battery cell is in operation, so that the gases that arise unintentionally during normal operation of the battery cell are always or at least at certain times discharged into the environment of the battery cell. Continuous operation of the battery cell is thus possible, with excessive accumulation of gases in the battery cell in the cell housing being avoided. Due to the cover arrangement, an escape of the electrolyte from the pressure relief valve is avoided and the functionality of the pressure relief valve is not impaired.

For example, the cover arrangement is formed by means of a labyrinth seal or a type of siphon. However, the covering arrangement particularly preferably comprises a membrane and is expediently formed by means of this. The membrane is arranged between the overpressure compensation element and the electrode arrangement and is therefore mechanically located between the electrode arrangement and the overpressure compensation element. Due to the use of the membrane, the required installation space is reduced and the energy density of the battery cell is therefore increased. The membrane is in particular designed in such a way that it is permeable to gas, but not to the electrolyte. In other words, the membrane is designed to be gas-open and electrolyte-tight. For example, the membrane is made from a polymer or a polymer matrix. In particular, the membrane is made of an elastomer, for example a thermoplastic elastomer, the material being chosen in particular such that damage due to or interaction with the electrolyte is avoided. In other words, the material is in particular inert to the electrolyte used. For example, the material used is polypropylene. Particularly preferably, the membrane is designed in multiple layers, with the individual layers being tailored to the respective use, so that the functions, according to which the membrane is electrolyte-tight and gas-open, can be divided among the different layers. This increases the selection of usable materials and consequently reduces manufacturing costs.

For example, the possible connection or connections are arranged such that they are spaced from the membrane. Alternatively, at least one of the connections is guided through the membrane. In this way, freedom of design is increased. In particular, the membrane is at least partially attached to the respective connection, for example directly or via further components. The membrane is expediently connected to the connection in a fluid-tight or expediently electrolyte-tight manner. For example, the connection here is such that it is also impermeable to gas. In this way, tightness is increased. Due to the other components of the membrane, gas can still pass through to the overpressure compensation element, which is why the functionality is not restricted due to the connection.

For example, the excess pressure compensation element is covered by the membrane, and the membrane is (also) attached to the wall, preferably fluid-tight. Particularly preferably, however, the entire wall is covered by the membrane, and the membrane is expediently fastened in a fluid-tight manner to other inner walls of the cell housing. For example, the membrane is glued or welded to the other inner walls. A distance is preferably formed between the membrane and the wall. This way there is an area where any gases can collect. Due to the comparatively large area of the membrane, gas passage is also possible, even if the membrane is designed to be comparatively dense. For example, an additional membrane is present, by means of which, for example, the wall of the cell housing opposite the wall is also covered. This means there is an increased space for collecting the gases and the electrolyte is particularly free of any gases that may arise. Alternatively, for example, the membrane is designed to be hollow cylindrical and connected to two of the inner walls, whereas the rest of the cell housing is spaced from the membrane. In other words, the membrane and thus also the electrode arrangement is surrounded on the circumference by means of a space which is formed between the membrane and the cell housing and which is kept free of the electrolyte. This means that there is a comparatively large area of space in which the gases can accumulate, and the area made available for the passage of gas is increased.

For example, the membrane is flat or flat. For example, if the membrane is hollow cylindrical, it is designed to be continuously curved. The membrane is particularly preferably corrugated. In this way, an area of the membrane is further enlarged, which is why gas passage through the membrane is made easier. This makes it possible to make the membrane comparatively dense, so that the electrolyte tightness is further improved.

In an alternative embodiment, for example, a bag is formed by means of the membrane, within which the electrode arrangement is arranged. For example, the bag is attached to the inner walls and thus also to the wall of the cell housing, which increases robustness. Alternatively, the bag is simply inserted loosely within the cell housing, making production easier. With other examples, the bag is designed to be closed and the electrode arrangement is completely surrounded on the outside by means of the membrane. In this way, tightness is increased. The bag is preferably arranged in such a way that it is open on one side, preferably at the upper end in the vertical direction. On the one hand, this makes it easier to fill in the electrolyte. On the other hand, it is possible in this way to manufacture the membrane from an electrolyte-tight and gas-tight material, which is why material costs are reduced. The gas-open connection of the electrolyte arrangement with the overpressure compensation element takes place via the open part of the bag.

Here, the membrane is expediently located mechanically between the electrode arrangement and consequently also the electrolyte and the overpressure compensation element, and the electrolyte is expediently held within the bag. Particularly preferably, the bag protrudes upwards in the vertical direction with respect to a fill level of the electrolyte, so that the electrolyte does not reach the overpressure compensation element even if the battery cell is tilted or shaken. In particular, the membrane is located here between the electrolyte and the overpressure compensation element, so that even if the electrolyte splashes or bubbles, the membrane prevents the electrolyte from reaching the overpressure compensation element.

The method for producing a battery cell with an electrode arrangement which is arranged within a cell housing, wherein an overpressure compensation element is introduced into a wall of the cell housing, which is connected to the electrode arrangement in a gas-open manner, and wherein a cover arrangement is arranged in the cell housing, by means of which the overpressure compensation element Separated in an electrolyte-tight manner from an electrolyte present in the cell housing, the electrode arrangement, the cover arrangement and the cell housing are first provided, with a separate overpressure compensation element being introduced into a wall of the cell housing. The cell housing preferably has several individual parts, which in particular are not yet attached to each other. At least the cell casing is open.

In a subsequent step, the electrode arrangement and the cover arrangement are arranged in the cell housing in such a way that the overpressure compensation element is connected to the electrode arrangement in a gas-open manner, with the overpressure compensation element being separated in an electrolyte-tight manner from an electrolyte present in the cell housing by means of the cover arrangement. For example, the electrolyte is subsequently filled into the cell housing, unless this already occurs when the cover arrangement and/or the electrode arrangement is arranged in the cell housing. Alternatively, for example, the cell housing is first closed and the electrolyte is filled in through another opening.

In one embodiment, for example, the electrode arrangement and the cover arrangement are first positioned in a suitable manner relative to one another and, for example, fastened to one another. This composite is then positioned in the cell housing. In an alternative, the cover arrangement is first arranged within the cell housing, in particular the wall or further walls of the cell housing being covered by means of the cover element. The electrode arrangement is subsequently positioned in the cell housing and/or the cover arrangement.

The invention further relates to a composite of such battery cells, the composite preferably being a battery module or a high-voltage battery. The invention further relates to a motor vehicle, such as a passenger car, with such a battery cell, in particular such a composite. The battery cell is preferably used to power a main drive of the motor vehicle.

The advantages and developments described in connection with the battery cell can also be applied analogously to the process/the network/the motor vehicle and to each other and vice versa.

• 1 schematisch vereinfacht ein Kraftfahrzeug, das mehrere baugleiche Batteriezellen aufweist,
• 2 schematisch in einer Schnittdarstellung eine der Batteriezellen,
• 3 ein Verfahren zur Herstellung der Batteriezelle,
• 4, 5 jeweils in einem Ablaufdiagramm Varianten der Herstellung der Batteriezelle, und
• 6 - 8 jeweils gemäß 2 weitere Varianten der Batteriezelle.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show in it:

• 1 schematically simplified a motor vehicle that has several identical battery cells,
• 2 schematically in a sectional view of one of the battery cells,
• 3 a process for producing the battery cell,
• 4 , 5 each in a flow chart of variants of the production of the battery cell, and
• 6 - 8th each according to 2 further variants of the battery cell.

Corresponding parts are provided with the same reference numbers in all figures.

In 1 A motor vehicle 2 is shown in a schematically simplified form in the form of a passenger car (car). The motor vehicle 2 has a number of wheels 4, at least some of which are driven by a drive 6 which includes an electric motor. The motor vehicle 2 is therefore an electric vehicle or a hybrid vehicle. The drive 6 has a converter, by means of which the electric motor is fed. The converter of the drive 6 is in turn powered by an energy storage device 8 in the form of a high-voltage battery. For this purpose, the drive 6 is connected to an interface 10 of the energy storage 8, which is inserted into an energy storage housing 12 of the energy storage 8, which is made of stainless steel.

Within the energy storage housing 12 of the energy storage 8, several identical battery modules (not shown) are arranged, each of which includes several battery cells 14. The battery cells 14 of each battery module are partly electrically connected in series with one another and partly electrically connected in parallel with one another. Some of the battery modules are in turn electrically connected in series with one another and these in turn are electrically connected in parallel with one another. The electrical assembly of the battery modules is electrically contacted with the interface 10, so that when the drive 6 is in operation, the battery modules and thus also the battery cells 14 are discharged or charged (recuperation). Due to the electrical connection, the electrical voltage provided at the interface 10, which is 400 V, is a multiple of the electrical voltage provided with each of the battery modules and also with each of the battery cells 14.

In 2 one of the identical battery cells 14 is shown in a schematically simplified sectional view. The battery cell 14 has a rigid, essentially cuboid cell housing 16, which is made of aluminum. The battery cell 14 is therefore a prismatic cell. An electrode arrangement 18, shown in dashed lines, is arranged within the cell housing 16 and comprises several electrodes, not shown in detail. The electrodes are divided into anodes and cathodes, which are stacked one on top of the other, with a separator arranged between each. Here, the anodes, cathodes and separators, for example, are initially separate from one another and are separated by means of attached to each other using suitable fasteners. Alternatively, for example, an anode, one of the cathodes and two of the separators are already attached to one another, so that a so-called mono cell is formed. The monocells are stacked one on top of the other and in particular form the electrode arrangement 18. In a further alternative, the electrode arrangement 18 is formed by means of a so-called “jelly roll” or comprises a separator belt folded several times in a Z-shape into which the anodes/cathodes are inserted.

The electrode arrangement 18 is electrically contacted with two connections 20, for example one of the connections 20 being electrically contacted with all anodes and the other with all cathodes of the electrode arrangement 18. The two connections 20 are guided through a boundary wall 22 which delimits the cell housing 16 in the vertical direction, for which purpose the boundary wall 22 has openings (not shown in more detail). The area between the edge of the openings and the connections 20 is designed to be fluid-tight, for which the connections 20 are designed accordingly. An electrical voltage is present at the connections 20 during operation, and this enables electrical energy to be removed and fed into the electrode arrangement 18 during operation.

The boundary wall 22 is formed by a cover of the cell housing 16, not shown, which is attached to a cup-shaped cell cup. An overpressure compensation element 26 is inserted into the wall 24 opposite the boundary wall 22, which forms the bottom of the cell housing 16 when the battery cell 14 is used as intended. For this purpose, the wall 24 has an opening 28 which is completely filled by the overpressure compensation element 26, the overpressure compensation element 26 being attached to the wall 24 in a fluid-tight manner. In this embodiment, the overpressure compensation element 26 is a rupture disk, so that the overpressure compensation element 26 is formed by means of the rupture disk. The rupture disk is constructed in such a way that it breaks when a pressure difference between a pressure inside the cell housing 16 and the surroundings of the cell housing 16 exceeds a certain limit. The rupture disk 26 initially tears until the pressure difference drops. If this does not happen, the rupture disk 26 will open completely and thus break.

Furthermore, a cover arrangement 30 is arranged within the cell housing 16, which is designed as a bag which is open upwards in the vertical direction and which is created from a suitably folded membrane 32. The membrane 30 is designed to be both electrolyte-tight and gas-tight. The bag is designed to be fluid-tight and is only inserted loosely into the cell housing 16, so that gas can pass between the cell housing 16 and the membrane 32. In a variant not shown in detail, the bag is attached to the cell housing 16 in sections. The electrode arrangement 18 is inserted into the bag formed by means of the cover arrangement 30, which protrudes beyond the bag in the vertical direction. The material requirement for the membrane 32 is therefore reduced and assembly and production are made easier. In this way, the electrode arrangement 18 is also connected to the overpressure compensation element 26 in a gas-open manner, and gas passage from the electrode arrangement 18 to the overpressure compensation element 26 is not prevented by the boundary wall 22. In summary, the cover arrangement 30 thus has the membrane 32, which is mechanically arranged between the overpressure compensation element 26 and the electrode arrangement 18.

The cover arrangement 30, namely the bag, is filled with an electrolyte 36 up to a filling level 34. The fill level 34 is located in the vertical direction below the upper end of the bag formed by the membrane 32, so that even if the cell housing 16 is tilted, the electrolyte 36 is prevented from leaking out of the bag. Thus, by means of the cover arrangement 30, the overpressure compensation element 26 is separated from the electrolyte 36 present in the cell housing 16 in an electrolyte-tight manner.

If unwanted chemical reactions of the electrolyte 36 with the electrode arrangement 18 occur during operation, gases can be formed and the volume of electrolyte 36 in the cell housing 16 decreases, so that the fill level 34 drops. However, since a comparatively large amount of electrolyte 36 is present in the cell housing 16, unhindered continued operation of the battery cell 14, namely feeding in/withdrawal of electrical energy, is still possible. However, due to the gases, an excess pressure arises in the cell housing 16. The resulting gases can reach the pressure compensation element 26 undisturbed and accumulate in particular on the bottom of the cell housing 16. If the overpressure exceeds the limit value, the overpressure compensation element 26, designed as a rupture disk, enters so that the gas can escape from the cell housing 16. Due to the cover arrangement 30, the electrolyte 36 is prevented from escaping from the cell housing 16, so that the battery cell 14 can continue to be used.

In 3 a method 38 for producing battery cells 14 of identical construction is shown. In the first step, turn 40 First the electrode arrangement 18, the cover arrangement 30 and the cell housing 16 are provided. The cell housing 16 already has the opening 28 in the wall 24 into which the overpressure compensation element 26 is inserted. In other words, the overpressure compensation element 26, which is a separate component from the wall 24, is introduced into the wall 24 of the cell housing 16.

In a subsequent second step 42, the electrode arrangement 18 and the cover arrangement 30 are arranged in the cell housing 16 in such a way that the overpressure compensation element 26 is connected to the electrode arrangement 18 in a gas-open manner, with the overpressure compensation element 26 being freed from the electrolyte present in the cell housing 16 by means of the cover arrangement 30 36 is separated electrolyte-tight. For this purpose, the bag in particular is positioned accordingly in the cell housing 16. Preferably, the electrolyte 36 is subsequently filled into the bag and the cell housing 16 is sealed in a fluid-tight manner.

In 4 A first variant of the method 38, namely the second step 42, is shown in a flow diagram. In this case, the electrode arrangement 18, to which the connections 20 are already attached, is first inserted into the bag-like covering arrangement 30. Subsequently, the composite of electrode arrangement 18 and cover arrangement 30, which are loose from one another, is inserted into the cell housing 16. In particular, the boundary wall 22 is formed by means of an initially separate cover, which is fastened to the other components of the cell housing 16 after the cover arrangement 30 has been positioned in the cell housing 16, the connections 20 being guided through the boundary wall 22.

In 5 a modification of the method 38 is shown. In the second step 45, the cover arrangement 30 is first positioned within the cell housing 16. The electrode arrangement 18 is then inserted into the bag-like cover arrangement 30 and thus also into the cell housing 16. The electrolyte 36 is then filled in and the boundary wall 22 is suitably positioned and attached to other components of the cell housing 16.

In 6 is according to the representation of the 2 a modification of the battery cell 14 is shown. In this variant, the boundary wall 22 is free of the openings with the connections 20 inserted therein, and into the connections 20 protrude through opposite side walls 44 of the cell housing 16. In this variant, the electrode arrangement 18 is also formed, for example, by means of a “jelly roll”, whereby the electrode arrangement 18 continues to be electrically contacted with the connections 20. The connections 20 extend through the cover arrangement 30, which is also designed as a bag, with the membrane 32 being opened in sections for the connections 20 to pass through. Here, the membrane 32 is attached to the connections 20 in a fluid-tight manner, so that the electrolyte 36 is prevented from escaping from the bag.

The wall 24 also has the opening 28, into which the overpressure compensation element 26 is inserted in a fluid-tight manner. The wall 24 is also formed here by means of the bottom of the cell housing 16. In comparison to the previous embodiment, however, the overpressure compensation element 26 is formed by means of a pressure relief valve. The pressure relief valve is designed in such a way that it opens at a lower pressure difference, namely a further limit value, between the pressure in the cell housing 16 and the pressure in the surroundings of the cell housing 16, so that the gases arising in the cell housing 16 are released via the pressure compensation element 26 can exit the cell housing 16. As soon as the pressure difference has fallen below another limit value, the pressure relief valve designed as a check valve closes, so that penetration of foreign particles into the cell housing 16 is avoided. In this variant of the battery cell 14, due to the design of the overpressure compensation element 26, essentially continuous degassing occurs during operation.

In 7 a further modification of the battery cell 14 is shown, with the cell housing 16 and the electrode arrangement 18 as well as the connections 20 not being changed. The overpressure compensation element 26 is also not changed. Only the cover arrangement 30 is modified, which continues to include the membrane 32. The material of the membrane 32 has been changed and is now designed to be gas-open, with the membrane 32 also continuing to be electrolyte-tight. To provide these functionalities, the membrane 32 has different layers that are formed using different materials.

The membrane 32 is shaped like a hollow cylinder and completely surrounds the electrode arrangement 18 on the circumference. The opposite ends of the hollow cylinder formed in this way are fastened in a fluid-tight manner, namely by means of gluing or welding, to further inner walls 46 of the cell housing 16, which are provided by means of the two opposite side walls 44. Here, the membrane 32 is spaced from the wall 24. As a result, a circumferential space 48 is formed between the cell housing 16 and the membrane 32. The electrolyte 36 is arranged within the membrane 32 so that the space 48 is free of the electrolyte 36. In summary, the entire wall 24 is covered by the membrane 32 and a part of the cell housing 16 is not in contact with the electrolyte 36. Consequently, corrosion is avoided there and the service life of the battery cell 14 is increased. In this variant, it is completely impossible for the electrolyte 36 to reach the overpressure compensation element 26, even in the event of a comparatively large shock or a tipping over of the battery cell 14.

The gases that arise unintentionally during operation enter the space 48 through the membrane 32, the passage of gas being essentially not hindered due to the comparatively large surface area of the membrane 32, so that essentially the same pressure inside the membrane 32 as outside the membrane 32, So in room 48, prevails. If the pressure difference between the pressure inside the cell housing 16 and the pressure outside the cell housing 16 again exceeds the further limit value, the gases are released into the environment of the cell housing 16 via the overpressure compensation element 26, with no escape of the electrolyte 36.

In 8th a further modification of the battery cell 14 is shown, in which only the cover arrangement 30 is changed compared to the previous embodiment. The cover arrangement 30 in turn has the membrane 32, which is made of the same material as in the previous variant. However, the membrane 32 is arranged essentially in a plane and is not curved. Due to waves introduced into the membrane 32, it is not completely arranged in one plane. As a result, the membrane 32 has an increased surface area compared to the completely flat design. By means of the membrane 32, the wall 24 and the overpressure compensation element 26 are also completely covered, with the membrane 32 being arranged at a distance in the vertical direction above the wall 24. The membrane 32 is in turn attached to the further inner walls 46 and the other inner walls (not shown) in a fluid-tight manner by means of welding or gluing, the respective welding or gluing seam being straight, which facilitates production. The electrolyte 36 is thus held above the wall 24 by means of the membrane 32.

In the vertical direction above the electrode arrangement 18, a further membrane 50 is arranged, which is constructed identically to the membrane 32 and which is also connected to the further inner walls 46 in a fluid-tight manner. An additional space 52 is thus created, which is also free of the electrolyte 36 and in which the gases can collect. The additional space 52 is fluidly connected to the overpressure compensation element 26 by means of a device shown in more detail, so that the gases can also be removed from there. Due to the corrugated design of the membrane 32 and the further membrane 50, an area that can be used for the passage of gas is increased.

The invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived from this by the person skilled in the art without departing from the subject matter of the invention. In particular, all of the individual features described in connection with the individual exemplary embodiments can also be combined with one another in other ways without departing from the subject matter of the invention.

Reference symbol list

2

motor vehicle

4

wheel

6

drive

8th

Energy storage

10

interface

12

Energy storage enclosure

14

Battery cell

16

Cell casing

18

Electrode arrangement

20

Connection

22

Boundary wall

24

Wall

26

Overpressure compensation element

28

opening

30

Cover arrangement

32

membrane

34

level

36

electrolyte

38

Proceedings

40

first step of work

42

second step

44

Side wall

46

another interior wall

48

Space

50

another membrane

52

additional space

Claims (9)

Battery cell (14) with an electrode arrangement (18) which is arranged within a cell housing (16), an overpressure compensation element (26) being introduced into a wall (24) of the cell housing (16), which is connected to the electrode arrangement (18) in a gas-open manner is, and wherein a cover arrangement (30) is arranged in the cell housing (16), by means of which the overpressure compensation element (26) is separated in an electrolyte-tight manner from an electrolyte (36) present in the cell housing (16). Battery cell (14). Claim 1 , characterized in that the overpressure compensation element (26) is inserted into a bottom of the cell housing (16). Battery cell (14). Claim 1 or 2 , characterized in that the overpressure compensation element (26) comprises a rupture disk. Battery cell (14) according to one of the Claims 1 until 3 , characterized in that the overpressure compensation element (26) comprises a pressure relief valve. Battery cell (14) according to one of the Claims 1 until 4 , characterized in that the cover arrangement (30) comprises a membrane (32) which is arranged between the overpressure compensation element (26) and the electrode arrangement (18). Battery cell (14). Claim 5 , characterized in that the entire wall (24) is covered by means of the membrane (32), the membrane (32) being fastened in a fluid-tight manner to further inner walls (46) of the cell housing (16). Battery cell (14). Claim 6 , characterized in that the membrane (32) is corrugated. Battery cell (14). Claim 5 , characterized in that a bag is formed by means of the membrane (32), within which the electrode arrangement (18) is arranged. Method (38) for producing a battery cell (14) according to one of Claims 1 until 8th , in which - an electrode arrangement (18), a cover arrangement (30) and a cell housing (16) are provided, an overpressure compensation element (26) being introduced into a wall (24) of the cell housing (16), - the electrode arrangement (18) and the cover arrangement (30) can be arranged in the cell housing (16) in such a way that the overpressure compensation element (26) is connected to the electrode arrangement (18) in a gas-open manner, the overpressure compensation element (26) being moved from one in the cell housing (18) by means of the cover arrangement (30). 16) existing electrolyte (36) is separated electrolyte-tight.

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