Methods for adjusting the internal pressure in a battery cell and battery arrangement

Abstract

The invention relates to a method for adjusting the cell internal pressure in at least one battery cell (12), wherein a battery cell (12) is provided which comprises a cell housing (16) in which a cell interior (18) is enclosed, wherein an initial cell internal pressure (P) prevails in the cell interior (18), and wherein a gas (22) is introduced into the cell housing (16) via a closable first opening (24) in the cell housing (16) until the cell internal pressure (P) reaches a predetermined first pressure threshold (G1).

Description

The invention relates to a method for adjusting the internal cell pressure in at least one battery cell. The invention furthermore also relates to a battery arrangement for a motor vehicle.Battery cells, in particular for motor vehicle batteries, for example high-voltage batteries, expand over the service life, which is also referred to as "swelling". There are two causes of this, among others. On the one hand, the volume of the active material in the cell increases as a result of electrochemical processes, and on the other hand, decomposition processes in cell chemistry produce gas which accumulates in the interior of the cell and leads to an increased internal cell gas pressure over the lifetime. The amount of gas formed depends on the cell chemistry and the operating conditions of the cell. In particular, high temperatures and a large SOC (state of charge) stroke promote gas formation. The gas that arises remains within the cell in current projects. The generation of gas is an undesirable side effect. Active material is consumed in the formation of the gas. This leads to a reduction of the electrochemically active substances within the cell. A high internal gas pressure can lead to cell wall lift-off. Starting from a defined pressure, for safety reasons, a rupture membrane, which is often provided, also opens in the cell housing in order to prevent undefined rupture of the cell.JP 061 630 71 A describes a method for producing a nickel-hydrogen battery, according to which the inert gas is introduced into the still open battery housing in a sealed treatment chamber filled with an inert gas and the battery housing is then sealed by a lid.The introduction of an inert gas into a battery during its production leads to an even more early rise in the internal pressure.DE 10 2011 077 676 A1 describes a battery cell which has a housing and an electrode ensemble in the housing, and also a filling body arranged in the housing. This is intended to reduce the free volume in the battery cell housing that can be taken up by formed gas.It is an object of the present invention to reduce the electrolyte loss due to gas formation in a battery cell and / or the swelling or the increase in pressure in the battery cell over the course of the service life.This object is achieved by a method and a battery arrangement having the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject matter of the dependent patent claims, the description and the figures.In a method according to the invention for adjusting the internal cell pressure in at least one battery cell, a battery cell is provided which comprises a cell housing in which a cell interior is enclosed, wherein an initial internal cell pressure prevails in the cell interior, and wherein a gas is introduced into the cell housing via a first opening in the cell housing until the internal cell pressure reaches a predetermined first pressure threshold value.The invention is based on the finding that the gas formation is reduced in the course of the service life paradoxically by a high gas pressure within a battery cell, i.e. a high internal cell pressure. Thus, for example, the gas formation is higher in conventional new cells due to the even lower internal gas pressure than in aged cells which have already formed an increased internal gas pressure. By introducing a gas into the cell interior, the initial cell internal pressure can thus advantageously be increased, which then leads to reduced gas formation within the battery cell and reduced swelling of the battery cell during the lifetime of the battery cell. In addition, owing to the reduced gas formation, the electrochemically active substances within the cell are also only reduced to a reduced extent. The cell chemistry to be initially introduced into a battery cell and in particular the required amount of an electrolyte can thereby advantageously be reduced, whereby in turn costs and weight can be saved.In particular, a cell chemistry is thus arranged in the cell interior of the battery cell. The cell chemistry can accordingly comprise an electrode arrangement, in stacked or wound form, for example comprising at least one positive electrode or electrode layer, at least one negative electrode or electrode layer and at least one separator located between these electrodes, and a liquid electrolyte. The battery cell may be, for example, a lithium-ion cell. The battery cell is provided, for example, in a form already produced. Filling with the gas up to the predetermined first pressure threshold value thus preferably takes place after the production of the battery cell. For example, the battery cell can be in a state already installed in a motor vehicle and / or at least in a state installed in a high-voltage battery or medium-voltage battery.The first opening can be configured closable, in particular reversibly openable and closable. A suitable interface can be provided through the first opening in the cell housing in a corresponding manner in order to introduce the gas into the cell interior. The opening can be correspondingly opened in order to introduce the gas into the cell housing, and after the predetermined first pressure threshold value is reached, the opening in the cell housing can be closed again.However, a closure for the opening does not necessarily have to be provided on the cell housing itself, but can also be provided, for example, in a filling device or a connection element of such a filling device, which is or is connected to the opening for filling with the gas. The connection element with the closure can then also remain on the battery cell, in particular permanently.Although filling the cell interior with the gas likewise leads to a certain swelling or swelling of the battery cell, since filling is preferably effected after the production of the battery cell, for example if it is already installed in the battery or in the motor vehicle, the handling of the battery cell and / or the transport of the battery cell is not made more difficult as a result and installation space requirements of the battery cell before or during installation are also not increased.The initial internal cell pressure prevailing in the cell interior is smaller than the first pressure threshold value. In other words, the internal cell pressure is increased by introducing the gas into the cell case. At the time of the introduction of the gas, preferably no cycling of the battery cell has yet taken place. In other words, the battery cell has not yet undergone a charging and discharging cycle at this time.The battery cell can be, for example, a prismatic battery cell, but applications in round cells or pouch cells are also conceivable.The gas may be an inert gas, for example nitrogen or a noble gas, e.g. helium, argon, krypton, neon, radon, xenon or the like. The gas may also be, for example, CO2or another gas which is preferably selected such that it does not interact or react with the cell chemistry or at least does not interact negatively. The gas may also be a gas mixture, for example of two or more of the above-mentioned gases.According to a further advantageous embodiment of the invention, a gas is discharged from the cell interior via the first opening or an in particular closable second opening in the cell housing, in particular by means of a valve arranged e.g. in the cell housing, when the cell internal pressure exceeds a specific second pressure threshold value, which is greater than the first pressure threshold value. This advantageously allows a gas pressure limitation for the internal cell pressure to be provided. This in turn reduces swelling of the battery cell due to gas. The gas which arises in the cell interior over time can therefore advantageously be discharged at least in part when the internal cell pressure exceeds the determined second pressure threshold value, for example until the internal cell pressure has again lowered to a value below this second pressure threshold value. Thus, the internal cell pressure can be always maintained at a substantially constant level, in particular that of an optimum gas pressure for the battery cell. This in turn leads to the swelling of the battery cell also being kept substantially at a constant level over the course of the service life. A further increase in swelling over time can advantageously be avoided by discharging the gas, in particular the repeated discharge of the gas from the cell interior. This also requires less installation space for swelling compensation. Less installation space in turn makes it possible to provide more space for additional cells, in particular in a motor vehicle battery, as a result of which the range of the motor vehicle can be increased. In addition, lower swelling forces thus also arise in the battery or in the system, as a result of which material, installation space and costs can be saved overall. In addition, by setting the internal cell pressure to the optimum gas pressure, an increase in the service life of the battery cell can be achieved.The discharged gas can be, in particular, a different gas or a gas with a different gas composition than the gas which has been supplied to the cell interior. The discharged gas may, for example, partly comprise the gas which has been introduced into the cell interior beforehand, but also partly comprise gas which has been formed during operation of the battery cell. The discharged gas does not have to be, for example, a pure inert gas.Since additional gas is continuously produced in the cell interior over the course of the service life, at least a portion of this gas can be discharged repeatedly via the first and / or second opening in the cell housing if the second pressure threshold value is exceeded. In other words, this discharge of the gas can be effected not only once but repeatedly. As a result, the internal cell pressure can be maintained at a value which corresponds at most to the second pressure threshold value.The discharge of the gas can take place either via the same first opening in the cell housing via which the gas was also supplied, or an additional second opening can be provided in the cell housing.The first or second opening can in turn be configured closable, in particular reversibly openable and closable. The opening can be opened accordingly in order to discharge the gas from the battery cell, and after the predetermined second pressure threshold value is reached or undershot, the opening in the cell housing can be closed again. In this case, however, a closure for the opening also does not necessarily have to be provided on the cell housing itself, but can also be provided, for example, in a device or a connection element of such a device which is connected to the relevant opening, i.e. the first and / or second opening, for discharging gas from the cell. The connection element with the closure can then also remain on the battery cell, in particular permanently. The device with the connection element can be, in particular, the filling device with which the gas has also been filled into the battery cell. If two openings are provided in the cell housing for filling with the gas and for discharging gas, this device can also comprise two connection elements per cell, one connected to the first opening and one connected to the second opening. Otherwise, for filling with gas and discharging gas from the cell, only one common, combined connection element can also be provided as part of the device.It is particularly advantageous, as is provided according to a further advantageous embodiment of the invention, if the valve via which the gas is discharged from the cell interior is designed as a pressure relief valve which opens when the second pressure threshold value is exceeded and closes when the second pressure threshold value is undershot or reached. As a result, no active activation of the valve is advantageously required. The valve can thus open automatically as soon as the second pressure threshold value is exceeded. As a result, the internal cell pressure can be reliably kept below or at the maximum at the internal cell pressure corresponding to the second pressure threshold value.The valve can be arranged in the cell housing in the region of the first and / or second opening via which the gas is discharged from the cell, or can be provided in a line or the connection element of the device which is arranged at the relevant opening for discharging the gas from the cell.According to a further advantageous embodiment of the invention, the valve is designed as a controllable valve which is actuated in a predetermined manner, in particular repeatedly at predetermined time intervals, in order to open temporarily. The second opening in the cell housing can thus be configured with a valve which is actuated repeatedly in order to open temporarily. After opening, the valve can be closed again. The valve can open for a very short time in order to discharge a part of the gas in the cell interior and thereby reduce the internal cell pressure. As described above, the repeated opening makes it possible to keep the internal cell pressure below a specific limit value, in particular the second pressure threshold value. The opening does not necessarily have to be effected under pressure control, but can be effected, for example, at predetermined time intervals which are not necessarily the same. A suitable distance between the time intervals can be determined experimentally, for example, and be dependent on the aging of the cell or its charge throughput, for example, or the like.According to a further advantageous embodiment of the invention, the battery cell comprises a releasable cell degassing opening for emergency degassing of the battery cell, wherein the releasable cell degassing opening opens when the cell internal pressure exceeds a third pressure threshold value, which is greater than the first pressure threshold value, and in particular also greater than the second pressure threshold value.By means of such a releasable cell degassing opening for emergency degassing, controlled degassing of the battery cell in an emergency, for example in the event of a thermal runaway of such a battery cell, can be provided. Uncontrolled bursting can thus be prevented. By the above-described pressure limitation of the cell internal pressure, as can be achieved by discharging the gas from the cell interior, in particular the repeated discharge of such a gas, it is advantageously possible to prevent such an emergency degassing valve of the battery cell from being opened accidentally during normal operation of the battery cell by a temporarily excessively high internal pressure in the battery cell, especially toward the end of the service life. It is precisely in combination with the gas discharge from the cell interior when the second pressure threshold value is exceeded that it is thus also possible to reduce the risk of the releasable cell degassing opening, e.g. a rupture membrane, opening and, associated therewith, uncontrolled degassing of combustible and possibly harmful substances into the battery compartment. If, nevertheless, the battery cell undergoes thermal runaway and a resultant strong evolution of gas in the battery cell, this gas can advantageously be discharged from the battery cell via the cell degassing opening.The releasable cell degassing opening can be designed, for example, as a rupture disk or rupture membrane or the like.According to a further advantageous embodiment of the invention, the first opening in the cell housing is closed or closable by means of a closure device which is designed such that it opens for introducing the gas and prevents fluid from leaking out of the cell interior, at least at an internal cell pressure which is less than the second pressure threshold value, in particular wherein the closure device is designed as a nonreturn valve. By means of such a closure device, for example a check valve, it is thus advantageously possible to introduce the gas into the cell interior until the specific internal cell pressure, which is predetermined by the first pressure threshold value, is reached. Then, the supply of the gas into the cell interior can be ended accordingly. The closure device, in particular the nonreturn valve, then correspondingly prevents the gas filled into the cell interior or else other parts of the cell chemistry, for example the electrolyte, from being able to escape from the cell interior.The check valve and the above-mentioned valve, e.g. the overpressure valve or the controllable valve, can also be integrated in a common valve device. Such a valve device can be integrated into the first opening or into the connection element described above or in another part of a line of the device.However, it can also be provided that the gas is introduced into the cell interior and the gas is discharged from the cell interior via two separate openings in the cell housing. Then, for example, the first opening or the line connected thereto or the connection element connected thereto can be designed with a nonreturn valve, and the second opening or the line connected thereto or the connection element connected thereto can be designed with an overpressure valve or with a controllable valve.According to a further advantageous embodiment of the invention, the gas discharged from the cell interior is chemically converted and / or chemically bound, and / or is guided into a gas collecting container, in particular into an interior of a frame component of a battery housing, and / or filtered by means of a filter and / or supplied to an environment. These variants can also be combined with one another as desired. For example, the discharged gas can first be chemically converted or bound and then supplied to an environment. The gas volume can be reduced and / or the gas rendered harmless by the chemical conversion or bonding. Additionally or alternatively, the removed gas can also be filtered and then supplied to the environment, for example. This advantageously allows pollutants to be filtered out, which cannot then pass into the environment. The gas can also be collected, filtered or unfiltered, in a collecting container, in particular in gaseous form or alternatively also in converted or bound form.It is particularly advantageous if the gas collecting container is provided by an interior of a frame component of a battery housing. As a result, unused installation space can be used up to now in order to collect therein the gas discharged from the cell interior. The frame of such a battery housing can be designed, for example, as an extruded profile, in particular an extruded hollow profile, or can comprise frame parts made of such extruded profiles. These can optionally be additionally sealed, for example in the region of screw connections, and thus advantageously the cavities present in such a frame profile can be used as gas collecting containers.If the vehicle in which the battery arrangement is used is a hybrid vehicle with an internal combustion engine, the gas discharged from the cell interior can also be supplied to an intake tract of the internal combustion engine and in particular burned.According to a further advantageous embodiment of the invention, a line system with at least one fluid line is connected to the at least one first and / or second opening of the cell housing, in particular a hose system with at least one hose, wherein the gas is introduced into the cell interior via the line system and / or the gas is discharged from the cell interior. Such a line system or hose system can also be referred to as hose connection. The line system can also comprise a plurality of fluid lines or hoses, for example if a plurality of battery cells are to be or are to be connected to the hose system in a corresponding manner. The line system or hose system can also be configured annularly. For example, a plurality of battery cells can also be connected to a type of annular gas conducting system which is provided by such a fluid conducting system. It is furthermore advantageous if the line system can be flushed with fresh air in order to prevent accumulation of possibly combustible gases.The line system can be connected, for example, via the above-mentioned connection elements to the respective cell openings, i.e. the first and / or second opening.Preferably, such a line system is used to initially, in particular once, supply the gas to the battery cell or cells until the first pressure threshold value is reached, and then, during the operation or the service life of the battery cell or cells, to discharge the "excess" gas that arises in the cell interior from the cell or cells concerned, in order to maintain the cell internal pressure at the second pressure threshold value. Thus, such a line system can be used twice. An already present line system for the gas discharge can thus advantageously also be used, for example, simultaneously in order to initially subject the battery cells to an additional internal cell pressure.Nevertheless, it would also be conceivable for such a line system to be provided only for discharging gas from the cell interior and for only a second opening to be connected, for example, and for the cells to be filled with the gas to be carried out separately, for example via the first opening, for example by temporary connection of a gas filling device, for example a gas pressure cartridge or the like.The above-mentioned valves, for example the check valve and / or the overpressure valve or controllable valve, can be provided in the cell housing of the battery cell itself, namely in the region of the corresponding openings or also in the mentioned hose system or line system. At the interfaces between the line system and the battery cell, the line system is additionally connected to the cell housing in a fluid-tight manner. Escape of gas and also of other substances can thus be reliably prevented.According to a further advantageous embodiment of the invention, the at least one fluid line is segmented into a plurality of volume sections which are separated from one another by closure elements which can be released as a function of pressure. As a result, the gas collection container or a gas discharge into the environment can be saved to some extent. If, for example, the second pressure threshold value is exceeded by the internal cell pressure, gas is correspondingly discharged from the cell interior. The discharged gas accordingly reaches the line system, more precisely a first section of this line system, which directly adjoins the battery cell. In this volume section of the line system, the gas discharged from the cell can then be correspondingly collected, for example until a limit pressure assigned to the first closure element is exceeded. When this limit value is exceeded, the closure element opens accordingly and thus establishes a fluidic connection to the next volume section. The total volume which can now be taken up by the discharged gas has increased accordingly. As a result, the gas pressure within this volume decreases. If gas continues to be discharged from the cell and introduced into the line system over time, the gas pressure within the adjacent volume sections connected to one another ultimately becomes so great until the next closure element opens, and so on. Thus, a larger volume can be successively and always taken up by the discharged gas in the line system, for example until ultimately all volume sections are connected to one another. As a result, the interior of the line system can advantageously also serve simultaneously as a gas collecting container. A combination with the variants described above is likewise conceivable. These releasable closure elements can also be provided subsequently after the respective cell has been charged with the gas. For example, after installation in the module, the cell can first be filled with the gas via a hose. Subsequently, this tube can be sealed segment by segment by the closure elements after filling. When the pressure rises in the cell, these seals open from a respective assigned defined limit pressure and thus release the hose in sections, as a result of which the internal pressure of the cell can be limited to the required extent. In this embodiment, the degassing system can then advantageously be incorporated, optionally incl. Filters and so forth within the battery are dispensed with, since no gas is released or has to be released and / or is conducted into the environment.Furthermore, the invention also relates to a battery arrangement for a motor vehicle, which comprises at least one battery cell, which comprises a cell housing in which a cell interior is enclosed, wherein a cell chemistry is located in the cell interior, and wherein an initial cell internal pressure prevails in the cell interior. The battery arrangement has a device by means of which a gas can be introduced into the cell housing via a first opening in the cell housing, in particular a closable first opening, until the internal cell pressure reaches a predetermined first pressure threshold value.The advantages mentioned for the method according to the invention and its embodiments apply in the same way to the battery arrangement according to the invention.Furthermore, the invention also relates to a motor vehicle having a battery arrangement according to the invention or one of its configurations.The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle. The motor vehicle can also be designed as an electric vehicle.The invention also includes developments of the battery arrangement according to the invention, which have features as have already been described in connection with the developments of the method according to the invention. For this reason, the corresponding developments of the battery arrangement according to the invention are not described again here.The invention also includes the combinations of the features of the described embodiments. The invention therefore also comprises implementations which each have a combination of the features of a plurality of the described embodiments, provided that the embodiments have not been described as mutually exclusive.Exemplary embodiments of the invention are described below. The following shows: FIG. 1 shows a schematic illustration of a battery arrangement during the filling of a gas into battery cells according to an exemplary embodiment of the invention; FIG. 2 shows a schematic illustration of a battery arrangement during the discharge of gases from the battery cells according to a further exemplary embodiment of the invention; and FIG. 3 is a schematic illustration of a graphical illustration of the internal cell pressure of a battery arrangement according to a further exemplary embodiment of the invention over time in comparison with a conventional cell.The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another and that also develop the invention independently of one another. Therefore, the disclosure is intended to include combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.In the figures, identical reference numerals designate functionally identical elements.FIG. 1 shows a schematic illustration of a battery arrangement 10 according to an exemplary embodiment of the invention. The battery arrangement 10 comprises at least one battery cell 12 and in the present example three battery cells 12. The battery cells 12 each have a cell housing 16, in which a cell interior 18 is enclosed. In this case, cell chemistry can be located in the cell interior 18, but is not shown in the present case for reasons of clarity. In this case, a cell internal pressure P prevails in the cell interior 18. In order to enable emergency degassing in the case of, for example, thermal runaway of a battery cell 12, each cell 12 can also comprise an emergency degassing valve 20, for example in the form of a rupture membrane or the like. This has also been previously referred to as a releasable cell degassing opening 20. This cell degassing opening 20 opens passively, for example, as a function of pressure, starting from a cell internal pressure P of, for example, 10 bar or higher.Conventional cells expand over the lifetime, which is also referred to as swelling. This swelling is attributable firstly to electrochemical processes, by which the volume of the active material in the cell increases, and secondly to decomposition processes in cell chemistry, which produces gas which accumulates in the cell interior and leads to an increased cell internal pressure over the lifetime. By contrast, this gas formation is reduced by a high gas pressure in the cell interior. Thus, gas formation is higher for new cells than for aged cells which have already formed an increased internal gas pressure, for example.The invention or its embodiments now advantageously make it possible to obtain or set the respective as optimum as possible gas internal pressure P for each section in the life cycle of such a battery cell 12. When such a cell 12 is being created or produced, transported, stored and assembled in a system, in particular in a battery 14, the internal gas pressure P can be kept minimized, that is to say corresponds to an initial gas pressure, as has also been customary hitherto. After the end of the assembly and before the beginning of the cycling, the gas internal pressure P can be increased to a maximum of a defined value G 1, which was also referred to above as the first limit value. For this purpose, a gas, in particular an inert gas 22, can be supplied to the respective gas interior 18, as illustrated in FIG. 1. For this purpose, a closable opening 24 can be provided in the cell housing 16, which opening is designed as a check valve 26 in the present example. Thereby, it is possible to supply an inert gas 22 to the cell interior 18 until the first limit value G 1 of the cell internal pressure P is reached, for example, and then to stop the supply of the inert gas 22. Subsequently, no gas or other substance can escape from the cell interior 18 through this valve 24.By thus increasing the internal gas pressure P before the cycling of the cells 12, gas formation is reduced. By reducing gas formation, the required amount of liquid per cell 12 can be reduced, which in turn saves costs.The inert gas 22 can be supplied via a line system 28, in particular a hose system 30 with at least one hose 32. Such a hose system 30 can be connected to the respective first openings 24 of the cells 12 in a fluid-tight manner. By means of a pump or another device, not shown here, for example a gas reservoir, for example a gas cartridge or the like, connected to the hose system 28 in the region of an end 33 or other connection point 33, the inert gas 22 can then be correspondingly introduced into the respective cells 12. The cartridge or the gas reservoir connected to a corresponding connection can subsequently be removed.FIG. 2 shows a schematic illustration of a battery arrangement 10 according to an exemplary embodiment of the invention. This can be designed in particular as already described with reference to FIG. 1. FIG. 2 now shows the battery arrangement 10 in a later operating state of the battery 14.As the cells 12 age to an increasing extent or during their lifetime, increasingly more gas is formed in the cell interior, as described above. As a result, the internal cell pressure P increases steadily until it finally exceeds a specific limit value G 2, as shown in FIG. 2. Starting from this limit value G 2 or when this limit value G 2 is exceeded, an optional further opening 40 is enabled in the respective cell 12, which can be formed, for example, with a pressure relief valve 42 that opens as soon as the internal cell pressure P exceeds the second limit value G 2. The inert gas supply via the nonreturn valve 26 and the gas discharge via the overpressure valve 42 can optionally also take place via a common opening in the cell housing 16.Each cell 12 or each associated connection element of the line system 30 can be formed with such a pressure relief valve 42. The pressure relief valves 42 do not have to open simultaneously, but rather open in each case when the respective internal cell pressure P of the respective cell 12 exceeds the second limit value G 2. As a result, gas 22' can thus be advantageously discharged from the respective cell 12 again. As a result, the internal cell pressure P is lowered again, namely below the limit value G2 or at most to the limit value G2. As a result, the cell internal pressure P can always be maintained at a substantially constant level over the lifetime, which can be predefined by the limit value G 2. A gas pressure limitation is thus provided. This also reduces swelling of the cells 12 due to the gas generated in the cells 12 during operation and during charging. As a result, less installation space has to be kept available for swelling compensation, more space is provided for additional cells 12, as a result of which the range can be increased, and material, installation space and costs can in turn be saved by lower swelling forces in the system. In addition, this also allows an increase in the service life of the cells 12 to be achieved and the risk of the rupture membrane 20 opening too early and thus the uncontrolled degassing into the battery chamber as a result of the gas pressure limitation can be minimized.The openings 40 for the gas discharge are preferably arranged at the top, in particular with respect to an intended installation position in a motor vehicle or with respect to the direction of gravity. This simplifies the gas discharge of the excess gas 22'.The gas 22' discharged from the cells 12 can now advantageously be discharged via the line system 28. There are now several possibilities for this purpose for how the discharged gas 22' can be bypassed. For example, it can be directed into an environment 44, for example of the motor vehicle, in which the battery arrangement 10 is used. In this case, it is advantageous if the gas 22' passes, for example, beforehand through a filter device 46 for filtering any harmful substances from the gas 22'. The filtered gas 22' can thus be safely conducted into the environment 44. Alternatively or additionally, the gas 22' can also be chemically converted or bonded beforehand. The converted or bound gas can then either likewise be discharged into the environment 44 or otherwise collected in the vehicle or the battery arrangement 10. This collection possibility also exists in particular when no chemical conversion and / or filtering of the gas 22' takes place. For example, this can be led directly into a gas collecting container 48, which in the present example can be provided by an interior or cavity 50 of the aforementioned extruded hollow profile 38 of the frame 36 of the battery housing 34. As a result, unused construction spaces can be used for collecting and storing the gas 22'. This collecting container 48 can be emptied, for example, regularly, for example during maintenance or in the workshop, or the gas 22' can also be stored therein until the end of the service life of the battery 14.If technically expedient, the pressure in the cells 12 can be released during recycling of the battery and the gaseous and liquid constituents of the cells 12 or of the battery can be suctioned off via pressure and / or reduced pressure. The line system 28 can also be used for this purpose. Above all, removal of liquids in the recycling process makes possible cost savings.In general, each cell 12 may thus be provided with at least one opening 24, 40, which may be connected to a gas conducting system 28. A check valve 26 may be located on each cell 12 or alternatively in the gas conducting system 28, which check valve allows central filling of the cells 12 with an inert gas 22. A pressure relief valve 42 or alternatively a controlled valve allows gas pressure to be limited to a defined value. The gas conducting system 28 can also optionally be equipped with filters 46 and fire protection measures. Preferably, an annular gas guidance system 38 can be used, which can be flushed with fresh air from the environment 44 in order to prevent accumulation of possibly combustible gases. According to one variant, after installation in the module, the cells 12 can be filled via a hose, for example of the gas conducting system 28. This can be sealed segment by segment after filling. When the pressure rises in the relevant cell 12, these seals open from a defined pressure and release the hose in sections, whereby the internal pressure P of the cell 12 is limited to the required level. In this embodiment, the degassing system, i.e., filter 46, gas collection container 48, or the like inside the battery, can be omitted because no gas is released.FIG. 3 shows a schematic illustration of a graphical illustration of the internal cell pressure P of a battery arrangement 10 according to a further exemplary embodiment of the invention over time 1 in comparison with a conventional cell. The temporal profile of the cell internal pressure P of the battery arrangement 10 according to a further exemplary embodiment is illustrated by the curve K 1 and that of the conventional cell by the curve K 2. The curve K2 of the conventional cell increases substantially monotonically and linearly with time.According to this exemplary embodiment of the invention, the internal pressure P of the cells 12 is increased with the inert gas, i.e. the inert gas 22, e.g. during the production which takes place in the period Δt 1, in particular to the limit value G 1, which is between 2 bar and 4 bar inclusive, for example. The periods Δt 2 and Δt 3 form in total the vehicle life, i.e. the period during which the cell 12 or battery arrangement 10 is installed in a motor vehicle and is operated, for example. During a first time interval Δt 2 of the vehicle service life, the cell pressure P increases due to cell aging, in particular up to a maximum of the second limit value G 2, which may be approximately 6 bar, for example between 5.5 bar and 6.5 bar. In the subsequent time period Δt 3, the internal pressure P of the cell 12 is limited by the pressure relief valve 42 to a defined value, namely the limit value G 2. After the vehicle life and during the recycling Δt 4, the internal pressure P may be discharged.Overall, the examples show how an optimum gas pressure cell can be provided by the invention.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 061 630 71 A

[0003] DE 10 2011 077 676 A1

[0005]

Claims

Method for adjusting the internal cell pressure in at least one battery cell (12), characterized bythe steps of: - providing a battery cell (12) which comprises a cell housing (16) in which a cell interior (18) is enclosed, wherein an initial internal cell pressure (P) prevails in the cell interior (18), and - introducing a gas (22) into the cell housing (16) via a first opening (24) in the cell housing (16) until the internal cell pressure (P) reaches a predetermined first pressure threshold value (G1).Method according to Claim 1, characterized in that a gas (22') is discharged from the cell interior (18) via the first opening (24) or an in particular closable second opening (40) in the cell housing (16), in particular by means of a valve (42), when the cell internal pressure (P) exceeds a specific second pressure threshold value (G2) which is greater than the first pressure threshold value (G1).Method according to one of the preceding claims, characterized in that the valve (42) is designed as a pressure relief valve (42) which opens when the second pressure threshold value (G2) is exceeded and closes when the second pressure threshold value (G2) is undershot.Method according to one of the preceding claims, characterized in that the valve (42) is designed as a controllable valve which is actuated in a predetermined manner, in particular repeated at predetermined time intervals, in order to open temporarily.Method according to one of the preceding claims, characterized in that the battery cell (12) comprises a releasable cell degassing opening (20) for emergency degassing of the battery cell (12), wherein the releasable cell degassing opening (20) opens when the internal cell pressure (P) exceeds a third pressure threshold value which is greater than the second pressure threshold value (G2).Method according to one of the preceding claims, characterized in that the first opening (24) in the cell housing (16) is closed by a closure device (26) which is designed such that it opens for the introduction of the gas (22) and prevents fluid from escaping from the cell interior (18), in particular wherein the closure device (26) is designed as a nonreturn valve (26).Method according to one of the preceding claims, characterized in that a line system (28, 30) with at least one fluid line (32), in particular a hose system (30) with at least one hose (32), is connected to the at least one first and / or second opening (24) of the cell housing (16), wherein the gas (22) is introduced into the cell interior (18) via the line system (28, 30) and / or the gas (22') is discharged from the cell interior (18).Method according to one of the preceding claims, characterized in that the gas (22') discharged from the cell interior (18) is - chemically converted and / or bound; and / or - guided into a gas collecting container (48, 50), in particular into an interior (50) of a frame component (36) of a battery housing (34); and / or - filtered by means of a filter (46); and / or - supplied to an environment (44).Method according to one of the preceding claims, characterized in that the at least one fluid line (32) is segmented into a plurality of volume sections which are separated from one another by closure elements which can be released as a function of pressure.Battery arrangement (10) for a motor vehicle, which comprises at least one battery cell (12), which comprises a cell housing (16), in which a cell interior (18) is enclosed, in which an initial internal cell pressure (P) prevails, characterized in that the battery arrangement (10) has a device (28, 30), by means of which a gas (22) can be introduced into the cell housing (16) via a first opening (24) in the cell housing (16) until the internal cell pressure (P) reaches a predetermined first pressure threshold value (G1).

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