Battery system and use thereof

Abstract

The present invention relates to a battery system comprising a battery cell and a reversibly compressible body having a deformation sensor, and to the use of the compressible body in a battery system.

Description

[0001] Battery system and its use

[0002] The present invention relates to a battery system comprising a battery cell and a reversibly compressible body with a deformation sensor, as well as the use of the compressible body in a battery system.

[0003] Battery systems, especially rechargeable batteries, require powerful sensors that measure various electrical and mechanical properties for safe, efficient, and long-lasting operation. The corresponding sensor data is evaluated by a battery management system to optimally control the operation of the battery system. A battery or battery system typically consists of a large number of individual battery cells that electrochemically store the electrically supplied energy and make it available again as electrical energy when needed. Ideally, each cell is monitored individually, but this requires considerable effort, so the sensors must be cost-effective.

[0004] An important parameter to measure is the expansion of the battery cell during operation. During charging, the battery cell expands, while during discharging, it contracts. This volume change can be attributed to the electrochemical processes within the battery cell. This form of expansion is therefore reversible. Another form of expansion occurs due to the aging of the battery cell. This type of expansion is irreversible. Furthermore, the volume of the battery cell can also change due to damage. All of these expansion effects should be recorded using suitable sensors.

[0005] The cells of a battery system, such as a lithium-ion battery, should be preloaded with a certain mechanical pressure during operation. If the battery cell is clamped in a rigid housing, the pressure increases significantly as the battery cell expands. This can lead to damage to the battery cell or even destruction. A pressure sensor in the battery system can monitor the pressure increase, but cannot prevent it. Therefore, a better option is a mechanism that at least keeps the pressure increase during battery system operation within permissible limits.

[0006] Various patents address compensation for the expansion a battery cell experiences during operation. WO21130471 A1 describes a mechanism for swelling compensation in battery cells. A foam material absorbs the expansion and is compressed in the process. A sensor function is not disclosed in the patent.

[0007] Accordingly, the object of the present invention is to provide battery systems with both a monitoring function and a protection function. This object is achieved by the battery system described below.

[0008] The object is achieved by a battery system according to claim 1, as well as by the use of a compressible body according to claim 19.

[0009] The present invention proposes to provide a battery system comprising a compressible body with a sensor function that can measure the expansion and contraction of a battery cell with high sensitivity. The battery cell is subjected to a predetermined mechanical preload by the compressible body, thereby precompressing the compressible body. As the battery expands, the compressible body is further compressed, which, for example, can increase the electrical capacitance of a sensor or decrease the electrical resistance. It can be provided that the mechanical stress on the battery increases only slightly compared to the preload, so that the battery is subjected to only a small additional load.

[0010] The battery system comprises at least one battery cell and at least one reversibly compressible body with at least one deformation sensor.

[0011] The compressible body can therefore detect a deformation at at least one location on the compressible body. The compressible body acts as a deformation sensor. A first preferred variant provides that the compressible body corresponds to the deformation sensor(s).

[0012] The compressible body is in direct or indirect mechanical contact with a surface of the battery cell.

[0013] The compressible body is formed from an elastomer. The compressible body can therefore consist at least partially of an elastomer. Furthermore, the compressible body has at least one cavity. The cavity can, for example, be a volume completely or at least partially enclosed by the compressible body, which can be filled, for example, with air or another gas or a porous foam. The compressible body can also have a porous structure, which is formed, for example, by several of the cavities.

[0014] According to the invention, the compressible body is clamped together with the battery cell in a holding device of the battery system to generate a prestress.

[0015] According to the invention, the battery cell and the compressible body are clamped in such a way that the clamped compressible body is compressed compared to an unloaded state and exerts an adjustable pressure on the battery cell. The clamped body is more compressible by an expansion of the battery cell. This means that the compressed compressible body clamped together with the battery cell can be compressed more strongly by an expansion of the battery cell. Furthermore, the clamped compressible body is less compressible by a contraction of the battery cell. Thus, if the expansion of the battery cell decreases again or if the battery cell contracts, the compressible body can follow this contraction of the battery cell.A battery cell is defined as a battery cell at the time of installation into the battery system, i.e., a battery cell that has not yet experienced any aging-related volume change and can expand or contract based on this size. However, a battery cell can also be a battery cell that has experienced an aging-related volume change before or after installation and can expand or contract based on this.

[0016] In addition to the battery cell, the battery system has a reversibly compressible body that can be used simultaneously as an expansion sensor and as a preload spring for the battery cell or battery.

[0017] In this context, "clamped" means that the compressible body exerts or transmits a force on the battery cell in at least one direction. A clamped compressible body is therefore understood to be a compressible body to which pressure is exerted and which is thereby deformed. An unloaded compressible body, on the other hand, describes a compressible body in a force-free state, in which no external forces act on the compressible body that could lead to deformation of the compressible body. The compressible body can preferably be installed together with the battery cell in the holding device in such a way that the compressible body is compressed at the time of installation.

[0018] A direction in which a force acts at a point on the compressible body when clamping the compressible body with the battery cell in the battery system is referred to below as the clamping direction. In some embodiments, the clamping directions at different points on the compressible body or the battery cell can be aligned parallel to one another. In round or curved sections of the battery cell or, for example, cylindrical arrangements, the clamping directions at different points on the compressible body or the battery cell can, for example, not be aligned parallel to one another and can be aligned in a radial direction.

[0019] As already described above, the compressible body is formed with an elastomer, which means that the compressible body contains an elastomer or consists largely of an elastomer. The volume fraction of an elastomer in the compressible body can therefore be at least greater than 0%. In addition, the compressible body contains at least one cavity. The elastomer achieves the reversibility of compression when the compression pressure decreases. The cavity causes the body to be highly compressible. The cavity can be created by a periodic surface structure between different layers of the compressible body. Another possibility for creating the cavity is the formation of porosity in the compressible body. The porosity can be open or closed.

[0020] According to the invention, the compressible body is in direct or indirect contact with the surface of the battery cell, i.e. it touches the surface of the battery cell or there is another body in between that touches the battery cell and the compressible body. The subject matter of the invention is therefore a battery system that, using the deformation sensor of the compressible body, can record the geometric expansion and contraction of a battery or battery cell during operation and protects the battery from damage and destruction. Preferably, not only the pressure but also the geometric deformation is measured. In the monitoring system, the compressible body with deformation sensor simultaneously serves as a preload spring for the battery in order to keep the pressure acting on it within a desired pressure range and thus protect the battery from damage and destruction.The compressible body has a cavity structure that creates high compressibility in the relevant pressure range.

[0021] The compressible body is clamped together with the battery cell in a holding device in such a way that it is pre-compressed relative to its unloaded state, thereby exerting pressure on the battery cell. The compressible body thus acts as a preload spring for the battery cell.

[0022] In an advantageous embodiment of the battery system, the battery cell and the compressible body have a flat structure. Advantageously, the battery cell and the compressible body are arranged parallel to one another. It can be provided that the clamping direction, i.e., the direction in which the force generated by the clamping acts, is perpendicular to the surface on which the force acts. The clamping direction can therefore advantageously be oriented perpendicular to the contact surface. In some embodiments, the battery cell can, for example, be cuboid-shaped, and the compressible body can be in direct or indirect mechanical contact with a portion of a side surface of the cuboid-shaped battery cell.However, cylindrical or battery cells with round sections are also possible, so that the compressible body can also be in direct or indirect contact with a curved side of the battery cell, for example.

[0023] Advantageously, the compressible body is in direct or indirect contact with the surface of one side of the battery cell over its entire surface. The advantage of a compressible body that is in direct or indirect contact with the surface of one side of the battery cell over its entire surface is the uniform pressure exerted by the preload spring on the battery cell, which is beneficial for the battery cell's service life. In a mechanically tensioned battery system, the surface irregularities that are present in battery cells due to manufacturing and can generate high localized loads in the cell when tensioned are thus compensated for and the load is evenly distributed. Such localized tensions have a negative impact on service life and can be prevented with the battery system described.

[0024] In a preferred embodiment, the compressible body is reversibly compressible by at least 0.05 mm, preferably by at least 0.1 mm, particularly preferably by at least 0.2 mm. This means that, starting from the unloaded state, preferably immediately after installation, the compressible body is reversibly compressible by at least 0.05 mm, preferably by at least 0.1 mm, particularly preferably by at least 0.2 mm. Reversibly compressible means that, after compression, the compressible body can essentially return to the shape of the unloaded state. It is particularly advantageous if the compressible body is reversibly compressible in the clamping direction by the amounts mentioned above.

[0025] The expansion of known rechargeable battery cells during operation is more than 0.05 mm. To be able to detect this range with sensors, as well as further expansions, e.g., due to battery cell aging, the compressible body should be able to be compressed by at least 0.05 mm, preferably by at least 0.1 mm, and particularly preferably by at least 0.2 mm, even when clamped.

[0026] A further preferred embodiment provides that the compressible body has a rigidity in the unloaded state such that a pressure of less than 500 kPa, preferably less than 100 kPa, particularly preferably less than 25 kPa, needs to be applied to compress by 0.1 mm. The compressible body is therefore advantageously sufficiently easy to compress so that the battery is not exposed to excessive pressure, which could lead to damage. Particularly preferably, the clamped compressible body can have a rigidity such that a pressure of a maximum of 500 kPa, preferably a maximum of 100 kPa, particularly preferably a maximum of 25 kPa, needs to be applied to compress by 0.1 mm.

[0027] It is further preferred that the compressible body, in the clamped state, exerts a pressure of more than 5 kPa, preferably more than 10 kPa, particularly preferably more than 20 kPa on the battery cell and / or less than 10,000 kPa, preferably less than 5,000 kPa, particularly preferably less than 1,000 kPa. Preferably, immediately after the installation of the compressible body and the battery cell in the holding device of the battery system, the compressible body exerts a pressure of more than 5 kPa, preferably more than 10 kPa, particularly preferably more than 20 kPa. Preferably, immediately after the installation of the compressible body and the battery cell in the holding device of the battery system, the compressible body exerts a pressure of less than 10,000 kPa, preferably less than 5,000 kPa, particularly preferably less than 1,000 kPa.In a particularly preferred embodiment, the compressible body is designed such that the pressure exerted by the compressible body on a contact surface of the battery cell is uniform. Uniform in this context means that the pressures exerted at different points on the contact surface differ from each other by less than 50%, preferably less than 20%, particularly preferably less than 10%.

[0028] An advantageous embodiment provides that in the unloaded state the volume of the at least one cavity is at least 10%, preferably at least 20%, particularly preferably at least 30% of the total volume of the compressible body in the unloaded state. In this way, sufficient compressibility of the compressible body can advantageously be achieved. The total volume of the compressible body in the unloaded state can be understood as the volume enclosed by the outer surfaces of the compressible body. The volume of the at least one cavity refers to the total volume of all cavities if the compressible body has several cavities that are not connected to one another. In order to achieve sufficient compressibility of the compressible body, the volume proportion of the cavity orthe cavities in the unloaded state amount to at least 10%, preferably at least 20%, particularly preferably at least 30% of the volume of the compressible body.

[0029] It is preferred that the at least one cavity is delimited by at least one first wall section with a one- or two-dimensional periodic surface structure. Of the walls enclosing the cavity, one or more sections therefore have a one- or two-dimensional surface structure. The surface structure can be periodic, i.e., it can repeat itself spatially periodically. In particularly advantageous embodiments, the wall section having the surface structure can enclose an angle greater than 0° with the clamping direction or even be oriented perpendicular to the clamping direction. It can also be provided that the first wall section is designed such that a surface normal at a point on the first wall section is parallel to a clamping direction at this point, or advantageously deviates from the clamping direction by less than 45°, preferably less than 30°, particularly preferably by less than 10°.

[0030] Advantageously, the at least one cavity is delimited by a second wall section which lies opposite the first wall section and is designed such that the first wall section and the second wall section can interlock when the compressible body is compressed. For this purpose, for example, a protruding section of one wall section can be inserted into a recess in the other wall section when the compressible body is compressed. For this purpose, the second wall section can, for example, be designed to be at least partially or completely complementary to the first wall section. It is also particularly advantageous if the compressible body has an elastomer film. The elastomer film can be arranged between the first wall section and the second wall section, wherein the elastomer film is stretched when the wall sections interlock.In this way, for example, the stiffness of the compressible body can be influenced by the elastomer film and / or the design of the first and second wall sections. Therefore, an arrangement in which the at least one cavity in the compressible body has a wall section with a one-dimensional or two-dimensional periodic surface structure is preferred. This surface structure significantly facilitates the compression of the compressible body, since the material of the wall sections can escape into the cavity.It may also be advantageous if the compressible body has a second one-dimensional or two-dimensional periodic surface structure that is arranged complementarily to the first one-dimensional or two-dimensional periodic surface structure, and if an elastomer film is located between the two one-dimensional or two-dimensional periodic surface structures, which is stretched when the two complementarily arranged one-dimensional or two-dimensional periodic surface structures are pressed together. This allows particularly large increases in capacitance during compression, giving the deformation sensor high measurement sensitivity.

[0031] Independently of this, an embodiment of the invention is also preferred in which the compressible body has a porous structure. This can mean, for example, that the cavity is filled with a foam or that the compressible body consists of a foam.

[0032] In a particularly advantageous embodiment of the invention, it is provided that the compressible body has at least one deformation sensor with two electrical connections.

[0033] In a preferred embodiment, the deformation sensor is designed as a capacitive deformation sensor, wherein the deformation sensor has at least two electrodes arranged in the compressible body and each electrically connected to one of the terminals. The compressible body can further comprise a dielectric arranged between the at least two electrodes. An electrical capacitance between the electrodes can therefore be increased by an expansion of the battery cell and reduced by a contraction of the battery cell. Configurations are also possible in which the electrical capacitance between the electrodes can be reduced by an expansion of the battery cell and increased by a contraction of the battery cell.

[0034] In such an embodiment, an electrical capacitance can be measured on the compressible body. For this purpose, the compressible body contains at least one dielectric and at least two electrodes, wherein the dielectric is arranged between the electrodes. Upon compression of the compressible body, the capacitance between the electrodes changes. This allows an expansion of the battery cell to be detected. The compressible body is therefore a capacitive deformation sensor or the compressible body contains a capacitive deformation sensor. In preferred embodiments, the capacitance increases upon compression of the compressible body, for example, as a result of the expansion of the battery cell. Upon contraction of the battery cell and the associated expansion of the compressible body, the capacitance decreases. However, the reverse is also possible, i.e.a reduction in capacity upon compression of the compressible body due to the expansion of the battery cell and an increase in capacity upon expansion of the compressible body due to the contraction of the battery cell.

[0035] It is further preferred that the at least one deformation sensor contains at least three electrodes, which are arranged at least partially parallel to one another and / or opposite one another and of which the two outer electrodes are electrically connected to one another. In this context, parallel also refers to arrangements in which the electrodes each enclose angles of less than 45°, preferably less than 15°, particularly preferably less than 5°. A dielectric can be arranged between each of the electrodes. In some embodiments, the two dielectrics and / or the two outer electrodes can also be formed in one piece. The compressible body can therefore also contain more than one dielectric and more than two electrodes.With two dielectrics and three electrodes, the two dielectrics are preferably located between the three electrodes, which are arranged at least partially parallel to one another. The two outer electrodes can be set to ground potential during capacitance measurement. This allows the electrical potential of the inner electrode to be shielded against external electric fields. The two dielectrics between the three electrodes also roughly double the capacitance compared to just one dielectric. This is particularly advantageous with small electrode surfaces, as the capacitance can be measured more accurately. The dielectrics of the compressible body are preferably made of an elastomer or contain an elastomer. The at least one cavity can also be part of the dielectric. Likewise, a foam structure can form the dielectric or be part of the dielectric.

[0036] When the compressible body is compressed, the volume of the cavity decreases. This increases the permittivity of the dielectric, because the volume fraction of the air-filled cavity with low permittivity decreases compared to the volume fraction of the elastomer with higher permittivity. This can, for example, change the capacitance between the electrodes. It is also possible that the electrodes also deform when the compressible body is deformed, which can change the capacitance between the electrodes.

[0037] The electrodes in the compressible body are advantageously made at least partially or entirely of an elastomer containing conductive particles. This constitutes a conductive elastomer composite. The concentration of the conductive particles is preferably well above the percolation limit, so that conductivity is maintained even under severe deformation of the elastomer composite.

[0038] In a further preferred embodiment, the at least one deformation sensor is designed as a resistive deformation sensor, wherein the deformation sensor has at least one electrically conductive part that is arranged in the compressible body and is electrically connected to the two terminals in such a way that a resistance between the two terminals can be reduced by an expansion of the battery cell and increased by a contraction of the battery cell, or can be increased by an expansion of the battery cell and reduced by a contraction of the battery cell. Advantageously, an electrical resistance is therefore measured on the compressible body. For this purpose, the compressible body contains at least one electrically conductive part that contains or consists of an elastomer with electrically conductive particles. Furthermore, the compressible body contains at least one cavity.When the compressible body is compressed, the electrical resistance between two electrical connections on the compressible body decreases. This change in resistance can be caused, for example, by the electrically conductive part having the shape of a cone, which is deformed upon compression of the compressible body. The associated change in geometric dimensions also changes the electrical resistance. If, for example, the cone tip is compressed, it becomes shorter and wider, causing the electrical resistance along the cone axis to decrease. With this arrangement of the compressible body, an expansion of the battery cell can also be detected. The compressible body is thus a resistive deformation sensor or the compressible body contains a resistive deformation sensor.It can be advantageous if the cone axis coincides with the clamping direction at the location of the cone, i.e. the direction in which the force of the clamped body acts at the location of the cone, or deviates from the clamping direction by less than 45°, preferably less than 20°, particularly preferably less than 10°.

[0039] It is further preferred that the at least one dielectric is formed from an elastomer, contains a cavity, or consists of the cavity, and / or at least one of the at least two electrodes is formed from an elastomer with conductive particles. Further advantageous embodiments of the resistive deformation sensor are possible in which at least the electrically conductive part is formed from an elastomer with conductive particles and / or contains a cavity and / or consists of a foam and / or contains a foam.

[0040] In a further advantageous embodiment, it is provided that at least one of the at least two electrodes or the electrically conductive part is flat. In this case, at least one of the at least two electrodes or the electrically conductive part can be curved, preferably in the unloaded or clamped state of the compressible body, particularly preferably curved with an angle of curvature of at least 30°. Flat design can mean that the electrode or the electrically conductive part extends in at least two directions that are oriented perpendicular to one another. It is advantageous if a flat electrode or a flat electrically conductive part extends by at least 1 mm, particularly advantageously by at least 3 mm, very particularly advantageously by at least 5 mm in at least one of these directions or both of these directions.

[0041] In the capacitive deformation sensor, it is therefore advantageous if at least one electrode has a flat shape, with dimensions in two perpendicular dimensions each being at least 1 mm, preferably at least 3 mm, and particularly preferably at least 5 mm. It is also preferred that the at least one flat electrode is not flat, but rather has a curve, i.e., it is not a simple plate capacitor. The curvature should preferably be at least 30 degrees.

[0042] The dielectric, the electrodes and / or the electrically conductive part may each advantageously contain or consist of an elastomer. An elastomer of the dielectric, of at least one of the electrodes and / or of the electrically conductive part can advantageously be silicone, fluorosilicone, polyurethane (PUR), polynorbornene, natural rubber (NR), styrene-butadiene (SBR), isobutylene-isoprene (II R), ethylene-propylene-diene terpolymer (EPDM / EPM), polychlorobutadiene (CR), chlorosulfonated polyethylene (CSM), acrylonitrile-butadiene (NBR), hydrogenated acrylonitrile-butadiene (HNBR), a fluororubber such as Viton, a thermoplastic elastomer such as thermoplastic styrene copolymers (styrene-butadiene-styrene (SBS), styrene-ethylene-butadiene-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS), styrene-ethylene-ethylene-propylene-styrene- (SEEPS) or styrene-isoprene-styrene (SIS) copolymer),partially cross-linked blends based on polyolefins (from ethylene-propylene-diene rubber and polypropylene (EPDM / PP), from nitrile-butadiene rubber and polypropylene (NBR / PP) or from ethylene-propylene-diene rubber and polyethylene (EPDM / PE)) or thermoplastic urethane copolymers (aromatic hard segment and ester soft segment (TPU-ARES), aromatic hard segment and ether soft segment (TPU-ARET) or aromatic hard segment and ester / ether soft segment (TPU-AREE)) or consisting thereof.

[0043] Furthermore, it is preferred that the dielectric comprises an elastomer which contains electrically polarizable particles such as barium titanate, lead zirconate titanate or titanium dioxide and / or electrically conductive particles made of carbon such as, for example, soot, graphite, graphene or carbon nanotubes, metals such as, for example, iron, copper, silver or gold or conductive polymers such as polyaniline, polyacetylene, polypyrrole, polyparaphenylene or polythiophene or an organic modification to increase the permittivity.

[0044] It is also advantageous if at least one of the electrodes or the electrically conductive part contains conductive particles of carbon such as soot, graphite, graphene or carbon nanotubes, metals such as iron, copper, silver or gold or conductive polymers such as polyaniline, polyacetylene, polypyrrole, polyparaphenylene or polythiophene.

[0045] The conductive particles in the electrodes and / or in the electrically conductive part of the compressible body are advantageously selected from the following list: carbon particles such as soot, graphite, graphene, carbon nanotubes, metal particles of copper, silver, gold or iron, silver nanowires, metal-coated carbon particles or conductive polymers such as polyaniline, polyacetylene, polypyrrole, polyparaphenylene or polythiophene.

[0046] In some advantageous embodiments, it can be provided that the at least one compressible body has two or more deformation sensors, each of which is arranged at different locations on the compressible body.

[0047] It can therefore be provided that the compressible body contains more than one deformation sensor. At least one of the deformation sensors can be designed as a capacitive deformation sensor or as a resistive deformation sensor. In the case of two capacitive deformation sensors, the compressible body contains more than one combination of dielectric(s) and electrodes, at each of which the capacitance can be measured, for example, via separate connections. In the case of two resistive deformation sensors, the compressible body contains more than one conductive part, at each of which the electrical resistance can be measured via separate connections.Embodiments are also possible in which a compressible body has at least one resistive deformation sensor and one or more capacitive deformation sensors or in which the compressible body has at least one capacitive deformation sensor and one or more resistive deformation sensors.

[0048] Regardless of the design of the deformation sensors, a design of a compressible body with multiple deformation sensors allows the expansion and contraction of the battery cell to be measured at different locations using just one compressible body. The compressible body can be in the form of a flat mat with the deformation sensors distributed across the surface. The arrangement of the deformation sensors across the surface of the mat can take the form of a one-dimensional row or a two-dimensional array, but irregular arrangements of the deformation sensors on the mat are also possible. It is preferred that the mechanical stiffness of such a sensor mat, which is determined by the local pressure required for a specific local compression, is virtually the same at all locations on the mat.This means that the stiffness at the points where a deformation sensor is located is comparable to the stiffness at the points where no deformation sensor is located and advantageously deviates from this by less than 50%, preferably less than 20%, particularly preferably by less than 10%. This means that the pressure that the sensor mat exerts on the battery cell as a preload spring can be approximately the same at different points on the contact surface of the battery cell and advantageously deviate by less than 50%, preferably less than 20%, particularly preferably by less than 10%. Even with an array of sensors, i.e. several deformation sensors that are distributed locally and are integrated into the compressible body, the body has a virtually uniform stiffness across the surface, resulting in a homogeneous pressure distribution on the battery cell.

[0049] Preferably, the battery system comprises at least two compressible bodies, each of which can be used as a deformation sensor. This provides more than one deformation sensor. In this case, the expansion and contraction of the battery cell can be measured at different locations. This provides information about the inhomogeneity of the expansion, i.e., it is possible to determine, for example, where the battery cell expands most strongly.

[0050] The battery system preferably has at least two battery cells and at least two compressible bodies. It is preferred that exactly one compressible body is arranged between two battery cells. It is also preferred that a compressible body is arranged between each two battery cells and / or, particularly preferably, a rigid wall of the holding device is arranged between each two battery cells, each with a compressible body. The compressible bodies can be arranged alternately between the cells. If the individual battery cells are mechanically decoupled from one another, for example by a rigid and stiff housing or a rigid wall of the holding device, the expansion and contraction of this one specific battery cell can be detected using the compressible body and the sensors integrated therein.If these battery cells are arranged one behind the other in the form of a mechanical series circuit and are also separated from each other by a compressible body, only one of the compressible bodies could function as a deformation sensor, i.e. have a deformation sensor, and record the cumulative expansion and contraction of several cells, which would result in significant cost savings with only a slightly limited reduction in cell information.

[0051] In a further preferred embodiment of the battery system, the compressible body comprises a temperature sensor, an ultrasonic sensor, a pressure sensor, an electrical sensor, and / or an impedance sensor. Efficient battery management requires data on various battery properties. To meet this requirement, the battery system can contain additional sensors. This particularly applies to a temperature sensor, but other sensors such as ultrasonic sensors or electrical sensors, such as current, voltage, or impedance sensors, can also be part of the battery system according to the invention.

[0052] In a further preferred embodiment of the battery system, the battery system comprises electronics configured to measure at least a resistance between the two terminals of the deformation sensor and / or a capacitance between the two terminals of the deformation sensor. Furthermore, the battery system can thus comprise electronics for measuring the electrical capacitance or electrical resistance of the compressible body. The electronics preferably contain a microprocessor. Known measuring methods can be used to determine the electrical capacitance or electrical resistance.

[0053] Additional functional layers based on an elastomer composite can be integrated into the compressible body. Flame-retardant or flame-retardant additives or even ceramifying particles can be incorporated into the elastomer. These prevent or delay thermal transfer from one cell to the neighboring cell in the event of thermal burnout of a battery cell, thus preventing or delaying a thermal chain reaction throughout the entire battery module, a so-called "thermal runaway." Thermally conductive particles can also be incorporated to specifically transport thermal energy toward the module base during operation. Thermally switchable particles can also be incorporated, which enable good heat dissipation during operation and poor heat dissipation (thermal insulation between the individual cells) in the event of thermal damage.Such thermal damage can be detected by the additional integrated temperature sensors, which serve as trigger signals for switching the thermal conductivity.

[0054] In preferred embodiments of the invention, the compressible body undergoes a dimensional change in the clamping direction during prestressing by at least 0.1% and a maximum of 99%, preferably at least 0.5% and a maximum of 95%, particularly preferably at least 1% and a maximum of 90%. During prestressing, the compressible body is compressed. The length of the compressible body in the clamping direction is thus shortened by the prestressing, in particular by at least 0.1% and a maximum of 99%, preferably by at least 0.5% and a maximum of 95%, particularly preferably by at least 1% and a maximum of 90%.

[0055] The compressible body behaves like a spring, which is compressed by the preload when clamped. To ensure high measurement sensitivity of the deformation sensor contained in the compressible body, the characteristic curve of the compressible body, which represents the pressure acting on the compressible body as a function of the compression of the compressible body, should have a low gradient. A conventional compression spring generally exhibits an increasing gradient of the pressure-compression characteristic curve with increasing compression. The pressure-compression characteristic curve of the compressible body has an initial gradient, which is determined by the quotient of the preload and the resulting compression (preload compression).It is advantageous if the gradient of the pressure-compression characteristic of the compressible body in the subsequent compression range between the pre-load compression and twice the value of the pre-load compression takes a maximum of twice the value of the initial gradient.

[0056] According to the invention, the compressible body can be used as a pre-tensioning device for exerting pressure on the battery cell and / or as a deformation sensor for detecting the expansion and / or contraction of the battery cell.

[0057] Various embodiments of the invention will be schematically illustrated below using 13 figures. The figures serve as exemplary representations, and the scope of protection of the application is not limited solely to the illustrated embodiments; combinations of individual features of different embodiments are also conceivable. Examples include the use of multiple compressible bodies of different embodiments in a single battery system, or multiple differently designed deformation sensors in a single compressible body.

[0058] It shows:

[0059] Fig. 1 The individual components of a first embodiment of a battery system.

[0060] Fig. 2 The individual components of another embodiment of a battery system.

[0061] Fig. 3 Another embodiment of a battery system in sectional view and in different expansion states of the battery cell.

[0062] Fig. 4 Another embodiment of a battery system in sectional view and in different expansion states of the battery cell.

[0063] Fig. 5 Another embodiment of a battery system in sectional view and in different expansion states of the battery cell.

[0064] Fig. 6 Another embodiment of a battery system in sectional view and in different expansion states of the battery cell.

[0065] Fig. 7 Another embodiment of a battery system in sectional view and in different expansion states of the battery cell.

[0066] Fig. 8 Another embodiment of a battery system in sectional view and in different expansion states of the battery cell.

[0067] Fig. 9 Another embodiment of a battery system in sectional view and in different expansion states of the battery cell.

[0068] Fig. 10 Another embodiment of a battery system in a sectional view and with different expansion states of the battery cell. Fig. 11 Another embodiment of a battery system in a sectional view and with different expansion states of the battery cell.

[0069] Fig. 12 Another embodiment of a battery system in sectional view and in different expansion states of the battery cell.

[0070] Fig. 13 Another embodiment of a battery system with curved surfaces.

[0071] Figure 1 shows the components of a battery system 1 according to the invention in separate form: the holding device 4, the battery cell 2, and the compressible body 3 with a capacitive deformation sensor 5. The compressible body is shown in its basic form in the uncompressed, i.e., unloaded state (Figure 1c), as well as in the compression generated to preload the battery cell (Figure 1d), in a stronger compression (Figure 1e), and in a nearly complete compression (Figure 1f). In the illustrated embodiment, with increasing compression of the capacitive deformation sensor, the measurable electrical capacitance increases from the initial value Co in the unloaded state through the values ​​Ci and C2 to C3 at nearly complete compression.

[0072] Figure 1a shows the holding device 4 in which the battery cell 2 can be clamped together with the compressible body 3. The battery cell is shown in Figure 1b, and the compressible body in variously compressed states is shown in Figures 1c, d, e and f. Figure 1c shows the compressible body 3 by way of example in the unloaded state, i.e. in a state in which no external forces act on the compressible body that could lead to its deformation. The compressible body 3 has a cavity 31 which, in the embodiment shown, is delimited by a first wall section 32 and a second wall section 33. The two wall sections 32 and 33 have a spatially repeating, i.e. periodic, surface structure.The second wall section 33 is designed such that it can engage with the first wall section 33 when the compressible body is compressed, see, for example, Figures 1d, 1e, and 1f. Furthermore, in the embodiment of Figures 1c-1f, the compressible body has two terminals 51, 52, each of which is electrically connected to an electrode 53, 54. The two electrodes 53, 54 are arranged in the compressible body 3. In the embodiment shown here, the electrodes 53, 54.

[0073] 54 is arranged in the cavity 31 of the compressible body 3. A dielectric 55 is arranged between the electrodes 54, 54. In the illustrated embodiment, the dielectric 55 is formed from an elastomer. However, embodiments are also possible in which the dielectric

[0074] 55 is formed from an elastomer with cavities, for example, a porous foam. Independently of this, embodiments are possible in which the dielectric 55 is formed from the entire cavity 31 or a region of the cavity 31 and contains only a gas, for example, air.

[0075] Figure 2 shows the components of another embodiment of a battery system 1 according to the invention in separate form: the holding device 4, the battery cell 2, and the compressible body 3 with a resistive deformation sensor 5. The compressible body 3 is shown in its basic form in the unloaded state (Figure 2c), as well as in the compression generated to preload the battery cell 2 (Figure 2d), in a stronger compression (Figure 2e), and in a nearly complete compression (Figure 2f). With increasing compression of the resistive deformation sensor, the measurable electrical resistance drops from the initial value R in the illustrated embodiment.o in the unloaded state over the values ​​Ri and R2 up to R3 at almost complete compression.

[0076] Figure 2c shows a compressible body 3 with a resistive deformation sensor 5, which has an electrically conductive part 56, 58. The electrically conductive part is electrically connected to two terminals 51, 52. Upon compression of the electrically conductive part 56, 58, the electrical resistance between two ends of the electrically conductive part 56, 58 changes, with the first end of the electrically conductive part 56 being connected to a first of the terminals 51, 52 and the second end of the electrically conductive part 58 being connected to the second of the terminals 51, 52. In the illustrated embodiment, the electrically conductive part has conical contact elements. The conical contact elements create an electrical connection between the first and second ends of the electrically conductive part 56, 58.The conical contact elements can be deformed upon compression of the compressible body, see, for example, Figures 2d, e, f. The associated change in the geometric dimensions also changes the electrical resistance: For example, if the conical tip of the contact element is compressed in the embodiment of Figure 2, it becomes shorter and wider, thereby reducing the electrical resistance along the conical axis, which in this embodiment is parallel to the clamping direction. The invention is not limited to electrically conductive parts 56, 58 with conical contact elements. These contact elements can also be rib-shaped, knob-shaped, or irregularly structured, for example.Furthermore, other designs of the electrically conductive part 56, 58 are possible as long as the resistance between two ends of the electrically conductive part 56, 58 can change upon compression and / or decompression of the electrically conductive part 56, 58.

[0077] 1. Example

[0078] Figure 3 shows an embodiment of a battery system 1 with a battery cell 2 and a compressible body 3 in a holding device 4 in the form of a housing. The compressible body 3 has a capacitive deformation sensor 5. The compressible body 3 has two elastomer foils with complementary profiles, which form the first wall section 32 and the second wall section 33 and delimit the cavity 31. Furthermore, the compressible body has a dielectric 55 formed as an unprofiled elastomer foil 59 with two electrodes 53.

[0079] 54, with the electrodes 53 and 54 on both sides of the dielectric

[0080] 55 are arranged between the profiles. When the deformation sensor 5 is compressed, the profiles, or the first wall section 32 and the second wall section 33, increasingly engage with each other and in the process stretch the elastomer film 59 serving as the dielectric 55, thereby increasing the electrical capacitance between the electrodes 53, 54. The electrodes 53, 54 are each electrically connected to one of the terminals 51, 52. The elastic stretching of the elastomer film 59 also causes recovery when the compressible body 3 is relieved of pressure. Shown are the equilibrium state of compression of the compressible body 3 due to the mechanical prestress of the battery cell 2, a more strongly compressed state due to the expansion of the battery cell 2 during operation, such as during charging, and a state of strong compression due to extreme expansion of the battery cell 2.

[0081] 2. Example

[0082] Figure 4 shows a further embodiment of a battery system 1 with a battery cell 2 and a compressible body 3 in a holding device 4 in the form of a housing. The compressible body 1 has a capacitive deformation sensor 5. The compressible body 3 has two elastomer films with complementary profiles, which form the first wall section 32 and the second wall section 33 and delimit the cavity 31. Furthermore, the compressible body has a dielectric 55 designed as an unprofiled elastomer film 59 with three electrodes 53, 54, 57, two of the electrodes 53 and 57 being arranged on both sides of the elastomer film 59 and one of the electrodes 54 being arranged inside the elastomer film 59. The dielectric 55 or the elastomer film 59 is arranged together with the electrodes 53, 54, 57 between the profiles.The two outer electrodes 53, 57 of the three electrodes 53, 54, 57 are both electrically connected to one of the terminals 51. The inner electrode 54 is electrically connected to the other terminal 52. When the deformation sensor 5 is compressed, the profiles increasingly interlock and in the process expand the dielectric 55, thereby increasing the electrical capacitance between the electrode layers 53, 54, 57. The two outer electrodes 53, 57 on the elastomer film 59 can be set to ground potential, whereby the inner electrode 54 can be shielded against external electrical fields. The elastic stretching of the elastomer film 59 also causes the deformation sensor 5 to reset when the load is removed. Shown are the equilibrium state of compression of the compressible body 3 due to the mechanical prestress of the battery cell 2, a more strongly compressed state due to the expansion of the battery cell 2 during operation, for exampleduring charging as well as a state of strong compression due to extreme expansion of the battery cell 2. 3. Example.

[0083] Figure 5 shows a further embodiment of a battery system 1 according to the invention with a battery cell 2 and a compressible body 3 in a holding device 4 in the form of a housing. The compressible body 3 has a capacitive deformation sensor 5. The compressible body 3 has two elastomer films with complementary profiles, which form the first wall section 32 and the second wall section 33 and delimit the cavity 31. The electrodes 53, 54 of the capacitive deformation sensor 5 are formed in this embodiment as electrode layers on the surfaces of the two profiles, i.e., the first wall section 32 and the second wall section 33. Furthermore, the compressible body has a dielectric 55, which has both an unprofiled elastomer film 59 and is formed at least partially from the cavity 31.When the deformation sensor 5 is compressed, the profiles increasingly interlock, stretching the elastomer film 59. As the electrode layers 53, 54 on the profiles approach each other, the electrical capacitance between the electrode layers 53, 54 increases. The elastic stretching of the elastomer film 59 also causes recovery when the compressible body 3 is relieved of pressure. Shown are the equilibrium state of compression of the compressible body 3 due to the mechanical prestressing of the battery cell 2, a more strongly compressed state due to the expansion of the battery cell 2 during operation, such as during charging, and a state of strong compression due to extreme expansion of the battery cell 2.

[0084] 4. Example

[0085] Figure 6 shows a further embodiment of a battery system 1 according to the invention with a battery cell 2 and a compressible body 3 in a holding device 4 in the form of a housing. The compressible body 3 has a capacitive deformation sensor 5. The compressible body 3 has two elastomer films with complementary profiles, which form the first wall section 32 and the second wall section 33 and delimit the cavity 31. The electrodes 53, 57 of the capacitive deformation sensor 5 are formed in this embodiment as electrode layers on the surfaces of the two profiles, i.e., the first wall section 32 and the second wall section 33. Furthermore, the compressible body has a dielectric 55, which has both an unprofiled elastomer film 59 and is formed at least partially from the cavity 31.The elastomer film 59 has a third electrode 54, which is arranged as an electrode layer inside the elastomer film 59. The two electrodes 53, 57 formed as electrode layers on the surfaces of the profiles are both electrically connected to one of the terminals 51, while the electrode 54 inside the elastomer film 59 is electrically connected to the other terminal 52. During compression of the compressible body 3, the profiles increasingly interlock, thereby stretching the elastomer film 59. As the electrodes 53, 57 on the profiles and the electrode 54 in the elastomer film 59 move closer together, the electrical capacitance between the electrode layers increases. The two outer electrodes 53, 57 on the profile surfaces can be set to ground potential, thereby shielding the inner electrode 54 from external electric fields.The elastic stretching of the elastomer film 59 also causes recovery when the compressible body 3 is relieved of pressure. Shown are the equilibrium state of compression of the compressible body 3 due to the mechanical prestressing of the battery cell 2, a more strongly compressed state due to the expansion of the battery cell 2 during operation, such as during charging, and a state of strong compression due to extreme expansion of the battery cell 2.

[0086] 5. Example

[0087] Figure 7 shows a further embodiment of a battery system 1 according to the invention with a battery cell 2 and a compressible body 3 in a holding device 4 in the form of a housing. In this embodiment, the compressible body 3 has a resistive deformation sensor 5. The resistive deformation sensor 5 has two terminals 51, 52 and an electrically conductive part 56, 58. The terminals are each electrically connected to one side of the electrically conductive part 56, 58. In the illustrated embodiment, the electrically conductive part 56, 58 has an elastomer film with a profile 58 on one side and an unprofiled elastomer film 56 on the other side. The profile of one elastomer film 58 contains several conical contact tips.Both elastomer films 56, 58 are electrically conductive, which allows an electrical resistance to be measured, for example, when the two films 56, 58 are connected to an electrical voltage source via the terminals 51, 52. Upon compression of the compressible body 3, the contact tips of the elastomer film 58 are increasingly compressed, reducing the electrical resistance between the electrical terminals 51, 52 of the deformation sensor 5. The elastic compression of the profile also causes recovery when the compressible body 3 is relieved of pressure. Shown are the equilibrium state of compression of the compressible body 3 due to the mechanical prestress of the battery cell 2, a more strongly compressed state due to the expansion of the battery cell 2 during operation, such as during charging, and a state of strong compression due to extreme expansion of the battery cell 2.

[0088] 6. Example

[0089] Figure 8 shows a further embodiment of a battery system 1 according to the invention with a battery cell 2 and two compressible bodies 3a, 3b in a holding device 4 in the form of a housing. The compressible bodies 3a, 3b can have capacitive or resistive deformation sensors 5a, 5b. As the battery cell expands, the deformation sensors 5a, 5b are increasingly compressed, whereby the electrical capacitances between the electrodes of the capacitive deformation sensors increase or the electrical resistances between the electrical connections of the resistive deformation sensors decrease. The elastic deformation of the compressible bodies 3a, 3b also causes the compressible bodies 3a, 3b to recover when the load is released.Shown are the equilibrium state of compression of the compressible bodies 3a, 3b due to the mechanical prestressing of the battery cell 2, a more strongly compressed state due to the expansion of the battery cell 2 during operation, such as during charging, and a state of strong compression due to extreme expansion of the battery cell 2. The deformation sensors 5a, 5b can measure the deformation of the battery cell 2 at various points on the battery cell 2. This can also be used to detect, for example, uneven deformation of the battery cell 2. Of course, embodiments are also possible in which one compressible body 3a has a resistive deformation sensor 5a and the other compressible body 3b has a capacitive deformation sensor 5b. Furthermore, embodiments are conceivable in which only one of the two compressible bodies 3a has a deformation sensor 5a.

[0090] 7. Example

[0091] Figure 9 shows a further embodiment of a battery system 1 according to the invention, comprising a battery cell 2 and a compressible body 3 in a holding device 4 in the form of a housing. In this embodiment, the compressible body 3 contains two deformation sensors 5a, 5b. As the battery cell 2 expands, the deformation sensors 5a, 5b are increasingly compressed, which can increase the electrical capacitances between the electrodes of the capacitive deformation sensors or decrease the electrical resistances between the electrical terminals of the resistive deformation sensors. The elastic deformation of the compressible body 3 also causes recovery when the compressible body 3 is relieved of load.Shown are the equilibrium state of compression of the compressible body 3 due to the mechanical prestressing of the battery cell 2, a more strongly compressed state due to the expansion of the battery cell 2 during operation, such as during charging, and a state of strong compression due to extreme expansion of the battery cell 2. The capacitive and / or resistive deformation sensors 5a, 5b in the compressible body 3 can measure the deformation of the battery cell 2 at various positions. This also allows for the detection of uneven deformation of the battery cell 2. Since the deformation sensors 5a, 5b are part of a compressible body 3, this also ensures that approximately equal pressure is exerted on the battery cell across the surface of the compressible body.

[0092] 8. Example

[0093] Figure 10 shows a further embodiment of a battery system 1 according to the invention with three battery cells 2a, 2b, 2c and three compressible bodies 3a, 3b, 3c arranged in an alternating sequence in a common holding device 4 in the form of a housing. One of the compressible bodies 3a contains two deformation sensors 5a, 5b. As the battery cells 2a, 2b, 2c expand, the three compressible bodies 3a, 3b, 3c are increasingly compressed. For the two deformation sensors 5a, 5b in the compressible body 3a, the electrical capacitances between the electrodes increase in the case of capacitive deformation sensors, and the electrical resistances between the electrical connections decrease in the case of resistive deformation sensors. The elastic deformation of the compressible bodies 3a, 3b, 3c also causes them to recover when the load is removed, for example by contraction of the battery cells 2a, 2b, 2c.The two deformation sensors 5a, 5b of one compressible body can detect an averaged expansion or contraction of the three battery cells 2a, 2b, 2c. Only the equilibrium state of compression of the three compressible bodies 3a, 3b, 3c due to the mechanical preload of the three battery cells 2a, 2b, 2c is shown here.

[0094] 9. Example

[0095] Figure 11 shows a further embodiment of a battery system 1 according to the invention with three battery cells 2a, 2b, 2c and three compressible bodies 3a, 3b, 3c in a holding device 4 in the form of a housing. The compressible bodies 3a, 3b, 3c each contain two deformation sensors 5a, 5b, 5c, 5d, 5e, 5f, which can be formed, for example, by capacitive or resistive deformation sensors. A rigid wall 41a, 41b is located between each two battery cells 2a, 2b, 2c, each with a compressible body 3a, 3b, 3c. Thus, each of the three arrangements consisting of a battery cell 2a, 2b, 2c and a compressible body 3a, 3b, 3c is located in a separate housing. Thus, the compressible body 3a, 3b, 3c in a housing absorbs the deformation of the associated battery cell 2a, 2b, 2c and is not influenced by other battery cells 2a, 2b, 2c or other compressible bodies 3a, 3b, 3c.As a battery cell 2a, 2b, 2c expands, the deformation sensors (5a, 5b), (5c, 5d), (5e, 5f) belonging to the adjacent compressible body 3a, 3b, 3c are increasingly compressed, which can increase the electrical capacitances between the electrodes of the capacitive deformation sensors or decrease the electrical resistances between the electrical terminals of the resistive deformation sensors. The elastic deformation of the compressible bodies 3a, 3b, 3c also causes them to recover when the load is removed, for example, by contraction of the respective battery cell 2a, 2b, 2c. Figure 11 only shows the equilibrium state of compression of the three compressible bodies 3a, 3b, 3c due to the mechanical prestressing of the three battery cells 2a, 2b, 2c.

[0096] 10. Example

[0097] Figure 12 shows a further embodiment of a battery system 1 according to the invention with a battery cell 2 and a compressible body 3 in a holding device 4 in the form of a housing, in a view in which the battery cell 2 is located behind the compressible body 3. The compressible body 3 contains a total of twelve deformation sensors 5a, 5b,..., which are arranged in the form of a 3x4 matrix and can be formed, for example, from capacitive or resistive deformation sensors. As the battery cell 2 expands, the deformation sensors 5a, 5b,... are increasingly compressed, whereby the electrical capacitances between the electrodes of the capacitive deformation sensors increase or the electrical resistances between the electrical connections of the resistive deformation sensors decrease. The elastic deformation of the compressible body 3 also causes the compressible body 3 to recover when the load is released.The twelve capacitive or resistive deformation sensors 5a, 5b,... allow the deformation of the battery cell 2 to be measured at various positions with spatial resolution. This allows even uneven deformation of the battery cell 2 to be detected with high accuracy. Since the deformation sensors 5a, 5b,... are part of a compressible body 3, this also ensures that approximately the same pressure is exerted on the battery cell 2 across the entire surface of the compressible body 3.

[0098] 11. Example

[0099] Figure 13 shows a further embodiment of a battery system 1 according to the invention with a battery cell 2 and a compressible body 3 in a holding device 4 in the form of a housing. In this embodiment, the battery cell 2 has a curved surface 21 against which the compressible body 3 rests. The compressible body 3 is clamped together with the battery cell 2 in the holding device 4 and transmits a force to the battery cell 2 that is oriented substantially perpendicular to the curved surface 21. In cylindrical arrangements, the force can act, for example, in a radial direction. Here, too, further embodiments are possible in which the system has a plurality of compressible bodies, and / or in which compressible bodies have a plurality of deformation sensors, and / or in which the battery system has a plurality of battery cells.

[0100] The research that led to these results was funded by the European Union.

[0101] List of reference symbols

[0102] 1 battery system

[0103] 2,2a,b,c battery cell

[0104] 3,3a,b,c compressible body

[0105] 4 Holding device

[0106] 5.5a-f sensor

[0107] 6 Electronics

[0108] 21 Surface of the battery cell

[0109] 31 cavity

[0110] 32 first wall section

[0111] 33 second wall section

[0112] 41a, b Wall of the holding device

[0113] 51 connection

[0114] 52 connection

[0115] 53 Electrode

[0116] 54 Electrode

[0117] 55 Dielectric

[0118] 56 electrically conductive part

[0119] 57 Electrode

[0120] 58 electrically conductive part (with conical contact tips)

[0121] 59 Elastomer film

Claims

Patent claims 1. A battery system (1) comprising at least one battery cell (2) and at least one reversibly compressible body (3) having a deformation sensor (5) which is in direct or indirect mechanical contact with a surface of the battery cell (2), wherein the compressible body (3) is formed with an elastomer and has at least one cavity (31), and the compressible body (3) is clamped together with the battery cell (2) in a holding device (4) of the battery system (1) to generate a prestress such that the clamped compressible body (3) is compressed compared to an unloaded state and exerts an adjustable pressure on the battery cell (2), the clamped compressible body (3) is more strongly compressible by an expansion of the battery cell (2), and the clamped compressible body (3) is less strongly compressible by a contraction of the battery cell (2).

2. Battery system (1) according to the preceding claim, characterized in that the battery cell (2) and the compressible body (3) have a flat structure and are preferably arranged parallel to one another.

3. Battery system (1) according to one of the preceding claims, wherein the compressible body (3) is at least 0.05 mm, preferably is reversibly compressible by at least 0.1 mm, particularly preferably by at least 0.2 mm.

4. Battery system (1) according to one of the preceding claims, wherein the compressible body (3) has a rigidity in the unloaded state such that a pressure of less than 500 kPa, preferably less than 100 kPa, particularly preferably less than 25 kPa, has to be applied for compression by 0.1 mm.

5. Battery system (1) according to one of the preceding claims, wherein the compressible body (3) in the clamped state exerts a pressure of more than 5 kPa, preferably more than 10 kPa, particularly preferably more than 20 kPa on the battery cell (2) and / or exerts less than 10,000 kPa, preferably less than 5,000 kPa, particularly preferably less than 1,000 kPa on the battery cell.

6. Battery system (1) according to one of the preceding claims, wherein the compressible body (3) is designed such that a pressure exerted by the compressible body (3) on a contact surface of the battery cell (2) is uniform.

7. Battery system (1) according to one of the preceding claims, wherein the compressible body (3) is designed such that in the unloaded state the volume of the at least one cavity (31) is at least 10%, preferably at least 20%, particularly preferably at least 30% of the total volume of the compressible body (3).

8. Battery system (1) according to one of the preceding claims, characterized in that the at least one cavity (31) is delimited by at least one first wall section (32) with a one- or two-dimensional periodic surface structure and / or the compressible body (3) has a pore structure.

9. Battery system (1) according to the preceding claim, characterized in that the at least one cavity (31) is formed by a two- th wall section (33) is delimited by a one- or two-dimensional periodic surface structure, which lies opposite the first wall section (32) and is designed to be complementary to the first wall section (32) at least in regions, so that the first wall section (32) and the second wall section (33) can interlock when the compressible body (3) is compressed, and the compressible body (3) has an elastomer film (59) which is arranged between the first wall section (32) and the second wall section (33), wherein the elastomer film (59) is stretchable when the wall sections (32, 33) interlock.

10. Battery system (1) according to one of the preceding claims, characterized in that the compressible body (3) contains at least one deformation sensor (5) with two electrical connections (51, 52) and the at least one deformation sensor has: at least two electrodes (53, 54) which are arranged in the compressible body (3) and are each electrically connected to one of the connections (51, 52), and a dielectric (55) which is arranged between the at least two electrodes (53, 54), wherein an electrical capacitance between the electrodes (53, 54) can be increased by an expansion of the battery cell (2) and reduced by a contraction of the battery cell (2), or can be reduced by an expansion of the battery cell (2) and increased by a contraction of the battery cell (2);or at least one electrically conductive part (56, 58) which is arranged in the compressible body and is electrically connected to the two terminals (51, 52) in such a way that an electrical resistance between the two terminals (51, 52) can be reduced by an expansion of the battery cell (2) and increased by a contraction of the battery cell (2), or by an expansion; the battery cell (2) can be enlarged and can be reduced by a contraction of the battery cell (2).

11. Battery system (1) according to the preceding claim, characterized in that the at least one dielectric (55) is formed from an elastomer and preferably contains at least one cavity; and / or at least one of the at least two electrodes (53, 54) is formed from an elastomer with conductive particles; or the electrically conductive part (56, 58) is formed from an elastomer with conductive particles and preferably contains at least one cavity.

12. Battery system (1) according to one of the preceding claims 10-11, characterized in that at least one of the at least two electrodes (53, 54) or the electrically conductive part (56, 58) is flat and is preferably curved in the unloaded or clamped state of the compressible body (3), particularly preferably curved with an angle of curvature of at least 30°.

13. Battery system (1) according to one of the preceding claims 10-12, characterized in that the at least one deformation sensor (5) contains at least three electrodes (53, 54, 57) which are arranged at least partially parallel to one another and of which the two outer electrodes (53, 57) are electrically connected to one another.

14. Battery system (1) according to one of the preceding claims 10-13, characterized in that the at least one compressible body (3) has two or more deformation sensors (5a-f), which are each arranged at different locations of the compressible body (3).

15. Battery system (1) according to one of the preceding claims, characterized in that the battery system (1) has at least two compressible bodies (3a, 3b), each having one or more deformation sensors (5).

16. Battery system (1) according to one of the preceding claims, comprising at least two battery cells (2a, 2b) and at least two compressible bodies (3a, 3b), wherein exactly one compressible body (3a or 3b) is located between two battery cells (2a, 2b), and preferably a compressible body (3a or 3b) is located between each two battery cells (2a, 2b) and wherein a rigid wall (41a, b) of the holding device (4) is particularly preferably located between each two battery cells (2a, 2b) each with a compressible body (3a, 3b).

17. Battery system (1) according to one of the preceding claims, characterized in that the compressible body (3) has a temperature sensor, an ultrasonic sensor, a pressure sensor, an electrical sensor, such as preferably a voltage or current sensor, or an impedance sensor.

18. Battery system (1) according to one of the preceding claims 10-17, further comprising electronics (6) which are configured to measure an electrical resistance between the two terminals of the deformation sensor (51, 52) and / or an electrical capacitance between the electrodes (53, 54) and / or the two terminals of the deformation sensor (51, 52).

19. Battery system (1) according to one of the preceding claims, characterized in that the compressible body (3) undergoes a dimensional change in the clamping direction by at least 0.1% and a maximum of 99%, preferably at least 0.5% and a maximum of 95%, particularly preferably at least 1% and a maximum of 90% during pre-tensioning.

20. Use of the compressible body (3) of the battery system (1) according to one of the preceding claims, as a pretensioning device for exerting pressure on the battery cell (2) and / or as a deformation sensor for detecting the expansion and / or contraction of the battery cell (2).

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