Storage device for electric energy

Abstract

The invention relates to a device (1) for storing electric energy, comprising a plurality of storage cells (2) for storing the electric energy, and a plurality of apparatuses (3) for at least temporarily compressing the storage cells (2), wherein the apparatuses (3) each have a casing (5) with a plastic film, and a fluid is contained in the apparatuses (3) for at least temporarily compressing the storage cells (2). The casings (5) are each formed by a multi-layer film (8) having a plurality of layers (9, 10, 12, 13, 14).

Description

[0001] STORAGE DEVICE FOR ELECTRICAL ENERGY

[0002] The invention relates to a device for storing electrical energy comprising a plurality of storage cells for storing the electrical energy and a plurality of devices for at least temporarily compressing the storage cells, wherein the devices each have a casing with a plastic film and a fluid is contained in the devices for at least temporarily compressing the storage cells.

[0003] It is known that rechargeable battery cells often require consistent and uniform external compression / surface pressure throughout their service life in order to maintain defined / specified operating parameters. This can also help prevent aging effects. Over their service life, some battery cells grow or swell due to aging (so-called "swelling"). In addition to permanent growth, some battery cells also experience a significant change in volume during operation due to the chemical processes taking place. Particularly for battery cells with solid electrolytes, so-called solid-state accumulators, homogeneous surface pressure is advantageous and important in order to prevent the formation of cracks and defects at the interfaces between the anode, electrolyte, and cathode.

[0004] To address these problems, WO 2016 / 034356 A2 proposes a clamping device for battery cells. The device comprises a container for holding a fluid, which comprises a space with a variable volume. The container is designed such that one or more battery cells can be clamped. The container comprises a membrane that is bubble-like, bag-like, cushion-like, or drum-like and is elastic or stretchable. The membrane can comprise a plastic film, metallized film, metal foil, or fabric.

[0005] The present invention is based on the object of providing a device for storing electrical energy which is improved with regard to its service life.

[0006] This problem is solved with the device for storing electrical energy mentioned above, in which the casings are each formed by a multi-layer film comprising several layers. The advantage here is that the multi-layered casing allows it to be better adapted to the operating conditions. By using different materials, an improvement in the properties of the casing can be achieved that is not achievable with a single-layer variant, since such designs represent a compromise between the different requirements of the casing. The multi-layer structure allows the individual layers of the film to be made thinner, allowing more expensive materials to be used for the layers without (significantly) increasing the overall cost of the casing. This, in turn, allows the use of materials that can be better adapted to the requirements of the cells or the general conditions of use of the energy storage device.If necessary, weight can also be saved by using lighter materials for layers subject to less stress.

[0007] According to a preferred embodiment of the invention, it can be provided that each storage cell is arranged directly adjacent to a device for at least temporary compression of the storage cells. Unlike in the aforementioned prior art, partial tensioning of the cells does not occur via direct contact between the cells themselves, but rather a surface pressure adapted to the cells can be achieved separately for each cell. This makes it easier to take different aging behavior into account in an energy storage device according to the invention. Furthermore, if an energy management system (EMS) is present, it is possible to respond better to the "needs" of the cells during charging.

[0008] According to another embodiment of the invention, at least one of the devices for at least temporarily compressing the storage cells can contain an elastic element or a rigid element. With the elastic element or the rigid element, a more uniform pressure distribution can be achieved, thus enabling a more homogeneous surface pressure, or a minimum distance between the storage cells can be ensured via this elastic or rigid element.

[0009] According to another embodiment of the invention, due to the multi-layered casing of at least one of the devices, a layer of a fire-resistant material can be arranged in the casing for at least temporary compression of the storage cells. This makes it possible, on the one hand, to provide a so-called heat shield in the energy storage device. On the other hand, it can also be used to "wall off" the energy storage device or at least individual storage cells for a longer period of time in the event of a fire.

[0010] In a further embodiment of the invention, it can be provided that the casings of the devices for at least temporarily compressing the storage cells have a first layer made of a first polymeric plastic, a second layer made of a second polymeric plastic, and a layer made of a metal, wherein the metal layer is arranged between the first layer made of the first polymeric plastic and the second layer made of the second polymeric plastic. This makes it possible, on the one hand, to impart improved fluid tightness, in particular for gases, to the casing via the metal layer. By arranging the metal layer between two polymer layers, electrical insulation of the metal layer can also be achieved. In addition, the outer polymer layer can impart improved mechanical stability to the casing, whereas the inner polymer layer can be better adapted to the fluid used.This polymer layer can also be used to form the shell through improved weldability with the appropriate choice of material.

[0011] According to one embodiment of the invention, the multi-layered casing can also include a reinforcement layer to improve mechanical strength. This reinforcement layer can also compensate for or transition between different material properties of the casing layers, thereby improving the strength and durability of the multi-layer film composite.

[0012] According to one embodiment, the reinforcement layer can be made of or comprise a fiber material, allowing the shell, despite the reinforcement, to still exhibit appropriate flexibility or adaptability to the surface of the energy storage cells in contact with it. Furthermore, the aforementioned heat shield can also be easily created by incorporating or co-incorporating appropriate fibers, such as ceramic fibers, graphite fibers, or aramid fibers, into the reinforcement layer.

[0013] To reduce potential leakage points, according to one embodiment of the invention, each of the casings of the devices for at least temporarily compressing the storage cells can have only one connection for introducing the fluid. Besides this fluid connection, the casings in this embodiment have no further fluid connection, in particular no fluid connection for discharging the fluid to a heat exchanger. Thus, after filling, each of the devices for at least temporarily compressing the storage cells in this embodiment forms a self-contained system.

[0014] According to another embodiment of the invention, however, it can be provided that several of the devices for at least temporarily compressing the storage cells are connected to one another via fluid lines. Although this embodiment also creates a self-contained system within the energy storage device, so that no fluid is discharged to the outside, pressure equalization between these devices can be achieved through the communication between at least some of the devices for at least temporarily compressing the storage cells.

[0015] According to a further embodiment of the invention, the casing of at least one of the devices for at least temporarily compressing the storage cells can be provided with at least one sensor element. This simple integration of the sensor element into the device for storing electrical energy enables improved monitoring of the storage cells, allowing for a more rapid response in the event of a security emergency.

[0016] For a better understanding of the invention, it is explained in more detail using the following figures.

[0017] They show in a highly simplified, schematic representation:

[0018] Fig. 1 shows a device for storing electrical energy;

[0019] Fig. 2 embodiments of a device for at least temporary compression of the memory cells of the device according to Fig. 1;

[0020] Fig. 3 embodiments of a multilayer film for the devices for at least temporary compression of the storage cells of the device according to Fig. 1;

[0021] Fig. 4 A variant of a device for at least temporary compression of the memory cells of the device according to Fig. 1;

[0022] Fig. 5 Further embodiments of a multilayer film for the devices for at least temporarily compressing the storage cells of the device according to Fig. 1. By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or identical component designations, whereby the disclosures contained in the entire description can be transferred mutatis mutandis to identical parts with identical reference symbols or identical component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and in the event of a position change, these positional information must be transferred mutatis mutandis to the new position.

[0023] Fig. 1 shows a device 1 for storing electrical energy (also referred to as a storage device). Device 1 for storing electrical energy (hereinafter referred to as device 1) comprises a plurality of storage cells 2 for storing the electrical energy (hereinafter referred to as storage cells 2). The number of storage cells 2 shown in Fig. 1 is not intended to be limiting, but merely serves to clarify the invention. The storage cells 2 can be, for example, prismatic cells or so-called pouch cells. The storage cells 2 can be, for example, lithium polymer cells, but they can also have a different chemistry. In particular, however, the invention is preferably used for storage cells 2 that are subject to a change in volume during operation, as is known, for example, from lithium polymer cells.The device 1 is in particular a rechargeable battery or accumulator.

[0024] In addition to the memory cells 2, the device 1 also comprises a plurality of devices 3 for at least temporarily compressing the memory cells 2 (hereinafter referred to only as devices 3). With regard to the devices 3, it should also be noted that the number of devices 3 shown in Fig. 1 should not be understood as limiting, but that it only serves to clarify the invention.

[0025] The devices 3 are in particular directly / immediately adjacent to the storage cells 2.

[0026] The term compression is to be understood to mean that when the volume of the storage cells 2 increases, for example as a result of the storage cells 2 swelling, a pressure is exerted on the devices 3, which in turn counteracts the pressure of the storage cells 2, so that they are subject to a surface pressure. The term "compression" in the sense of the invention therefore refers to the compression acting on the cells. The term "at least temporarily" is to be understood to mean that the compression occurs at least when the volume of the storage cells 2 increases. In the initial position, i.e. when the storage cells 2 have their original volume, the devices 3 can also only rest against the storage cells 2 without exerting any pressure or surface pressure on them, although this is possible within the scope of the invention.

[0027] The storage cells 2 and the devices 3 are preferably arranged in a common housing 4.

[0028] In the following, only one device 3 is described in more detail. However, the devices 3 of a device 1 are preferably all designed identically, so that the following statements regarding one device 3 also apply to the other devices 3 of the device 1, unless expressly stated otherwise.

[0029] The device 3 has a casing 5, which in one embodiment is better shown in Fig. 2. The casing 5 defines a cavity or an interior space 6 surrounded by the casing. The interior space 6 can be completely surrounded by the casing 5, but the casing 5 has at least one filling opening or a connection 7 for supplying a fluid into the interior space 6. During operation of the device 1, under normal conditions (if there is no leakage), the interior space 6 is filled with a fluid, so that the device 3 can bring about the effect described above.

[0030] The fluid is preferably a gas or a gas mixture, such as air, carbon dioxide, or an inert gas such as helium, argon, or nitrogen. However, the fluid can also be a liquid, such as water or an oil, e.g., silicone oil. Mixed variants are also possible, in which both a gas and a liquid are present as the fluid in the interior space 6, in order to thereby vary the degree of compressibility of the devices 3.

[0031] The connector 7 can be made of the same material as the casing 5. Alternatively, the connector 7 can also be made of another material, such as a hard plastic, which is bonded to the casing, for example, by adhesive bonding or welding. The casing 5 has a multilayer film 8 (also referred to as a multilayer film) comprising several layers, or is formed from it, or consists of it.

[0032] As can be seen from Fig. 2, the casing 5 has or consists of two multi-layer films 8, which have at least a first layer 9 and a second layer 10. The two multi-layer films 8 are connected to one another in connecting regions 11. The interior space 6 is formed by this partial connection of the two multi-layer films 8. The connecting regions 11 preferably extend along the outer circumference of the multi-layer films 8. The dashed lines in Fig. 2 indicate that the interior space 6 can also be divided into two or more partial interior spaces in order to prevent total failure of the device 3 in the event of a leak. For this purpose, the partial interior spaces are completely separate from one another. Each partial interior space can have its own connection 7 for filling with the fluid.The separation of the partial interior spaces from one another can be achieved by partially connecting the two multilayer films 8, thereby forming at least one further connecting region 11. It should be noted in this context that Fig. 2 is a schematic drawing, ie, no web needs to be formed in the optional connecting region 11, as shown.

[0033] As an alternative to the design with two multi-layer films 8, only one multi-layer film can be used, which is, for example, “folded” or turned over in the middle so that one side edge of the device 3 is formed by this “folding area”.

[0034] Preferably, the two multilayer films 8 are of identical design. Alternatively, the two multilayer films 8 can also be different from each other. For example, the materials used in the multilayer films 8 can be different and / or the number of layers can be different.

[0035] The first layer 9 consists of or comprises a first material. The second layer 10 consists of or comprises a second material. It is possible for the first material and the second material to be the same. However, the first material is preferably different from the second material.

[0036] In general, the materials used in the multilayer film 8 can be selected from a group comprising polymeric materials, metals, fiber materials, ceramic materials. Polymeric materials can be, for example, thermoplastics or elastomers. The thermoplastic can, for example, be selected from a group comprising or consisting of polyethylene (PE), polyoxymethylene (POM), polyamide (PA), in particular PA 6, PA 66, PA 11, PA 12, PA 610, PA 612, polyphenylene sulfide (PPS), cross-linked polyolefins, preferably polypropylene (PP), polyethylene terephthalate (PET). The elastomer can be selected from a group comprising or consisting of thermoplastic elastomers such as, for example,thermoplastic vulcanizates olefin-, amine-, ester-based, thermoplastic polyurethanes, in particular thermoplastic elastomers based on ether / ester, styrene block copolymers, silicone elastomers, EPDM (ethylene-propylene-diene elastomers), NBR (acrylonitrile-butadiene elastomers).

[0037] It should be mentioned at this point that a polymeric material is understood to be a synthetic or natural polymer made from corresponding monomers.

[0038] Fiber materials can be formed from fibers and / or threads selected from a group comprising or consisting of glass fibers, aramid fibers, carbon fibers, ceramic fibers, mineral fibers such as basalt fibers, natural fibers such as hemp, sisal, rubberized fibers and / or threads and combinations thereof.

[0039] The fibers and / or threads in the fiber reinforcement can be in the form of a nonwoven fabric, for example, a nonwoven, or as a woven or knitted fabric. When using a woven fabric, different weave types are possible, particularly plain weave, twill weave, or satin weave.

[0040] The basis weight of the fiber material can be between 10 g / m 2 and 1000 g / m 2 , preferably between 100 g / m 2 and 250 g / m 2 The fiber material can form a closed layer, which enables a uniform material bond, for example, to the plastic of the first layer 9 and / or the second layer 10. Furthermore, properties of the multilayer film 8, such as thermal expansion or creep tendency, can be influenced.

[0041] However, it is also possible to use an open-mesh fabric or scrim with a surface weight between 10 g / m 2 up to 90 g / m 2 to use.

[0042] The fiber material can be formed as a single layer. However, it is also possible for the fiber material to have several, possibly separate, individual layers, for example two or three, wherein at least some of the multiple individual layers can consist of fibers and / or threads that are different from the rest of the individual layers.

[0043] The metallic material can be selected from a group comprising or consisting of aluminum, copper, silver, gold, etc., whereby alloys of these or with these metals can also be used.

[0044] The metallic material can form a separate layer. However, it is also possible to use a metallized plastic film, whereby the plastic can be selected from the polymer materials mentioned above. If a metallized plastic film is used, the aforementioned metals can be used for the metallization. The metallization preferably has a layer thickness selected from a range of 5 nm to 100 nm.

[0045] In the two-layer design, the first layer 9 can be a polymeric material and the second layer 10 can also be a polymeric material or a metal or a metallized plastic film or a fiber layer. In the context of the invention, the first layer 9 is generally the layer of the multi-layer film that is closest to the interior 6. Preferably, the first layer 9 is formed from or consists of a sealing film, e.g. made of PP. This has the advantage that the multi-layer films 8 can be directly connected to one another to form the connecting regions 11. However, it is also possible to use other plastics, which are then bonded together, for example with an adhesive. Two-component adhesive systems based on polyurethane or silicone, or even hot-melt adhesive systems, are particularly suitable for this purpose. In this case, thermosetting plastics can also be used as polymeric materials.

[0046] According to an embodiment shown in Fig. 3, the multilayer film 8 can comprise the first layer 9, the second layer 10, and a further layer 12, which forms an intermediate layer between the first layer 9 and the second layer 10. The first and second layers 9, 10 can be connected directly to the further layer 12 or via further intermediate layers.

[0047] In the three-layer design, the first layer 9 can consist of a first polymeric plastic, for example PP, the second layer 10 of a second polymeric plastic, for example PET, and the further layer 12 can be designed as a reinforcement layer, wherein the further layer 12 of the metal is arranged between the first layer 9 of the first polymeric plastic and the second layer 10 of the second polymeric plastic.

[0048] The reinforcement layer can be formed from a fiber material mentioned above, from a metal or metallic material, from an adhesive, etc. In the case of a metal, the reinforcement layer can also have a barrier effect, although in this case, the effect of reinforcing the multilayer film 8 is not necessarily the primary focus. When configured as a reinforcement layer, the additional layer 12 can also have a mineral filling. Examples of mineral fillings (mineral fillers) that can be used include calcium carbonate, talc, quartz, wollastonite, kaolin, or mica.

[0049] As an alternative to this three-layer structure, the multilayer film 8 can also comprise or consist of a first layer 9 made of a polymeric material, a further layer 12 formed as a reinforcement layer, and a second layer 10 made of a metal, in this order. In this case, the reinforcement layer is not formed by a metal or a metallic material.

[0050] As indicated in Fig. 3, the multilayer film 8 can also have one or more additional layers 13, 14. The materials for these additional layers 13, 14 can be selected from the materials mentioned above. For example, the multilayer film 8 can have the following structure (in this order): first layer 9 made of a first polymeric material, in particular a heat-sealable plastic, further layer 12 made of an adhesive, second layer 10 made of a metal, additional layer 13 made of an adhesive, additional layer 14 on a second polymeric material that is different from the first polymeric material, optionally a further adhesive layer, and optionally a layer made of a third polymeric material that is preferably different from the first and / or second polymeric material.

[0051] According to a further embodiment, the multilayer film 8 can also have or consist of at least one layer of a fire-resistant material. The fire-resistant material can be, for example, a ceramic material or graphite, mica, synthetic elastomers, etc. The fire-resistant material can also be in fibrous form, so that it can simultaneously form the reinforcement layer. The fire-resistant material can form at least one of the layers 10, 12, 13, 14 or an additional layer if present.

[0052] It is possible for only one of the devices 3 of the device 1, or for several or all of them to have such a layer made of a fire-resistant material. For example, only the outer devices 3 can be formed with such a layer made of a fire-resistant material.

[0053] The individual layers 9, 10, 12, 13, 14 of the multilayer film 8 can have a layer thickness between 10 pm and 200 pm. If a metallic material is used as one of the layers 9, 10, 12, 13, 14, this layer thickness can be between 7 pm and 50 pm, in particular between 10 pm and 20 pm.

[0054] To connect the individual layers 9, 10, 12, 13, and 14 to form the multilayer film 8, these can be bonded together using adhesives, as described above. The adhesives mentioned above are suitable for this purpose. In addition to adhesives, the laminate can also be produced using coextrusion and extrusion coating, for example. Of course, a combination is also possible, whereby several polymer materials are coextruded and adhesively laminated to one another with an extrusion-coated metal or (fiber) reinforcement layer. In general, all known processes for producing composite films or film laminates can be used.

[0055] It is also possible to use a shaping device, e.g. a laminating press or a laminating device, to produce the multi-layer film 8.

[0056] The formation of the connecting regions 11 is preferably carried out by means of a welding process, e.g. by thermal impulse welding, laser welding, IR welding, ultrasonic welding, high-frequency welding.

[0057] As can be seen from Fig. 1, according to a preferred embodiment, each of the storage cells 2 can be arranged directly adjacent to a device 3. Alternatively, there is also the possibility of devices 3 being arranged between the housing 4 and the storage cells 2, as is also shown in Fig. 1.

[0058] It is possible for the devices 3 to have a surface area that is at least approximately equal to the surface area of ​​the memory cells 2, so that one device 3 is arranged per memory cell 2. Thus, a device 3 is arranged between each of the memory cells 2, so that none of the memory cells 2 is in direct contact with another memory cell 2.

[0059] Alternatively, it can be provided that several memory cells 2 are adjacent to a common device 3. In this case, too, the memory cells 2 can be separated via the devices 3, so that none of the memory cells 2 is in direct contact with another memory cell 2. For this purpose, the device(s) 3 can be arranged in a meandering pattern between the memory cells 2.

[0060] According to a further embodiment, indicated by dashed lines in Fig. 2, an elastic element 15 or a rigid element 16 can be contained in the interior 6 of at least one of the devices 3, preferably in all devices 3 of the device 1. The elastic element 15 can be, for example, a gel cushion or an elastomer element or a foam element. The rigid element 16 can be, for example, a plate made of a hard plastic. A combination of an elastic element 15 and a rigid element 16 is also possible, so that the insert element formed therefrom is compressible.

[0061] In principle, the casing 5 can be provided with multiple connections 7 through which a fluid is supplied to the interior 6. Preferably, however, the casing 5 has only a single connection 7. This connection 7 serves only to supply the fluid to the interior 6 and is sealed fluid-tight after the device has been filled. During operation of the device 1, the device 3 thus forms a self-contained fluid system.

[0062] According to another embodiment variant shown in Fig. 4, several of the devices 3 can be connected to one another by fluid lines 17, thus enabling pressure equalization between the devices 3 during operation. The fluid lines 17 can also be formed, for example, in a cover, a side wall, or a base of the housing 4 of the device 1.

[0063] Fig. 5 shows a variant embodiment in which the casing 5 of at least one of the devices 3 has at least one sensor element 18. Several or all of the devices 3 can also be equipped with at least one sensor element 18. The sensor element 18 can be, for example, a temperature sensor or a pressure sensor, in particular in order to be able to better monitor the storage cells 2.

[0064] As can be seen from Fig. 5, the at least one sensor element 18 can be arranged within one of the layers 9, 10, 12, 13, 14 of the multilayer film 8 or on the multilayer film 8. It is also possible for the at least one sensor element 18 to be arranged between two layers 9, 10, 12, 13, 14 of the multilayer film 8.

[0065] According to a further embodiment, a reinforcing element can be arranged in at least one of the connecting regions 11 of the device 3. The reinforcing element can, for example, be strip-shaped, but it can also have a different shape, for example, in the form of an eyelet or the like.

[0066] This at least one reinforcing element can, in particular, consist at least partially or entirely of a polymeric plastic, which can, in particular, be selected from the plastics mentioned above. The at least one reinforcing element can also be used for fastening the devices 3 in the device 1.

[0067] To produce the device 3, one or two multilayer films 8 are connected to one another in the connecting regions 11 such that the interior space 6 is formed. For example, with two multilayer films 8, the connecting regions 11 can be formed over their entire circumference. Then, at least one fluid, preferably a gas, is introduced into the interior space 6 via the connection 7. After reaching a predeterminable pressure in the interior space 6, the fluid supply is interrupted and the connection 7 is closed. If the storage cells 2 swell over their service life, the interior space tapers accordingly, but the pressure in the interior space 6 and thus the compression acting on the storage cells 2 is kept at least approximately constant. When using a gaseous fluid, the device 3 can be provided with an equalizing vessel (e.g.a membrane expansion vessel) or at least be connected to a larger air volume in relation to the expansion volume.

[0068] It is possible for the device 3 to have a frame element, if required, in which the sleeve 5 is arranged or by which the sleeve 5 is held. The frame element can be rigid or, if appropriate, also compressible, in that the frame element is formed from a combination of an elastic or compressible element, for example an elastomer, and a rigid element. Alternatively or additionally, this compressible embodiment can also be achieved structurally by designing the frame element accordingly. For example, the frame element can be designed with a C- or W-shaped frame cross-section. If appropriate, this frame element can be formed from a thermoplastic, which can have elastomer inserts in the recesses created by the C- or W-shape of the frame cross-section.

[0069] The frame element can be a circumferentially closed frame. However, a frame element that extends only over a portion of the circumference of the shell can also be used. If necessary, the frame element can consist of individual, unconnected frame elements.

[0070] The invention relates to a device 1 for storing electrical energy. However, the device 3 for at least temporarily compressing storage cells 2 of such a device can constitute an independent invention if it is designed according to at least one of the embodiment variants described above.In particular, this device 3 has at least one of the following features: a casing 5 formed by a multi-layer film 8 comprising a plurality of layers 9, 10, 12, 13, 14; an elastic element 15 or a rigid element 16 contained in the interior 6; a layer of a fire-resistant material in the multi-layer film 8; a first layer of a first polymeric plastic, a second layer of a second polymeric plastic, and a layer of a metal, wherein the metal layer is arranged between the first layer of the first polymeric plastic and the second layer of the second polymeric plastic; a reinforcing layer in the multi-layer film 8, which is formed, for example, from or comprises a fiber material; a casing 5 having only a single connection 7 for a fluid; a casing 5 having at least one sensor element 18.

[0071] The exemplary embodiments show and describe possible design variants of the device for storing electrical energy. It should be noted at this point that combinations of the individual design variants are also possible. For the sake of clarity, it should be noted that, in order to facilitate a better understanding of the structure of the device for storing electrical energy, it is not necessarily drawn to scale.

[0072] Reference symbol list

[0073] Furnishings

[0074] memory cell

[0075] device

[0076] Housing

[0077] Covering

[0078] Interior

[0079] Connection

[0080] Multilayer film

[0081] Position

[0082] Position

[0083] Connection area

[0084] Position

[0085] Position

[0086] Position

[0087] element

[0088] element

[0089] Fluid line

[0090] Sensor element

Claims

Patent claims 1. Device (1) for storing electrical energy, comprising a plurality of storage cells (2) for storing the electrical energy and a plurality of devices (3) for at least temporarily compressing the storage cells (2), wherein the devices (3) each have a casing (5) with a plastic film and a fluid is contained in the devices (3) for at least temporarily compressing the storage cells (2), characterized in that the casings (5) are each formed by a multi-layer film (8) having a plurality of layers (9, 10, 12, 13, 14).

2. Device (1) according to claim 1, characterized in that each memory cell (2) is arranged directly adjacent to a device (3) for at least temporary compression of the memory cells (2).

3. Device (1) according to claim 1 or 2, characterized in that an elastic element (15) or a rigid element (16) is contained in at least one of the devices (3) for at least temporarily compressing the storage cells (2).

4. Device (1) according to one of claims 1 to 3, characterized in that a layer of a fire-resistant material is arranged in the casing (5) of at least one of the devices (3) for at least temporary compression of the storage cells (2).

5. Device (1) according to one of claims 1 to 4, characterized in that the casings (5) of the devices (3) for at least temporarily compressing the storage cells (2) have a first layer (9) made of a first polymeric plastic, a second layer (10) made of a second polymeric plastic and a layer (12) made of a metal, wherein the layer (12) made of the metal is arranged between the first layer (9) made of the first polymeric plastic and the second layer (10) made of the second polymeric plastic.

6. Device (1) according to one of claims 1 to 5, characterized in that the casings (5) of the devices (3) have a reinforcing layer for at least temporary compression of the storage cells (2).

7. Device (1) according to claim 6, characterized in that the reinforcing layer is formed from a fiber material or comprises a fiber material.

8. Device (1) according to one of claims 1 to 7, characterized in that each of the casings (5) of the devices (3) for at least temporary compression of the storage cells (2) has only a single connection (7) which is used for introducing the fluid.

9. Device (1) according to one of claims 1 to 8, characterized in that several of the devices (3) for at least temporary compression of the storage cells (2) are connected to one another by fluid lines (17).

10. Device (1) according to one of claims 1 to 9, characterized in that the casing (5) of at least one of the devices (3) for at least temporarily compressing the storage cells (2) has at least one sensor element (18).

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