Battery cells for performing safety tests

Abstract

A battery cell for performing safety testing comprises: a plurality of anodes of a layered structure, a plurality of cathodes of a layered structure, and a plurality of separator layers for electrically insulating the anodes and cathodes, wherein the anode has a centrally arranged anode conductor and a coating with an anode active material arranged on both sides of the anode conductor, wherein the cathode has a centrally arranged cathode conductor and a coating with a cathode active material arranged on both sides of the cathode conductor, wherein at least a pair consisting of a first and a second anode coated on one side and / or a pair consisting of a first and a second cathode coated on one side are provided, wherein the pair consisting of a first and a second anode coated on one side and / or the pair consisting of a first and a second cathode coated on one side are respectively arranged adjacent to each other on their uncoated sides, so that a gap is formed between adjacent uncoated sides of the anode and / or the cathode, for introducing a starting element for initiating a short circuit.

Description

Technical Field

[0001] The invention relates to a battery cell, a system and a method for carrying out a safety test. Background Art

[0002] With the increasing acceptance of electric vehicles, the requirements for the safety of battery cells as energy sources for electric vehicles are also increasing. The risk here arises from a short circuit in the battery cell, which leads to the fact that not only individual battery cells but the entire battery module are damaged. The cause of such a short circuit is, for example, an overload of the battery cell that occurs locally during the charging phase. For example, in lithium-ion batteries, this leads to the deposition of elemental lithium at the anode and the growth of so-called dendrites. Dendrites can pierce the separator layer between the anode and the adjacent cathode and ultimately establish contact between the anode and the cathode, which causes a short circuit. The heat generated in the short circuit can also ignite the flammable electrolyte, which can spread to adjacent batteries and ultimately the entire battery module.

[0003] In order to improve the safety of battery cells, different methods are known from the prior art. For example, document US 2018 / 0198132 A1 proposes introducing a current collector into a battery cell or battery, by means of which the short-circuit resistance can be greatly increased in abnormal situations in the event of a short circuit, and the short-circuit current can be greatly reduced, so that the heat generated by the short circuit is greatly reduced and the safety performance of the battery is improved.

[0004] However, this known safety mechanism is only useful if the short circuit in the battery cell is known quickly and sufficiently. In order to be able to better estimate and predict the possible risk of a short circuit, up to now, disadvantageously, too little is known about the battery processes in the battery cell that lead to a short circuit. Therefore, in order to increase safety, it is necessary to study the short-circuit behavior of the battery cell more accurately.

[0005] Different methods are known from the prior art (e.g. from US 2018 / 0123166 A1) in which a short circuit is deliberately caused in a battery cell in order to study the behavior of the battery in this situation and thereby obtain further knowledge about the short-circuit behavior of the battery cell. In such a safety test, the battery cell is stimulated to generate a short circuit in the laboratory, for example, by forcibly introducing a conductive nail, by deforming the battery, by overheating, by an external short circuit, by introducing high-energy laser radiation or fusible alloys and wax, or by introducing external particles. The induced short circuit is preferably performed here depending on a large number of other variable parameters, and can contribute to a better understanding of the short-circuit behavior of the battery cell in this way. However, the disadvantage of the known method is that in this solution, the material is brought into the battery, the active material from the battery is removed or the battery must be opened, so that the state of the battery cell is significantly different from the natural battery state of the battery cell in the case of an artificially initiated short circuit. This in turn reduces the persuasiveness of the safety test. Summary of the invention

[0006] Therefore, the object of the present invention is to at least partially overcome the disadvantages described above and, in particular, to propose a battery cell for use in safety tests which can be manufactured in a structurally simple and cost-effective manner and which in particular provides the most convincing possible information about the natural battery behavior of the battery cell during safety tests.

[0007] The above object is achieved by a battery cell according to the invention, a system according to the invention and a method according to the invention. Further features and details are obtained from the description and the drawings. The technical features disclosed for the battery cell according to the invention also apply here in conjunction with the system according to the invention or the method according to the invention and vice versa, so that reference can always be made to each other with regard to the disclosure of the individual inventive aspects.

[0008] The battery cell according to the invention for carrying out a safety test comprises a plurality of anodes of a layered structure, a plurality of cathodes of a layered structure, and a plurality of separator layers for electrically insulating the anodes and cathodes, wherein the anode has a centrally arranged anode conductor and a coating with an anode active material arranged on both sides of the anode conductor, and the cathode has a centrally arranged cathode conductor and a coating with a cathode active material arranged on both sides of the cathode conductor. According to the invention, at least a pair of first and second anodes coated on one side and / or a pair of first and second cathodes coated on one side are also provided, wherein the pair of first and second anodes coated on one side and / or the pair of first and second cathodes coated on one side are arranged adjacent to each other on their uncoated sides in such a way that a gap is formed between adjacent uncoated sides of the anode and / or cathode, which are adjacent to each other, for introducing an initiating element for initiating a short circuit between an anode and / or cathode coated on one side and an adjacent anode and / or cathode coated on both sides. It is obvious that in addition to the pair of anodes and cathodes coated on one side and / or the pair of cathodes coated on one side provided according to the invention, additional anodes and / or cathodes coated on one side may be arranged in the battery cell according to the invention. These can then be arranged in particular at the edge or in the middle in a wound battery stack, since the outermost layers of the battery cell according to the invention are then no longer coated on both sides but only on one side, for example.

[0009] Typical battery cells are designed in particular in the form of lithium-ion battery cells, as are currently provided for use in smartphones, laptops, electric or hybrid vehicles. It is also conceivable, however, that typical battery cells are designed in the form of sodium-ion batteries, magnesium-ion batteries or zinc, aluminum or other metal oxide batteries, in which a short circuit between the anode and cathode of the battery can occur due to dendrite growth. Preferably, the battery cell can be designed as a pouch cell.

[0010] In the context of the present invention, a layered anode or layered cathode may be understood in particular to be a planar mass of anode or cathode material in which the layer thickness is less than the layer width. In the case of a double-sided coated anode or cathode, the anode or cathode conductor is coated on both sides, while in the case of a single-sided coated anode or cathode, the anode or cathode is coated only on one side.

[0011] A typical separator layer for electrically insulating the anode and / or cathode can preferably be formed from a microporous polymer, in particular from a microporous polymer membrane, and can be implemented, for example, in multiple layers. Likewise, the separator layer can be formed from a fine, preferably ceramic-coated nonwoven fabric, which provides not only high flexibility but also high temperature resistance and thus has a greater safety against thermally induced runaway of the battery. Likewise, for example, in the context of a design of a battery cell as a solid-state battery, it can be provided that a ceramic, polymer or sulfide is arranged between the anode and cathode layers and forms a "separator layer".

[0012] With a view to producing a short circuit between an electrode coated on one side and an adjacent electrode coated on both sides according to the invention as quickly and controlled as possible, pairs of electrodes coated on one side can be formed as pairs of anodes coated on one side.

[0013] In view of the effective absorption and conduction of electrons, it can be provided according to the invention in particular that the anode conductor and / or cathode conductor is formed by a metal plate, wherein the metal plate is preferably arranged substantially parallel to the adjacent separator layer at the anode and / or cathode. Advantageously, the anode conductor element can be formed by a copper material and / or the cathode conductor element can be formed by an aluminum material. A typical metal plate can be designed in particular in the form of a conductor or a metal film. Likewise, porous conductors such as, for example, a grid structure can be conceivable.

[0014] In the context of the invention, it is known that by means of the design according to the invention of a representative battery cell, a short circuit can be initiated without significantly changing the structure of the battery or destroying the battery structure, so that the battery cell used for the safety test differs only slightly from the battery cell normally used. It is also known that by simulating the design of the short circuit in the battery cell as realistically as possible, particularly convincing information about the natural battery behavior of the battery cell with respect to the generation of the short circuit can be obtained. With the help of this information, effective measures for increasing the safety of the battery cells and battery modules can then be obtained in a particularly targeted manner.

[0015] The electrodes coated on one side obtained within the scope of the battery cell according to the invention have a lower impedance due to the larger conductor cross section and therefore tend to operate more strongly than other electrodes. In the case of a battery cell designed as a lithium-ion battery, this leads to so-called "lithium plating", in which metallic lithium is deposited on the anode, which ultimately leads to a short circuit.

[0016] As already described, the structural changes are preferably arranged at the anode, but it is also conceivable that the structural changes are arranged at the cathode. Likewise, more than one first and second electrodes coated on one side can also be arranged in a battery cell. In this way, for example, in addition to the preferably modified anode, the individual cathodes can also be modified in order to increase the load and change the balance relative to the adjacent anodes. In this way, adjacently arranged anodes can be overloaded and promote "plating" at the anode, thereby increasing the probability of damage. In such an embodiment, it is particularly advantageous that the cathode is not led into instability, which it does not receive in normal operating conditions.

[0017] In the context of the structurally simple and at the same time effective generation of short circuits within battery cells, it can be advantageously provided that the starter element is formed in the form of a deformation element for deforming adjacent anodes and / or cathodes coated on one side. Such a deformation element can be understood in particular as an element which presses the adjacent electrode against the corresponding counter-electrode in order to increase the current density at the interface between the electrodes and thus promote dendrite growth. With increasing state of charge (SoC) and life, the electrodes naturally expand, which thus also additionally strengthens the influence of the deformation element. In order to further support the generation of short circuits, it can be provided according to the invention in particular that the starter element changes its shape, preferably increases its volume. The starter element can advantageously have different shapes, sizes and distributions in this case in order to generate different numbers and different sizes of areas for internal short circuits.

[0018] In order to minimize the structural complexity when introducing the starting element, it is particularly conceivable that the starting element is arranged partially in the gap for introducing the starting element. In the case of such a local arrangement of the deformation element, in particular, there is still enough space in the gap to accommodate other elements, such as cooling elements, sensors or buffer elements, etc. Such a buffer element surrounding the starting element can, for example, selectively delay the influence of the starting element, by the buffer element, for example, only being pressed together over time as the battery's service life increases and the influence of the starting element increases over time.

[0019] In order to simulate the aging of the battery realistically, it can typically also be provided that the starting element completely fills the gap for introducing the starting element. Such complete filling prevents in particular the rapid local formation of dendrites, which leads to a short circuit between the anode and the cathode, so that the battery can achieve minimal aging.

[0020] In view of the most effective possible deformation of the adjacent anode or cathode coated on one side, it can be particularly advantageous if the starting element is formed from a metallic material or plastic, wherein the starting element can preferably be compressed equally or more difficultly than the separator layer. In addition, the starting element can be designed in this way to be voltage-stable with respect to the conductor metal and the electrolyte. In the context of particularly rapid short-circuit starting, it can be alternatively or additionally provided according to the invention that additional elements for compressing the anode or cathode are introduced into the coating of the anode and / or cathode on one side. In this way, the anode and / or cathode coated on one side can be bonded, for example, with an active material, for example with a thinner metal part, etc., before coating, in order to compress the electrode in the subsequent coating, so that the "lithium plating" (in the case of the battery cell being implemented as a lithium-ion battery) is used more and more intensively.

[0021] Likewise, it is conceivable to form the activation element in multiple parts in view of the targeted activation of the short circuit in the battery cell. Thus, the activation element can be formed, for example, as a deformation element, which has a first part, for example in the form of a metal spike and additionally includes a second part, which is formed, for example, from plastic and preferably fills the remaining free space around the metal spike.

[0022] In the context of remote targeted control, it is likewise conceivable that the activation element can be externally actuated, wherein the actuation can preferably be effected via direct wiring or by radio.

[0023] In order to locally increase the lithium ion concentration and thereby promote the formation of one or more dendrites and thereby generate a short circuit between the anode and cathode of the battery, different embodiments of the starter element can be provided according to the invention. Thus, the starter element can be formed as a heating element and / or a deformation element (Verformungselement) for volume or shape change and / or an explosion element and / or a storage element for releasing material and / or a coil for generating a magnetic field and / or a permanent magnet and / or a ferromagnetic material. The released material can be formed in particular in the form of a chemical substance for stimulating dendrite growth.

[0024] Likewise, the object of the invention is a system for performing safety tests by generating a short circuit between an anode and / or cathode coated on one side of a battery cell and an adjacent anode and / or cathode coated on both sides. Here, the system according to the invention comprises the battery cell described above and the starter element described above.

[0025] Likewise, the object of the present invention is a system for performing a safety test by generating a short circuit between an anode and / or cathode coated on one side and an adjacent anode and / or cathode coated on both sides of a battery cell. Here, the system according to the invention comprises the battery cell described above and a control device for actuating a starter element. The system according to the invention thus has the same advantages as those already described in detail with respect to the battery cell according to the invention.

[0026] Likewise, the object of the present invention is a method for carrying out a safety test, in particular when using a battery cell as described above. In this case, the method according to the invention comprises the following steps: issuing a control signal for activating a starter element, which is arranged in the gap between two adjacent uncoated surfaces of a pair of anodes coated on one side and / or a pair of cathodes coated on one side; receiving a control signal via the starter element; and activating the starter element in order to cause an electrical short circuit between the anode and / or cathode coated on one side and the adjacent anode and / or cathode coated on both sides. The method according to the invention thus has the same advantages as have been described in detail with respect to the battery cell according to the invention or the system according to the invention. A representative method can be supported in particular by carrying out a rapid, periodic charge and discharge cycle of the battery cell, which additionally facilitates the formation of a short circuit. In addition, a slight deformation of the battery cell by an external local load around the starter element arranged in the battery can also be provided in order to additionally facilitate the formation of a short circuit. In this case, the external local load can, for example, also be so large that the starter element is driven directly through the electrode, for example as an internal "nail test (Nageltest, sometimes also called Nagel's test)". BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Further advantages, features and details of the invention are apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the description may be essential to the invention individually or in any combination.

[0028] in:

[0029] Figure 1 A schematic diagram of a known battery cell is shown in a plan view (above) and in an enlarged cross-sectional view of a portion of the battery cell (below).

[0030] Figure 2 A schematic diagram of a known battery cell is shown in cross section,

[0031] Figure 3 A schematic diagram of a battery cell according to the present invention is shown in a cross-sectional view according to a first embodiment.

[0032] Figure 4a According to a first embodiment, a schematic diagram of a part of a battery cell according to the present invention is shown in a cross-sectional view.

[0033] Figure 4b According to a second embodiment, a schematic diagram of a part of a battery cell according to the present invention is shown in a cross-sectional view.

[0034] Figure 5 A schematic diagram shows the individual steps of the method according to the invention for carrying out a safety test. DETAILED DESCRIPTION

[0035] Figure 1 A schematic diagram of a known battery cell 2 is shown in a plan view (above) and in an enlarged view of a section of the battery cell 2 (below).

[0036] exist Figure 1 The battery cell 2 shown in the figure and formed in the form of a soft bag cell can be implemented, for example, as a lithium-ion battery and (as can be seen at present) has a plurality of anodes 6 of layered structure, a plurality of cathodes 8 of layered structure and a plurality of separator layers 4 for electrically insulating the anodes 6 and / or the cathodes 8. An anode conductor 10 is arranged in each case in the anode 6, and a cathode conductor 12 is arranged in the cathode 8. Layers 14, 16 consisting of an anode active material and a cathode active material are arranged on both sides to the anode conductor 10 and the cathode conductor 12, respectively. In addition, a battery housing layer 5 is arranged around the outside of the alternating multilayer structure, which can be formed, for example, from aluminum and can be configured to be additionally electrically insulated inwardly. In order to measure the electrode potential of the cathode 8 and the anode 6 of the battery cell 2, two terminal lugs (Anschlussfahne) 15 are also led out of the battery cell 2, which are electrically connected to the anode layer 6 or the cathode layer 8, respectively.

[0037] Figure 2 A schematic partial view of a known battery cell 2 is shown in cross section.

[0038] In particular, a part of the alternately constructed multilayer structure consisting of anode 6, separator layer 4, cathode 8 and separator layer 4 can be seen from this cross-sectional view. As can also be seen, the anode 6 is each constructed from an anode conductor 10, which is coated on both sides with a layer 14 consisting of an anode active material, while the cathode 8 has a cathode conductor 12, which is coated on both sides with a layer 16 consisting of a cathode active material. Obviously, the battery cell 2 can also include elements (not shown in this view), such as, for example, a battery housing layer 5 or further anodes 6, cathodes 8 and separator layers 4.

[0039] Figure 3 A schematic diagram of a battery cell according to the invention is shown in cross section according to a first exemplary embodiment.

[0040] Here, the battery cell 2 comprises a plurality of anodes 6 of layered construction, a plurality of cathodes 8 of layered construction, and a plurality of separator layers 4 for electrically insulating the anodes 6 and cathodes 8, wherein the anode 6 comprises a centrally arranged anode conductor 10 and a coating 14 with an anode active material arranged on both sides to the anode conductor 10, and the cathode 8 comprises a centrally arranged cathode conductor 12 and a coating 16 with a cathode active material arranged on both sides to the cathode conductor 12. In addition to the anodes 6 and cathodes 8 coated on both sides, the battery cell 2 according to the invention comprises in the present case a pair of a first and a second anode 6' coated on one side, which are arranged adjacent to one another on their uncoated sides such that a gap 18 is formed between adjacent adjacent uncoated sides of the anode 6' for introducing a starter element 20 for starting a short circuit between the anode 6' coated on one side and the adjacent cathode 8 coated on both sides. It is also obvious here that the battery cell 2 can also comprise elements (not shown in this view), such as, for example, battery housing layers 5 or further anodes 6, 6', cathodes 8, 8' and separator layers 4.

[0041] According to the present exemplary embodiment, the anode conductor element 10 and the cathode conductor element 12 are designed in the form of metal plates which are arranged substantially in a plane-parallel to the separator layer 4 adjoining the anode 6 and the cathode 8 .

[0042] In view of efficient conduction and absorption of electrons and preferably a cost-effective embodiment, the anode conductor element 10 is currently formed from a copper material and the cathode conductor element 12 is formed from an aluminum material.

[0043] Figure 4a According to a first exemplary embodiment, a schematic diagram of a detail of a battery cell 2 according to the invention is shown in cross section.

[0044] According to Figure 4a , in which only two anodes 6', which are arranged opposite one another and are coated on one side, are shown, each of which has a layer 14' of an anode active material and an anode conductor 10. The two anodes 6' are arranged relative to one another in such a way that a gap 18 is arranged between the anodes 6' for arranging a starting element 20 for starting a short circuit between the anode 6' coated on one side and the adjacent cathode 8 coated on both sides (not shown here).

[0045] The starting element 20 is here presently formed in the form of a deformation element for deforming the adjacent anode 6' coated on one side, which presses the adjacent electrode 6' against the corresponding counter-electrode 8 in order to increase the current density at the interface between the electrodes 6', 8 and thus promote dendrite growth. In order to further support the generation of the short circuit, the starting element 20 can, for example, change its shape, preferably increase its volume. The starting element 20 can here, for example, have different shapes, sizes and distributions in order to generate different numbers and sizes of areas for the internal short circuit.

[0046] With a view to achieving the most efficient possible deformation of the adjacent anode 6 ′ and / or cathode 8 ′ coated on one side, the starter element 20 can be formed from a metallic material or a plastic, wherein the starter element 20 can preferably be as difficult or more difficult to compress than the separator layer 4 .

[0047] In the context of particularly rapid short-circuit starting, it can also be provided alternatively or additionally that additional elements for compressing the anode 6' or cathode 8' are introduced into the coating 14', 16' on one side of the anode 6' and / or cathode 8'. In this way, the anode 6' and / or cathode 8' coated on one side can be bonded with active material, for example with thinner metal parts, etc., before coating, in order to compress the electrode 6', 8' in the subsequent coating, so that the "lithium plating" (in the case of a battery cell designed as a lithium-ion battery) is used more and more intensively.

[0048] Figure 4b According to a second exemplary embodiment, a schematic diagram of a detail of a battery cell according to the invention is shown in a sectional view.

[0049] According to this second embodiment, the starter element 20 is designed in the form of a heating element, which, like the deformation element, can also be responsible for locally increasing the lithium ion concentration and thus promoting the formation of one or more dendrites, which ultimately generate a short circuit between the anode 6 ′ and the adjacent cathode 8. In addition to the deformation element and the heating element, the starter element 20 can be designed as an explosion element and / or a storage element for releasing material and / or a coil and / or a permanent magnet and / or a ferromagnetic material for generating a magnetic field.

[0050] In order to minimize the structural complexity when introducing the starter element 20, the starter element can be as shown in Figure 4a , as shown in FIG. 2b, it is only partially arranged in the gap 18 for introducing the starting element 20.

[0051] It is likewise conceivable, however, that the starting element 20 completely fills the gap 18 for the introduction of the starting element 20 .

[0052] Furthermore, the actuating element 20 can also be formed in multiple parts and, for example, as a deformation element, which has a first part, for example, formed in the form of a metal spike and additionally comprises a second part, which is formed, for example, from plastic and preferably fills the remaining free space around the metal spike.

[0053] As part of a remote targeted control, it is likewise conceivable that the activation element 20 can be externally actuated, wherein the actuation preferably takes place via direct wiring or by radio.

[0054] Figure 5The schematic diagram shows the individual steps of the method according to the invention for carrying out a safety test, in particular using a battery cell 2 according to the invention.

[0055] The method according to the invention comprises the following steps: issuing 30 a switching signal for activating a starting element 20, which is arranged in a gap 18 between two adjacent uncoated surfaces adjacent to each other of a pair consisting of anodes 6' coated on one side and / or a pair consisting of cathodes 8' coated on one side; receiving 32 a control signal via the starting element 20; and activating 34 the starting element 20 in order to cause an electrical short circuit between the anodes 6' and / or cathodes 8' coated on one side and the adjacent anodes 6 and / or cathodes 8 coated on both sides.

[0056] With the battery cell 2 according to the invention, the system 1 according to the invention and the method according to the invention for carrying out a safety test, it is particularly possible to generate a short circuit between the anode 6 and the cathode 8 in the battery cell 2 in a targeted manner by means of the design according to the invention, which provides particularly convincing information about the real short-circuit behavior of the battery cell due to its particularly realistic imitation of the natural short-circuit behavior of the battery cell. With the information obtained in this way, it is particularly possible to introduce safety measures for the use of the battery cell in an effective and targeted manner.

[0057] Reference Symbols List

[0058] 1 System for performing safety testing

[0059] 2 Battery cells for safety testing

[0060] 4. Partition layer

[0061] 6 Anodes coated on both sides

[0062] 6' Anode coated on one side

[0063] 8 Cathode coated on both sides

[0064] 8' Cathode coated on one side

[0065] 10 Anode conductor

[0066] 12 Cathode conductor

[0067] 14 Anode active material coating on double-sided coated anodes

[0068] 14' Anode active material coating on a single-sided coated anode

[0069] 15 Lug

[0070] 16. Cathode active material coating on double-sided coated cathode

[0071] 16' Cathode active material coating on a single-sided coated cathode

[0072] 18 Gap

[0073] 20 Starter element

[0074] 30 Switching signal issuance

[0075] 32 Receiving switch signals

[0076] 34 Activation of the starter element

Claims

1. A battery cell (2) for performing a safety test, comprising: - a plurality of anodes (6) of layered construction, - a cathode (8) having a multi-layer structure, - a plurality of separator layers (4) for electrically insulating the anode (6) and the cathode (8), - wherein the anode (6) has a centrally arranged anode conductor (10) and a coating (14) with an anode active material arranged on both sides of the anode conductor (10), - wherein the cathode (8) has a centrally arranged cathode conductor (12) and a coating (16) with cathode active material arranged on both sides of the cathode conductor (12), It is characterized in that At least a pair of first and second anodes (6') coated on one side and / or a pair of first and second cathodes (8') coated on one side are provided, wherein the pair of first and second anodes (6') coated on one side and / or the pair of first and second cathodes (8') coated on one side are arranged adjacent to each other on their uncoated sides in such a way that a gap (18) is formed between adjacent uncoated sides of the anodes (6') and / or cathodes (8') adjacent to each other for introducing a starter element (20) for starting a short circuit between the anodes (6') and / or cathodes (8') coated on one side and the adjacent anodes (6) and / or cathodes (8) coated on both sides.

2. The battery unit (2) according to claim 1, characterized in that: The actuation element (20) is designed as a deformation element for deforming an adjacent anode (6') and / or cathode (8') coated on one side.

3. The battery cell (2) according to claim 1 or 2, characterized in that: The actuating element (20) is arranged partially in the gap (18) for introducing the actuating element (20).

4. The battery cell (2) according to claim 1 or 2, characterized in that: The starting element (20) completely fills the gap for introducing the starting element (20).

5. The battery unit (2) according to claim 1 or 2, characterized in that: The actuating element (20) is formed of a metallic material or a plastic, wherein the actuating element can be as difficult or more difficult to compress than the separator layer (4).

6. The battery unit (2) according to claim 1 or 2, characterized in that: The actuating element (20) is formed in multiple parts.

7. The battery unit (2) according to claim 1 or 2, characterized in that: The activation element (20) can be externally activated, wherein the activation takes place via direct wiring or by radio.

8. The battery unit (2) according to claim 1 or 2, characterized in that: The activation element (20) is formed as a heating element and / or a deformation element for volume or shape change and / or an explosion element and / or a storage element for releasing material and / or a coil for generating a magnetic field and / or a permanent magnet and / or a ferromagnetic material.

9. A system (1) for performing safety testing by generating a short circuit between an anode (6') and / or cathode (8') coated on one side and an adjacent anode (6) and / or cathode (8) coated on both sides of a battery cell (2), comprising: - A battery cell (2) according to any one of claims 1 to 8, - A control device for actuating the activation element (20).

10. A method for performing a safety test when using a battery cell (2) according to any one of claims 1 to 8, comprising the following steps: - issuing (30) a control signal for activating a starter element (20) which is arranged in a gap (18) between two adjacent uncoated surfaces of a pair of anodes (6') coated on one side and / or a pair of cathodes (8') coated on one side, - receiving (32) said control signal via said activation element (20), - activating (34) the starter element (20) in order to produce an electrical short circuit between an anode (6') and / or cathode (8') coated on one side and an adjacent anode (6) and / or cathode (8) coated on both sides.

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