Method for the permanent closing of holes with overpressure protection and adhesive element for the method

Abstract

The invention relates to a method for closing a through cut-out (10) in a battery cell (12), comprising the following method steps: a) producing or providing an adhesive element (14), comprising: i) an adhesive layer (16) comprising an adhesive compound, ii) a carrier layer (18), arranged on the adhesive layer (16), comprising a first carrier ply (19), and b) adhesively bonding the adhesive element (14) by means of the adhesive layer (16) to the battery cell (12) such that the adhesive element (14) completely covers the through cut-out (10) and the through cut-out (10) is closed in a fluid-tight manner by the adhesive element (14), wherein the adhesive element (14) comprises a pressure opening region (20) which is at least partially surrounded by a weakened region (22) formed in the carrier layer (18), wherein the average thickness of the carrier layer (18) in the weakened region (22) is smaller than the average thickness of the carrier layer (18) in the pressure opening region (20), wherein the adhesive element (14) is configured such that the action of a predefined opening pressure on the pressure opening region (20) at least partially irreversibly destroys the adhesive element (14) in the weakened region (22) and forms a through hole (24) in the adhesive element (14), and wherein the adhesive element (14) is adhesively bonded such that the pressure opening region (20) at least partially covers the through cut-out (10) in the battery cell (12).

Description

Method for permanently closing holes with overpressure protection and adhesive element for the method The invention relates to a method for closing a continuous recess in a battery cell. When manufacturing complex products, it is often necessary to provide holes in the processed components and substrates for manufacturing reasons. These holes allow further processing steps to be carried out during the manufacturing process, for example, by providing access to an interior space where additional components are to be arranged. However, at the end of the manufacturing process, these holes are often no longer required and are even detrimental for numerous end applications, for example, because they allow the ingress of moisture or contaminants.For this purpose, it is known in the prior art to permanently close corresponding through-holes in substrates during production, wherein in particular the use of adhesive elements, for example so-called die cuts, represents an efficient possibility for permanently closing holes, as disclosed for example in EP 3569406 A1, EP 3943283 A1 or EP 3992259 A1. In many cases, however, continuous recesses in the substrate serve more than just manufacturing purposes. Rather, it may be necessary to control the pressure inside substrates, such as battery casings or battery cells. Suitable pressure regulation devices, such as valves, must be provided in the area of ​​the continuous recesses for the necessary pressure management. So-called overpressure protection devices, sometimes also referred to as "burst systems," are of particular importance in the area of ​​pressure management inside substrates. Such overpressure protection devices, which are usually more complex in design, serve, for example, to protect the installed components in electronic devices and enable pressure equalization with the environment by releasing the excess pressure through venting. Corresponding overpressure protection devices are particularly relevant for battery housings or battery cells, such as those used today in the field of electromobility, for example. These battery housings contain the components of the electrochemical cells. The electrochemical cells serve to electrochemically store and generate energy and are available, for example, in the form of so-called pouch cells, cylindrical, or prismatic cells. Such electrochemical cells, such as lithium-ion batteries, represent complex and, in some cases, failure-prone systems, particularly since they often contain flammable substances, especially electrolytes, and high temperatures can occur during operation. The pouch cell has the advantage of being virtually infinitely variable in geometry and highly scalable in size. The so-called "coffee bag cell" is also relatively simple to manufacture compared to other cell types, but requires significantly more effort at the module level for reliable operation. Currently the second most common cell design in automotive engineering, it is characterized by good temperature dissipation and simple energy management. This is made possible by the free positioning of the cell conductors and the electrode stacking (anode on cathode, separated by a separator). The prismatic cell typically consists of stacked anode and cathode packages, known as a cell stack. The rigid metallic housing format offers space-saving advantages when packaging the cells into modules. Although the production of the prismatic cell housing is more complex, it offers high safety and energy density at the module level. The prismatic cell is characterized by a nearly perfect combination of energy density and safety with a long service life. It is currently the most common cell format in electric cars. The cylindrical cell is a proven technology in battery manufacturing. Due to its design, this cell type has a limited maximum charge capacity. Therefore, many cells are required for high performance. Unlike the commonly stacked prismatic cells or pouch cells, cylindrical cells consist of only one anode and cathode, which are wound into a cylindrical roll separated by a separator. As a result, in the worst case, batteries can experience what is known as thermal runaway. In the course of such a thermal runaway, the released gases or the evaporation of liquid components often lead to a strong buildup of pressure inside the battery cells, which can lead to uncontrolled destruction of the battery casing, which in turn can damage surrounding battery cells, resulting in an unwanted chain reaction in the worst case. For this reason, high-performance pressure relief devices for battery housings and battery cells are particularly important for safety. The increasing relevance of electromobility in the automotive industry and the growing use of electrochemical energy storage systems are leading to a constant interest in improving pressure relief devices that are particularly suitable for use with battery housings and battery cells. A prior art overpressure relief device is disclosed, for example, in CN 107178638 A. Prior art overpressure relief devices are often technically complex components that typically require significant manufacturing effort to fit into the continuous recesses of the substrates. They also exhibit a comparatively high weight and a certain volume. Furthermore, corresponding prior art bursting systems often have to be specifically designed for certain hole geometries and, in many cases, are not flexibly adaptable to different dimensions of the holes to be sealed. The primary object of the present invention was to eliminate or at least reduce the disadvantages of the prior art. In particular, it was the object of the present invention to provide a method for closing a continuous recess in a battery cell, which method enables a reliable and fluid-tight closure of the continuous recesses, but which, as a result of an overpressure, enables a reliable pressure reduction by venting. It was an object of the present invention that the method to be specified should be feasible using components that require the smallest possible installation space and have a low dead weight. In addition, it was an object of the present invention that the closing of the through-holes should be particularly easy in the method to be specified, wherein easy automation should desirably be ensured. It was a further object of the present invention that the method to be specified should be particularly time- and cost-efficient to carry out, in particular with high throughput rates, wherein the storage costs associated with the storage of the components to be used in the method should also be as low as possible. It was a supplementary object of the present invention that the method to be specified should be particularly flexible for closing through-holes with different hole geometries due to the components to be used and ideally should not require any specific adaptation of the components used for different hole geometries. In light of the above, it was an object of the present invention to provide a pressure-protected battery cell produced by the method to be specified. Furthermore, it was an object of the present invention to provide a component for permanently closing holes with overpressure protection, which can be used in the method to be specified and also to provide a use based thereon. The inventors of the present invention have now found that the objects described above can surprisingly be achieved if, instead of complex, constructive bursting systems for closing through-holes in battery cells, specific adhesive elements are used with which the through-hole can be glued over in a fluid-tight manner, but which, due to a weakening in the carrier layer, comprise a pressure opening region which, due to a predetermined opening pressure, breaks open largely irreversibly, so that pressure equalization can take place through the resulting through-hole in the adhesive element, as defined in the claims. Surprisingly, this design of adhesive elements and their use in corresponding processes not only enables a reliable and fluid-tight closure of This not only allows for continuous recesses in battery cells, but also allows for reliable opening behavior due to overpressure, which can be precisely adjusted by varying the extent of the weakening of the carrier layer. The inventors have found that the comparatively simple design of the adhesive element and its easy application result in a particularly advantageous process. The corresponding adhesive elements are not only particularly easy to automate and cost-effective to produce, but also have a particularly low weight and volume. Advantageously, the corresponding adhesive elements and thus the corresponding process have a high tolerance for deviations in the hole geometry, allowing manufacturing tolerances to be reduced and the adhesive elements used to seal continuous recesses of different dimensions. The above-mentioned objects are thus achieved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements. Such embodiments, which are designated as preferred below, are combined in particularly preferred embodiments with features of other embodiments designated as preferred. Combinations of two or more of the embodiments designated as particularly preferred below are thus particularly preferred. Likewise preferred are embodiments in which a feature of one embodiment designated as preferred to any extent is combined with one or more further features of other embodiments designated as preferred to any extent. The invention relates to a method for closing a continuous recess in a battery cell, comprising the method steps: a) producing or providing an adhesive element, comprising: i) an adhesive layer comprising an adhesive mass, ii) a carrier layer arranged on the adhesive layer, comprising a first carrier layer, and b) Adhering the adhesive element to the battery cell by means of the adhesive layer such that the adhesive element completely covers the continuous recess and the continuous recess is closed in a fluid-tight manner by the adhesive element, wherein the adhesive element comprises a pressure opening region which is at least partially surrounded by a weakened region formed in the carrier layer, wherein the average thickness of the carrier layer in the weakened region is smaller than the average thickness of the carrier layer in the pressure opening region, wherein the adhesive element is designed such that the action of a predetermined opening pressure on the pressure opening region at least partially irreversibly destroys the adhesive element in the weakened region and forms a through-hole in the adhesive element, and wherein the adhering of the adhesive element takes place such that the pressure opening region at least partially covers the continuous recess in the battery cell. The method according to the invention serves for sealing, in particular the fluid-tight sealing of through-holes in battery cells, in particular holes, and is particularly relevant in practice for sealing holes through which an interior space in the battery cell is fluidly connected to the environment. Accordingly, a method according to the invention is preferred, wherein the battery cell comprises an interior space which is fluid-tightly sealed by adhering the adhesive element to the through-hole. The recess, also referred to as an opening or hole, is preferably circular; alternatively, the recess has the shape of an elongated hole, i.e., an elongated opening whose narrow sides are closed by semicircles whose diameters correspond to the width of the elongated hole. The long sides of the elongated hole run parallel to each other. However, other shapes such as ovals or ellipses are also possible. The method according to the invention is particularly suitable for use in the closure of battery cells, since in many cases, due to the high number of individual elements, these cells particularly benefit from the low weight and low manufacturing costs of the solution found within the scope of the present invention. Additionally or alternatively, a method according to the invention is also preferred, wherein the battery cell comprises one or more materials selected from the group consisting of metals, composite materials, for example, comprising glass or carbon fibers, and plastics. preferably plastics and metals, particularly preferably metals such as aluminum, especially coated metals. A person skilled in the art will understand that a battery cell may also comprise more than one continuous recess, but that in this case, it is preferred if all of the recesses are closed using the method according to the invention. Alternatively, the continuous recesses present in the battery cell could also be partially closed using the method according to the invention and partially closed using other methods, for example, using conventional adhesive elements without overpressure protection. Accordingly, a method according to the invention is preferred, wherein the battery cell comprises two or more continuous recesses, wherein preferably all of the continuous recesses are closed using the method. The adhesive element to be used in the method according to the invention is, in accordance with the understanding of a person skilled in the art, a flat adhesive element, i.e. it has a significantly greater extent in the two spatial directions of a plane than in the direction orthogonal to the plane. Such adhesive elements can be produced, for example, using methods that are well known to those skilled in the art and that are also used, for example, in the production of other adhesive elements. Typically, such flat adhesive elements are separated from a larger adhesive composite using a suitable cutting process, which was previously produced, so that the adhesive elements are available in large quantities. The separation can be carried out, for example, by punching out the adhesive elements, in which cases they are usually referred to as a diecut.Thus, a method according to the invention is preferred, wherein the adhesive element is produced by punching the adhesive element out of an adhesive composite comprising an adhesive layer and a carrier layer arranged on the adhesive layer, wherein the weakened region is preferably created before punching. A method according to the invention is particularly preferred in this respect, wherein the adhesive element is a die-cut product. As an alternative to the production of the adhesive elements in the process, for example by punching, these can also be simply provided in the process according to the invention, for example by purchasing them from a supplier. The adhesive elements used comprise an adhesive layer and a carrier layer, which are connected to each other, as is known to the expert in the field of adhesive technology from many Adhesive tapes and similar adhesive products. The adhesive layer serves to adhere the adhesive element to the substrate and ensures the necessary adhesion of the adhesive element to the substrate to prevent unwanted, premature detachment in the event of relatively low pressure differences between the two sides of the substrate or under other mechanical stress. The adhesive can be applied to the entire surface of the carrier layer. Preferably, the adhesive is applied to the carrier layer in such a way that adhesive is applied only to the areas of the carrier layer that extend beyond the perimeter of the hole. For a circular hole, the adhesive would then be in the form of a ring on the carrier layer. With a view to achieving the most efficient process possible, which in particular enables particularly easy application of the adhesive elements, but also allows for easy correction of imperfect application if necessary, the inventors propose implementing the adhesive as a pressure-sensitive adhesive. Accordingly, a process according to the invention is preferred, wherein the adhesive is a pressure-sensitive adhesive. According to expert understanding, a pressure-sensitive adhesive is an adhesive that possesses pressure-sensitive adhesive properties, i.e., the ability to form a permanent bond to a substrate even under relatively light pressure. Such pressure-sensitive adhesive tapes are generally permanently tacky even at room temperature, meaning they exhibit a certain viscosity and tackiness, allowing them to wet the surface of a substrate even under light pressure. Without wishing to be bound by this theory, it is often assumed that a pressure-sensitive adhesive can be considered an extremely viscous liquid with an elastic component, which consequently possesses characteristic viscoelastic properties that lead to the permanent tackiness and pressure-sensitive adhesive capacity described above.It is assumed that with corresponding pressure-sensitive adhesives, mechanical deformation leads to both viscous flow processes and the build-up of elastic restoring forces. The partial viscous flow serves to achieve adhesion, while the partial elastic restoring forces are particularly necessary to achieve cohesion. The relationships between rheology and pressure-sensitive adhesiveness are known in the art and are described, for example, in “Satas, Handbook of Pressure Sensitive Adhesives Technology”, Third Edition, (1999), pages 153 to 203. The storage modulus (G') and the loss modulus (G") are usually used to characterize the degree of elastic and viscous components. These are determined using dynamic mechanical analysis (DMA), for example using a rheometer, as disclosed, for example, in WO 2015 / 189323 A1. In the context of the present invention, an adhesive is preferably understood as pressure-sensitive adhesive and thus as a pressure-sensitive adhesive if, at a temperature of 23 °C in the deformation frequency range of 10° to 10 1 rad / sec G' and G“ each at least partly in the range of 10 3 up to 10 7 Pa lie. As a possible alternative embodiment to the preferred embodiment as a pressure-sensitive adhesive described above, it is conceivable to design the adhesive as a reactive adhesive, i.e. as an adhesive that only cures as a result of a curing step, the resulting curing of the adhesive and its effect as a structural adhesive making this embodiment particularly interesting for applications in which comparatively high predetermined opening pressures are to be set. For certain applications, a method according to the invention is therefore preferred, wherein the adhesive is a curable adhesive, preferably a radiation-curing and / or thermally curing adhesive, the method preferably additionally comprising the following method step after method step b): c) At least partial curing of the curable adhesive. In the inventors' estimation, a major advantage of the process according to the invention is that it is very flexible with regard to the chemical nature of the adhesive used in the adhesive element. According to the inventors' estimation, the fundamental functionality of the process according to the invention arises primarily from the interaction of a specifically weakened carrier layer with a generic adhesive, and is therefore not limited to chemically specific adhesives. This advantageously enables the selection of suitable adhesives in light of the other application requirements, in particular with regard to adhesion to the respective substrate and / or temperature resistance for the intended areas of application. However, the inventors have succeeded in identifying adhesives with which, in their estimation, particularly high-performance adhesive elements can be obtained.A process according to the invention is preferred, wherein the adhesive comprises one or more polymers selected from the group consisting of polyurethanes, poly(meth)acrylates and synthetic rubbers, preferably poly(meth)acrylates and synthetic rubbers, particularly preferably poly(meth)acrylates. In the context of the present invention, the term "poly(meth)acrylates" encompasses, in accordance with the understanding of one skilled in the art, polyacrylates and polymethacrylates as well as copolymers of these polymers. Poly(meth)acrylates may contain minor amounts of monomer units that are not derived from (meth)acrylates. In the context of the present invention, a "poly(meth)acrylate" is understood to mean a copolymer whose monomer base consists of a mass fraction of 70% or more, preferably 90% or more, particularly preferably 98% or more, of monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic esters, and methacrylic esters, based on the mass of the monomer base. The mass fraction of acrylic ester and / or methacrylic ester is preferably 50% or more, particularly preferably 70% or more.Poly(meth)acrylates are generally accessible by radical polymerization of acrylic and / or methacrylic-based monomers and, if appropriate, other copolymerizable monomers. In the inventors' estimation, it is advantageous for certain applications to embody the adhesive as a foamed adhesive, for example, as a syntactically foamed adhesive, which utilizes expanded microballoons, as are generally known from the prior art, or as a physically foamed adhesive, which can be produced, for example, using a propellant gas. Such foamed adhesives often exhibit advantages, particularly with regard to shock resistance. In this respect, it can be considered an advantage of the process according to the invention that, in the inventors' estimation, foaming of the adhesive does not impede the fundamental functionality of the adhesive elements according to the invention.Accordingly, for certain applications, a process according to the invention is preferred, wherein the adhesive is a foamed adhesive, wherein the adhesive is preferably a physically foamed adhesive and / or comprises one or more components selected from the group consisting of hollow spheres and at least partially expanded microballoons. In principle, all conventional activated adhesive systems can be used as activatable adhesives. Activation is usually achieved through the application of energy, for example, actinic radiation, heat, or mechanical energy such as ultrasound or friction. Heat-activated adhesives can generally be divided into two categories: thermoplastic heat-activated adhesives (hot melt adhesives) and reactive heat-activated adhesives (reactive adhesives). This classification also includes adhesives that fit into both categories, namely reactive thermoplastic heat-activated adhesives (reactive hot melt adhesives). Heat-activated adhesives can already be pressure-sensitive at room temperature. Heat activation increases the bond strength. Thermoplastic adhesives are based on polymers that reversibly soften upon heating and solidify again upon cooling. Thermoplastic adhesives based on polyolefins and copolymers of polyolefins and their acid-modified derivatives, ionomers, thermoplastic polyurethanes, polyamides, polyesters and their copolymers, and also block copolymers such as styrene block copolymers have proven particularly advantageous. In contrast, reactive heat-activated adhesives contain reactive components. These components are also referred to as "reactive resins," in which heating initiates a crosslinking process that ensures a permanent, stable bond after the crosslinking reaction is complete. Such adhesives preferably also contain elastic components, such as synthetic nitrile rubbers or styrene block copolymers. Due to their high flow viscosity, such elastic components impart particularly high dimensional stability to the heat-activated adhesive, even under pressure. Radiation-activated adhesives are also based on reactive components. These components can include, for example, polymers or reactive resins in which irradiation initiates a crosslinking process that ensures a permanent, stable bond after the crosslinking reaction is complete. Such adhesives preferably also contain elastic components, as described above. Radiation-activated pressure-sensitive adhesives must be distinguished from radiation-crosslinked pressure-sensitive adhesives, in which the adhesive properties are adjusted during the production of the adhesive tape by means of radiation crosslinking. For pressure-sensitive adhesives, radiation activation occurs during application. After radiation activation, the adhesive is generally no longer tacky. Activated pressure-sensitive adhesive tapes also include pressure-sensitive adhesive tapes composed of two or more adhesive films, as disclosed in DE 10 2013 222 739 A1. These are activated by bringing the two or more adhesive films into contact. A reactive adhesive is defined as an adhesive that cures under external influences, particularly under the influence of moisture or high-energy radiation, to a technically relevant extent or with a significant change in at least one application-related property, thereby achieving bond strengths that significantly exceed those of conventional pressure-sensitive adhesives or conventional pressure-sensitive adhesive tapes. This is particularly evident in lap-shear values. For example, very good pressure-sensitive adhesive tapes achieve values ​​around 1 MPa, and reactive adhesive tapes achieve values ​​in the range of 3 MPa. Preferably, the adhesive is a reactive adhesive with the following composition: (i) at least one reactive component, particularly preferably an epoxy resin, (ii) at least one photoinitiator, (iii) at least one polymer comprising a total of more than 60.0 wt.%, based on the total weight of the reactive adhesive. According to the invention, a reactive component is understood to be an adhesive component that, under the influence of high-energy radiation, in particular UV radiation, crosslinks to form macromolecular structures through a chemical buildup reaction and thus contributes significantly to the curing of the adhesive. In extreme cases, the reactive component causes the curing of the adhesive. Reactive components, also known as reactive resins, differ significantly from adhesive resins commonly used in adhesives, particularly in pressure-sensitive adhesives. According to the general understanding of experts, an "adhesive resin" is understood to be an oligomeric or polymeric resin that only ensures adhesion (the tack, the Intrinsic tack) of the pressure-sensitive adhesive is increased compared to the pressure-sensitive adhesive containing no tackifier resin, but which is otherwise identical. Tackifier resins typically contain no reactive groups other than CC double bonds (“unsaturated resins”), since their properties are not intended to change over the lifetime of the pressure-sensitive adhesive; accordingly, they do not react to form macromolecular structures. Typical tackifier resins are, for example, partially or fully hydrogenated resins based on rosin and rosin derivatives, hydrogenated polymers of dicyclopentadiene, partially, selectively, or fully hydrogenated hydrocarbon resins based on C5, C5 / C9, or C8 monomer streams, polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene and / or α3-carene, hydrogenated polymers of preferably pure C5 and C9 aromatics; Terpene-phenolic resins, rosin resins and adhesive resins based on acrylates and methacrylates.The presentation of the state of knowledge in the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, 1989, Chapter 25 "Tackifier Resins") is expressly referred to. Within the scope of the invention, the reactive component is preferably an oxetane resin, an epoxy resin, or a mixture of these resins; accordingly, the reactive adhesive preferably comprises at least one oxetane resin, an epoxy resin, or a mixture of these resins. An oxetane resin is understood to be a compound that has at least one polymerizable oxetane group per molecule. Correspondingly, an epoxy resin is understood to be a compound that has at least one polymerizable epoxide group per molecule. In particular, the oxetane or epoxide groups are polymerizable via a ring-opening reaction. The resins in question can have one or more oxetane or epoxide groups. Their other structure is fundamentally arbitrary; the resins can be monomeric, oligomeric, or polymeric and can be aliphatic, cycloaliphatic, or aromatic. If the reactive adhesives comprise one or more polymers containing oxetane and / or epoxide groups, in particular one or more such poly(meth)acrylates, these are not considered oxetane or epoxy resins.Polymeric oxetane or epoxy resins differ from these polymers in particular in their molecular weight, as they have a weight-average molecular weight of a maximum of 50,000 g / mol. The reactive component is particularly preferably an epoxy resin; accordingly, the reactive adhesive preferably comprises at least one epoxy resin. The epoxy resin preferably has at least two, more preferably more than two, epoxy groups per molecule. Generally, the average number of epoxy groups per molecule is given, which is the quotient of the total number of epoxy groups in the epoxy resin and the total number of epoxy resin molecules present. The epoxy resin preferably has an average of more than two epoxy groups per molecule. The epoxy resin may comprise linear polymers with terminal epoxy groups, for example diglycidyl ethers of polyoxyalkylene glycols; polymers with backbone oxirane units, for example polybutadiene polyepoxides; and polymers with side epoxy groups, for example glycidyl methacrylate polymers or copolymers with a maximum molecular weight of M w = 50,000 g / mol. The epoxy resin may also comprise materials containing cyclohexene oxide groups, for example epoxycyclohexanecarboxylates such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate. The epoxy resin may also comprise monomeric glycidyl ethers, for example glycidyl ethers of polyhydric phenols obtained by reacting a polyhydric phenol with an excess of chlorohydrin such as epichlorohydrin. The epoxy resin may also contain compounds such as octadecylene oxide, epichlorohydrin, styrene oxide, vinylcyclohexene oxide, glycidol, glycidyl methacrylate, diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, vinylcyclohexene dioxide, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-metadioxane, bis(3,4-epoxycyclohexyl)adipate, dipentene dioxide, epoxidized polybutadiene, epoxysilanes, for example ß-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane; fire-retardant epoxy resins, for example brominated bisphenol-type epoxy resins; 1,4-butanediol diglycidyl ether; hydrogenated bisphenol A-epichlorohydrin-based epoxy resins (such as Epikote 828 LVEL) and polyglycidyl ethers of phenol formaldehyde novolac (such as Araldite ECN 1299). The reactive adhesive preferably comprises at least one cycloaliphatic epoxy resin, in particular selected from the group consisting of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (for example Uvacure 1500 from Dow), 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate. In one embodiment, the reactive adhesive comprises at least one liquid and at least one solid epoxy resin. Particularly preferably, the weight ratio of liquid epoxy resin to solid epoxy resin is 1:3 to 3:1. If several liquid and / or solid epoxy resins are present, this refers to the totality of all liquid or solid epoxy resins. If the reactive adhesive comprises one or more epoxy resins, it preferably contains epoxy resins in a total amount of 18 to 60 wt.%, based on the total weight of the reactive adhesive. In particular, more than 20 wt.% is contained, particularly preferably 20 to 50 wt.%. In a further embodiment of the reactive adhesive tape according to the invention, the reactive component contains at least 10% by weight of epoxy resins that are liquid at 25°C, based on the total weight of the reactive component. The proportion of such liquid epoxy resins in the reactive component is in particular 10 to 90% by weight, more preferably 20 to 75% by weight. Reactive adhesive tapes with such ratios of liquid to solid epoxy components exhibit particularly balanced adhesive properties in the uncured state. If a reactive adhesive tape with particularly good flow properties is desired, the proportion of liquid epoxy resins is preferably 50 to 80% by weight. For applications in which the reactive adhesive tapes must bear a higher load even in the uncured state, a proportion of 15 to 45% by weight is particularly preferred. Either a liquid epoxy resin or a mixture of different liquid epoxy resins can be used. Preferred liquid epoxy resins are bisphenol A diglycidyl ether or bisphenol F diglycidyl ether with dynamic viscosities of less than 30 Pas at 25 °C, for example available from Olin (formerly DOW) under the designation DER 331, 332, 383, 330, 317, 321, 3212, 322, 323, 324, 325, 329, 362, 353, 354; as well as cycloaliphatic epoxy resins such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2- methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexane carboxylate and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate. Preferred solid epoxy resins are bisphenol A diglycidyl ether, for example available from Olin (formerly DOW) under the designation DER 661, 61 16, 662E, 6224, 662UH, 663U, 663UE, 664, 664U, 664UE. Other solid epoxy resins are known based on phenol or cresol novolaks and are marketed, for example, by DIC under the brand name Epiclon (600 series, 700 series and 800 series). According to the invention, the dynamic viscosity is determined using a cylindrical rotational viscometer with a standard geometry according to DIN 53019-1 (2008-09). Viscosity is measured at a temperature of 25 °C and a shear rate of 1 / s. A substance with a viscosity of less than 500 Pas is considered "liquid." More preferably, the reactive component comprises a maximum of 60 wt.% epoxycyclohexyl-based epoxy resins, in particular from 5 to 80 wt.%, more preferably from 15 to 60 wt.%, based on the total weight of the reactive component. The use of liquid epoxycyclohexyl-based resins has a beneficial effect on the adhesive properties of the reactive adhesives in the uncured state, particularly when 10 to 40 wt.% are used. If, however, proportions of 40 to 80 wt.% are used, the high reactivity of the epoxycyclohexyl derivatives allows reactive adhesive tapes to be produced that have an open time of at least 1 minute and then cure very quickly and completely within 24 hours. Epoxycyclohexyl-based epoxy resins can, for example, be selected from the group consisting of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, and bis((3,4-epoxycyclohexyl)methyl)adipate-dicyclopentadiene dioxide, as well as combinations thereof. These compounds are advantageous due to their high reactivity, and very soft reactive adhesive tapes can be produced with them. If stronger adhesive tapes are desired, this can be achieved by using polymers containing epoxycyclohexyl groups, which are obtainable via radical polymerization of 3,4-epoxycyclohexylmethyl methacrylate, optionally with comonomers. The reactive component can have an average functionality of alkylene oxide groups of 1.0 to 6.0, particularly 1.75 to 3.2, which allows high bond strengths to be achieved. The network density can be reduced using reactive diluents, resulting in less brittle adhesives, especially with high reactive component contents. Such reactive diluents typically have a functionality of 1.0. In one embodiment, the reactive adhesive comprises at least two different epoxy resins B1 and B2, wherein • the epoxy resin B1 has a dynamic viscosity of less than 500 Pa*s at 25 °C, measured according to DIN 53019-1 at a measuring temperature of 25 °C and a shear rate of 1 / s, and • the epoxy resin B2 has a softening temperature of at least 45 °C or a dynamic viscosity of at least 1000 Pa*s at 25 °C, measured according to DIN 53019-1 at a measurement temperature of 25 °C and a shear rate of 1 / s, each measured using a cylindrical rotational viscometer with a standard geometry. The proportion of epoxy resin B1 is preferably 10 to 90 wt.%, particularly preferably 20 to 75 wt.%, and the proportion of epoxy resin B2 is 10 to 90 wt.%, preferably 25 to 80 wt.%, each based on the total weight of the reactive component. The molecular weight of the epoxy-containing material can vary from 58 to 50,000 g / mol. A photoinitiator is understood to be a compound that can initiate a chemical reaction under the influence of high-energy radiation. The photoinitiator is preferably a UV initiator. UV initiators are generally known to those skilled in the art. The photoinitiator is particularly preferably a UV initiator for cationic curing. The photoinitiator is most preferably a sulfonium-, iodonium-, or metallocene-based photoinitiator. The reactive adhesive may comprise one or more photoinitiators. The reactive adhesive, if it comprises one or more photoinitiators, preferably contains photoinitiators in a total amount of 0.05 to 3, more preferably 0.1 to 1.5, in particular 0.4 to 1.3 wt.%, based on the total weight of the reactive adhesive. Such an adhesive is disclosed, for example, in WO 2023 / 274875 A1. Thermally curing adhesives, also referred to as heat-activated adhesives (hereinafter referred to for short, but with the same meaning, as "heat-activated adhesives"), are adhesives that are activated by the application of thermal energy (usually when a certain activation temperature is exceeded) and are applied in this state. A distinction must be made between two systems when it comes to bonding: Thermoplastic heat-activated adhesive systems (hot melt adhesives) set physically upon cooling (usually reversibly), while reactive heat-activated adhesive systems (reactive systems) set chemically (usually irreversibly). Mixed systems also exist, i.e., adhesives that can be assigned to both categories: reactive thermoplastic heat-activated adhesives (reactive hot melt adhesives). The activation temperature of heat-activated adhesives can be determined by DSC measurement, whereby the activation temperature of thermoplastic systems is considered to be the melting point, i.e. the temperature TSP of the peak extreme value of the melting process (measurement by means of dynamic differential calorimetry (DSC) according to DIN 53765:1994-03 on a 50 g sample, heating rate 10 °C / min) and for reactive systems the temperature T RP the peak extreme value of the corresponding curing reaction (measurement by means of differential scanning calorimetry (DSC) according to DIN 53765:1994-03 on a 50 g sample, heating rate 10 °C / min). Heat-activated adhesives may exhibit a certain degree of tack at room temperature, but this is not necessary to achieve bonding. Thermoplastic adhesives are based on polymers that reversibly soften upon heating and solidify again upon cooling. In contrast, reactive heat-activated adhesives contain reactive components. These latter components are also referred to as "reactive resins," in which heating initiates a curing process that, once the curing reaction is complete, ensures a permanent, stable bond, even under pressure. Therefore, so-called hardeners are often present that can react with the reactive resins. Preferably, such heat-activated adhesives also contain elastic components, for example, synthetic nitrile rubbers. Such elastic components impart the heat-activated adhesive Due to their high flow viscosity, they have particularly high dimensional stability even under pressure during application. In principle, all heat-activated adhesive systems can be used as heat-activated adhesives, including thermoplastic heat-activated systems, reactive systems, and mixed systems. In particular, systems that do not exhibit any inherent tack at room temperature can also be used. If systems are selected that exhibit inherent tack at room temperature and / or below the activation temperature, the adhesive film can be pre-positioned on the substrate surface to be bonded, for example, by activating the heat-activated adhesive prior to the actual bonding. The following describes, purely by way of example and without intending to limit the teachings of the invention, some typical systems of heat-activated adhesives that have proven particularly advantageous in connection with the present invention. Such adhesives are disclosed, for example, in WO 2013 / 020765 A1. A thermoplastic heat-activated adhesive contains a thermoplastic base polymer. This polymer exhibits good flow behavior even at low contact pressure, so that the final bond strength, which is relevant for the durability of a permanent bond, is achieved within a short contact time, thus enabling rapid bonding even on rough or otherwise critical substrates. All known thermoplastic adhesives can be used as thermoplastic heat-activated adhesives. Exemplary compositions are described, for example, in EP 1 475 424 A1. For example, the thermoplastic adhesive can contain one or more of the following components or even consist of them: polyolefins and their copolymers, for example ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, polyamides and their copolymers, polyesters and their copolymers, polyurethanes, or styrene block copolymers. Preference is given to those described in paragraph

[0027] The thermoplastic adhesives listed in EP 1 475 424 A1 are used. Other thermoplastic adhesives, which are particularly suitable for special applications such as the bonding of Particularly suitable adhesives for bonding glass substrates are described in EP 1 956 063 A2. Thermoplastic adhesives whose melt viscosity is increased by rheological additives, for example, by adding fumed silica, carbon black, carbon nanotubes, and / or other polymers as blending components, are preferred. This viscosity-increasing function is also performed synergistically by the filler of the invention. A reactive heat-activated adhesive, on the other hand, advantageously comprises an elastomeric base polymer and a modifying resin, wherein the modifying resin comprises an adhesive resin and / or a reactive resin. The use of an elastomeric base polymer makes it possible to obtain adhesive layers with excellent dimensional stability. Depending on the specific application, all heat-activated adhesives known from the prior art can be used as reactive heat-activated adhesives. This includes, for example, reactive heat-activated adhesive films based on nitrile rubber or its derivatives, such as nitrile butadiene rubber, or blends of these base polymers that additionally contain reactive resins, such as phenolic resins; one such product is commercially available under the name tesa 8401. The nitrile rubber imparts pronounced dimensional stability to the heat-activated adhesive film due to its high flow viscosity, which allows for high adhesive strengths on plastic surfaces after a crosslinking reaction. Furthermore, other reactive heat-activated adhesive compositions can also be used, such as adhesive compositions containing a bondable polymer in a mass fraction of 50 to 95 wt.% and an epoxy resin or a mixture of several epoxy resins in a mass fraction of 5 to 50 wt.%. The bondable polymer advantageously contains 40 to 94 wt.% acrylic acid compounds and / or methacrylic acid compounds of the general formula CH2=C(R 1 )(COOR 2 ) (R 1 represents a radical selected from the group comprising H and CH3, and R 2represents a radical selected from the group comprising H and linear or branched alkyl chains having 1 to 30 carbon atoms), 5 to 30 wt.% of a first copolymerizable vinyl monomer having at least one acid group, in particular a carboxylic acid group and / or sulfonic acid group and / or phosphonic acid group, 1 to 10 wt.% of a second copolymerizable vinyl monomer having at least one epoxide group or an acid anhydride function, and 0 to 20 wt.% of a third A copolymerizable vinyl monomer having at least one functional group that differs from the functional group of the first copolymerizable vinyl monomer and the functional group of the second copolymerizable vinyl monomer. Such an adhesive enables bonding with rapid activation, with the final bond strength being achieved within a short time, thus ensuring a strong bond on a non-polar substrate. Another usable reactive heat-activated adhesive that offers particular advantages contains 40 to 98 wt.% of an acrylate-containing block copolymer, 2 to 50 wt.% of a resin component, and 0 to 10 wt.% of a hardener component. The resin component contains one or more resins selected from the group comprising adhesive strength-enhancing (tackifying) epoxy resins, novolak resins, and phenolic resins. The hardener component is used to crosslink the resins from the resin component. Due to the strong physical crosslinking within the polymer, this type of formulation offers the particular advantage of allowing adhesive layers with a greater overall thickness to be achieved without compromising the overall strength of the bond. This makes these adhesive layers particularly suitable for compensating for unevenness in the substrate.In addition, such an adhesive has good aging resistance and only low outgassing behavior. Further advantageous embodiments of the heat-activatable adhesives can be found in EP 2 607 439 A1 or WO 2008 / 020036 A1 . Since the invention is also intended in particular for use in battery cells, the adhesive should also be compatible with the electrolyte solutions found in electrochemical cells; water-based acrylate adhesives are particularly suitable for this purpose. With a view to achieving the most material-saving production and good handling properties, the inventors propose that the dimensions of the adhesive layer and the carrier layer should be as similar as possible. Even if it may be preferable for some applications to have the carrier layer protrude beyond the adhesive layer, it is particularly preferred with regard to production efficiency if the latter is completely covered by the adhesive layer. Thus, a method according to the invention is preferred, wherein the carrier layer is 50% or more, preferably 70%, of the adhesive layer on one side. or more, particularly preferably 90% or more, most preferably 95% or more, particularly preferably substantially completely covered by the adhesive layer. According to the invention, the carrier layer comprises a first carrier layer, wherein in practice the carrier layer will in many cases consist essentially of this carrier layer. Also relevant for most embodiments is a method according to the invention wherein the adhesive layer is arranged on the first carrier layer. It can be seen as an advantage that the method according to the invention is fundamentally very flexible with regard to the material selection of the first carrier layer and that the person skilled in the art can resort to typical materials which are already known as carrier materials in the field of adhesive technology. In this respect, however, the inventors have succeeded in identifying suitable materials with which very reliable and high-performance adhesive elements can be obtained for use in the method according to the invention. Preference is given to a method according to the invention in which the first carrier layer comprises a film selected from the group consisting of plastic films, for example polyester films, PEEK films, PAEK films, polyimide films or polyamide films, in particular polyester films, and metal foils, preferably metal foils. Preference is given to a method according to the invention additionally or alternatively. Particularly for more demanding applications, for example, where the adhesive closure is expected to be subjected to significant thermal and / or chemical and / or mechanical stress during use, it is possible for the carrier layer to comprise, in addition to the first carrier layer, additional carrier layers that serve, for example, to optimize the physicochemical properties, in particular the surface properties. A preferred method according to the invention is one in which the carrier layer comprises one or more, particularly preferably two or more, additional carrier layers, wherein the carrier layers of the carrier layer are preferably bonded to one another by intermediate adhesive layers. According to the inventors' assessment, a particularly preferred embodiment is one in which the carrier layer comprises a protective film as an additional layer, which shields the underlying carrier layers, in particular the first carrier layer, from environmental influences and is particularly advantageous when the first carrier layer is made of metal, since this can prevent unwanted corrosion and any resulting damage to the first carrier layer in the long term. A method according to the invention is preferred, wherein the carrier layer as a further Carrier layer comprises a protective film on the side of the first carrier layer facing away from the adhesive layer, wherein the protective film is preferably selected from the group consisting of plastic films, wherein the protective film particularly preferably substantially completely covers the surface of the carrier layer. According to the invention, the through-hole is completely covered with the corresponding adhesive elements and thus sealed in a fluid-tight manner. Those skilled in the art will understand that this type of overpressure protection, which is explained in more detail below, means that this fluid-tight seal can be broken open as a result of the application of pressure. For this purpose, a weakened area is provided in the adhesive element according to the invention, in which the average thickness of the carrier layer is reduced compared to the rest of the adhesive element, so that the carrier layer has a reduced mechanical load-bearing capacity in the weakened area and thus represents a type of predetermined breaking point in the carrier layer. Advantageously, the predetermined opening pressure, i.e. the pressure as a result of which the overpressure protection is intended to take effect, can be adjusted by the extent to which the weakened area is reduced.A method according to the invention is preferred, wherein the carrier layer in the weakened region has an average thickness in the range from 5 to 250 pm, preferably in the range from 20 to 200 pm, particularly preferably in the range from 30 to 150 pm, and / or wherein the average thickness of the carrier layer in the weakened region is 2 to 95%, preferably 5 to 80%, particularly preferably 5 to 60% smaller than the average thickness of the carrier layer in the pressure opening region. Those skilled in the art will therefore understand that the adhesive element is designed to form a through-hole as a result of the action of a predetermined opening pressure on the pressure opening area. In accordance with the understanding of those skilled in the art, this action of a predetermined opening pressure refers to a pressure difference between the two sides of the adhesive element, as occurs, for example, when the adhesive element covers a recess in an otherwise closed vessel and an increase in pressure occurs inside the vessel. Those skilled in the art will understand that the predetermined opening pressure does not refer to the ambient pressure, which is experienced equally by all sides and areas of the adhesive element, so that no force is exerted on the pressure opening area relative to the rest of the adhesive element. In other words, the predetermined opening pressure thus refers to an opening pressure difference. The term "at least partially irreversibly destroyed" used in the context of the present invention means, in accordance with the expert understanding, that complete destruction of the weakened area is not necessary, as long as the destruction is sufficient to form a through-hole in the adhesive element. For example, a circular weakened area that completely surrounds a pressure opening area could be destroyed only over part of its circumference as a result of the predetermined opening pressure, so that the pressure opening area is only partially released from the adhesive element. Likewise, the destruction does not have to be completely irreversible.Due to the physico-chemical properties of typical adhesives, in particular their flow behavior, it would be at least theoretically conceivable that a pressure opening area pressed back into the adhesive element could, despite the irreversibly destroyed carrier layer, be at least provisionally closed via the interaction of the adhesive in such a way that the raised pressure opening area is held in position by the adhesive layer. Even though it is theoretically conceivable to provide larger, flatter areas of reduced thickness, and such more complex weakened areas may be useful for specific applications, the inventors believe that, with a view to precisely opening the weakened area while simultaneously simplifying production, it is preferable to form it essentially as a groove-shaped recess, i.e., as an elongated depression, in the carrier layer. Accordingly, a method according to the invention is preferred, wherein the weakened area is formed as a groove-shaped recess in the carrier layer. Those skilled in the art will understand that the resistance that the adhesive element can offer to an applied pressure difference after the hole has been closed is significantly influenced by the mechanical strength of the carrier layer or the first carrier ply, whereas the contribution of the adhesive layer is less, particularly since in many cases it will be flowable to a certain extent. Accordingly, unless the predetermined opening pressure is to be effective at very low pressures, it is expedient to form the carrier layer without completely continuous perforations in order to prevent premature fluid passage at low pressures. A method according to the invention is preferred, wherein the weakened region does not comprise a recess that completely penetrates the carrier layer, in particular not the first carrier ply. Due to the above-described significant influence of the carrier layer on the predetermined opening pressure and the mostly existing flow behavior of the adhesive, it is advantageously not necessary to have a to provide a reduction in the average thickness corresponding to and complementary to the weakened region, thereby simplifying production. Against this background, a method according to the invention is preferred, wherein the average thickness of the adhesive layer in the weakened region is 20% or less, preferably 10% or less, particularly preferably 5% or less, very particularly preferably 1% or less, especially preferably 0.1% or less, smaller than the average thickness of the adhesive layer in the pressure opening region. Those skilled in the art will understand that the dimensions of the pressure opening area depend on the shape of the weakened area. The pressure opening area, which is at least partially detached from the adhesive element in the event of overpressure, is thus defined in its shape and dimensions by the predetermined breaking point that causes this, i.e., the weakened area. In this respect, the inventors believe that a variety of basic shapes can be provided for the pressure opening area. With a view to simple application and secure adhesion of the adhesive element to the substrate, it is often expedient to orient the shape of the pressure opening area to the shape of the recess to be covered and to arrange the pressure opening area relatively centrally in the adhesive element.Consequently, a method according to the invention is preferred, wherein the pressure opening region has a basic shape selected from the group consisting of circles, partial circles, in particular semicircles, ovals, or polygons, preferably selected from the group consisting of circles, semicircles, and ovals. Additionally or alternatively, a method according to the invention is preferred, wherein the pressure opening region has a basic shape that essentially corresponds to the cross-section of the continuous recess. In all embodiments, a method according to the invention is particularly preferred, wherein the center point of the adhesive element lies in the pressure opening region. The inventors have recognized that the method according to the invention and the adhesive element to be used thereby advantageously make it possible, with comparatively small changes in the manufacturing process of the adhesive element, to influence how far the adhesive element is opened when the overpressure protection device is activated, and thus to influence the fluid flow. A very wide opening through-hole is thereby obtained in particular when the pressure opening area is surrounded as far as possible by the weakened area. In one embodiment, it is particularly interesting to cover the pressure opening area essentially completely with the To surround the weakened area, so that it is particularly easy to completely remove a pressure opening area lifted out of the adhesive element as a result of an applied overpressure. Accordingly, a method according to the invention is preferred, wherein the pressure opening area, based on the circumference of the pressure opening area, is surrounded by the weakened area to 50% or more, preferably to 70% or more, particularly preferably to 90% or more, very particularly preferably to 95% or more, especially preferably to substantially 100%, of the circumference. As an alternative embodiment, the inventors propose that a partial section of the circumference of the pressure opening area deliberately not provide a weakened area, so that an unweakened twist remains between the raised pressure opening area and the remaining adhesive element, which advantageously prevents the raised pressure opening area from being torn off too easily as a result of mechanical stress and, for example, remaining as a foreign body in the housing. Thus, a method according to the invention is preferred, wherein the pressure opening area, based on the circumference of the pressure opening area, is not surrounded by the weakened area to the extent of 0.1 to 10%, preferably 0.2 to 5%, particularly preferably 0.5 to 2%, of the circumference. The weakened area in the adhesive element, i.e., the local reduction in the average thickness of the carrier layer, can, according to the inventors' assessment, be advantageously created using a wide range of possible processes. Punching is particularly suitable for producing adhesive elements in large quantities, whereas the use of laser structuring is particularly suitable for setting particularly precise weakened areas. In this respect, a method according to the invention is preferred, wherein the weakened area in the adhesive element is created using material-removing or cutting processing methods, preferably using laser structuring or punching. In the course of developing the present invention, the inventors experimented with various directions from which the material processing of the adhesive elements could be carried out. Initially, an attempt was made to process the material from the direction of the carrier layer, i.e., from the side facing away from the adhesive layer. While this resulted in satisfactory weakened areas, it was partly hampered, particularly in mechanical processing methods, by the fact that the force acting on the carrier layer also influences the underlying adhesive layer, and this can, for example, be pressed against the substrate, which can lead to unwanted adhesion and / or deformation of the adhesive layer. The inventors have recognized that, surprisingly, the weakened region can be produced more easily if the carrier layer is processed from the side covered with the adhesive layer, i.e. if the processing takes place virtually through the adhesive layer. This is surprisingly possible because the adhesive layer is flowable to a certain extent due to the adhesive mass and any local material displacement produced during the processing of the carrier layer can be compensated for relatively easily over time. For some applications, a method according to the invention is preferred, wherein the weakened region in the adhesive element is produced by processing the side of the carrier layer facing away from the adhesive layer.However, a particularly preferred alternative is a method according to the invention, wherein the weakened region in the adhesive element is produced by machining the side of the carrier layer covered with the adhesive layer, wherein the machining preferably takes place through the adhesive layer. Those skilled in the art will understand that the predetermined opening pressure is significantly influenced by the design of the adhesive element used, and in particular by the dimensions and configuration of the weakened region, so that the structural design of the adhesive elements makes it possible to precisely adjust the desired opening behavior. According to the inventors' assessment, in cases where the predetermined opening pressures are very low, an inherently reduced structural integrity of the entire adhesive elements is often achieved, whereby production-related deviations in the weakened region and the resulting absolute fluctuations in the predetermined opening pressure can manifest themselves as relatively large relative uncertainties. Accordingly, the inventors propose not to select an excessively low predetermined opening pressure.At the same time, particularly high predetermined opening pressures place, at least indirectly, higher demands on the adhesives to be used and their adhesive strength to the battery cell, since the aim is to prevent adhesive failure of the entire adhesive element and thus premature venting before the pressure opening area is opened. Accordingly, in addition to targeted lower limits for the opening pressure, the inventors also propose ranges and associated upper limits that, in the inventors' opinion, are appropriate for numerous applications and can be easily adjusted using typical adhesives and carrier materials. A method according to the invention is preferred, wherein the predetermined opening pressure is 10 kPa or more, preferably 50 kPa or more. particularly preferably 70 kPa or more, most preferably 100 kPa or more, and / or wherein the predetermined opening pressure is in the range from 10 to 2000 kPa, 20 to 1500 kPa, preferably in the range from 30 to 1200 kPa, particularly preferably in the range from 50 to 1100 kPa, most preferably in the range from 100 to 1000 kPa. An advantage of the method according to the invention can be seen in the fact that the necessary bonding of the adhesive elements is particularly simple, especially compared to bursting systems known from the prior art, and can therefore also be easily automated. Accordingly, a method according to the invention is also preferred in which the bonding of the adhesive element is automated, preferably using a robot arm. For optimal opening in the event of overpressure, the inventors propose arranging the pressure opening area essentially concentrically over the continuous recess. A preferred method according to the invention is one in which the pressure opening area is arranged concentrically over the continuous recess. A particularly simple design, which offers great flexibility with regard to the hole geometry to be closed, is achieved when the pressure opening area is smaller than the through-hole to be closed, so that the through-hole is located completely above the pressure opening area in plan view. In these cases, a method according to the invention is preferred, wherein the pressure opening area has a smaller area than the cross-section of the through-hole, and the adhesive element is preferably bonded such that the pressure opening area is arranged completely above the through-hole. In order to be able to achieve small predetermined opening pressures despite large predetermined loading pressures, i.e., for example, a high resistance to external load factors, the inventors propose the provision of an additional cover element, which can be applied to the adhesive layer and whose dimensions expediently correspond as closely as possible to the dimensions of the pressure opening area. In this case, the cover element reduces or prevents an adhesive interaction between the adhesive layer in the area of ​​the pressure opening area and the battery cell, so that the adhesive element can be bonded, for example, exclusively via the adhesive layer. Interaction of the adhesive layer is fixed outside the pressure opening area. When pressure is applied from the outside, i.e. from the side facing away from the adhesive layer, the adhesive element, as a result of the overlap, offers resistance to undesired opening, which resistance can advantageously be increased even further by the additional structural integrity of the cover element, since this too would first have to be deformed to break open. Viewed from the other direction, however, the cover element prevents an adhesive interaction between the relevant part of the adhesive layer and the edge of the battery cell in the area to be lifted out during overpressure opening and thus again allows the setting of even low predetermined opening pressures.Consequently, a method according to the invention is particularly preferred, wherein the adhesive element additionally comprises a cover element which is attached to the side of the adhesive layer facing away from the carrier layer in the print opening area, wherein the cover element preferably substantially does not protrude beyond the print opening area and / or wherein the dimensions of the cover element preferably substantially correspond to the dimensions of the print opening area, or wherein the continuous recess is at least partially, preferably completely, covered with a cover element before the adhesive element is stuck on, wherein the dimensions of the cover element preferably substantially correspond to the dimensions of the print opening area, wherein the adhesive element is stuck on in such a way that the print opening area at least partially, preferably completely, covers the cover element.Those skilled in the art will understand that a method according to the invention is expedient wherein the cover element does not comprise an adhesive. Rather, a method according to the invention is preferred wherein the cover element comprises a film selected from the group consisting of plastic films and metal foils. The inventors have succeeded in specifying suitable dimensions for the adhesive layer, the carrier layer (and the optionally present cover element). A method according to the invention is preferred, wherein the adhesive layer has an average thickness in the range of 5 to 1500 μm, preferably in the range of 10 to 500 μm, particularly preferably in the range of 35 to 100 μm, and / or wherein the carrier layer has an average thickness in the range of 30 to 2000 μm, preferably in the range of 40 to 1000 μm, particularly preferably in the range of 50 to 500 μm, and / or wherein the Cover element has an average thickness in the range of 5 to 340 pm, preferably in the range of 10 to 200 pm, particularly preferably in the range of 12 to 100 pm. If the carrier layer is a metal foil, it has, in particular, an average thickness of 30 μm to 1000 μm, preferably 50 μm to 750 μm, more preferably 300 μm to 500 μm. According to an alternative, the metal foil can have a thickness of 80 μm to 100 μm. The person skilled in the art will understand that the invention also relates to an adhesive element which can be used in the method according to the invention and with which the advantages described above can be obtained.The adhesive element for permanently closing holes with overpressure protection, preferably in a method according to the invention, comprises: i) an adhesive layer comprising an adhesive, and ii) a carrier layer arranged on the adhesive layer, comprising a first carrier layer, wherein the adhesive element comprises a pressure opening region which is at least partially surrounded by a weakened region formed in the carrier layer, wherein the average thickness of the carrier layer in the weakened region is smaller than the average thickness of the carrier layer in the pressure opening region, wherein the adhesive element is designed such that the action of a predetermined opening pressure on the pressure opening region at least partially irreversibly destroys the adhesive element in the weakened region and forms a through-hole in the adhesive element. According to the inventors, not only the method according to the invention and the adhesive element according to the invention used therein are advantageous, but the advantages are also transferred directly to the correspondingly produced substrates, which have an advantageous overpressure protection, wherein in particular the easy automated application, the low weight and the low volume of the adhesive elements according to the invention as well as the reliable opening at predetermined opening pressures result in overpressure-protected substrates that are particularly suitable for battery cells.The invention accordingly also relates to an overpressure-protected battery cell, preferably producible by the method according to the invention, comprising a fluid-tight sealed interior with at least one fluid-tight sealed opening, wherein the sealed opening is fluid-tight sealed with an adhesive element according to the invention, wherein the pressure opening region of the adhesive element at least partially covers the sealed opening, wherein the overpressure-protected battery cell. is arranged so that the adhesive element is at least partially irreversibly destroyed in the weakened area as a result of a predetermined overpressure in the interior, so that pressure can be reduced in the interior through the through hole formed in the adhesive element. Finally, the invention also relates to the use of an adhesive element for permanently closing a hole in a battery cell and for creating an overpressure protection device, wherein the hole is closed with the adhesive element in such a way that the pressure opening area at least partially covers the hole in the battery cell. Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying figures. In the figures: Fig. 1 is a first schematic exploded view of the structure of an adhesive element according to the invention before application to the battery cell in a preferred embodiment; Fig. 2 is a second schematic exploded view of the structure of an adhesive element according to the invention before application to the battery cell in a preferred embodiment; Fig. 3a is a schematic cross-sectional view through an adhesive element according to the invention in a preferred embodiment; Fig. 3b is a schematic cross-sectional view through a variant of the adhesive element according to the invention in a preferred embodiment; Fig. 4 is a schematic representation of an overpressure-protected battery cell according to the invention with closed overpressure protection; and Fig. 5 is a schematic representation of an overpressure protected battery cell according to the invention with the overpressure protection device open. Fig. 1 shows a first schematic exploded view of the structure of an adhesive element 14 according to the invention before application to the battery cell 12, as is done in a method according to the invention. The adhesive element 14 according to the invention comprises an adhesive layer 16, via which the adhesive element can be attached to the battery cell 12 such that the continuous recess 10 in the battery cell 12 is sealed in a fluid-tight, in particular gas-tight, manner. The example shown in Fig. 1 is a metallic battery cell, with only one wall of the battery cell being shown, which delimits its interior. In the example shown, the adhesive layer 16 comprises a pressure-sensitive adhesive based on poly(meth)acrylates, which can also be syntactically foamed, for example, by using expanded microballoons. The adhesive layer 16 is arranged on the first carrier layer 19 of a multi-layer carrier layer 18 and is bonded to it by the adhesion of the adhesive. In the example shown in Fig. 1, it can be seen from the exploded view that the first carrier layer 19 is essentially completely covered on one side by the adhesive layer 16. This becomes clearer from the view in Fig. 2, in which the exploded view of Fig. 1 is partially merged, so that the connection between the first carrier layer 19 and the adhesive layer 16 becomes clear. In Figs. 1 and 2, the first carrier layer 19 is a metal foil with an average thickness of approximately 80 μm. Beyond the first carrier layer 19, the carrier layer 18 comprises a protective film 26 made of polyethylene terephthalate as a further layer, which is bonded to the first carrier layer 19 via an intermediate adhesive layer 30, which is also applied over the entire surface. This protective film 26 is optionally present; according to a preferred variant, it is omitted. In Figs. 1 and 2, it can be clearly seen that the adhesive element 14 in the carrier layer 18 comprises a pressure opening region 20 formed by a weakened region 22. The pressure opening region 20 is located centrally in the adhesive element 14 and, in the example shown, is essentially circular, so that its basic shape essentially corresponds to the continuous recess 10 in the battery cell 12, which is to be closed in the method according to the invention. Due to this construction, the adhesive element 14 according to the invention is designed so that the action of a predetermined opening pressure on the pressure opening area 20, for example as a result of an overpressure prevailing inside the battery cell 12, in Weakened area 22 can cause at least partially irreversible destruction, through which a through hole 24 is formed in the adhesive element 14. In the example shown, the weakened region 22 is formed as a groove-shaped recess in the carrier layer 18, which extends through the protective film 26 into the first carrier layer 19 and substantially completely surrounds the pressure opening region 20, wherein the average thickness of the carrier layer 18 in the region of the weakened region 22 is reduced by approximately 20 to 60% compared to the original thickness of the carrier layer 18 and thus also compared to its average thickness in the pressure opening region 20, depending on the desired opening pressure. In Fig. 1 it can be seen that the adhesive layer 16 in the example shown has a substantially constant average thickness, which is due to a mechanical formation of the weakened region 22 by punching, which in this case takes place from the direction of the carrier layer 18 and which does not influence the adhesive layer 16. In the examples of Figs. 1 and 2, the adhesive element 14 according to the invention is bonded in an automated manner using a robot arm, for example, in the method according to the invention, with the pressure-opening region 20 and the continuous recess 10 being arranged concentrically in the example shown. To achieve advantageous anisotropy in the opening behavior, the bonding is carried out such that the pressure-opening region 20 protrudes beyond the edge of the continuous recess 10 over the entire circumference, so that the overlap can resist externally applied load pressure. In order to enable a precise adjustment of the desired opening pressure despite the overlap of the adhesive element 14 according to the invention with the edge of the continuous recess 10, the adhesive element 14 according to the invention comprises a cover element 28 formed from plastic film, the dimensions of which substantially correspond to those of the pressure opening area 20 and which substantially completely covers the adhesive layer 16 in the pressure opening area 20. Fig. 3a visualizes the structure of an adhesive element 14 according to the invention in a cross-sectional view, wherein the schematically illustrated adhesive element 14 corresponds in many aspects to the adhesive element 14 of Figs. 1 and 2 with regard to its structure. However, Fig. 3a indicates that the processing of the carrier layer 18 for producing the weakened area 22 can also be carried out at least partially through the adhesive layer 16, wherein advantageously, due to the flow behavior of the adhesive layer 16, no processing traces, for example in the form of a reduced thickness, remain in it even after a short time. Fig. 3b shows the adhesive element 14 according to the invention in a cross-sectional view according to Fig. 3a, with the cover element 28 missing. The adhesive layer 16 is applied in a ring shape to the carrier layer 18. Fig. 4 now shows a pressure-protected battery cell 12 according to the invention, the continuous recess 10 of which is sealed in a fluid-tight manner by the adhesive element 14, as can be obtained, for example, starting from Figs. 1 and 2. Due to the previously described structure of the adhesive element 14 and its arrangement over the continuous recess 10, the pressure-protected battery cell 12 can be designed such that it can withstand a load pressure of 400 kPa or more acting from the direction of the carrier layer 18 without causing destruction of the adhesive element 14 in the weakened region 22. In fact, in the inventors' experiments, a corresponding structure was even able to withstand irradiation of the pressure-protected battery cell 12 with a high-pressure water jet cleaner (IPX9K, ISO 20653:2013) without causing the closure to fail. At the same time, it is possible to specifically set a predetermined opening pressure, for example in the range of 5 to 200 kPa, upon the application of this pressure in the desired opening direction, i.e., for example, from the inside outwards, the pressure opening region 20 is lifted out of the adhesive element 14 as a result of at least partial destruction of the weakened region 22, thereby forming a through-hole 24 through which the excess pressure can be released. The final state resulting from the engagement of the overpressure protection device is schematically visualized in Fig. 5, wherein in advantageous embodiments, the complete detachment of the pressure opening region 20 from the adhesive element 14 is additionally avoided by the weakened region 22 not being guided over the entire circumference, so that an unweakened connection remains between the pressure opening region 20 and the legal adhesive element 14. List of reference symbols 10 Continuous recess 12 battery cells 14 Adhesive element 16 Adhesive layer 18 Carrier layer 19 First support layer 20 Pressure opening area 22 Weakened area 24 Through hole 26 protective film 28 Cover element 30 intermediate adhesive layer

Claims

Claims 1. A method for closing a continuous recess (10) in a battery cell (12), comprising the method steps: a) producing or providing an adhesive element (14), comprising: i) an adhesive layer (16) comprising an adhesive compound, ii) a carrier layer (18) arranged on the adhesive layer (16), comprising a first carrier layer (19), and b) adhering the adhesive element (14) to the battery cell (12) by means of the adhesive layer (16), such that the adhesive element (14) completely covers the continuous recess (10) and the continuous recess (10) is closed in a fluid-tight manner by the adhesive element (14), wherein the adhesive element (14) comprises a pressure opening region (20) which is surrounded at least in sections by a weakened region (22) formed in the carrier layer (18), wherein the average thickness of the carrier layer (18) in the weakened region (22) is smaller than the average thickness of the carrier layer (18) in Pressure opening area (20),wherein the adhesive element (14) is designed such that the action of a predetermined opening pressure on the pressure opening region (20) at least partially irreversibly destroys the adhesive element (14) in the weakened region (22) and forms a through-hole (24) in the adhesive element (14), and wherein the adhesive bonding of the adhesive element (14) takes place such that the pressure opening region (20) at least partially covers the through-hole (10) in the battery cell (12).

2. The method according to claim 1, wherein the weakened region (22) is formed as a groove-shaped recess in the carrier layer (18).

3. The method according to claim 1 or 2, wherein the predetermined opening pressure is 10 kPa or more.

4. Method according to one of claims 1 to 3, wherein the carrier layer (18) comprises a protective film (26) as a further carrier layer on the side of the first carrier layer (19) facing away from the adhesive layer (16).

5. Method according to one of claims 1 to 4, wherein the adhesive element (14) additionally comprises a cover element (28) which is attached to the side of the adhesive layer (16) facing away from the carrier layer (18) in the pressure opening region (20).

6. Method according to one of claims 1 to 5, wherein the adhesive element (14) is bonded by the pressure opening region (20) projecting at least partially beyond the edge of the continuous recess (10) in such a way that the bonded adhesive element (14) withstands the action of a predetermined load pressure on the carrier layer (18) in the pressure opening region (20), so that the adhesive element (14) is not irreversibly destroyed in the weakened region (22) and no through hole (24) is formed in the adhesive element (14).

7. The method of claim 6, wherein the predetermined loading pressure is in the range of 10 to 1500 kPa.

8. The method according to any one of claims 1 to 7, wherein a water-based acrylate adhesive is used as the adhesive.

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