CN112436236A

CN112436236A - Method for producing a layer system of a battery cell

Info

Publication number: CN112436236A
Application number: CN202010788615.0A
Authority: CN
Inventors: P·席希特尔; D·A·韦伯
Original assignee: Volkswagen Automotive Co ltd
Current assignee: Volkswagen Automotive Co ltd
Priority date: 2019-08-09
Filing date: 2020-08-07
Publication date: 2021-03-02
Anticipated expiration: 2040-08-07
Also published as: DE102019212014A1; CN112436236B

Abstract

Method for producing a layer system of a battery cell. The invention relates to a method for producing a layer system (2) of a battery cell (4), wherein a porous layer material (14) having an open pore structure (16, 16 ') is produced, wherein a gas capture material (24) for binding cell gases is introduced into the pore structure (16, 16 '), and wherein the layer material (14) is treated such that the pores (18, 20) of the pore structure (16, 16 ') are partially closed.

Description

Method for producing a layer system of a battery cell

Technical Field

The invention relates to a method for producing a layer system of a battery cell. The invention also relates to such a layer system and to the use of such a layer system and to a battery cell having a corresponding layer system.

Background

An electric or motor-driven or electrically or motor-drivable motor vehicle, such as an electric vehicle or a hybrid vehicle, usually comprises an electric motor which can be used to drive one or two axles. For the supply of electrical energy, the electrical machine is usually connected to a (high-voltage) battery pack in the vehicle as an electrical energy accumulator.

In particular, an electrochemical battery is to be understood here and in the following as a so-called secondary battery (Sekund ä rbatterie) for a motor vehicle. In the case of such (secondary) vehicle battery packs, the consumed chemical energy can be recovered by means of an electrical charging process. Such a vehicle battery is, for example, embodied as an electrochemical accumulator, in particular as a lithium-ion accumulator. In order to generate or provide a sufficiently high operating voltage, such vehicle batteries usually have at least one battery module, in which a plurality of individual battery cells are modularly wired.

These battery cells are embodied, for example, as electrochemical (thin) layer cells. These thin-film batteries have a layered structure with a cathode layer (cathode) and with an anode layer (anode) and with a separator layer (separator) introduced between the cathode layer and the anode layer. These constituents are passed through by, for example, a liquid electrolyte (flessigelektrolyt) which produces ionic compounds or charge compensation of these constituents. In this case, the ion conduction is based on the conductive salt of the battery cell, which is typically lithium ions.

During the transfer through the electrolyte, the lithium ions are surrounded by a so-called solvating shell, which is formed by the organic molecules of the electrolyte and the ions of the conductive salt. In this case, the spatial dimensions of the solvating shell (solvating sleeve) can be characterized by a Stokes radius, which ranges between about 0.2nm and 1nm, depending on the solvent used. This corresponds approximately to a diameter between 0.4nm and 2 nm.

The separator layer is typically a porous membrane constructed from a polymer or ceramic. In other words, the layer system of the separator is provided with a porous structure. The separator layer electrically separates the anode and the cathode from each other and thus prevents short-circuiting of the battery cell.

Pore structure is to be understood here and in particular below as a spatial arrangement or distribution of a plurality of pores in the layer material forming the layer system. In this case, hole-like openings or recesses or depressions, in particular cavities or cavities, in the layer material are understood to be holes. According to IUPAC, such pores are distinguished by their (pore) size. The so-called macropores (Makroporen) have an average pore diameter of more than 50nm (nanometers), wherein the mesopores (Mesoporen) have an average pore diameter of between 2nm and 50nm, and wherein the micropores (Mikroporen) have an average pore diameter of less than 2 nm. Correspondingly, the porosity of the layer material is referred to as macropore, mesopore or micropore.

In this case, the pore size and the pore distribution of the separator or of the layer system of the separator are generally in a range which allows lithium ions in the electrolyte solution to pass easily. Typically, a macroporous membrane having an average pore size of less than 1 μm (micrometer) is used.

During operation of the lithium ion battery, decomposition reactions occur within the battery cell that release gases, i.e., produce gaseous reactions or produce products. This gas formation or gas generation occurs more and more during the charging process, in particular during the first charging step. These (battery) gases are associated with an electrolyte material, in which usually substantially oxygen (O) is formed₂) And carbon dioxide (CO)₂). Such cell gases are typically electrically neutral, i.e., not charged unlike the ions of the conductive salt, such that the cell gases have substantially no solvating shell in the electrolyte. Thus, these gases typically have relatively small stokes radii.

The gases formed accumulate inside the battery cell and cause an increase in volume or a volume expansion of the battery cell and/or other undesirable side reactions.

The battery cells are usually arranged within a battery housing in order to be protected from external influences. A plurality of battery cells are often stacked in a cell stack and fastened by means of a clamping system and accommodated in a common cell housing. The increase in volume of the or each battery cell due to the gas can lead to damage (rupture) or complete destruction of the battery or the battery housing or to opening of the provided rupture membrane of the battery housing.

In this case, it is possible, for example: the installation space present in the battery housing is designed with respect to such an increased volume of the battery cell, whereby the installation space requirement of the battery cell increases and the energy density of the battery cell decreases. Additionally or alternatively, for example, it is likewise possible: an additional pressure relief valve is provided on the battery housing, which should prevent (explosive) rupture of the battery housing. Such a pressure relief valve, while preventing rupture of the battery housing, still results in failure of the battery cell when triggered.

And generally does not prevent the formation of cell gases. However, it is possible, for example: such cell gases are bound by means of a gas trap (Gasf ä nger) in order to avoid or at least reduce the harmful effects of these cell gases, such as a pressurization inside the battery cell. A "gas trap" or "gas trapping material" is to be understood here and in particular below as a material which absorbs and/or adsorbs, i.e. physically and/or chemically binds, the emerging cell gases to it. In other words, the gas trap can absorb or adsorb the emerging cell gases or can also chemically convert these cell gases in a reaction and thus bind them.

A battery cell is known from KR 20150014668A, in which a gas-absorbing substance is introduced as a gas trap. In this case, the gas trap is arranged in a medium to large pore support matrix having an average pore size between 0.01 μm and 5000 μm.

A battery housing for a battery cell is described in KR 101625820B 1, wherein the inner wall of the battery housing is equipped with an oxygen trap, and wherein an additional pocket-like or chamber-like cavity is provided in the battery housing to accommodate the cell gases.

Disadvantageously, such gas trap designs require the introduction of an additional carrier system for the gas trapping material into the battery cell or into the cell housing. Such carrier systems have additional installation space requirements in the battery cell or in the battery housing, as a result of which the installation space requirements of the battery cell itself increase and the energy density of the battery cell disadvantageously decreases.

From JP 2007242454 a battery cell with a mesoporous separator layer is known, which battery cell is equipped with an amine as a gas trap.

JP 2008146963 a describes a layer system for a separator of a solid-state battery cell, in which a gas trap is mixed under the separator material.

Disadvantageously, the introduced gas trap, due to the pore size of the mesopores or macropores of the layer system, is accessible not only for the cell gases but also for the conductive salts and the electrolyte. As a result, the reaction or decomposition products of the gas trap can be returned back into the cell interior, for example into the electrolyte, and undesirable side reactions can thereby be caused.

Disclosure of Invention

The invention is based on the task of: a method is described which is particularly suitable for producing a layer system of a battery cell. In the case of such a layer system, the escape of reaction products from the gas trap into the battery cell should be prevented in particular reliably and simply. The invention is also based on the task of: a particularly suitable layer system and a particularly suitable use of such a layer system and a particularly suitable battery cell are described.

According to the invention, this object is achieved with respect to the method by the features of claim 1; with regard to this layer system, this object is achieved by the features of claim 7; and with regard to this application, this task is solved with the features of claim 9; with regard to the battery cell, this object is achieved by the features of claim 10. Advantageous embodiments and further developments are the subject matter of the respective dependent claims. In contrast, the advantages and embodiments mentioned in connection with the method can also be transferred to the layer system and/or to the application and/or to the battery cell, and vice versa. The conjunction "and/or" is to be understood here and in the following such that the features associated by means of the conjunction can be configured not only jointly but also as alternatives to one another.

The method according to the invention is suitable and designed for producing a layer system of a battery cell. In this case, a porous layer material is produced which has an open pore structure, i.e. has a plurality of pores. Next, a gas trapping material for trapping cell gases occurring during operation of the battery cell is introduced into the pore structure. According to the method, the following steps are provided: the layer material is treated such that the pores of the pore structure are partially closed. I.e. the holes are not completely closed but only partially closed, which means that the respective hole openings remain. In this way, a method for producing a layer system is achieved which is particularly suitable for a battery cell.

In this case, the remaining pore openings preferably have a diameter approximately equal to that of micropores or submicropores.

The resulting mean pore opening is preferably arranged, with respect to the stokes radius, on the one hand sufficiently large so that (uncharged) cell gases, in particular oxygen and/or carbon dioxide, can enter the pores. On the other hand, these pore openings are preferably small enough in size so that conductive salts having a solvating shell, such as lithium ions, cannot enter the interior of the pores without peeling off their solvating shell. The exfoliation of the solvated shell is energetically unfavorable for the conductive salt, so that the conductive salt is thus prevented from entering the pores. In particular, the pore opening sizes are small enough so that reaction products and/or decomposition products of the gas capture material do not escape from the pore interior. This means that: the gas trapping material traps the cell gases in the partially closed pores, while reaction products and/or decomposition products cannot reach the cell interior.

According to the invention, it is therefore provided that: causing pore openings of the pore structure which are on the one hand large enough for the entry of the cell gases or gas molecules of the cell gases into the pores and which on the other hand are arranged small enough that reaction products and/or decomposition products of the conductive salts and/or gas-trapping materials of the battery cells cannot flow into or out of the pores. In other words, according to the invention, precisely defined dimensions of the openings of the holes are specified, which are specific to the cell gases formed in the battery cell, so that other cell components cannot easily enter the holes and by-products cannot pass back into the cell from the holes.

Unlike the prior art, the gas trapping material is not simply mixed with or beneath the layer material. By introducing the gas capture material into the pore structure and subsequently partially closing the pores, direct contact of the gas capture material with the (liquid) electrolyte (liquid electrolyte) of the battery cell is substantially prevented. By reducing the pore openings, the pores, and thus the gas trapping material, are substantially inaccessible to the electrolyte. According to the invention, the pore openings are dimensioned in this case with respect to the gas molecules of the battery gas present such that only these gas molecules can enter the pores. Thus, the gas capture material is not in direct contact with the electrolyte of the battery cell, but only with the cell gas of the battery cell. In this case, it is suitable that the decomposition products and/or reaction products do not fit through the pore openings and therefore cannot escape from the pore structure.

The layer system is preferably a cell component of the battery cell, i.e. an electrode layer or a separator layer. This means that: the cell assembly itself is designed as a carrier system for the gas capture material, so that no additional carrier system with additional installation space requirements is required in the battery cell or the cell housing.

Especially using a membrane material as the layer material. This means that: the layer system is in particular embodied as a separator layer or as a separator of a battery cell.

In the case of liquid battery cells, i.e. battery cells with liquid electrolyte, the layer material or separator material is for example a polymer or ceramic material. In the case of a solid-state battery cell, the layer material is, for example, a material of a solid-state electrolyte that functions as a separator in the solid-state battery cell. In the case of solid state battery cells, thermal events, especially at the cathode side, are the main cause of the formation of oxygen as cell gas, wherein suitably especially the pore structure at the cathode side is provided with an oxygen trapping material.

The pore openings are preferably reduced such that the size of the pore inlets is smaller than the diameter of the conductive salt in the electrolyte of the battery cell, as determined by the stokes radius. Since the stokes radius depends on the solvent, the pore openings are preferably dimensioned solvent-specifically in this case. In a particularly preferred embodiment of the method, the pore openings are reduced such that the retained average pore opening is less than 0.5 nm. In other words, the pores eventually have, on average, through-pores with a diameter of less than 0.5 nm. In this way, a method for producing a layer system is achieved which is particularly suitable for a battery cell. It is thereby ensured that only the cell gas or cell gas molecules can pass through the pore opening.

Preferably, the pores have in this case a medium or large pore size, wherein only the pore inlets or pore openings are reduced to the diameter of the micropores or submicropores.

In order to produce, in particular, an open pore structure, i.e. an open porosity of the layer material, it is possible, for example, to chemically etch the layer material or to treat the layer material by means of electrolysis. Open porosity is to be understood in this case to mean, in particular, a pore structure in which the pores are at least partially converted into one another or open to one another. Subsequently, the preferably mesoporous or macroporous produced is provided with a gas trapping material. Subsequently, the holes are partially closed.

In order to close these holes, provision is made in an advantageous embodiment for: the layer material is heat treated. It is thereby possible to reduce the pore opening particularly simply and reliably to preferably less than 0.5 nm.

In this case, the (treatment) temperature of the heat treatment depends substantially on the layer material used. In the case of polyethylene material (PE) or other polymeric materials, a heat treatment, for example at about 100 ℃ to 150 ℃, is sufficient to cause the shrinkage phenomenon of the pore openings and to reduce the porosity of the layer material. In the case of ceramic layer materials or solid electrolyte materials, the temperature at which the heat treatment is required is in the sintering range of these materials or ceramics, for example between 700 ℃ and 1200 ℃.

In a preferred embodiment of the method, a hierarchical pore structure of the layer material is produced. In this case, a hierarchical pore structure is to be understood in particular as a pore structure having a plurality of first pores with a comparatively large pore size and a plurality of second pores with a comparatively small pore size, wherein the second pores are arranged in particular on the wall of the first pores or in the circumferential direction of the first pores. This means that: the resulting open pore structure of the layer material essentially forms a system of pores leading to each other, wherein smaller pores lead to larger pores, in particular in the peripheral direction of these larger pores. Thus, the smaller second pores increase the inner surface of the pore structure or layer material.

The larger first pores are, for example, embodied as macropores or mesopores, wherein the second pores which are hierarchically open to these macropores or mesopores are, in particular, embodied as mesopores or micropores. In this case, the gas trapping material is introduced in particular into the second pores, wherein the pore openings of the second pores immediately into the larger first pores are reduced to an average diameter of less than 0.5 nm. A particularly suitable pore structure of the layer material is thereby achieved. In this case, the larger (first) pores ensure as unhindered as possible electrolyte transfer of the conductive salt, wherein the smaller (second) pores at the edges of the larger pores have the gas trapping material and the cell gas is thus bound particularly reliably and safely by the enlarged pore surface.

The gas capture material is, for example, suitable and configured for capturing or binding carbon dioxide. For example, lime, amino-modified zeolite, lithium-silicon Monoethanolamine (MEA), Diethanolamine (DEA), Triethanolamine (TEA), N-Methyldiethanolamine (MDEA), 2- (2-amino-ethyl) ethanol (DGA), 2-amino-2-methylpropanol (AMP), epoxy compounds, and amine compounds can be used as the gas capture material for such a carbon dioxide trap.

Alternatively, the gas trapping material may be adapted and configured for trapping or binding oxygen, for example. For example, ascorbic acid, erythorbic acid, gallic acid and salts thereof, tocopherol, hydroquinone, catechol, dibutyl-hydroxytoluene, dibutylated hydroxyanisole, pyrogallol, sorbose, glucose, lignin, an iron-based material, hemoglobin, thiosulfate, a redox active resin, or a zeolite group may be used as a gas trapping material for such an oxygen trap.

In a particularly advantageous embodiment of the method, phosphane is used as a gas capture material, in particular as an oxygen trap. Phosphanes are not typically used in battery cells to bind oxygen because the reaction product formed is a viscous oil. However, by virtue of the small pore inlets according to the invention or by virtue of the pore openings being arranged to be less than 0.5nm, the oil formed is reliably retained within the pores. It is thereby possible to: a phosphane or a phosphane compound is used as a gas capturing material or an oxygen capturing material. In this way, a new degree of freedom is achieved in the production of layer systems with integrated gas capture materials, as a result of which particularly flexible methods can be achieved.

In one contemplated embodiment, activated carbon particles incorporating a gas capture material are incorporated into the pore structure. In other words, the gas trapping material is introduced indirectly into the pore structure. This means that: the activated carbon particles are impregnated, for example, with a gas trapping material and are subsequently introduced into the pore structure or the cells of the layer material. Activated carbon has a porosity in the mesoporous or microporous range. Suitably, the pores of the activated carbon particles are partially closed in this case such that the retained average pore opening is less than 0.5 nm. Preferably, the pores of the pore structure of the layer material are only partially blocked to the extent that the activated carbon particles cannot slip or escape from the open pore structure of the layer material. Suitably, the activated carbon particles within the layer material do not form a percolation network, so that the electrical insulation properties of the layer material are not adversely affected.

The layer system according to the invention is suitable and configured for a battery cell. The layer system is arranged in particular as a separator layer between the cathode and the anode of the battery cell and has a porous layer material having a pore structure and at least one gas capture material introduced or integrated into the pore structure. In this case, the pores of the pore structure have an average pore opening of less than 0.5 nm. A particularly suitable layer system of the battery cell is thereby achieved. In this case, the diameter of the hole openings is dimensioned with respect to the gas molecules of the emerging cell gas such that only these gas molecules can pass through these hole openings. The layer system is produced in particular by means of the method described above.

In one expedient embodiment, the battery cell is a lithium ion battery cell, preferably a lithium ion battery cell with a liquid electrolyte.

In a preferred application, the layer system described above is used as a separator in a battery cell. As a result, a battery cell can be achieved which has a particularly compact construction space and improved performance. In particular, in the case of such battery cells, no additional carrier structure or functional structure of the battery housing, such as a pressure relief valve, is required.

The battery cell according to the invention has a cathode and an anode and the layer system described above as a separator arranged between the cathode and the anode. The battery cell according to the invention is particularly compact and has a particularly high energy density for a given structural size. Preferably, the battery cell is part of a vehicle battery of an electrically driven or electrically drivable motor vehicle, in particular an electric vehicle or a hybrid vehicle. As a result, a vehicle battery pack is achieved which has a particularly compact installation space and improved performance. This results in a reduction in the installed weight of the vehicle battery pack, which is advantageously shifted to the range of the motor vehicle.

Drawings

Subsequently, embodiments of the present invention are explained in detail with reference to the drawings. In which, in a schematic and simplified illustration:

fig. 1 shows a flow chart of a production method according to the invention for a layer system;

fig. 2 shows a battery cell with a layer system embodied as a separator;

fig. 3 shows a layer system with a pore structure in a first embodiment in section;

FIG. 4 shows in section a hierarchical pore according to the pore structure of FIG. 3;

fig. 5 shows in section a layer system in a second embodiment with a pore structure with a plurality of activated carbon particles; and

fig. 6 shows the pores of the activated carbon granules according to fig. 5 in sections.

Throughout the drawings, parts and parameters corresponding to each other are provided with the same reference numerals throughout.

Detailed Description

Fig. 1 shows a schematic and simplified illustration of a flow chart of a method according to the invention for producing a layer system 2 of a battery cell 4 shown in fig. 2. The battery cell 4 has a layered structure with two electrode layers, namely a cathode layer (cathode) 6 and an anode layer (anode) 8, and with a separator layer in the form of a layer system (separator) 2 arranged between the cathode layer and the anode layer. The cathode 6 and the anode 8 are each conductively coupled to a conductive body 10.

According to the method, in order to produce the layer system 2, the layer material 14 is provided with the pore structure 16 in a first method step 12 (fig. 3 to 6). For this purpose, a plurality of

pores

18, 20 are introduced into the layer material 14, for example by means of chemical etching or by means of electrolysis, which form an open pore structure 16. In this case, the

pores

18, 20 are, in particular, mesopores or micropores.

In the embodiment illustrated schematically and simplified in fig. 3 and 4, the pore structure 16 is graded in this case, which means that: the pore structure 16 has an upper level pore 18 with a larger pore size and a lower level pore 20 with a smaller pore size. Fig. 3 shows a section a of the layer system 2 according to fig. 2, wherein fig. 4 shows a section B of the hole 18 according to fig. 3.

In this case, the size of the holes 18 is large enough so that the conductive salt of the battery cells 4 can easily flow through the layer system 2. The holes 20 are introduced in particular into the outer circumference of the larger holes 18 or on the edge of the larger holes 18. In fig. 3, the holes 18 are provided with reference numerals by way of example only.

In a second method step 22, a gas trapping material 24 (fig. 4, 6) is introduced into the layer material 14 or into the pore structure 16. The gas trapping material 24 is for example an oxygen trap, preferably a phosphane.

In a third method step 26, the layer material 14 is thermally treated, so that the pore openings of the open pore structures 16 are reduced or reduced. In this case, the hole openings between the holes 18 and the hole openings 28 between the

holes

18 and 20 are partially closed. In this case, the pore openings 28 are reduced such that the remaining average pore opening 28 is less than 0.5 nm. In other words, the pores 20 after the method step 26 have on average through-pores with a diameter of less than 0.5 nm. In other words, the pore opening 28 has a diameter that approximately corresponds to the size of a micropore or a sub-micropore.

Subsequently, a second embodiment of the invention is explained in detail with reference to fig. 1, 5 and 6. Fig. 5 shows a section a of the layer system 2 according to fig. 2, wherein fig. 6 shows a section C of the hole 18 according to fig. 5.

In this embodiment, the aperture arrangement 16' has only apertures 18. In this case, the gas capture material 24 is introduced into the pore structure 16' in method step 22 indirectly by means of activated carbon particles 30. To this end, mesoporous or microporous activated carbon particles 30 are produced in a method step 32. This means that: the activated carbon granules 30 are provided with holes 20'. In fig. 5, the activated carbon granules 30 are provided with reference numerals by way of example only.

The porous activated carbon particles 30 are then impregnated with the gas capture material 24 in method step 34 and then introduced into the cells of the pore structure 16' in method step 22 so that the activated carbon particles 30 do not form a percolation network.

In method step 26, the layer material 14 provided with activated carbon particles 30 is heat-treated in this way. By means of this heat treatment, the pore openings 28' of the pores 20' of the activated carbon particles 30 are partially closed on the one hand, so that the resulting pore openings 28' have a diameter of less than 0.5 nm. On the other hand, the pore openings between the pores 18 are partially closed so that the activated carbon particles 30 cannot slip out of the pores 18 of the pore structure 16'.

According to the invention, the pore openings 28, 28 'of the pore structure 16 or of the activated carbon particles 30 are caused by the method to be sufficiently large for the cell gas or gas molecules of the cell gas to enter the pores 20, 20' on the one hand, and to be arranged sufficiently small for the reaction products and/or decomposition products of the conductive salts and/or the gas capture material 24 of the battery cells 4 not to flow into the pores 20, 20 'or out of the pores 20, 20' on the other hand. In other words, according to the invention, a precisely defined dimension of the hole openings 28, 28' is specified, which dimension is specific to the cell gas formed in the battery cell 4, so that other cell components cannot easily enter these 20, 20' holes and by-products cannot pass back from these holes 20, 20' into the battery cell 4.

The invention as claimed is not limited to the embodiments described above. Rather, other variants of the invention can also be derived from the person skilled in the art within the framework of the claims disclosed, without departing from the subject matter of the invention claimed. Furthermore, especially all individual features described in connection with these different embodiments can also be combined in other ways within the framework of the disclosed claims without departing from the subject matter of the claimed invention.

List of reference numerals

Layer 2 system

4-cell battery

6 cathode

8 anode

10 electric conductor

12 method step

14 layers of material

16. 16' pore structure

18 holes

20. 20' hole

22 method step

24 gas trapping material

26 method step

28. 28' hole opening

30 activated carbon particles

32. 34 method step

Claims

1. Method for producing a layer system (2) of a battery cell (4),

-wherein a porous layer material (14) with an open pore structure (16, 16') is produced,

-wherein a gas trapping material (24) for binding cell gases is introduced into the pore structure (16, 16'), and

-wherein the layer material (14) is processed such that the pores (18, 20) of the pore structure (16, 16') are partially closed.

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

it is characterized in that the preparation method is characterized in that,

partially closing the pores (20) of the pore structure (16) such that the retained average pore opening (28) is less than 0.5 nm.

3. The method according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

-subjecting the layer material (14) to a heat treatment, thereby closing the holes (18, 20).

4. The method of any one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

a hierarchical pore structure (16) of the layer material (14) is created.

5. The method of any one of claims 1 to 4,

it is characterized in that the preparation method is characterized in that,

phosphane is used as a gas trapping material (24).

6. The method of any one of claims 1 to 5,

it is characterized in that the preparation method is characterized in that,

introducing activated carbon particles (30) doped with the gas capture material (24) into the pore structure (16').

7. Layer system (2) for a battery cell (4), having a porous layer material (14) and at least one gas capture material (24),

-wherein the gas trapping material (24) is introduced into the pore structure (16, 16') of the layer material (14), and further wherein

-wherein the pores (18, 20) have a pore opening (28) of less than 0.5 nm.

8. Layer system (2) according to claim 7,

it is characterized in that the preparation method is characterized in that,

the battery cells (4) are lithium ion battery cells.

9. Use of the layer system (2) according to claim 7 or 8 as a separator in a battery cell (4).

10. Battery cell (4) having a cathode (6) and having an anode (8) and having a layer system (2) according to claim 7 or 8 arranged between the cathode and the anode as a separator.