Electrochemical electrode assembly, electrochemical storage cell, and method for producing an electrochemical electrode assembly

Abstract

The invention relates to an electrochemical electrode assembly for an electrochemical storage cell, comprising a sequence of layers comprising at least a first electrode (10), a second electrode (20), and a separator layer (30) arranged between the first and second electrode (10, 20). The separator layer (30) has an elastic and porous material into which an electrolyte is incorporated and which is reversibly deformable under the effect of a pressure exerted by one of the electrodes depending on the state of charge.

Description

[0001] ELECTROCHEMICAL ELECTRODE ARRANGEMENT,

[0002] ELECTROCHEMICAL STORAGE CELL AND METHOD FOR PRODUCING ONE

[0003] ELECTROCHEMICAL ELECTRODE ARRANGEMENT

[0004] The following disclosure relates to an electrochemical electrode assembly for an electrochemical storage cell. Furthermore, a method for producing an electrochemical electrode assembly for an electrochemical storage cell, an electrochemical storage cell, and a vehicle with such a storage cell are described.

[0005] State of the art

[0006] Battery cells form the basis not only for electromobility, but for virtually all areas of modern life. To meet the rapidly increasing demand for batteries, numerous different lithium-ion batteries have been developed. They differ not only in size and design, but also in the chemical composition of their components and usually have different voltage ranges.

[0007] An electrochemical storage cell typically has various electrodes, at least one positive electrode (cathode) and one negative electrode (anode), which can be electrically contacted via current collectors and are separated from each other by a separator. Each electrode has at least one active material, optionally together with additives such as electrode binders and electrical conductivity additives, which is applied to an electrically conductive carrier (e.g., a metal foil) as a current collector for the respective electrodes. The main function of a separator in an electrochemical storage cell is to electrically separate the anode and cathode and to enable the exchange of charge carriers, such as lithium ions, via a space filled with electrolyte.

[0008] The trend in separator design is toward increasingly thinner structures (approximately 10 pm) to reduce the inactive portion of the cell, thus creating more space for active components and higher energy densities. One example of this is the base film, which provides porosity for electrolyte storage. However, in current separator designs, the base film is increasingly being reduced, and the focus is often on ceramic coatings. This trend toward thinner separators has the advantage of supporting energy density at the cell level and reducing cell resistance, but also poses safety risks, especially in a "dynamic" volume-changing system such as silicon-rich high-energy cells.

[0009] For example, the reversible volume expansion of a silicon-rich anode due to lithium incorporation and removal poses a major challenge for cell designs of all formats – including prismatic / pouch (stack), cylindrical wound, and flat wound designs. Volume expansion that exceeds the outer dimensions of the electrode stack or coil leads to high pressure conditions in the spatially confined system, which can cause the separator structure to collapse. If there are no or insufficient pores in the separator, lithium transport through the electrolyte is hindered, if not completely prevented. In extreme cases, the expansion of the coil / stack can even lead to the expansion of the outer casing, leading to a short circuit / cell death and / or the opening of the casing.

[0010] The object is to provide an electrode assembly for an electrochemical storage cell with an improved separator design. Furthermore, a method for producing an electrochemical electrode assembly for an electrochemical storage cell and a vehicle with such a storage cell are to be specified.

[0011] These objects are achieved by an electrode arrangement for an electrochemical storage cell and a method for producing an electrochemical electrode arrangement for an electrochemical storage cell, as well as a vehicle having the features of the independent and subordinate patent claims. Advantageous embodiments and further developments are set out in the dependent claims.

[0012] Summary

[0013] It is understood below that each feature described with respect to any embodiment may be used alone or in combination with other features described herein, and may be used in combination with one or more features of any other embodiment, or in any combination of any other embodiment, unless explicitly described as an alternative. Furthermore, equivalents and modifications not described below may be used without departing from the scope of the claimed subject matter.

[0014] An electrochemical storage cell refers below to an electrochemical-based energy storage device, in particular a rechargeable energy storage device, which is suitable for storing electrical energy and supplying it to a consumer, for example a consumer in a vehicle. Below, the term "lithium-ion battery" is used synonymously for all terms commonly used in the art for lithium-containing galvanic elements and electrochemical storage cells (cell for short), such as lithium battery, lithium cell, lithium-ion cell, lithium polymer cell, lithium-ion battery cell, and lithium-ion accumulator. This includes, in particular, rechargeable batteries, so-called secondary batteries. The terms "battery" and "electrochemical storage cell" are also used synonymously with the terms "lithium-ion battery" and "lithium-ion cell."

[0015] The term "electrode arrangement" refers to a sequence of layers or films. In an electrochemical storage cell, the layers follow one another in a layer sequence. However, this does not mean that the layers specified here must follow one another directly. Rather, intermediate layers may also be provided, such as a separator, insulator, electrode binder, coatings, and electrical conductivity additives, which can be applied to an electrically conductive carrier of the respective electrodes.

[0016] An electrochemical storage cell typically has several electrodes: a positive electrode (cathode) and a negative electrode (anode), which can be electrically contacted via current collectors. Each of these electrodes comprises at least one active material, optionally together with additives such as electrode binders and electrical conductivity additives, which is applied to an electrically conductive carrier (e.g., a metal foil) as a current collector for the respective electrodes.

[0017] An electrochemical storage cell comprises one or more electrochemical electrode assemblies, for example, an electrode assembly with multiple anodes, cathodes, and / or separator layers in the layer sequence. Non-porous and solid collector foils made of aluminum (for the positive electrode) or copper (for the negative electrode) are typically used as current collectors. Such collector foils are typically impermeable to liquid electrolyte and gases.

[0018] A cathode comprises a cathode active material for the current collector. The cathode active material can comprise a plurality of particles bound in an electrode binder. The cathode active material can comprise a layered oxide such as a lithium nickel manganese cobalt oxide (NMC, for example NMC 622 or NMC 811), a lithium nickel cobalt aluminum oxide (NCA), a lithium cobalt oxide (LCO), or a lithium nickel cobalt oxide (LNCO). The layered oxide can, in particular, be an overlithiated layered oxide (OLG). Other suitable cathode active materials include compounds with a spinel structure, such as lithium manganese oxide (LMO) or lithium manganese nickel oxide (LMNO), LFP (lithium iron phosphate), and lithium iron phosphate with manganese intercalation (LFMP). In addition to a binder, the cathode can contain a conductive additive or a solid electrolyte.

[0019] An anode comprises an anode active material, a binder, and optionally additional conductive additives for the current collector. The anode active material is, for example, a material from the group consisting of carbonaceous materials, silicon, silicon suboxide, silicon alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys, and mixtures thereof. The anode active material is preferably selected from the group consisting of synthetic graphite, natural graphite, graphene, mesocarbon, doped carbon, hard carbon, soft carbon, fullerene, silicon-carbon composite, silicon, surface-coated silicon, silicon suboxide, silicon alloys, lithium, aluminum alloys, indium, tin alloys, cobalt alloys, and mixtures thereof.

[0020] An electrochemical electrode arrangement for an electrochemical storage cell is described below. According to one embodiment, the electrode arrangement comprises a layer sequence with at least a first electrode and a second electrode. At least one separator layer (or separator for short) is arranged between the first and second electrodes. The separator layer comprises a porous material in which an electrolyte is embedded. The material is also elastic and reversibly deformable under pressure exerted by one of the electrodes. The electrode arrangement is, for example, part of an electrochemical storage cell. During operation, the storage cell can be charged and supply an electrical load, for example a vehicle or load in a vehicle, with power. During operation, the electrochemical electrode arrangement alternates between (at least partially) charged and discharged states.The electrodes can exhibit reversible volume changes as a result of charging and discharging. Volume expansion at the particle level creates a corresponding pressure within the electrode array. The separator layer, or multiple separator layers, are elastic and reversibly deformable under pressure. Pressure is exerted, for example, by one or more of the electrodes depending on the state of charge.

[0021] As a result, a separator layer has a volume buffer effect, i.e. a volume change caused by a charge state can be compensated for by a corresponding elastic deformation of the separator layer. For example, a volume occupied by the layer sequence remains essentially constant under pressure changes or within a predetermined (safety) volume. By choosing the material and / or number of separator layers or layer thicknesses, the volume buffer effect can be adjusted inversely to the volume change of the electrodes. Ideally, the separator layer(s) are compressed by the amount by which the electrode (or electrodes) expand, and vice versa. In this way, the electrode arrangement can occupy an essentially constant volume even during operation or remain within the boundaries of a housing or safety volume.Critical and safety-relevant pressures that could deform or damage a cell casing can be reduced or completely avoided in this way.

[0022] The concept proposed here is based in particular on the considerations outlined below. One aspect concerns the use of a separator layer which, in addition to its electrically insulating and ion-conducting function (ion conduction, for example, for lithium-ions), also has additional functionality, improving the process speed during filling with electrolyte and increasing the service life and safety of the storage cell. By designing a thicker, highly porous, and at the same time elastic separator, a volume-buffering effect can be induced. A larger pore volume of the separator both accelerates the process and enables uniform filling of the cell, for example, through the stack / winding of an electrochemical storage cell, which generally represents the most time- and therefore cost-critical point in the industrial production of the cell.

[0023] For example, depending on the cell's state of charge, lithium is incorporated into the anode (anode thickness expansion), the separator is compressed, the pores shrink, and electrolyte is forced out of the pores and can migrate into the expanded anode. A favorable layer design compresses the separator by the amount by which the anode expands. This keeps the external dimensions of the stack / winding and the pressure conditions constant, significantly supporting stable cell operation.

[0024] In one embodiment, the elastic and porous material is reversibly deformable under pressure such that the volume occupied by the layer sequence remains substantially constant under pressure changes. In other words, the volume occupied by the layer sequence does not exceed a predetermined volume under pressure changes.

[0025] In one embodiment, the first electrode is arranged between the second electrode and a further second electrode. A further separator layer is arranged between the first and further second electrode. In this way, the first electrode is surrounded by two second electrodes and separated or electrically insulated by respective separator layers. The layer sequence consisting of the first electrode, second electrodes and the separator layers in between can be supplemented by further separator layers that enclose the outer second electrodes. Due to the properties of the separator layers, the volume of the resulting layer sequence remains essentially constant under pressure changes or within certain limits, such as a housing. The layer sequence can be supplemented with further electrodes and separator layers depending on the requirements of an application.In addition, one or more electrode arrangements can be provided in an electrochemical storage cell.

[0026] In one embodiment, the first electrode is designed as a swelling anode. For example, the first electrode is designed as a swelling silicon anode. Swelling anodes are a current focus of research and development. Silicon-based anode materials typically have a much higher specific capacity, for example, 3600 mAh / g for pure silicon, compared to conventional graphite, which is limited to a maximum theoretical capacity of approximately 372 mAh / g for the fully imithiated state LiCe. The large volume change of silicon (approximately 400%, based on crystallographic densities) upon introduction of lithium is, along with its high reactivity in the charged state, one of the main obstacles to the commercialization of this type of anode and can be reduced or even overcome with the concept presented here.

[0027] In one embodiment, the elastic and porous material comprises spring elements. The spring elements are designed to make the separator layer reversibly deformable under pressure. The spring elements represent material properties and / or structures in the separator layer that impart the properties of a mechanical spring to the separator layer as a whole. The spring elements impart or support the elasticity of the separator layer, allowing it to reversibly respond to pressure exerted by the electrodes through deformation (contraction and expansion).

[0028] In one embodiment, the elastic and porous material comprises pores. The pores are reversibly compressible and expandable under pressure. The material of the separator layer forms the pores according to its porosity as a material property. The pores represent cavities in the separator layer whose size, at least on average, is suitable for receiving and storing the electrolyte of the electrode assembly. The pores themselves can have elastic properties and deform under pressure. However, this is not generally required of the material. Rather, the separator layer can comprise an elastic material and a porous material.

[0029] In one embodiment, the pores are elongated with a longitudinal axis. The pores are preferably aligned with the longitudinal axis along a preferred direction in the separator layer. Pores can form randomly or according to a distribution. In this embodiment, the pores are predominantly directional. The preferred direction is, for example, aligned along the axis along which the pressure acts due to the volume expansion of the electrodes. This direction is, for example, substantially perpendicular to the layer sequence (including the electrodes).

[0030] In one embodiment, the elastic and porous material comprises a polymer. The polymer can, for example, form polymer coils that create cavities for the storage of the electrolyte and also have elastic properties, i.e., function as spring elements. In one embodiment, the separator layer is formed as a single layer. Alternatively, the separator layer comprises several sublayers. At least one sublayer comprises the porous and elastic material, in which an electrolyte is embedded, and which is reversibly deformable under pressure, so that the volume occupied by the layer sequence remains essentially constant under pressure changes.

[0031] Furthermore, an electrochemical storage cell is proposed. In one embodiment, the storage cell comprises an electrochemical electrode arrangement according to one of the previously discussed aspects. Furthermore, the storage cell comprises a housing in which the electrochemical electrode arrangement is arranged and electrically contacted. The housing can, for example, comprise or be a round housing, a pouch for a pouch cell, or a prismatic housing.

[0032] Furthermore, a method for producing an electrochemical electrode assembly for an electrochemical storage cell is proposed. The electrode assembly comprises a layer sequence comprising a first and a second electrode. In one embodiment, a separator layer is formed between the first and second electrodes. The separator layer is formed from an elastic and porous material that is reversibly deformable under pressure, so that, for example, a volume occupied by the layer sequence remains substantially constant under pressure changes. An electrolyte is embedded in the separator layer.

[0033] Furthermore, a vehicle is proposed. The vehicle, in particular an electric vehicle, comprises at least one electrode arrangement according to one of the aspects presented above.

[0034] The following describes exemplary embodiments with reference to the accompanying drawings. These provide further details, preferred embodiments, and further developments.

[0035] Identical or functionally identical components are provided with the same reference numerals in the figures. The components shown, as well as their relative sizes, are not to scale. To the extent that components and parts are functionally identical in the various figures, their description is not necessarily repeated for each of the following figures. Brief description of the drawings

[0036] In detail, schematically show

[0037] Figure 1 shows an embodiment of an electrode arrangement for an electrochemical storage cell

[0038] Figure 2 shows an embodiment of a separator layer,

[0039] Figure 3 shows another embodiment of a separator layer,

[0040] Figure 4 shows another embodiment of a separator layer, and

[0041] Figure 5 shows another embodiment of a separator layer.

[0042] Detailed description

[0043] Figure 1 shows an exemplary embodiment of an electrode arrangement for an electrochemical storage cell. The electrode arrangement comprises a layer sequence that may include multiple electrodes and separator layers. Three electrodes are shown as an example, arranged between separator layers. The separator layers spatially and electrically separate the electrodes from one another. The layer sequence shown can be expanded with additional electrodes and separator layers, which is indicated in the figure by dots on the left and right edges. The number of layers used is limited solely by the present application and is limited here only for the purpose of clarity.

[0044] In this exemplary embodiment, a first electrode 10 is designed as an anode. The first electrode 10 comprises an anode current collector 11 and an anode active material 12 embedded in a matrix of electrically conductive additive and binder. The anode active material 12 is, for example, a material from the group consisting of carbon-containing materials, silicon, silicon suboxide, silicon alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys, and mixtures thereof. For example, the anode active material 12 is selected from the group consisting of synthetic graphite, natural graphite, graphene, mesocarbon, doped carbon, hard carbon, soft carbon, fullerene, silicon-carbon composite, silicon, surface-coated silicon, silicon suboxide, silicon alloys, lithium, aluminum alloys, indium, tin alloys, cobalt alloys, and mixtures thereof.

[0045] For example, the anode or anodes are designed as swelling or shrinking anodes (or lithium metal anodes). In this example, the anode active material 12 comprises silicon. Silicon-based anodes are a promising development for lithium-ion batteries. Silicon has a high specific capacity, meaning it can store more lithium ions per gram than, for example, graphite. This makes silicon an attractive material for anodes. The anode active material 12 comprises, for example, silicon particles or silicon nanowires with conductive binders, electrically conductive additives, and carrier materials. This mixture is applied to the anode current collector 11. Alternatively, nanostructures such as porous silicon or silicon nanoparticles can be used.One advantage of silicon as an anode material 12 is its ability to absorb and release lithium ions on a larger scale during the charging and discharging process. However, the absorption of lithium ions leads to a volume change in the silicon material, which can lead to mechanical stress and fractures. This is often referred to as "volume expansion."

[0046] The illustrated second electrodes 20 are designed as cathodes. A second electrode 20 also comprises a cathode current collector 21 and a cathode active material 22. The cathode active material 22 can comprise a plurality of particles bound into an electrode binder. The cathode active material 22 can comprise a layered oxide such as a lithium nickel manganese cobalt oxide (NMC, for example NMC 622 or NMC 811), a lithium nickel cobalt aluminum oxide (NCA), a lithium cobalt oxide (LCO), or a lithium nickel cobalt oxide (LNCO). The layered oxide can, in particular, be an overlithiated layered oxide (OLG). Other suitable cathode active materials 22 are compounds with spinel structure, such as lithium manganese oxide (LMO), lithium iron phosphate (LFP), lithium iron phosphate with manganese intercalation (LFMP) or lithium manganese nickel oxide (LMNO).In addition to a binder, the cathode can contain a conductive additive or solid electrolyte. The electrode current collectors 11, 21 each comprise a conductive material. Examples of lithium-ion-based electrochemical storage cells include copper (Cu) for an anode current collector 11 and aluminum (Al) for a cathode current collector 21.

[0047] The separator layers 30 are arranged between the electrodes 10, 20 or comprise the electrode arrangement. The separator layers 30 comprise a separator material that is both porous and elastic. The separator layers 30 comprise a material that is permeable to the ions that serve as charge carriers for the respective electrochemical storage cell. In the case of a lithium-ion battery, the separator layers 30 are permeable to lithium ions. Due to their porosity, an electrolyte can be incorporated into the separator layers 30. Furthermore, the separator layers 30 are reversibly deformable under pressure such that the volume occupied by the layer sequence remains essentially constant under pressure changes. Due to their porosity, the separator material forms pores, so that the separator layers 30 comprise a pore space made up of pores. The electrolyte is incorporated into the pores and thus fills the pore space.The pore size is (at least on average) designed so that the pores or pore space can accommodate the electrolyte or electrolyte particles. The electrolyte can be a liquid or a solid electrolyte.

[0048] A possible electrolyte consists of at least one dissolved lithium salt in at least one solvent. In so-called "non-aqueous" electrolytes of LIBs, lithium hexafluorophosphate (LiPF6) salt is dissolved in organic carbonates, for example, as mixtures of ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), diethyl carbonate (DEC), and / or ethyl methyl carbonate (EMC). Additives such as VC (vinylene carbonate) and, for Si-containing anodes, especially fluoroethylene carbonate (FEC), have positive effects on the long-term stability of the cell.

[0049] The illustration in Figure 1 shows the exemplary electrode arrangement in a charged state (bottom) and in a discharged state (top). It is indicated that the separator layers 30 have different layer thicknesses in the different states. In this exemplary embodiment, the layer thickness of the separator layers 30 decreases with ongoing charging compared to the discharged state. In addition, the layer thickness of the anode (or the first electrode 10) changes inversely, i.e., the layer thickness of the anode increases with ongoing charging compared to the discharged state. This volume expansion of the anode is compensated for by the opposing contraction of the separator layers 30. In this sense, the separator layers 30 have a volume-buffering effect. The volume expansion of the anode is reversible and, when the anode layer thickness contracts, is compensated for by an expansion of the separator layers 30.Further details are explained in connection with the following figures.

[0050] Figure 2 shows an exemplary embodiment of a separator layer. The separator layer 30 is filled with an electrolyte 40 or mixed with a solid electrolyte. The electrolyte 40 is indicated by dashed lines. The separator layer 30 shown can be implemented as a single layer or as part of a layer sequence comprising multiple separator layers. Furthermore, an electrochemical electrode arrangement typically contains multiple separator layers. Where reference is made to one separator layer in the following, the discussed features and technical effects can be applied equally to multiple separator layers.

[0051] The separator layer 30 comprises an elastic and porous material. The material is represented in the figure by resilient elements 31, which, for example, compress under the application of force (shown in the figure below) and reversibly expand again after the force is released (shown in the figure above). The force can be applied by an anode swelling during the charging process, for example, an anode with a silicon content in the anode active material 12, so that a compression pressure acts on the separator layer 30. As the discharge progresses, the separator layer 30 is relieved of stress because the anode contracts. The compression pressure on the separator layer 30 decreases accordingly. By designing a thicker, highly porous, yet elastic separator 30, a volume-buffering effect is induced.

[0052] Also shown is a filling of the separator layer 30 with electrolyte 40 (dashed line). In the figure above, the separator layer 30 is filled with electrolyte 40. The electrolyte is embedded in the pores of the layer. A larger pore volume of the separator layer 30 accelerates and guarantees the uniform filling of the cell throughout the stack / winding of an electrochemical storage cell (the most time- and therefore cost-critical point in assembly). This can improve the process speed for filling a cell with electrolyte. When the electrochemical storage cell is charged, the state of the electrode arrangement changes. For example, lithium ions are incorporated into the anode during charging. The layer thickness of the anode increases (e.g., swelling of the Si anode).Due to the swelling of the anode caused by the incorporation of lithium into the anode (expansion of the anode thickness), the separator layers 30 are compressed during cell operation, shrinking the pores. As a result, electrolyte 40 is forced out of the pores of the separator layers 30 and can migrate into the expanded anode. With an optimal design, the separator layers are compressed by the amount by which the anode swells. This keeps the external dimensions of the cell (e.g., stack / winding) and the pressure conditions constant, significantly supporting stable cell operation.

[0053] Polymer coils, which can be produced by chain polymerization, can serve as separator material 30, for example. The term "polymer coil" refers to an unstructured, chaotic collection of polymer chains or polymer molecules. A polymer coil is formed, for example, when polymer chains are loosely intertwined, which leads to non-covalent bonds (van der Waals forces or hydrogen bonds) through the interaction of end groups, or when they are in a disordered state. A polymer coil can occur in both the solution and the solid state. In solution, polymer coils can be formed by the interplay between polymer concentration, solvent molecules, and the movement of the polymer chains. In the solid state, polymer coils can arise due to the way the polymer chains were joined during the production of the material or due to the influence of external forces such as temperature or pressure.The structure and properties of a polymer coil can play an important role in the mechanical, thermal, and optical properties of a polymer material. The organization of the polymer chains within the coil can influence the material properties, such as elasticity, toughness, or permeability to gases and liquids. Polymer coils therefore comprise coiled or crimped polymer threads that form a kind of spring structure that can be elastically deformed, for example, stretched again after a release of force. Examples include long-chain polyolefins such as polyethylene (PE) or polypropylene (PP).

[0054] On the one hand, the polymer coils represent resilient elements that impart elasticity and the volume buffer effect to the separator layer. On the other hand, the polymer coils can form a pore structure into which the electrolyte or electrolyte particles can be embedded. Figure 3 shows a further exemplary embodiment of a separator layer. The separator layer 30 explained in connection with Figure 2 comprises, for example, a layer containing the separator material. As shown in Figure 3, the separator layers 30 themselves can be constructed from multiple layers, such as three layers. A middle layer 32 can comprise the porous and elastic separator material, as described above. In particular, the middle layer 32 is at least elastic and can preferably also be porous. The outer layers 33, 34 are, for example, only porous. This can be achieved using a different material, for example a different polymer.Alternatively, the layers can be made of the same material, but differ in the degree of polymerization from the other layers. For example, the spring elements or polymer coils mentioned above may only be significantly present in the middle layer. In this example, pores are formed in the three layers into which electrolyte can be absorbed. In contrast, only the middle layer is elastic and reversibly deformable under pressure.

[0055] Figure 4 shows another embodiment of a separator layer. The separator layer 30 shown can be a single layer or part of a layer sequence comprising multiple separator layers. Furthermore, an electrochemical electrode arrangement typically comprises multiple separator layers. While reference is made to one separator layer in the following, the discussed features and technical effects can be applied equally to multiple separator layers.

[0056] Pores 35 are indicated in the figure. Also shown is the filling of the separator layer 30 with electrolyte 40 (dashed line). In the figure, the separator layer 30 is filled with electrolyte 40 at the top. The electrolyte is embedded in the pores 35 of layer 40, which are depicted as rectangles. The rectangles represent elongated pores, which are arranged, for example, along a preferred direction in the separator layer. In the layer sequence, the preferred direction is perpendicular to the plane of the separator layer and thus also perpendicular to the electrode (anode).

[0057] When the electrochemical storage cell is charged, the state of the electrode arrangement changes. For example, lithium ions are incorporated into the anode during charging. The anode layer thickness increases (e.g., swelling of the Si anode). Due to the swelling of the anode due to the incorporation of lithium into the anode (expansion of the anode thickness), the separator layers 30 are compressed during cell operation, and the pores 35 are compressed and take up a smaller pore volume. This is indicated graphically in the figure by circles, which result from the initially shown rectangles under pressure. Regardless of the specific shape of the pores, the pore volume becomes smaller under pressure. As a result, electrolyte 40 is forced out of the pores 35 of the separator layers 30. Free electrolyte is available to fill the anode and can migrate into the expanded anode.In an optimal design, the separator layers 30 are compressed by the amount by which the anode swells. This keeps the cell's external dimensions (e.g., stack / winding) and pressure conditions constant, significantly supporting stable cell operation.

[0058] Figure 5 shows an example pore of a separator layer. The figure depicts a pore 35, which is discussed as representative of the pores in the separator layer or layers 30. Initially, the pore 35 is relaxed and filled with electrolyte 40 (see figure on the left). Charging the electrochemical cell causes ions (here lithium ions) to be incorporated into the electrode 10 (here the anode). This causes the anode to swell, increase its volume, and exert a corresponding pressure on the separator layer 30. Electrolyte 40 is forced out of the pore 35 by pressure (here: on the "short side" of the elongated pores) and is thus released. Free electrolyte is available to fill the anode and can migrate into the expanded anode.

[0059] The pore structure is so stressed by the charging process that, upon discharging the cell, it reversibly expands back into the upright pore with respect to the preferred direction. In other words, the pores 35 themselves represent the spring elements introduced in connection with Figure 2 and impart elasticity to the separator layer 30. The degree of deformability of the pores under the pressure of the anode expansion can be influenced by the shape and orientation of the pores in the separator layer 30, so that the external dimensions of the cell and the pressure conditions can be kept essentially constant during alternating charging and discharging.

[0060] Although the disclosure has been illustrated and described in detail using exemplary embodiments, the invention is not limited by the exemplary embodiments. Rather, other variations of the disclosure may be derived therefrom by those skilled in the art without departing from the scope of the invention as defined by the claims.

[0061] List of reference symbols

[0062] 10 first electrode

[0063] 11 Anode current collector 12 Anode active material

[0064] 20 second electrode

[0065] 21 cathode current collectors

[0066] 22 Cathode active material

[0067] 30 separator layer 31 resilient element

[0068] 32 middle layer

[0069] 33 outer layer

[0070] 34 outer layer

[0071] 35 Pore 40 Electrolyte

Claims

1 . An electrochemical electrode arrangement for an electrochemical storage cell comprising a layer sequence with at least: - a first electrode (10), - a second electrode (20), - a separator layer (30) arranged between the first and second electrodes (10, 20), wherein: - the separator layer (30) comprises an elastic and porous material in which an electrolyte is embedded and which is reversibly deformable under a pressure exerted by one of the electrodes as a function of the state of charge, so that a volume occupied by the layer sequence remains substantially constant under pressure changes, so that the volume occupied by the layer sequence does not exceed a predetermined volume.

2. The electrode arrangement according to the preceding claim, wherein - the first electrode (10) is arranged between the second electrode (20) and a further second electrode (20), and - a further separator layer (30) is arranged between the first and further second electrode (20).

3. The electrode arrangement according to one of the preceding claims, wherein the first electrode (10) is designed as a swelling anode, for example as a swelling silicon anode.

4. The electrode arrangement according to one of the preceding claims, wherein the elastic and porous material comprises spring elements which are configured to make the separator layer (30) reversibly deformable under pressure.

5. The electrode assembly according to any one of the preceding claims, wherein the elastic and porous material comprises pores (35) that are reversibly compressible and expandable under pressure.

6. The electrode arrangement according to one of the preceding claims, wherein the pores (35) are elongated with a longitudinal axis, and the pores (35) are aligned with the longitudinal axis preferably along a preferred direction in the separator layer (30).

7. The electrode assembly according to any one of the preceding claims, wherein the elastic and porous material comprises a polymer.

8. The electrode arrangement according to one of the preceding claims, wherein - the separator layer (30) is formed as a single layer, or - the separator layer (30) comprises a plurality of partial layers, wherein at least one partial layer comprises the elastic and porous material in which an electrolyte is embedded and which is reversibly deformable under pressure, so that the volume occupied by the layer sequence remains substantially constant under pressure changes.

9. An electrochemical storage cell, - an electrochemical electrode arrangement according to one of the preceding claims, and - a housing in which the electrochemical electrode arrangement is arranged and electrically contacted.

10. A method for producing an electrochemical electrode arrangement for an electrochemical storage cell with a layer sequence comprising a first and second electrode (10, 20), wherein: - a separator layer (30) is formed between the first and second electrodes (10, 20), - the separator layer (30) is formed from an elastic and porous material which is reversibly deformable under pressure, so that a volume occupied by the layer sequence remains substantially constant under pressure changes, and - an electrolyte is incorporated into the separator layer (30).

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