Electrode assembly for an energy storage cell

Abstract

The invention relates to an electrode assembly (100, 200) for an energy storage cell (300), comprising: A first electrode, which comprises a current collector (110) of a first metal and a layer (120) having an active material in which alkali-metal-ions can be stored, and which is arranged at the current collector (110); a second electrode, which comprises an array of nanostructures (140) of a metal oxide of a second metal, wherein the nanostructures (140) of the array of nanostructures (140) comprise cavities which are configured to store alkali-metal; a metal base layer (150) of a third metal which is mechanically connected to the array of nanostructures (140); wherein the layer (120) having an active material is arranged between the current collector (110) and the array of nanostructures (140).

Description

[0001] ELECTRODE ASSEMBLY FOR AN ENERGY STORAGE CELL

[0002] The present invention is directed to an electrode assembly for an energy storage cell, an energy storage cell, a device and a method, for manufacturing an electrode assembly.

[0003] In the field of energy storage cells, in particular rechargeable energy storage cells, alkali- metal-ion based batteries, in particular lithium-ion batteries, are widely used.

[0004] The applications for such energy storage cells are for example electrical or electronic devices, such as smartphones, computers and in the field of electromobility, such as electric or hybrid vehicles and in stationary energy storage applications. At such batteries an electrode assembly is used where alkali-metal-ions can be stored in an active material, such as graphite as an anode, and wherein the stored alkali-metal-ions then can be used for providing an electrical current for an electrical device. Lithium-ion batteries currently comprise a higher energy density compared to other batteries such as sodium- ion batteries, at least at normal operating temperatures.

[0005] However, compared to lithium, sodium has a better availability regarding the required effort for obtaining the material and the overall available volume. Known sodium-ion batteries, however, comprise electrodes of hard carbon as active materials for anodes. Hard carbon can provide a lower capacity at reasonable rates in comparison to graphite being the standard for lithium-ion cells. Sodium-ions have a larger radius than lithium, therefore they are less suitable for being stored in graphite.

[0006] It is known from US 2020 / 194773 A1 to use an array of metal oxide nanostructures as a template in the manufacturing process of an electrode assembly, whereby the array of metal oxide nanostructures is removed before the electrode assembly is completed.

[0007] It is known from CHEN JINGJUAN ET AL: "Performance of through-hole anodic aluminum oxide membrane as a separator for lithium-ion battery", JOURNAL OF MEMBRANE SCIENCE, vol. 461, 1 July 2014 (2014-07-01), pages 22-27 to use an array of metal oxide nanostructures as a separator between the positive electrode and the negative electrode of an electrode assembly, forming a diffusion path for Li ions between the positive electrode and the negative electrode, not playing any role in the electrochemical reactions or storage of Li ions in the electrodes. It is known from KR 101 319 461 B1 to use an array of metal oxide nanostructures as an active material at the positive electrode of an electrode assembly.

[0008] It is known from US 2014 / 212733 Al to use an array of metal oxide nanostructures as active material at the negative electrode, wherein alkali-metal ions chemically react with the metal oxide of the nanostructures for storing alkali-metal ions in the reaction product.

[0009] It is an object of the present invention to provide an improved electrode assembly for an energy storage cell which can make use of alkali-metal-ions.

[0010] A solution to this problem is provided by the teaching of the independent claims. Various preferred embodiments of the present invention are provided by the teachings of the dependent claims.

[0011] A first aspect of the solution is directed to an electrode assembly for an energy storage cell, comprising: (i) A first electrode, which comprises (i-a) a current collector, in particular a metal foil, of a first metal, in particular aluminium or copper, and (i-b) a layer having an active material in which alkali-metal-ions, in particular lithium-ions or sodium-ions, can be stored, and (i-c) which is arranged at the current collector; (ii) a second electrode, which comprises (ii-a) an array of nanostructures of a metal-oxide of a second metal, in particular aluminium, wherein (ii-b) the nanostructures of the array of nanostructures comprise cavities which are configured to store alkali-metal (iii) a metal base layer of a third metal which is mechanically connected to the array of nanostructures (iv); wherein the layer having an active material is arranged between the current collector and the array of nanostructures.

[0012] Where the term "comprising" or “including” is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated.

[0013] Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). The term "one" as used herein are defined in the sense of "one or more". The terms "another" and "a further" and any other variant thereof are to be understood in the sense of "at least one more".

[0014] The term "plural" as used herein shall be understood in the sense of "two or more".

[0015] The term "configured" or "set up" to perform a certain function (and respective variations thereof) as used herein shall be understood as meaning that the corresponding material, item or device is already present in a configuration or setting in which it can perform the function or that it is at least adjustable - i.e. configurable - in such a way that it can perform the function after corresponding adjustment, taking into account other materials, items or devices with which the concerned material, item or device is specified to form a larger device or system. In this context, the configuration can be carried out, for example, by means of a corresponding setting of parameters of a process sequence or of switches or the like for activating or deactivating functionalities or settings. In particular, the device can have several predetermined configurations or operating modes, so that the configuration can be performed by means of a selection of one of these configurations or operating modes.

[0016] The term "electrode stack" as used herein is to be understood in particular as a device comprising a plural of electrode assemblies according to the disclosure. Such an electrode assembly can be configured to store chemical energy and to release electrical energy. The electrode assembly can be repeated as often as desired within the electrode stack. Preferably, the electrode assembly can be wound up to form an electrode coil. In the following, the term "electrode stack" is also used for electrode coils or other arrangements of electrode assemblies such as a so-called “z-folded” arrangement. Before electrical energy is released, stored chemical energy is converted into electrical energy. During charging, the electrical energy supplied to the electrode stack is converted into chemical energy and stored.

[0017] The term "current collector" as used herein is to be understood as a component that is made from an electronically conductive material and which is applied to an electrochemically active material in which electrochemical reactions take place at the positive electrode or negative electrode in order to collect electrons from or distribute electrons to the electrochemically active material and thereby provide a low-resistance path for the flow of electric current. The term "electrolyte" as used herein refers to a liquid or solid material through which ions, in particular sodium-ions, can move, enabling current transport between electrodes of a battery, in particular between a cathode and an anode. In contrast to the electronic conductivity (by electrons) in the electrode materials, the electrolyte must be ionically conductive, i.e. conduct the electric current by transporting charged atoms or molecules (ions). In particular, the electrolyte has a high electrical resistance. The electrolyte is preferably chemically stable against decomposition in a wide temperature window and electrochemically stable in the widest possible voltage window. Ideally, it is non-toxic and non-flammable and has at least a high flash point and a low heat of combustion. Liquid systems may be favoured over polymer and solid electrolytes due to their better ion conductivity.

[0018] The term "separator" or "separator layer" as used herein means, in particular, an electronically insulating device which separates and distances an anode from a cathode. Preferably, a separator layer is applied to an anode layer and / or a cathode layer. Preferably, the separator layer is formed as an independent body. The separator or the separator layer can also at least partially contain an electrolyte, whereby the electrolyte preferably contains sodium ions. The electrolyte can also be electrochemically effectively connected to neighbouring layers of an electrode stack or electrode coil. Preferably, a separator is thin-walled, particularly preferably in the form of a microporous film. Preferably, the separator layer or the separator extends at least partially over a boundary edge of at least one electrode. Particularly preferably, the separator layer or the separator extends beyond all boundary edges of neighbouring electrodes.

[0019] The term "active material" as used herein means in particular a material which can be electrochemically active and which is suitable for coating electrodes for battery cells and in which alkali-metal- ions, in particular sodium ions, can be stored. In particular, the active material for a cathode can be a Prussian blue analogue, a sodium layered oxide, such as sodium manganese oxide, sodium iron manganese oxide, a polyanionic material, such as sodium vanadium iron phosphate, a combination of the aforementioned materials or another material.

[0020] The term “alkali-metal” as used herein means in particular a plurality of zerovalent atoms of the chemical elements lithium or sodium. The term alkali-metal-ion means an ion of chemical elements lithium or sodium. The term "substantially equal" as used here means in particular that two values, in particular distance values, do not deviate from each other by more than 10%, in particular not more than 5%.

[0021] The electrode assembly according to the first aspect can enable a higher energy density compared to electrode assemblies which comprise a second electrode, an anode, with a layer having an active material, because according to the current disclosure, the alkali- metal-ions can be stored directly in the cavities of the nanostructures as alkali-metal and not in a chemical bond as in traditional Li-ion or Na-ion electrode assemblies.

[0022] For example, at lithium-ion based electrode-assemblies the lithium-ions can be stored via intercalation in a graphite structure, which means the lithium-ions are then spatially separated due to the structure of the graphite. In the current invention, when the alkali- metal-ions are stored in the nanostructures, they are deposited as metal.

[0023] Overall, the stored ion-density per volume can be improved by the electrode assembly according to the first aspect. This can enable an energy storage cell with a higher energy density which comprises such an electrode assembly. In operation of the electrode assembly, i.e. , when the electrode assembly is charged or discharged, the array of nanostructures can act as separator when none of the cavities of the nanostructures is completely filled with metal-alkali. As in this case no additional separator is needed, the electrode assembly is smaller in height compared to an electrode assembly with an additional separator. The metal base layer can enable an easy and efficient connection to the array of nanostructures. Thereby the metal base layer can act as a current collector.

[0024] In the following, certain preferred embodiments of the electrode assembly will be described, which can be arbitrarily combined with each other or with other aspects of the present solution, unless such combination is explicitly excluded or technically impossible.

[0025] In some embodiments the second metal is the same as the third metal and the nanostructures of the array of nanostructures comprise an oxidized metal of the third metal, in particular aluminium-oxide (AI2O3). This array of nanostructures of an oxidized metal of the metal base layer enables an efficient manufacturing process because it is based on the same metal as the metal base layer and can be achieved by an anodization process of the metal base layer. This also enables that the metal base layer and the array of nanostructures are directly mechanically connected. In some embodiments the metal oxide of the second metal is electronically insulating.

[0026] In some embodiments the second metal is aluminium, the oxide AI2O3of which is by its nature electronically insulating.

[0027] This is advantageous because in such a case, during charging of the electrode assembly, in other words during deposition of the alkali-metal, the alkali-metal is first deposited closest to the metal base layer an then progressively fills up the cavities, whereas with an electronically conducting oxide of the second metal, alkali-metal deposition would occur randomly in the cavities, leading to a much lower degree of filling.

[0028] It is noted that a material is considered electronically insulating if it has an electronic conductivity of at most 1 pS / cm, and preferably of at most 1 nS / cm.

[0029] In some embodiments the third metal is aluminium or copper, because it is cheap and corrosion resistant inside a battery.

[0030] In some embodiments the electrode assembly comprises an interface between the metal base layer and the array of nanostructures, wherein the metal base layer and the array of nanostructures are directly, meaning without intermediate layer, mechanically connected.

[0031] Preferably the metal base layer and the array of nanostructures are directly mechanically connected over at least 90%, preferably at least 95% and more preferably at least 98% of the area of the interface.

[0032] In some embodiments the electrode assembly comprises an interface between the metal base layer and the array of nanostructures, wherein the metal base layer and the array of nanostructures are electrically connected over at least 90%, preferably at least 95% and more preferably at least 98% of the area of the interface.

[0033] The interface between the metal base layer and the array of nanostructures is limited to the surfaces at which the metal base layer and the array of nanostructures would be in contact if they were pressed together at sufficient pressure to ensure good contact but without deforming them. The area of said interface therefore excludes holes, indentations, cavities etc in one or both of the metal base layer and the array of nanostructures. In some embodiments the first metal, the second metal and the third metal are the same. This enables a more effective manufacturing because only one metal is required.

[0034] In some embodiments the electrode assembly comprises a separation layer which is arranged between the layer having an active material and the array of nanostructures, and which electronically isolates the first electrode from the second electrode. This separation layer can avoid a short cut by avoiding an electrical connection between the first electrode and the second electrode.

[0035] In some embodiments the cavities comprise openings which are facing the layer having an active material. This enables an efficient storing of the alkali-metal when a bias is applied to the electrode assembly in the charging process, because in this case the movement of the alkali-metal-ions is directed towards the openings.

[0036] In some embodiments the nanostructures are arranged in a hexagonal closest packing. This enables a high ratio of nanostructures per area, which enables a high number of alkali-metal-ions which can be stored in the array of nanostructures. In this way the energy density which can be provided by the electrode assembly can be increased.

[0037] In some embodiments the cavities are at least partially filled with alkali-metal, in particular before assembling an energy storage cell including the electrode assembly. This ensures a sufficient number of alkali-metal-ions at the electrode assembly when operated at the energy storage cell.

[0038] In some embodiments the nanostructures of the array of nanostructures comprise nanotubes, which are aligned to each other. Such nanotubes can be grown by anodizing of a metal sheet, such as the metal foil. During such an anodization process a voltage can be applied and causing side walls of neighbouring nanotubes to repel each other, and nanotubes with aligned walls can grow. The alignment of the tube shapes enables that the alkali-metal can be stored in the nanostructures and exit the nanostructures as alkali-metal-ions efficiently.

[0039] In some embodiments, materials with which alkali-metal ions can chemically react at STP or in which alkali-metal ions can intercalate at STP are absent from the array of nanostructures and from the metal base layer and from any space, if present, between the metal base layer the array of nanostructures. It is noted that STP means standard temperature and pressure, as defined by IIIPAC.

[0040] In some embodiments each of the nanotubes of the array of nanotubes has a diameter regarding its cross-section which is between 10 and 500 nm, in particular 10 nm to 100 nm, in particular 400 nm to 500 nm. With increasing diameter, the available energy density by the array of nanostructures can be increased. With decreasing diameter, a guidance of the deposition of the alkali-metal-ions into the cavities of the nanostructures as alkali-metal can be improved. A diameter range between 10 nm and 100nm is therefore advantageous for guiding the deposition of the alkali-metal-ions into the cavities. A diameter range between 400 nm to 500 nm is advantageous as it enables a higher available energy density by the array of nanostructures.

[0041] A second aspect of the solution is directed to an energy storage cell comprising a housing, an electrode assembly of any of the preceding claims which is arranged in the housing and wherein the housing is at least partially filled with an electrolyte with alkali- metal-ions wherein the electrolyte at least partially encloses the electrode assembly.

[0042] In some embodiments, the energy storage cell is an energy storage cell having an alkali- metal anode, in other words an energy storage cell having a metallic anode, in yet other words an energy storage cell of the type known in the technical field as lithium metal energy storage cell or sodium metal energy storage cell.

[0043] A third aspect of the present solution is directed to a device comprising an energy storage cell of the second aspect.

[0044] A fourth aspect of the solution is directed to a method for manufacturing an electrode assembly. The method comprises: (i) Providing a first electrode, which comprises a current collector, in particular a metal foil, of a first metal and a layer having an active material in which alkali-metal-ions can be stored, and which is arranged at the current collector; (ii) Providing a second electrode, which comprises an array of nanostructures, in particular nanotubes, of a second metal, in particular a metal oxide, wherein the nanostructures of the array of nanostructures comprises cavities which are configured to store alkali-metal; (iii) Providing a metal base layer of a third metal which is mechanically connected to the array of nanostructures; (iv) Arranging the layer having an active material of the first electrode between the current collector and the array of nanostructures.

[0045] In some embodiments the array of nanostructures is manufactured, in particular before manufacturing the electrode assembly, comprising the steps: (i) Providing a sheet of a the second metal (ii) Anodizing the surface of the sheet to obtain a patterned metal sheet with an anodized structure of the second metal which is grown on the seeds; (iii) Removing the anodized structure for obtaining a regular pattern at the surface of the sheet; (iv) Anodizing the patterned metal sheet for growing aligned nanostructures of an anodized metal.

[0046] In some embodiments a process for removing the patterned metal sheet is applied. This enables to separate the patterned metal sheet from the nanostructures to obtain the nanostructures as a separate structure.

[0047] The various embodiments and advantages described above in connection with the first aspect similarly apply to the other aspects.

[0048] Further advantages, features and applications are provided in the following detailed description of preferred embodiments and the appended figures, wherein:

[0049] Fig. 1 schematically illustrates a cross-sectional view of an electrode assembly according to an embodiment;

[0050] Fig. 2 schematically illustrates a cross-sectional view of an electrode assembly according to a further embodiment;

[0051] Fig. 3 schematically illustrates a cross-sectional view of a battery cell according to an embodiment; and

[0052] Fig. 4 Manufacturing scheme of an array of nanostructures.

[0053] In the figures, identical reference signs are used for the same or mutually corresponding elements.

[0054] DETAILED DESCRIPTION OF EMBODIMENTS

[0055] Fig. 1 schematically illustrates a cross-sectional view of an electrode assembly 100 according to an embodiment of the invention. The electrode assembly 100 comprises a metal foil 110, which can comprise or consist of for example aluminium or copper. At a surface of the metal foil 110 a layer 120 having an active material is arranged which is configured to store alkali-metal-ions such as sodium-ions, lithium-ions or potassium ions, for example, in case of lithium, lithium nickel manganese cobalt oxide or lithium iron phosphate, or, in the case of sodium, Prussian blue analogs such as Na2Fe[Fe(CN)6, sodium nickel manganese cobalt oxide, sodium vanadium phosphate or sodium iron phosphate.

[0056] The electrode assembly 100 further comprises nanostructures 140, in particular nanotubes, and a metal base layer 150. The nanostructures 140 are, in this example but not necessarily, based on the same metal as the metal base layer 150 and can be obtained by anodizing the metal base layer 150. As a result, the nanostructures 140 comprise, or are of formed from, an oxidized metal of the metal base layer 150.

[0057] For example, the metal base layer can be made of aluminium or an aluminium alloy, whereas the nanostructures then have aluminium-oxide, AI2O3. The nanostructures 140 can be obtained by a process as described in Fig. 4.

[0058] Further the electrode assembly 100 comprises a separation layer 130 which is electrically isolating with respect to electrons, but which can be permeated by ions, in particular by alkali-metal-ions.

[0059] The nanostructures can be arranged as an array of nanostructures 140 wherein each of the nanostructures comprise a cavity which is closed on one side and has an opening on an opposite side to the closed side, whereas the openings are facing the separation layer 130.

[0060] Ideally, the nanostructures 140 are arranged in a hexagonal closest packing which can result in a packing efficiency of about 90%. The density of the aluminium-oxide can be up to 4g / cm3. The nanostructures 140, in particular nanotubes, can comprise a diameter in their cross-section between 20 nm and 500 nm. With increasing diameter, the available energy density by the array of nanostructures 140 can be increased. With decreasing diameter, a guidance of the deposition of the alkali-metal-ions into the cavities of the nanostructures 140 as alkali-metal can be improved.

[0061] The nanostructures are straight and extend parallel to each other in a first direction, which is, in figs. 1-3 the vertical direction. The array of nanostructures 140 preferably has a thickness, meaning a dimension in the direction from the metal foil 110 to the metal base layer, in other words a dimension in the first direction, of between 1 and 100 pm, and in this example circa 50 pm.

[0062] The cavities in the array of nanostructures 140 are, in this example, closed at their lower end. The thickness of the oxide material forming the closure of the cavities is preferably between 10 and 100nm, and in this example circa 20nm.

[0063] The metal foil 110 and the layer 120 together form a first, positive, electrode of the electrode assembly 100, and the array of nanostructures 140 together form a second, negative electrode of the electrode assembly 100.

[0064] The metal foil 110, respectively the metal base layer 150, act as current collectors in the electrode assembly 100.

[0065] Fig. 2 schematically illustrates a cross-sectional view of an electrode assembly 200 according to a further embodiment.

[0066] In contrast to the electrode assembly according to Fig. 1 the electrode assembly 200 according to Fig. 2 does not comprise a separation layer 130. Other than that, the electrode assemblies of Figs. 1 and 2 are identical.

[0067] Such an electrode assembly 200 without a separation layer 130 requires less space and the overall energy density of a battery cell 300 comprising an electrode assembly 200 can be improved.

[0068] It is also possible that in the electrode assemblies according to Figs. 1 and 2 the nanostructures 140 are used without the metal base layer 150. In this case in a manufacturing process for manufacturing the nanostructures 140 the metal base layer 150 is etched away as is described in Fig. 4. In such a case an alternative metal base layer 150, to act as current collector, needs to be provided.

[0069] As an example a metal base layer 150 made of copper, with an array of nanostructures 140 made of aluminium oxide, can be used. The interface between the metal base layer 150 and the array of nanostructures 140 should preferably be such that areas without electrical contact are minimised. Therefore it is preferential that the metal base layer 150 and the array of nanostructures 140 should be both mechanically and electrically connected over a large proportion of the area of their interface.

[0070] In case the array of nanostructures 140 is manufactured according to steps (a)-(d) of the method described below, as a consequence of the manufacturing method 100% of interface of the the metal base layer 150 and the array of nanostructures 140 is electrically and mechanically connected. In case the array of nanostructures 140 is manufactured by including step (e) of the method described below, pressure needs to be applied to the metal base layer 150 and the array of nanostructures 140 to ensure good contact.

[0071] Fig. 3 schematically illustrates a cross-sectional view of a battery cell 300 according to an embodiment in a charged state. The battery cell 300 comprises a housing 310 in which an electrode assembly 100 according to Fig. 1 is arranged. It is also possible that instead of the electrode assembly 100 an electrode assembly 200 according to Fig. 2 or another electrode assembly which relates to the current disclosure is arranged in the housing 310. The battery cell 300 comprises electrical connections for receiving a voltage by an electrical device between the metal foil 110 and the metal base layer 150 of the nanostructures 140.

[0072] The housing is filled with an electrolyte, which is conductive to alkali-metal-ions, for example sodium-ions. After a completed charging process at least a substantial number of the alkali-metal-ions, in particular more than half of the alkali-metal-ions, and in an ideal case all of the alkali-metal-ions, are deposited into the cavities of the nanostructures 140 as alkali-metal due to an applied voltage using the electrical connection 330 In case there is no separation layer 130 present, as in the electrode assembly 200 of Fig. 2, the nanostructures 140 act as separator between the metal foil 110 and the metal base layer 150 if none of the nanostructures 140 is completely filled with alkali-metal.

[0073] In a discharge process when an electrical device 320 is using the electrical energy of the battery cell 300, the alkali-metal is removed as alkali-metal-ions from the nanostructures 140 and an electrical current can flow between the metal base layer 150 and the metal foil 110 via the electrical connection 330 and the electrical device 320. The alkali-metal- ions are then stored in the layer 120 having an active material.

[0074] Fig. 4 Manufacturing scheme of an array of nanostructures 140.

[0075] Step (a) comprises providing a metal sheet 410, for example of aluminium.

[0076] Step (b) anodizing the surface of the metal sheet 410 to obtain a patterned metal sheet 160 and a structure 420 of an anodized metal, for example aluminium-oxide. In some embodiments the patterned metal sheet 160 relate to the metal base layer 150 according to Figs. 1 to 3.

[0077] Step (c) comprises removing the structure 420 of anodized metal for obtaining the patterned metal sheet 160. This enables aligned nanostructures 140. In case such an alignment is not required the method can be carried out without step (c). Therefore step (c) is optional.

[0078] Step (d) comprises anodizing the surface of the patterned metal sheet 160 for growing aligned nanostructures 140, in particular nanotubes, of an oxidized metal on the patterned metal sheet 160; In some embodiments the patterned metal sheet 160 in combination with the aligned nanostructures relate to the metal base layer 150 and the nanostructures 140 according to Figs. 1 to 3.

[0079] Step (e) comprises applying a process for removing the patterned metal sheet 160 to obtain the aligned nanostructures 140 of the oxidized metal. This can be achieved by briefly applying a very high voltage. It is also possible to carry out the method without step (e). Therefore, step (e) is optional.

[0080] In case the metal sheet is made from aluminium, the product obtained after step (d) or step (e) is also known as anodic aluminium oxide.

[0081] While above at least one exemplary embodiment has been described, it has to be noted that a great number of variations thereto exists. Furthermore, it is appreciated that the described exemplary embodiments only illustrate non-limiting examples of how the present solution can be implemented and that it is not intended to limit the scope, the application or the configuration of the herein-described apparatus’ and methods. Rather, the preceding description will provide the person skilled in the art with constructions for implementing at least one exemplary embodiment of the solution, wherein it has to be understood that various changes of functionality and the arrangement of the elements of the exemplary embodiment can be made, without deviating from the subject-matter defined by the appended claims and their legal equivalents.

[0082] LIST OF REFERENCE SIGNS

[0083] 100, 200 Electrode Assembly

[0084] 110 Metal foil

[0085] 120 Layer having an active material

[0086] 130 Separation layer

[0087] 140 Nanostructures

[0088] 150 Metal base layer

[0089] 160 Patterned metal sheet

[0090] 300 Battery cell

[0091] 310 Housing

[0092] 320 Device

[0093] 330 Electrical connection

[0094] 340 Electrolyte

[0095] 350 Deposited metal

[0096] 400 Manufacturing scheme of an array of nanostructures

[0097] 410 Metal sheet

[0098] 420 Anodized metal structure

[0099] (a) Providing a metal sheet

[0100] (b) Anodizing the metal sheet

[0101] (c) Removing anodized metal

[0102] (d) Growing nanostructures

[0103] (e) Removing anodized metal

Claims

CLAIMS1.- An electrode assembly (100, 200) for an energy storage cell (300), comprising: a first electrode, which comprises a current collector (110) of a first metal and a layer (120) having an active material in which alkali-metal-ions can be stored, and which is arranged at the current collector (110); a second electrode, which comprises an array of nanostructures (140) of a metal oxide of a second metal, wherein the nanostructures (140) of the array of nanostructures (140) comprise cavities which are configured to store alkali-metal; a metal base layer (150) of a third metal which is mechanically connected to the array of nanostructures (140); wherein the layer (120) having an active material is arranged between the current collector (110) and the array of nanostructures (140).2.- The electrode assembly (100, 200) of claim 1, wherein the electrode assembly has a positive electrode, wherein the positive electrode is said first electrode.3.- The electrode assembly (100, 200) of any of the preceding claims, wherein the second metal is aluminium.4.- The electrode assembly (100, 200) of claim 3, wherein the third metal is aluminium or copper.5.- The electrode assembly (100, 200) of any of the preceding claims, wherein the second metal is the same as the third metal and the nanostructures (140) of the array of nanostructures (140) comprise an oxidized metal of the third metal.6.- The electrode assembly (100, 200) of claim 5, wherein the oxidized metal of the third metal is aluminium-oxide7.- The electrode assembly (100, 200) of any of the preceding claims, wherein the metal oxide of the second metal is electronically insulating.8.- The electrode assembly (100, 200) of any of the preceding claims, wherein the electrode assembly (100, 200) comprises an interface between the metal base layer (150) and the array of nanostructures (140), wherein the metal base layer (150) and the array of nanostructures (140) are directly mechanically connected.9.- The electrode assembly (100, 200) of claim 8, wherein the metal base layer (150) and the array of nanostructures (140) are directly mechanically connected over at least least 90%, preferably at least 95% and more preferably at least 98% of the area of the interface.10.- The electrode assembly (100, 200) of any of the preceding claims, wherein the electrode assembly (100, 200) comprises an interface between the metal base layer (150) and the array of nanostructures (140), wherein the metal base layer (150) and the array of nanostructures (140) are electronically connected over at least least 90%, preferably at least 95% and more preferably at least 98% of the area of the interface.11.- The electrode assembly (100, 200) of any of the preceding claims, wherein the cavities comprise openings which are facing the layer (120) having an active material.12.- The electrode assembly (100) of any of the preceding claims, wherein the nanostructures of the array of nanostructures (140) comprise nanotubes (140) which are aligned to each other.13.- The electrode assembly (100, 200) of claim 12, wherein each of the nanotubes of the array of nanotubes (140) has a diameter regarding its cross-section which is between 10 and 500 nm.14.- The electrode assembly (100) of any of the preceding claims, wherein the cavities are cavities which are closed at the side facing the metal base layer (150).15.- The electrode assembly (100) of any of the preceding claims, wherein the array of nanostructures (140) is a layer of said nanostructures (140).16.- The electrode assembly (100) of any of the preceding claims, wherein the array of nanostructures (140) is a layer of a metal oxide of the second metal, wherein the cavities are linear cavities which are present in the layer of the metal oxide of the second metal.17.- The electrode assembly (100) of claim 16, wherein the linear cavities extend in a mutually parallel direction.18.- The electrode assembly (100) of claim 16 or 17, wherein the linear cavities extend in a direction which is the same as, or deviates less than 25° from, a direction defined by a normal vector of the layer of the metal oxide of the second metal.19.- The electrode assembly (100) of any of claims 16 to 18, wherein the linear cavities extend over a distance which is at least 95%, and preferably at least 99.0%, and more preferably at least 99.8% of the thickness of the layer of the metal oxide of the second metal.20.- The electrode assembly (100, 200) of any of the preceding claims, wherein the electrode assembly (100,200) has a negative electrode, wherein the negative electrode is said second electrode.21.- The electrode assembly (100, 200) of any of the preceding claims, wherein the first metal, the second metal and the third metal are the same.22.- The electrode assembly (100, 200) of any of the preceding claims, wherein the nanostructures (140) are arranged in a hexagonal closest packing.23.- The electrode assembly (100) of any of the preceding claims, wherein the cavities are at least partially filled with alkali-metal.24.- The electrode assembly (100) of any of the preceding claims, wherein the second electrode is arranged between the metal base layer (150) and the layer (120) having an active material.25.- The electrode assembly (100) of any of the preceding claims, comprising a separation layer (130) which is arranged between the layer (120) having an active material and the array of nanostructures (140), and which electronically isolates the first electrode from the second electrode.26.- The electrode assembly (100) of any of the preceding claims, wherein materials with which alkali-metal ions can chemically react at STP or in which alkali-metal ions can intercalate at STP are absent from the array of nanostructures (140) and from the metal base layer (150) and from any space between the metal base layer (150) the array of nanostructures (140).27.- The electrode assembly (100) of any of the preceding claims, wherein graphite, hard carbon, silicon, silicon-oxides, tin, tin-oxides, phosphorous, titanium-oxide, and vanadium-oxide are absent from the array of nanostructures (140) and from the metal base layer (150) and from any space between the metal base layer (150) the array of nanostructures (140).28.- An energy storage cell (300) comprising a housing (310), an electrode assembly (100, 200) of any of the preceding claims which is arranged in the housing (310) and wherein the housing (310) is at least partially filled with an electrolyte (340) with alkali- metal-ions wherein the electrolyte (340) at least partially encloses the electrode assembly (100, 200).29.- An energy storage cell (300) according to claim 28, wherein the energy storage cell is an energy storage cell having an alkali metal anode.30.- A device comprising an energy storage cell (300) of claim 28 or 29.31.- A method for manufacturing an electrode assembly (100) comprising the steps: providing a first electrode, which comprises a current collector (110) of a first metal and a layer (120) having an active material in which alkali-metal-ions can be stored, and which is arranged at the current collector (110); providing a second electrode, which comprises an array of nanostructures (140) of a second metal, wherein the nanostructures (140) of the array of nanostructures (140) comprise cavities which are configured to store alkali-metal; providing a metal base layer (150) of a third metal which is mechanically connected to the array of nanostructures (140); arranging the layer (120) having an active material of the first electrode between the current collector (110) and the array of nanostructures (140).32.- The method of claim 31 , wherein the array of nanostructures (140) is manufactured comprising the steps: providing a sheet (410) of a metal; anodizing the surface of the sheet to obtain a patterned metal sheet (160) with an anodized structure of the second metal; removing the anodized structure (420) for obtaining the patterned metal sheet (160); anodizing the patterned metal sheet (160) for growing aligned nanostructures (140) of an anodized metal. 33.- The method of claim 32, comprising applying a process for removing the patterned metal sheet (160).34.- The method according to any of claims 31 to 33, wherein the electrode assembly (100) is an electrode assembly according to any of claims 1 to 27.35.- Use of anodic aluminium oxide for storing alkali metal in an energy storage cell, wherein the anodic aluminium oxide comprises cavities, wherein the alkali metal is stored in the cavities.

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