DE102016217394A1 - Process for the solvent-free production of an electrode - Google Patents

Abstract

The invention relates to a method for producing an electrode (9) comprising at least one current collector (1) and at least one active material layer (2c, 2d), the method comprising the following method steps: a) providing a current collector (1) in the form of a sheet or a film or a composite film; b) providing a freestanding active material film (2a, 2b) comprising at least one active material and at least one binder, and optionally at least one conductive additive; c) applying at least one active material film (2a, 2b) on at least one surface (3a, 3b) of the current collector (1); d) inductively heating the current collector (1) to a temperature which makes it possible to heat at least the components of the at least one active material film (2a, 2b) in contact with the current collector (1) to a temperature above the softening temperature of the binder; wherein the current collector (1) facing away from surface (7a, 7b) of the at least one active material foil (2a, 2b) is not heated.

Description

State of the art

The present invention is a process for the solvent-free production of an electrode and the electrode thus produced and their use.

Electrodes comprising a current collector and an electrode active composition applied thereto are used in many areas of energy storage and power generation. Examples include electrodes for lithium-ion batteries (LIB) or fuel cells. Two fundamentally different processes for coating the current collector with the electrode active material (hereinafter also referred to as active material) are described in the prior art, namely the application of an active material slurry (so-called slurry process) and the application of a freestanding active material film.

The production of electrodes from freestanding active material films has the advantage of a solvent-free process management. Manufacturing methods are known from the prior art and, for example, in EP 1 644 136 A1 described. The active material composition for making the freestanding active material film comprises at least one electrode active material and at least one fibrillated binder. For example, the resulting composition can be formed into a stable freestanding active material sheet by means of an extruder and / or calender. The free-standing active material foil can then be laminated on a metallic arrester, the current collector. In order to cause adhesion of the active material film to the surface of the current collector, heat energy is usually supplied so as to achieve at least partial plasticization of the binder.

US 2013/309414 A1 discloses a process for the solvent-free production of an electrode, wherein a current collector is provided with an active material layer comprising a binder. The active material layer is then heated to make a connection between the current collector and the active material layer. The heating takes place by means of a heating element which is positioned so that the surface of the active material layer facing away from the current collector is preferably heated. The superficial heating can cause this surface to stick in a simultaneous or subsequent rolling step or to adhere to the roll (cf. WO 2012/151341 A1 ). In addition, there is a compression of the active material layer, which preferably reduces the porosity of the active material layer on the surface facing away from the current collector surface. However, this is undesirable because, for example, the penetration of the electrolyte composition of a lithium-ion battery into the active material layer of the electrode is made more difficult.

US 2012/0288756 A1 discloses a method for producing an electrode, wherein a part of a surface of a current collector is provided with an active material layer in a slurry process, so that in each case the edge region of the current collector remains uncoated. This uncoated area is then heated inductively. This gives a marginal area with lower hardness. This can reduce the risk of breakage of the electrode.

The object of the present invention is to provide a process for the solvent-free production of an electrode in which the porosity of the accessible active material surface is not reduced. This object is achieved by the invention described below.

Disclosure of the invention

• a) Bereitstellen eines Stromsammlers;
• b) Bereitstellen einer freistehenden Aktivmaterialfolie, umfassend mindestens ein Aktivmaterial und mindestens ein Bindemittel, sowie ggf. mindestens einen Leitzusatz;
• c) Aufbringen der mindestens einen Aktivmaterialfolie auf mindestens eine Oberfläche des Stromsammlers;
• d) Induktives Erwärmen des Stromsammlers auf eine Temperatur, die es ermöglicht, die mit dem Stromsammler in Kontakt stehenden Bestandteile der mindestens einen Aktivmaterialfolie auf eine Temperatur oberhalb der Glasübergangtemperatur T_g mindestens eines in der Aktivmaterialfolie enthaltenen Bindemittels zu erwärmen;

wobei die von dem Stromsammler abgewandte Oberfläche der mindestens einen Aktivmaterialfolie im Wesentlichen nicht erwärmt wird. Das bedeutet, die Temperatur erhöht sich an der vom Stromsammler abgewandten Oberfläche vorzugsweise um weniger als 10°C.The invention relates to a process for the solvent-free production of an electrode comprising at least one current collector and at least one active material layer, the process comprising the following process steps:

• a) providing a current collector;
• b) providing a freestanding active material film comprising at least one active material and at least one binder, and optionally at least one conductive additive;
• c) applying the at least one active material film to at least one surface of the current collector;
• d) inductively heating the current collector to a temperature which makes it possible to heat the components of the at least one active material film in contact with the current collector to a temperature above the glass transition temperature T _{g of} at least one binder contained in the active material film;

wherein the surface of the at least one active material film facing away from the current collector is substantially not heated. This means that the temperature preferably increases by less than 10 ° C. at the surface facing away from the current collector.

The current collector consists of an electrically conductive material. Suitable materials from which the current collector can be formed are, for example, copper, aluminum, nickel or even alloys of these metals with other metals. Particularly preferred are aluminum and copper and their alloys. The current collector must also be heated inductively. The layer thickness is not particularly limited. The current collector is therefore preferably designed flat in the form of a sheet or a foil. Since the current collector does not have to impart stability-promoting properties and on the other hand increases the weight of the electrode, a thin configuration in the form of a film is preferred. For example, the current collector has a layer thickness of 1 to 500 .mu.m, preferably 3 to 200 .mu.m and in particular from 3 to 15 .mu.m.

In a further embodiment, the current collector may be made of a composite material comprising an electrically conductive material. For example, a composite foil can be used as a current collector comprising a metallized plastic film. As examples, plastic films, e.g. Polyolefin or polyester films are called, which are provided on at least one surface with a metal layer. The preferred plastics are polyethylene, polypropylene and polyethylene terephthalate. These guarantee as films with a layer thickness of for example 1 to 500 .mu.m, preferably 3 to 200 .mu.m and in particular from 3 to 15 .mu.m, a sufficient stability of the composite film. On at least one surface, preferably on both surfaces of the plastic film, a metal layer is vapor-deposited, in particular a copper or aluminum layer. Since this metal layer does not have a stability-increasing effect, the layer thickness of the metal layer may be ≦ 3 μm, e.g. ≤ 2 μm or ≤ 1 μm. Thus, the weight of the electrode can be effectively reduced.

The active material foil can be made by a method known to those skilled in the art, wherein a free-standing foil is made of an active material composition. Preferably, a dry active material composition is used. The active material composition can have components known per se for a corresponding energy store. For the exemplary and nonlimiting case of manufacturing an electrode for a lithium-ion battery, the active material for an anode may comprise, for example, graphite, preferably in a concentration greater than or equal to 90% by weight, based on the total weight of the active material composition For example, the cathode active material may include a lithium salt such as lithium nickel cobalt manganese oxide (NCM) or lithium manganese oxide (LMO), preferably at a level greater than or equal to 90% by weight based on the total weight of the active material composition. The active material is thus in particular a material or a substance or a substance mixture which can participate in the active charging processes or discharging processes of an energy spokesperson. In this case, the active material composition may further comprise at least one binder. The binder preferably comprises a polymeric material selected from polyvinylidene fluoride (PVDF), polytetrafluoroethene (PTFE), styrene-butadiene copolymer (SBR), and ethylene-propylene-diene terpolymer (EPDM). Most preferably, the binder comprises at least PVDF. Due to the pronounced fibril formation, this binder can be used particularly advantageously for producing a freestanding active material film of the active material composition. For example, the active material composition comprises polyvinylidene fluoride (PVDF) in a concentration of less than or equal to 5% by weight based on the total weight of the active material composition in which the above-described active material is dispersed. In addition, a conductive additive, such as conductive carbon compounds, such as carbon black, may preferably be added in a concentration of less than or equal to 5% by weight, based on the total weight of the active material composition. By Fibrillierungsprozesse can be formed from the composition of a pasty, moldable mass. Such methods are known in the art and eg in EP 1 644 136 . US 2015/0061176 A1 or US 2015/0062779 A1 described. The resulting mouldable mass can then be formed into a freestanding active material film and, if necessary, cut to size. This can preferably be done by using a calender.

The cut active material film is placed on at least part of the surface of the preformed current collector. In an alternative preferred embodiment, an endless sheet of active material is placed on at least part of the surface of an endless current collector. The resulting laminate can then be cut to the desired size.

As an additional ingredient, in one embodiment, the active material composition may comprise at least one solid electrolyte, in particular an inorganic solid electrolyte, capable of conducting cations, especially lithium ions. In accordance with the present invention, such solid inorganic lithium ion conductors include crystalline, composite and amorphous inorganic lithium ion solid conductors. Crystalline lithium ion conductors include, in particular, perovskite type lithium ion conductors, lithium lanthanum titanates, NASICON type lithium ion conductors, LISICON and thio-LISICON type lithium ion conductors, and the like Garnet-type lithium ion conductive oxides. In particular, the composite lithium-ion conductors include materials containing oxides and mesoporous oxides. Such solid inorganic lithium-ion conductors are used, for example, in the review article of Philippe Knauth "Inorganic solid Li ion conductors: An overview" Solid State Ionics, volume 180, issues 14-16, 25 June 2009, pages 911-916 described. According to the invention, it is also possible to include all solid lithium-ion conductors which are produced by C. Cao, et al. in "Recent advances in inorganic solid electrolytes for lithium batteries", Front. Energy Res., 2014, 2:25 to be discribed. In particular, the in EP1723080 B1 according to the invention described grenade. The solid electrolyte can be used in particular in the form of particles having an average particle diameter of ≥ 0.05 μm to ≦ 5 μm, preferably ≥ 0.1 μm to ≦ 2 μm. If the active material composition comprises a solid electrolyte, it may for example comprise from 0 to 50% by weight, preferably from 10 to 40% by weight, of the active material composition.

In a preferred embodiment, two active material sheets are used, each of which is placed on a surface of the current collector. In this case, an edge region of the current collector remain unoccupied. However, it is also possible for the surface of the current collector to be substantially complete, i. to ≥ 95%, preferably ≥ 98%, in particular ≥ 99%, with active material film (s) to occupy.

In order to achieve a strong bond between the current collector surface and the at least one active material film, plasticization of at least a portion of the binder contained in the active material film is effected. This is done by inductively heating the current collector to a temperature which makes it possible to heat at least the components of the at least one active material film in contact with the current collector to a temperature above the glass transition temperature T _{g of} at least one binder contained in the active material film. The arrangement of at least one current collector and at least one, on at least a part of the surface of the current collector launched, active material foil is placed for this purpose in the vicinity of an induction heating coil. The induction heating coil thus selectively heats the electrically conductive layer, ie the current collector. This is heated to a temperature which is above the glass transition temperature T _{g of} at least one binder of the active material film. If several binders or mixtures of binders are used, the current collector is heated at least to a temperature which is above the binder with the lowest glass transition temperature T _g .

However, overheating can cause large parts of the binders to melt. These can then be distributed uncontrollably in the active material layer and, for example, partially cover the surfaces of the active material particles. The covered active material particles are only insufficiently able to interact with the charge carriers of the electrolyte composition, for example in an energy storage system. To avoid this effect, the current collector is heated by the inductive heating to a temperature which is ≤ 20 ° C above the melting temperature T _{m of} the at least one binder contained in the active material film. Preferably, the temperature of the current collector is chosen so that it is above the glass transition temperature T _g and below the melting temperature T _{m of} the at least one binder. Particularly preferred is a temperature which is a range of 30 to 10 ° C below the melting temperature T _{m of} the binder having the lowest melting temperature.

The temperature of the current collector is regulated by the current flow in the induction heating coil. With known dimensions and arrangement of the current collector and the induction heating coil (size, shape and material, and distance from each other), the temperature of the current collector can be precisely controlled by the current flow in the induction heating coil. The current flow can be controlled by means of a second coil in the induction heating coil. This allows an indirect measurement of the temperature of the current collector.

The induction heating coil can be mounted in any position, provided it is close enough to the current collector to inductively heat it. The distance between the induction heating coil and the current collector is preferably ≦ 10 cm, more preferably ≦ 5 cm, in particular ≦ 3 cm.

While it is in principle sufficient to form an adhesive bond between the current collector and the active material film, when a narrow strip of the active material film is connected to the current collector, an areal connection is preferred for reasons of stability. To achieve this, the induction heating coil extends substantially over the entire width of the current collector to be occupied with active material. "Essentially the entire width" means at least 90% of the total width of the current collector to be occupied with active material, preferably at least 95%. This can be done by a single induction heating coil or by a plurality of induction heating coils, e.g. two, three or four induction heating coils arranged side by side can be achieved.

Along the longitudinal extent of the current collector (ie orthogonal to the layer thickness of the current collector and to the width of the current collector) The induction heating coil can likewise extend essentially over the entire extent of the current collector to be occupied by active material, ie over at least 90% of the total longitudinal extent of the current collector to be occupied by the active material foil, preferably at least 95% of the total longitudinal extent of the current collector. This can also be achieved by a single induction heating coil or by a plurality of induction heating coils arranged side by side. Such an arrangement allows a discontinuous production of the electrodes.

In a preferred embodiment, however, the electrode production is carried out continuously. In this case, the layer structure of the current collector and at least one active material layer is moved past the induction heating coil relative to the induction heating coil. In this case, it is only necessary to provide an induction heating coil which extends substantially the entire width of the current collector, while the longitudinal extent of the heating zone may be small. For example, this extent is 0.5 cm to 5 cm, in particular 3 to 4 cm. Thus, a continuous process, in particular a roll-to-roll process can be carried out, in which a laminate of at least one continuous foil made of an electrically conductive material as current collector and at least one continuous active material foil is produced continuously.

The heating of the current collector achieves softening or possibly also melting of the binders contained in the active material film which are located on the surface of the active material film facing the surface of the current collector. Incidentally, the active material sheet will change its temperature by not more than 50 ° C, preferably not more than 30 ° C. In particular, the surface of the active material foil facing away from the current collector is substantially not heated, i. their temperature preferably increases by less than 10 ° C. It thus forms a temperature gradient within the active material film, which has its maximum value at the surface of the current collector facing surface of the active material film.

In a preferred embodiment, the active material film undergoes a temperature change by the heat radiation of the inductively heated current collector, the active material film up to a layer thickness of <50%, preferably <30%, in particular <15% of the total layer thickness, starting from the surface facing the current collector Active material film is heated to a temperature above the glass transition temperature T _{g of} at least one binder contained in the active material film.

The inductive heating phase can be made short by the process control according to the invention, since the current collector is heated rapidly by the induction heating and only a superficial softening of the binder in the current collector facing surface of the active material film is necessary. The heating time is preferably less than 10 seconds, in particular less than 5 seconds. In a continuous process, a high running speed of the endless films of current collector and active material of more than 20 m / s, in particular more than 30 m / s is achieved. For example, a running speed of 40 m / s can be achieved.

The induction heating coil can be arranged both on the side of the at least one active material foil, as well as on the side of the at least one current collector. In one embodiment, pairs of induction heating coils may also be disposed on both sides. In a continuous process, a plurality of successive, spaced apart induction heating coils or induction heating coil pairs may also be arranged along the running direction of the laminate.

In one embodiment of the invention, the at least one active material foil is pressed onto the latter before, during and / or after the inductive heating of the current collector. This happens, for example, with a stamp, a press or a roller. Preferably, this pressing is performed with a roller, so as to allow a continuous process control. Particularly preferred is an embodiment in which the inductive heating is carried out by means of an induction heating device positioned in a roller, which presses the at least one active material film during the heating on the heated current collector. In this way, a particularly intimate bond is achieved.

The tools used, in particular the mentioned punches, presses or rollers are preferably made of materials which are not inductively heated. This ensures that unwanted softening of the binder occurs upon contact with the tools. Preferably, non-conductive ceramic materials or non-conductive polymers are used. In addition, if necessary, the tools can be provided with a cooling device in order to cool the produced laminate as quickly as possible. Cooled tools are preferably used after the inductive heating of the current collector is completed.

In a further embodiment, the device may additionally comprise an induction coil which measures the induced current flow in the foil measures and is integrated in a temperature control loop. This allows the exact control of the temperature of the current collector during inductive heating.

US 8,461,496 B2 describes a device which is suitable in principle for carrying out the method according to the invention. The document and the disclosure contained therein are therefore fully incorporated into this document.

The invention also provides an electrode comprising at least one current collector and at least one active material layer, wherein the active material layer comprises at least one electrode active material and at least one binder, and optionally at least one conductive additive, and is applied to at least one surface of the current collector, characterized in that the porosity of the active material layer gradually increases from the surface of the active material layer facing the current collector to the surface of the active material layer facing away from the current collector. This electrode structure is achieved by producing the electrode by the method according to the invention. By the inductive heating of the current collector, this transfers the heat to the surface of the active material layer facing the current collector. The active material layer is gradually heated from this surface and also gradually softens up to a layer thickness of <50%, preferably <30%, in particular <15%, of the total layer thickness, starting from the surface of the active material film facing the current collector. By pressing the active material layer on the current collector in the manufacturing process, a compression of the active material layer takes place. This compression causes a reduction in porosity in the softened part of the active material layer. After cooling of the composite, the resulting porosity gradient remains permanent.

The electrode according to the invention may advantageously be used to manufacture an energy storage system such as a battery, in particular a lithium-ion battery, a supercapacitor, a hybrid supercapacitor, a fuel cell (e.g., PEM-FC fuel cell) or an electrolyzer (e.g., PEM electrolyzer).

Advantages of the invention

The present invention makes it possible to provide an electrode for a variety of possible applications, wherein the electrode is produced in an economically and ecologically advantageous method. On the one hand, the process can largely dispense with the use of solvents and, on the other hand, saves the loss of unnecessary heat energy through the use of inductive energy transmission. In addition, electrodes are obtained which differ from conventionally produced electrodes in that the porosity of the active material layer is greatest at the surface of the electrode and decreases towards the current collector. Thus, the method makes it possible to produce an electrode into which an electrolyte composition can optimally penetrate. The electrochemical behavior, in particular the energy density, of the cells produced from this electrode is improved.

Brief description of the drawings

Embodiments of the invention will be explained in more detail with reference to the drawings and the description below.

It shows:

1 a schematic representation of an apparatus for performing the method according to the invention;

2 a schematic representation of an alternative device for carrying out the method according to the invention;

3 a schematic representation of another alternative device for carrying out the method according to the invention;

4 a schematic representation of another alternative device for carrying out the method according to the invention;

Embodiments of the invention

In 1 is a device for producing a double-sided coated current collector 1 represented by the method according to the invention. The electricity collector 1 is made of an electrically conductive metal, in this case for example made of aluminum, and has a layer thickness of 1 to 500 .mu.m, in this case 100 .mu.m. In addition, the current collector 1 can already be cut to the final shape, ie preformed, or configured in the form of an endless foil with a width of, for example, 3 to 30 cm. On the surface (s) 3a . 3b of the electricity collector 1 becomes a freestanding active material foil 2a . 2 B hung up. This comprises at least one active material, at least one binder and optionally a Leitzusatz. Freestanding active material foils 2a . 2 B and their preparation are known from the prior art. In the present case, the active material film comprises 2a . 2 B For example, 90 wt .-% Lithiumnickelcobaltmanganoxid (NCM), 5 wt .-% PVDF and 5 wt .-% Leitruß, each based on the Total weight of the active material foils 2a . 2 B , The layer thickness of the active material films 2a . 2 B is not limited and is present for example 150 microns. If this makes sense, it is also possible that the Aktivmaterialfolien 2a and 2 B are not identical, but differ, for example, in their composition or layer thickness. The active material foils 2a . 2 B In the present case, they are also guided as endless films and have the same film width as the current collector 1 ,

The active material foils 2a . 2 B be with the help of a tool, in this case with the help of rollers 5a . 5b , on the surfaces 3a . 3b of the electricity collector 1 pressed. Rollers are particularly suitable for the continuous implementation of the method. The rollers 5a . 5b are preferably made of an electrically non-conductive material, in this case for example of a ceramic material such as silicon nitride. This prevents inductive heating of the rolls 5a . 5b during operation. Optionally, the rollers can 5a . 5b additionally be actively cooled.

In the rollers 5a . 5b are each induction heating coils 4a . 4b arranged. These are designed so that they are capable of collecting electricity 1 to heat inductively. The non-electrically conductive active material films 2a . 2 B and the rollers 5a . 5b On the other hand, they are not heated.

The electricity collector 1 is thus at a temperature above the glass transition temperature T _g of the active material in the foils 2a . 2 B heated binder, which then in an area of the current collector 1 facing surfaces 6a . 6b the active material foils 2a . 2 B , which directly to the surfaces 3a . 3b of the heated electricity collector 1 borders, softens. The the electricity collector 1 remote surfaces 7a . 7b the active material foils 2a . 2 B are not heated during this process. Between the surfaces 6a and 7a the active material foil 2a or the surfaces 6b and 7b the active material foil 2 B a temperature gradient forms, which peaks at the current collector 1 facing surfaces 6a and 6b having.

The increase in temperature causes a partial softening of the active material films 2a . 2 B , whereby an adhesive bond of the current collector 1 facing surfaces 6a . 6b to the surfaces 3a . 3b of the electricity collector 1 is trained. At the same time the Aktivmaterialfolien 2a . 2 B through the rollers 5a . 5b partially compressed and thereby a porosity gradient in the active material films 2a . 2 B achieved. After cooling the Aktivmaterialfolien 2a . 2 B this remains in the material. The porosity is then at the current collector 1 remote surfaces 7a . 7b largest and takes to the electricity collector 1 facing surfaces 6a . 6b down continuously.

The laminated electrode 9 the device is in the direction of travel 8th taken continuously and can be rolled up and stored, for example, or processed directly.

The 2 to 4 show variations of in 1 illustrated device.

2 shows a device after 1 , which additionally the rollers 5c . 5d includes. These follow in the process implementation on the rollers 5a . 5b , The rollers 5c . 5d do not have induction heating coils and serve only to densify the active material sheets 2a . 2 B , In a preferred embodiment, the rolls are 5c . 5d cooled to remove heat from the electrode.

3 shows a device after 2 wherein the induction heating coils 4c . 4d not inside the rollers 5a . 5b are arranged, but immediately in front of the rollers 5a respectively. 5c , Such an arrangement has the advantage that the current collector 1 can be heated in a wider range or over a longer period of time and thus better adhesion is achieved. Furthermore, the induction heating coils can be 4c . 4d replace easily in case of failure.

4 shows a device after 2 , wherein the induction heating coil 4 directly to the electricity collector 1 before the lay-up point of the active material foils 2a . 2 B is arranged. This allows the inductive heating of the current collector 1 without interference by the active material foils 2a . 2 B ,

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1644136 A1 [0003]
• US 2013/309414 A1 [0004]
• WO 2012/151341 A1 [0004]
• US 2012/0288756 A1 [0005]
• EP 1644136 [0010]
• US 2015/0061176 A1 [0010]
• US 2015/0062779 A1 [0010]
• EP 1723080 B1 [0012]
• US 8461469 B2 [0028]

Cited non-patent literature

• Philippe Knauth "Inorganic Solid Li ion Conductors: An overview" Solid State Ionics, Vol. 180, Issues 14-16, June 25, 2009, pages 911-916 [0012]
• C. Cao, et al. in "Recent advances in inorganic solid electrolytes for lithium batteries", Front. Energy Res., 2014, 2:25 [0012]

Claims (10)

Method for producing an electrode ( 9 ) comprising at least one current collector ( 1 ) and at least one active material layer ( 2c . 2d ), the method comprising the following method steps: a) providing a current collector ( 1 ) in the form of a sheet or a foil or a composite foil; b) providing a freestanding active material film ( 2a . 2 B ), comprising at least one active material and at least one binder, and optionally at least one conductive additive; c) applying at least one active material film ( 2a . 2 B ) on at least one surface ( 3a . 3b ) of the current collector ( 1 ); d) Induction heating of the current collector ( 1 ) to a temperature that makes it possible, at least that with the current collector ( 1 ) in contact components of the at least one active material film ( 2a . 2 B ) to a temperature above the softening temperature of the binder; where the the electricity collector ( 1 ) facing away from the surface ( 7a . 7b ) of the at least one active material film ( 2a . 2 B ) is not heated. The method of claim 1, wherein the at least one active material film ( 2a . 2 B ) during or after inductive heating to the current collector ( 1 ) is pressed. Method according to claim 1 or 2, wherein the inductive heating is effected by means of at least one roller ( 5a . 5b ) positioned induction heating coil ( 4a . 4b ) and wherein the roller ( 5a . 5b ) the at least one active material foil ( 2a . 2 B ) while heating on the current collector ( 1 ) presses. Method according to one of claims 1 to 3, wherein the temperature of the current collector ( 1 ) indirectly via the current flow in the induction heating coil ( 4a . 4b ) is determined. Method according to one of claims 1 to 4, wherein the temperature of the current collector ( 1 ) is raised by the inductive heating to a temperature ≤ 20 ° C above the melting temperature of at least one of the in the active material film ( 2a . 2 B ) containing binder. Method according to one of claims 1 to 5, wherein the inductive heating takes less than 10 seconds, in particular less than 5 seconds. Electrode ( 9 ), comprising at least one current collector ( 1 ) and at least one active material layer ( 2c . 2d ), wherein the active material layer ( 2c . 2d ) comprises at least one active material and at least one binder, and optionally at least one conductive additive, and at least one surface ( 3a . 3b ) of the current collector ( 1 ), characterized in that the porosity of the active material layer ( 2c . 2d ) gradually from the current collector ( 1 ) facing surface ( 6a . 6b ) of the active material layer ( 2c . 2d ) to the current collector ( 1 ) facing away from the surface ( 7a . 7b ) of the active material layer ( 2c . 2d ) increases. Electrode ( 9 ), produced according to one of claims 1 to 6. Using an electrode ( 9 ) according to claim 7 or 8 for the production of an electrochemical energy storage system. Electrochemical energy storage system, in particular lithium-ion battery, comprising at least one electrode ( 9 ) according to claim 7 or 8.

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