CN115621407A

CN115621407A - Method for producing an electrode for a battery cell

Info

Publication number: CN115621407A
Application number: CN202210842736.8A
Authority: CN
Inventors: K.贾马达
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2021-07-16
Filing date: 2022-07-18
Publication date: 2023-01-17
Also published as: DE102021207601A1

Abstract

A method for manufacturing an electrode (1) for a battery cell (2); wherein the method has at least the following steps: a) Preparing a carrier material (4) of the electrode (1) coated with an active material (3); b) Loading the coated carrier material (4) with a pore-forming fluid (5) such that the fluid (5) is absorbed into the active material (3); c) The carrier material (4) loaded with the fluid (5) is heated and the fluid (5) is at least partially discharged from the active material (3) while forming pores.

Description

Method for producing an electrode for a battery cell

Technical Field

The invention relates to a method for producing an electrode for a battery cell. The active material disposed on the carrier material should in particular be admixed with a pore-forming agent. The carrier material comprises in particular a tape-shaped carrier material.

Background

Batteries, in particular lithium ion batteries, are increasingly used for driving motor vehicles. The battery is generally constructed of battery cells, each of which has a stack of anode, cathode and separator sheets. At least some of the anode and cathode strips are designed as current arresters for conducting the current supplied by the battery cells to consumers arranged outside the battery cells.

In the production of lithium ion battery cells, so-called carrier materials, in particular strip-shaped carrier materials, for example carrier films, are coated on both sides with a paste by means of a coating tool. The paste is composed of a plurality of components, active material, conductive carbon black, binder, solvent and, if necessary, other additives. After the coating of the respective single side, the coated carrier material is fed to a drying process in each case in order to evaporate the solvent contained and to firmly bond the remaining components to the carrier film. The carrier film forms the arrester of the cell.

The coating thus produced is porous. The porosity is reduced by calendering or calendering, since the coating is compacted here. Calendering is required in order to improve specific capacitance (based on volume) and conductivity.

The active material is compressed by about 40% when calendered. The calendering process is similar to the rolling process. The active material is compressed in a small deformation zone with a very high calendering force. The following problems arise during the calendering process:

first, due to the higher calendering force, the porosity is greatly reduced at the surface of the active material where the electrode is in contact with the calendering rolls. The anode is composed in particular of graphite as active material; the anode further comprises for example a binder SBR, a diluent CMS and conductive carbon. In particular, it was attempted to achieve an active material of 1.6g/cm ³ [ g/cc ] of]To increase the volumetric energy density of the battery cell. The high density also improves the conductivity of the battery cell. The reduction in porosity near the surface makes it more difficult for lithium ions to accumulate in the graphitic layer. This results in a more intensive Lithium deposition (Lithium Plating), i.e. the deposition of metallic Lithium, on the surface. The service life of the battery cell is greatly reduced thereby. Since the deformation takes place in a very small region (depending on the diameter of the roll) during rolling, there is a very high stress concentration in the small deformation region, wherein this stress concentration leads to cracks in the active material. In summary, high compression upon calendering is desirable, but high compression presents the problem of lithium precipitation.

Second, changes in pore structure and deformation of the active material for a defined range of pore sizes are critical factors that negatively impact the electrochemical capacity of the battery cell. The surface roughness and the porosity of the surface openings certainly influence the wetting behavior of the electrode with the electrolyte as a whole and vary with the compression ratio. Typically, the porosity is reduced by up to 30% upon calendering, but at the surface, at a degree of compaction (i.e. reduction in porosity) of 20%, deformation of the active material particles can already be observed. This means that the porosity is not uniformly distributed over the layer thickness of the active material. The porosity at the surface is greatly reduced relative to the porosity near the support material.

Particle deformation of the active material is limited to particles disposed on the surface of the active material, which affects the electrochemical capacity of the battery cell. The deformation of the particles on the surface, which is achieved by high calendering compression, leads to transport barriers for lithium ions during the electrochemical cycles, so that the long-term performance of these electrodes is greatly influenced for relatively high C-rates. With a high reduction in porosity of about 20% to about 26%, particularly large pores with a maximum diameter of between 2 μ [ microns ] and 5 μm are closed by compression. The effect of these missing "large" pores and overall smaller total pore volume on the surface on the electrochemical properties is one of the main causes of lithium extraction, which greatly reduces the service life of the battery cell.

Both the blocking or removal of large pores and the substantial reduction of the total pore volume results in a low amount of electrolyte/active material particle interfaces, which can be used for lithium ion transfer. The reduction of the electrolyte/active material particle interface can lead to problems with electrolyte wetting. This also leads to deterioration of electrochemical performance.

In order to solve the above problems, the following measures have been hitherto implemented:

adding porous carbon powder (porocarb) with higher porosity in higher portions; however, porocarb porous carbon powder is an expensive material;

reduce the compression ratio of the press delay to less than 20%; but this reduces the volumetric energy density of the battery cell and also reduces the conductivity of the active material;

adding 2% to 5% more conductive carbon so that the free space between the active material particles can be filled with the conductive carbon and conductivity is achieved even when the calendering compression is small.

However, these measures have the following disadvantages:

less compression during calendering means less volumetric energy density in the cell;

less compression upon calendering means less conductivity in the active material, since the conductive carbon cannot contact the active material particles;

more conductive carbon means greater spring back after calendering; the anode must be calendered in two steps, with an additional final step to compensate for spring back; this increases the space requirements and cost of the machine;

with a higher proportion of conductive carbon, the viscosity of the suspension or paste increases, which means longer drying times and difficulty in wetting the coating.

As a possible alternative solution, the active material can, for example, already be built up in different layers with different porosities. The uppermost layer has a higher porosity to compensate for the reduction in porosity caused by calendering compaction. But the coating process thereby becomes very complicated. Problems also arise in terms of cohesion between two adjacent coating layers.

Document CN 111725479A describes an electrode for a lithium-ion battery cell and a manufacturing method for this electrode. Here, the electrodes are coated with an active material, into which a pore-forming agent has been added.

The agent that forms the pores is added to the active material prior to coating with the carrier material, thereby affecting at least the chemical properties and viscosity of the active material.

Disclosure of Invention

The technical problem underlying the present invention is therefore to solve, at least in part, the problems described in the prior art. In particular, a method is to be proposed by means of which the porosity of the active material can be set in an advantageous manner.

The above problems are solved by a method for manufacturing an electrode for a battery cell. Advantageous further developments are the subject matter of the present application. The features specified individually in this application can be combined with one another in a technically expedient manner and can be supplemented by details from the description and/or the drawing, in which further embodiments of the invention are specified.

A method for producing an electrode for a battery cell is proposed. The method comprises at least the following steps:

a) Preparing a support material for an electrode coated with an active material;

b) Loading the carrier material of the coating with a pore-forming fluid such that the fluid is absorbed into the active material;

c) The carrier material loaded with the fluid is heated and the fluid is at least partially expelled from the active material in the event of pore formation.

The above-described (non-closed) division of the method steps into a) to c) is primarily intended only for differentiation and does not impose a defined order and/or relevance. The frequency of the method steps may also be different. It is also possible that the method steps overlap at least partially in time. Preferably steps a) to c) are carried out in the order given.

The electrode to be produced is intended in particular for use in a lithium-ion battery cell. The electrodes comprise, in particular, a carrier material, for example a copper or aluminum film. The support material used consists in particular of 10 to 12 μm thick copper for the anode and of 12 to 15 μm thick aluminum for the cathode. The support material is coated with the active material at least on the largest side and, if appropriate, also on the largest sides facing one another.

In particular, the active material includes at least one of carbon black (carbon black), NMC (lithium-nickel-cobalt-manganese as an active material for storing lithium), graphite (an active material for storing lithium), CNT (carbon nanotube), SBR (styrene-butadiene rubber as a binder), CMC (carboxymethyl cellulose polymer), PVDF (polyvinylidene fluoride), and porous graphite. Components of the material that are not binder materials are particularly considered active materials.

The support material of the electrode coated with the active material is produced in particular according to step a). The carrier material of the coating is provided in particular as a continuous material in the form of a strip. The web-shaped continuous material is conveyed in particular at least during steps b) and c) in a conveying direction. In particular, the active material is applied only to the support material and, if appropriate, is smoothed or provided in terms of the thickness of the coating, but has not yet been calendered.

During the calendering, the coated support material is guided through a roller device, which is optionally temperature-controlled and in this way can heat the coated support material. The coating is compacted by the rollers. Typically the density of the coating increases (porosity decreases) by at least 20%.

The carrier material of the coating is in particular subjected to a pore-forming fluid according to step b), so that the fluid is absorbed into the active material. The fluid is in particular in a liquid state. The fluid penetrates in particular into the porous active material. In particular, the total porosity present before step b) is at least 40%, preferably at least 60%, particularly preferably at least 80%, filled or filled with fluid before step c).

According to step c), the carrier material loaded with the fluid is heated in particular and the fluid is at least partially discharged from the active material with formation of pores (first heating stage).

The carrier material, which is in particular loaded with a fluid, is heated to at least one boiling temperature of the fluid, so that the fluid is discharged from the active material with formation of pores.

In particular between steps b) and c) in a further step x), the active material is compacted, in particular compacted by at least 15%, preferably by at least 20%, particularly preferably by at least 22%. In particular, it is compacted to at most 35%, preferably at most 30%.

In particular the active material is compacted in step x) to at least 1.5g/cm ³ [ g/cc ] of]Preferably at least 1.6g/cm ³ 。

In particular, step x) comprises calendering and step c) is carried out spatially separated from step x). In particular, calendering is carried out without heating devices, i.e. without a temperature-specific increase in the active material. The pores of the active material are additionally supported by the fluid absorbed in the active material, so that the compaction of the active material is uniform over the layer thickness. In particular, excessive compaction is prevented right on the surface of the coating. The calendering or compacting is carried out in particular at room temperature.

The rolls used in calendering can be excited in particular by ultrasonic excitation. The fluid can thereby be transferred into the pores of the coating of the carrier material.

In particular, step c) is carried out exclusively by thermal convection or thermal radiation, i.e. in particular not by thermal conduction. In particular the active material does not come into contact with heated rollers or (calendering) rollers. In particular, a radiant heater or a hot gas flow is provided, through which heat is conveyed to the active material.

The carrier material, in particular the coating, is treated as a continuous material at least during steps a) to c) and is divided into electrode sheets after step c), for example in step d).

In particular, step b) is carried out in a fluid-filled immersion bath through which the coated carrier material is conveyed.

In particular, the immersion tank is arranged in the housing. In particular, the pressure in the immersion tank is higher than the external pressure prevailing outside the housing. In particular, a double shell is provided, so that air from the environment cannot enter the inner housing or the immersion bath. The outer housing, which is made of a steel plate approximately 10mm thick, can at the same time be designed as an enclosure for protection against liquid leakage or explosion. The inner housing is constructed, inter alia, from stainless steel plate to resist corrosion. The inner casing is in particular made of refined steel sheet of about 5mm thickness.

Alternatively or additionally, the fluid is sprayed onto the active material in step b).

In particular, the coated support material is guided in the context of step b) through a series of rollers or rollers (hereinafter referred to as press rollers), which are located, for example, in a bath or, if appropriate, after the individual spraying devices, in order to be able to maximize the contact of the surface of the active material with the fluid. The surface of the active material is subjected to mechanical pressure, in particular by means of a pressure roller, so that the fluid penetrates into the active material and at least partially fills the pores.

In particular the coated support material is guided in the context of step b) through a series of rollers or rollers (hereinafter referred to as coating rollers), which are loaded with a fluid. The carrier material of the coating is in particular only acted upon by the fluid via the roller and is in particular not conveyed through the fluid. The application roller can be arranged, for example, partially in a dip tank or be acted upon with fluid by a spraying device.

When the carrier material of the coating is pressed to a particularly final thickness during compacting or calendering, some fluid is pressed out of the pores, since the fluid is particularly an incompressible medium. In order to prevent the fluid from being pressed out, carrier films, for example made of polyurethane material, can be arranged in particular on the upper and lower layers of the carrier material of the coating. The carrier film prevents in particular direct contact between the coated carrier material and the compacting roll or calender or calendering roll. The carrier film transmits the compaction or calendering force to the carrier material of the coating. The carrier film serves in particular as a sealing material to prevent the fluid from being squeezed out of the pores. After compacting or calendering, the carrier film can be removed from the coated carrier material and rolled up if necessary.

The coating roller can in particular have a structured surface, for example with concave depressions, for example to a depth of 20 μm and a maximum width of 1 to 10 mm. The transfer of fluid into the pores of the coating of the carrier material of the coating can thereby be improved.

In particular, the fluid has a boiling temperature or boiling point of at most 105 degrees celsius, preferably below 100 degrees celsius, particularly preferably below 95 degrees celsius, in the ambient conditions of step d), for example at an ambient pressure of about 1 bar.

In particular, the pore-forming fluid contains at least one of the following components, or is made only of such components, or contains only one or more of the following components:

ethers such as Tetrahydrofuran (THF); boiling temperature about 66 degrees celsius;

dichloromethane; boiling temperature about 39 degrees celsius;

light naphtha; at least molecules having 5 to 6 carbon atoms; boiling temperature between 30 and 90 degrees celsius;

an alcohol, such as methanol (boiling temperature about 65 degrees celsius), ethanol (boiling temperature about 78 degrees celsius), or 1-propanol (boiling temperature about 97 degrees celsius);

aldehydes such as propionaldehyde (boiling temperature about 46 degrees celsius), butyraldehyde (boiling temperature about 75 degrees celsius), or valeraldehyde (boiling temperature about 102 degrees celsius);

ketones such as 2-propanone (boiling temperature about 56 degrees celsius), 2-butanone (boiling temperature about 80 degrees celsius), or 2-pentanone (boiling temperature about 103 degrees celsius);

dimethyl carbonate (DMC-boiling temperature about 90 degrees Celsius).

In particular, the fluid comprises only the constituents of the electrolyte which are also used for the battery cell, so that the residual amount of fluid in the active material is not detrimental to the operation of the battery cell.

It is preferred to use a liquid that does not dissolve the binder in the active material, which is non-toxic and non-flammable. Among these requirements, tetrahydrofuran (THF) or dimethyl carbonate is particularly suitable.

In particular, the coated carrier material can be subjected to a stretching process (skindrawing) before step b) in order to set the thickness of the electrode or active material coating. Both sides of the coating or of the coated carrier material are compressed during drawing (skindawing), whereas only one side of the coating is treated in strip drawing (strip drawing, leveling/flattening). However, the compression during stretching is a maximum of 10%.

In particular, after step c), the coated carrier material is cut in a further step d). Cutting includes, for example, separating the web into individual electrode sheets and/or slitting and/or dividing the web into a plurality of smaller width strip materials (so-called slits).

During the notching, a (uncoated) collector region or arrester is formed on the carrier material.

The cutting is done in particular by mechanical slitting or blanking, by laser, water jet or ultrasonic cutting.

In particular in the context of step b) and after the loading with fluid, in particular before step x), the coated support material is guided through rollers or rollers (hereinafter referred to as press rollers) in order to assist the penetration of the fluid into the pores of the active material. The carrier material of the coating wetted with the fluid having the low boiling temperature is preferably wiped off with (titanium) rollers, so that the fluid penetrates deeper into the pores.

The carrier material, in particular the coating, is then (immediately) guided through a roller or roller (hereinafter referred to as a cleaning roller) again, by means of which excess fluid is removed from the surface of the active material. The cleaning roller is especially designed with a rubber surface. In this way, it is achieved that the fluid remains in the pores of the active material, but that more fluid present on the surface of the active material is removed.

Preferably, the scrub roller can be excited with vibrations so that excess fluid can be better removed from the surface of the active material.

Since the fluid of the carrier material used for applying the coating according to step b) can act as a lubricant, it is provided in particular that the carrier material of the coating is pressed into a (calender) roller provided for compacting the active material. For this purpose, between steps b) and x), the coated carrier material is guided by rollers or rollers, which are referred to below as friction rollers (friktionroll). The friction roller has a high coefficient of friction, in particular on the surface of the carrier material contacting the coating, by means of which the coated carrier material can be moved towards and past the (calendering) roller.

In particular step c) is carried out (immediately) after step x), wherein the compacted, coated support material is heated and dried by draining fluids from the active material. In particular, the heating of the active material is carried out by a heat source, such as an infrared heater or a fan. In the case of a carrier material coated on one side, the active material is heated in particular via the uncoated side of the carrier material, i.e. indirectly.

The active material is in particular heated to a temperature of maximally 100 to 110 degrees celsius, so that the active material is not damaged. The binder in the active material coating can typically withstand temperatures of up to 120 degrees celsius before softening and melting.

In particular, the active material is heated at least to a temperature equal to or greater than the maximum boiling temperature of the identified component in the fluid.

Due to the heating of the active material, the fluid accumulated in the active material evaporates. Air bubbles are expelled from the particularly compacted active material coating. Due to the air bubbles, new pores are formed in the active material and the existing pores are enlarged. These pores are used by the lithium ions for the intercalation process in operation after the battery cell. Lithium ions can thus easily penetrate into the active material because there are sufficient pores on the surface of the active material through the bubble discharge process. Lithium deposition, i.e. deposition of metallic lithium (lithium precipitation), is also greatly reduced thereby.

In particular, in step c), it is provided that the gaseous fluid is sucked off and, if appropriate, reused in step b). Suction means may be provided for this purpose.

The heating of the active material or of the coated carrier material takes place in particular in a (direct or through) chamber through which the coated carrier material is conveyed.

In particular, the coated support material is cooled after step c), for example by guiding the coated support material through rollers or rollers, which are referred to below as chill rollers. The cooling is carried out at a temperature of at most 40 degrees celsius.

In particular, after step c) or after cooling, the surface is examined by means of a (possibly optical) measuring device. It is checked here whether the surface of the active material is possibly damaged.

Furthermore, after step c), the thickness of the coated carrier material is checked, in particular by means of a (if appropriate optical or tactile, etc.) measuring device. The thickness can be corrected by varying step x) if necessary.

In particular according to step d), the coated carrier material is rolled up or directly transported for further processing.

Especially before or after step d), the coated carrier material is heated, for example in an oven, for two (2) to 15 hours, especially to a temperature of 100 to 110 degrees celsius (second heating stage). In particular, residues of the fluid, including water particles if present, are also removed from the pores of the active material.

In particular, when the electrode provided as an anode is subjected to high rolling compression or high compaction, the problem of closing or reducing the pores is greater. The proposed method steps can however also be used for arranging the electrode as cathode.

The proposed method has the following advantages:

as a result of the compaction (step x), the closure of the pores does not lead to lithium precipitation here;

after compaction (step x), the volume of the pores increases as a result of the fluid being expelled from the active material;

the fluid uptake in the active material coating can be controlled by mechanical pressure;

the fluid forms a lubricating film on the surface of the active material, reducing the friction between the roller and the carrier material of the coating; thereby reducing stretching of the active material in the direction of transport; thereby reducing folding in the carrier material and also reducing problems such as crack extension on the surface of the active material;

the fluid penetrates into the pores and creates a counter pressure during the compaction according to step x); the pores are not easily closed; the porosity decreases during compaction, but it is in particular not less than 2 microns; this means that not only is porosity increased by the outgassing of the fluid, but there is also a useful pore size greater than 2 microns;

high volumetric energy density of the electrode is achieved without reducing the pore volume;

the conductivity of the active material is increased by the high density achieved after compaction;

most of the proposed organic fluids are miscible with water; this means that all water particles remaining in the pores are mixed with the fluid and evaporate with the fluid and exit the pores during the first and second heating stages; in this way, the water content in the electrode can be greatly reduced, which has a positive effect on the performance of the battery cell.

Furthermore, a battery cell is proposed, which comprises at least a battery cell housing and at least one electrode arranged therein, which is produced by the method.

The battery cell comprises, in particular, a battery cell housing enclosing a volume, at least one first electrode film of a first electrode type, a second electrode film of a second electrode type, and a separating material and a liquid electrolyte arranged therebetween, which are arranged in the volume.

The battery cell is in particular a pouch cell (having a deformable battery cell housing formed by a pouch-shaped membrane) or a prismatic cell (having a dimensionally stable battery cell housing). The pouch-shaped film is a known deformable housing part which is used as a battery cell housing of a so-called pouch-shaped cell. It is a composite material here, for example comprising plastic and aluminum.

The battery cell is in particular a lithium ion battery cell.

The individual films of a plurality of electrodes designed as electrode films are arranged one above the other and in particular form a stack. The electrode films are respectively assigned to different electrode types, i.e. they are designed as anodes or cathodes. Here, anodes and cathodes are arranged alternately and separated from one another by a separating material.

A battery cell is a current storage device which is used, for example, in a motor vehicle to store electrical energy. In particular, motor vehicles have, for example, an electric motor for driving the motor vehicle (traction drive), wherein the electric motor can be driven by electrical energy stored in a battery cell.

Furthermore, a motor vehicle is proposed, which comprises at least one traction drive and a battery having at least one battery cell, wherein the traction drive can be supplied with energy from the at least one battery cell.

At least one system for data processing is provided, in particular, with means which are suitably equipped, configured or programmed to carry out the method or which carry out the method.

The means comprise, for example, a processor and a memory in which commands to be executed by the processor are stored, and data lines or transmission means which enable the transmission of commands, measured values, data or the like between the above-mentioned elements, such as the drive means, the driven rollers/rollers, the spraying means, the suction means, etc.

Furthermore, a computer program is proposed, which comprises commands that, when the program is executed by a computer, cause the computer to carry out the method or the steps of the method.

Furthermore, a computer-readable storage medium is proposed, which contains commands, which, when executed by a computer, cause the computer to carry out the method or the steps of the method.

The embodiments with respect to the method can be transferred in particular to a battery cell, a motor vehicle, a system for data processing and/or a computer-implemented method (i.e. a computer program and a computer-readable storage medium), and vice versa.

The use of the indefinite article "a" or "an" does not mean, especially in the claims and in the specification where the claims are interpreted, an adjective. Accordingly, the relevant terms and components are understood to be present at least once, but in particular also a plurality of times.

It is to be noted that the ordinal terms "first", "second", and so forth, "are used herein primarily (solely) to distinguish one from another object, quantity, or process, i.e., do not impose any particular dependency and/or order on the object, quantity, or process. If association and/or ordering is desired, it is expressly stated herein or apparent to one of ordinary skill in the art in view of the specifically described designs. The description of a component applies equally to all or most of the components as long as they can be present multiple times (at least one), but this is not necessarily so.

Drawings

The invention and the technical field are further elucidated on the basis of the figures. It is noted that the present invention is not limited by the embodiments. In particular, if not explicitly stated otherwise, some aspects may also be extracted from the facts stated in the figures and combined with other constituents and knowledge from the present description. It is to be noted in particular that the figures and the dimensional relationships shown in particular are merely schematic. Wherein:

FIG. 1: a cut-away side view of the first embodiment of the immersion tank is shown;

FIG. 2: a cut-away side view of a second embodiment of the immersion tank is shown;

FIG. 3: a cut-away side view of the spray device;

FIG. 4: a cut-away side view of the method after step b);

FIG. 5 is a schematic view of: a third embodiment directed to step b) of the method;

FIG. 6: a fourth embodiment directed to step b) of the method;

FIG. 7: a fifth embodiment directed to step b) of the method.

Detailed Description

Fig. 1 shows a cut-away side view of a first embodiment of an immersion tank 8.

The support material 4 of the electrode 1 coated with the active material 3 is produced in particular according to step a). The coated carrier material 4 is provided as a continuous material 6 in the form of a strip. The web-shaped web 6 is conveyed in the conveying direction 14 at least during steps b) and c). The active material 3 is only applied or applied to the carrier material 4 and, if necessary, smoothed or the thickness of the coating is adjusted, however, without being calendered.

According to step b), the coated carrier material 4 is in particular loaded with a pore-forming fluid 5, so that this fluid 5 is absorbed into the active material 4. The fluid 5 is in a liquid state. The fluid 5 penetrates in particular into the porous active material 3.

Step b) is carried out in a bath 8 filled with a fluid 5, through which the coated carrier material 4 is conveyed.

The immersion tank 8 is arranged in a housing 12. The pressure in the immersion tank 8 is higher than the external pressure existing outside the housing 12. The double shell is arranged so that ambient air cannot enter the inner housing 12 or the immersion tank 8. A gas 11, for example nitrogen, is introduced into the housing 8 through an inlet 13. The immersion bath 8 and the fluid 5 are thereby isolated from the environment by a gas 11. The housing 8 is sealed by a sealing means 10.

The coated carrier material 4 is guided in the course of step b) by a series of deflecting rollers 9 in the immersion bath 8, so that the carrier material 4 is conveyed through the fluid 5 and the surface of the active material 4 can be brought into maximum contact with the fluid 5. Mechanical pressure is also applied to the surface of the active material 4 by the turning roll 9, causing the fluid 5 to penetrate into the active material 4 and at least partially fill the pores.

Figure 2 shows a cut-away side view of a second embodiment of the immersion tank 8. Reference is made to the description of figure 1.

In this case, the coated carrier material 4 is unwound from a roll and fed into a bath 8, as shown differently with respect to fig. 1. The rolls are driven by a drive 16 so that the coated carrier material 4 is conveyed in a conveying direction 14. The carrier material 4 as a coating layer conveyed by the continuous material 6 is tensioned by the tensioning roller 17.

The coated carrier material 4 is guided in the course of step b) by a plurality of deflection rollers 9 located in the immersion bath 8, so that the carrier material 4 is conveyed through the fluid 5 and the surface of the active material 4 can be brought into maximum contact with the fluid 5.

In the context of step b) and still during the loading with the fluid 5 and before step x), the coated carrier material 4 is guided through a press roller 18, so that the press roller assists the penetration of the fluid 5 into the pores of the active material 3.

The coated carrier material 4 is guided immediately after this and after step b) by a cleaning roller 20, by which excess fluid 5 is removed from the surface of the active material 4.

Since the fluid 5 previously used for applying the carrier material of the coating according to step b) can have a lubricating effect, it is provided that the carrier material 4 of the coating is pressed into a (calender) roller 21 designed for compacting the active material 3. For this purpose, the coated carrier material 4 is guided between steps b) and x) by means of a friction roller 19. The friction roll 19 has a high coefficient of friction on the surface of the carrier material 4 contacting the coating, and the coated carrier material 4 can be moved by the friction roll 19 towards the (calendering) roll 21 and past the (calendering) roll 21.

Fig. 3 shows a cut-away side view of the spraying device 15. Reference is made to the description of figure 1.

In contrast to fig. 1, the immersion bath 8 is not provided here, but the coated carrier material 4 is supplied with the fluid 5 by means of a plurality of spray devices 15.

Fig. 4 shows a cut-away side view of the method after step b). Reference is made to the description of figure 2.

The calender roll 21 shown here in particular is arranged directly after the friction roll 19.

Between steps b) and c), in a further step x), the active material 3 is compacted or calendered. Step x) comprises calendering with calendering rolls 21. The calendering is carried out without heating means, that is to say without a targeted increase in the temperature of the active material 3 being carried out. The pores of the active material 3 are additionally supported by the fluid 5 absorbed in the active material 3, so that the compaction of the active material 3 is uniform over the entire layer thickness. Thereby preventing excessive compaction at the surface of the coating. Calendering or compaction is carried out at room temperature.

According to step c), the support material 4 loaded with the fluid 5 is heated and the fluid 5 is at least partially discharged from the active material 3 while forming pores (first heating stage).

The carrier material 4 loaded with the fluid 5 is heated to at least one boiling temperature of the fluid 5, so that the fluid 5 is discharged from the active material 3 with formation of pores.

Step c) is carried out exclusively by thermal convection or thermal radiation, i.e. in particular not by thermal conduction. The active material 3 is not in contact with a heated roller or (calender) roll. In particular, radiant heaters or hot gas streams are provided, through which heat is delivered to the active material.

The heating of the active material 3 is performed by a heat source 24, such as an infrared heater or a fan. In the case of a one-side coated carrier material 4, the active material 3 is heated by the uncoated side of the carrier material 4, i.e. indirectly.

The coated carrier material 4 is treated as a continuous material 6 at least during steps a) to c) and, after step c), is divided into electrode sheets or electrodes 1, for example in step d).

After step c), the coated carrier material 4 is cut in a further step d) in a cutting device 27. Cutting includes, for example, separating the web 26 into individual electrode sheets 7 or electrodes 1 and/or slitting and/or dividing the web 26 into a plurality of strip materials of smaller width (so-called slits). The electrodes 1 may be arranged in a stack and used in a battery cell 2.

During the cutting, a (uncoated) collector region or arrester is formed on the carrier material 4.

Due to the heating of the active material 3, the fluid 5 accumulated in the active material 3 evaporates. Air bubbles are expelled from the particularly compacted active material coating. Due to the bubbles, new pores are formed in the active material 3 and the existing pores are enlarged.

In step c), it is provided that the gaseous fluid 5 is sucked off and, if necessary, reused in step b). A suction device 22 can be provided for this purpose.

The heating of the active material 3 or the coated carrier material 4 takes place in a (direct or through) chamber 23 through which the coated carrier material 4 is conveyed.

After step c) the coated carrier material 4 is cooled, by guiding the coated carrier material 4 over a cooling roller 25. The cooling is carried out at a temperature of at most 40 degrees celsius.

After step c) and even after cooling, the surface is inspected by a (if necessary optical) measuring device 26. Here, it is checked whether the surface of the active material 3 is possibly damaged.

Furthermore, after step c), the thickness of the coated carrier material 4 is checked by means of a (if necessary optical or tactile, etc.) measuring device 26. The thickness can be corrected by varying step x) if necessary.

According to step d), the coated carrier material 4 is transported for further processing.

Fig. 5 shows a third embodiment for step b) of the method. Reference is made to the description of figure 2.

In contrast to fig. 2, it is shown here that the coated carrier material 4 is guided in the context of step b) by a coating roller 28 which is loaded with the fluid 5. The carrier material 4 coated here is loaded with the fluid 5 only by the coating roller 28 and is not transported through the fluid 5 itself. The application roller 28 can be arranged, for example, partially in the immersion tank 8 or be loaded with the fluid 5 by means of a spraying device 15 or a conveying means 29, for example a sponge.

The coated carrier material 4 is guided in the course of step b) by a plurality of deflection rollers 9, so that the carrier material 4 is conveyed through the coating roller 28 and the surface of the active material 3 can come into contact with the fluid 5.

In the context of step b) and still during the loading with the fluid 5 and before step x), the coated carrier material 4 is guided through a pressure roller 18 such that it assists the penetration of the fluid 5 into the pores of the active material 3.

The coated carrier material 4 is guided immediately after this and after step b) by a cleaning roller 20, by which excess fluid 5 is removed from the surface of the active material 3.

Fig. 6 shows a fourth embodiment for step b) of the method. Reference is made to the description of figure 3.

In contrast to fig. 3, the application roller 28 is here acted upon by the spraying device 15 with the fluid 5. The spraying device 15 delivers the fluid 5 onto a delivery means 29, here a sponge, which in turn contacts the application roller 28.

Fig. 7 shows a fifth embodiment for step b) of the method. Reference is made to the description of figure 5.

In contrast to fig. 5, it is shown here that the coated carrier material 4 is guided in the course of step b) by a coating roller 28 which is acted on by the fluid 5. The carrier material 4 coated here is loaded with the fluid 5 only by the coating roller 28 and is not transported through the fluid 5 itself. The application roller 28 is also acted upon with the fluid 5 by a belt-like transport means 29. The conveying means 29 is guided by the deflecting rollers 9 and here through the immersion bath 8. The fluid 5 is absorbed by the transport means 29 and transported in the direction of the application roller 28. The application roller 28 can be designed as a calender roller 21, in order to be able to carry out the compaction of the active material 3 in this case.

List of reference numerals:

1. electrode for electrochemical cell

2. Battery cell

3. Active material

4. Carrier material

5. Fluid, especially for a motor vehicle

6. Continuous material

7. Electrode plate

8. Immersion tank

9. Steering roller

10. Sealing device

11. Gas (es)

12. Shell body

13. Inlet port

14. Conveying device

15. Spraying device

16. Drive device

17. Tension roller

18. Press roll

19. Friction roller

20. Cleaning roller

21. Calendering roller

22. Suction device

23. Chamber

24. Heat source

25. Cooling roller

26. Measuring device

27. Cutting device

28. Coating roller

29. Transmission device

Claims

1. A method for manufacturing an electrode (1) for a battery cell (2); wherein the method has at least the following steps:

a) Preparing a carrier material (4) of the electrode (1) coated with an active material (3);

b) Loading the coated carrier material (4) with a pore-forming fluid (5) such that the fluid (5) is absorbed into the active material (3);

c) The carrier material (4) loaded with the fluid (5) is heated, and the fluid (5) is at least partially discharged from the active material (3) while forming pores.

2. Method according to claim 1, wherein between steps b) and c) the active material (3) is compacted in a further step x).

3. The method according to claim 2, wherein the active material (3) is compacted to at least 1.5g/cm in step x) ³ The density of (c).

4. A method according to one of the preceding claims 2 and 3, wherein step x) comprises calendering and step c) is carried out spatially separated from step x).

5. Method according to one of the preceding claims, wherein step c) is carried out solely by thermal convection or thermal radiation.

6. Method according to one of the preceding claims, wherein the coated carrier material (4) is treated as a continuous material (6) at least during steps a) to c) and is divided into electrode sheets (7) after step c).

7. Method according to one of the preceding claims, wherein step b) is carried out in a bath (8) filled with a fluid (5), through which bath the coated carrier material (4) is conveyed.

8. Method according to one of the preceding claims 1 to 6, wherein the fluid (5) is sprayed onto the active material (3) in step b) or is applied onto the active material (3) by means of an application roller (28).

9. Method according to one of the preceding claims, wherein the fluid (5) has a boiling temperature of maximum 105 ℃ under the ambient conditions of step d).

10. Method according to one of the preceding claims, wherein the pore-forming fluid (5) comprises at least one of the following components:

ethers, such as Tetrahydrofuran (THF);

dichloromethane;

light naphtha; at least molecules having 5 to 6 carbon atoms;

alcohols, such as methanol, ethanol or 1-propanol;

aldehydes, such as propionaldehyde, butyraldehyde or valeraldehyde;

ketones, such as 2-propanone, 2-butanone or 2-pentanone;

dimethyl carbonate.