Method for coating a carrier material with an active material for producing an electrode film of a battery cell

Description

[0001] The invention relates to a method for coating a carrier material with an active material for producing an electrode foil of a battery cell. The carrier material comprises, in particular, a strip-shaped carrier material.

[0002] Batteries, especially lithium-ion batteries, are increasingly being used to power motor vehicles. Batteries are typically composed of cells, each of which has a stack of anode, cathode, and separator plates. At least some of the anode and cathode plates are designed as current collectors, diverting the current provided by the cell to a load located outside the cell.

[0003] During the production of a lithium-ion battery cell, a so-called carrier material, in particular a strip-shaped carrier material, e.g., a carrier foil, is coated on both sides with a slurry using an application tool. The slurry consists of several components, including an active material, conductive carbon black, a binder, solvents, and possibly other additives. After each coating on one side, the coated carrier material is subjected to a drying process to evaporate the solvent contained therein and firmly bond the remaining components to the carrier foil. The carrier foil forms a current collector for the battery cell.

[0004] The resulting coating is porous. Calendering reduces porosity by compacting the coating. Compaction is necessary to increase specific capacitance (relative to volume) and electrical conductivity.

[0005] The known process of coating the anode and cathode with a slurry, followed by drying and final calendering and cutting has the following problems: Additional costs and energy requirements arise for the drying solvent (e.g. NMP - N-methyl-2-pyrrolidone - for the cathode and water for the anode); densification must be achieved by calendering, a process that causes wrinkling and requires complex machinery; it is difficult to produce coatings from different layers with different densities; this may require the coating-calendering-coating-calendering cycle to be carried out more frequently, which extends production time and increases operating costs; the coating adhesion is poor, which can lead to delamination.

[0006] Dry coating (solvent-free) is proposed by some suppliers as an alternative to wet coating (using a slurry). However, dry coating has the following disadvantages: After dry coating, a heated calendering process is required to melt and evenly distribute the binder; this increases costs. Different layers with different densities are difficult to produce; the adhesion of the active material to the carrier material (before calendering) is low.

[0007] The known methods therefore have the following disadvantages: The coated substrate must undergo various processes, such as coating and calendering; the substrate must be rewound after each process step; this causes bending stresses on the electrode and also particle contamination; the individual processes increase the space requirements, costs and also waste; layer-by-layer coating and layer-by-layer compaction in the calender are difficult; drying and recycling the solvent are energy-intensive processes and also incur high costs; the solvent NMP is a hazardous substance and must be handled carefully; the viscosity of the slurry plays a decisive role in the quality of the coating; the rheology depends on the conductive carbon, binder and solvent; problems with the inclusion of air / gas in the wet coating can occur if degassing is not carried out correctly.The adhesion of the coating to the substrate depends on the drying zones; drying too quickly can cause cracks and / or reduce adhesion; calendering is associated with problems such as wrinkling due to uneven stretching of coated and uncoated areas; high compression during calendering can lead to lithium plating in the anode; low compression can lead to a loss of conductivity in the cathode.

[0008] There are known solutions to address the problems associated with wet coating. Replacing wet coating with dry coating (solvent-free coating) is primarily accomplished in two different ways: Dry mixes are sprayed onto the substrate by electrostatic discharge according to the aerosol principle; this creates porous layers of the coating; the coating is then calendered at high temperature (approx. 150°C) so that the binder is softened and evenly dispersed; the dry mix is ​​applied to the substrate with a roller / vibrator / screen and then calendered at temperature; a spray mechanism is therefore not necessary, i.e. coating and calendering are integrated into a single operation, or calendering can be carried out later using additional rollers.

[0009] The above solutions still have the following problems: Heavy mixing stress during dry mixing can lead to agglomeration of the conductive carbon black and impair viscosity; adhesion of the coating by electrostatic aerosol discharge alone is low; this leads to delamination during recoating during winding; a calendering process is required for densification; wrinkling of the substrate in processes where coating and calendering are carried out with a roller; in this case, calender rollers must be heated, resulting in high energy consumption.

[0010] US 2013 / 273407 A1 discloses providing an active material of an electrode foil with a heat-resistant coating. This coating is applied in the form of a dry coating via a Laval nozzle.

[0011] US Pat. No. 8,936,830 B2 relates to a method and apparatus for the uniform, continuous coating of a substrate. The coating material is applied to the substrate via a Laval nozzle.

[0012] US 2003 / 0219542 A1 and US 2002 / 0168466 A1 each disclose a method for applying a coating via a supersonic nozzle.

[0013] US Pat. No. 8,142,569 B2 discloses a device for producing a battery cell. A metal foil is coated with an active material. The coating is applied using a Laval nozzle.

[0014] A method for producing a solid-state battery is known from US 2020 / 0 176 752 A1.

[0015] The object of the present invention is to at least partially solve the problems cited with reference to the prior art. In particular, a method is to be proposed by which an active material can be arranged on a carrier material. This is intended to achieve a high level of efficiency in the manufacturing process while simultaneously maintaining low costs and high product quality.

[0016] A method having the features according to patent claim 1 contributes to the solution of these objects. Advantageous further developments are the subject of the dependent patent claims.

[0017] A method for coating a carrier material with an active material for producing an electrode foil of a battery cell is proposed. The coating is carried out using a Laval nozzle, wherein the Laval nozzle has at least one converging first section, a second section with a smallest flow cross-section (of the Laval nozzle or of the three sections), and a diverging third section arranged sequentially along a flow direction. The method comprises at least the following steps: a) introducing a first gas stream via the first section into the Laval nozzle; b) introducing a first particle stream comprising a binding material for the active material via the third section into the Laval nozzle; c) mixing the first gas stream and the first particle stream and accelerating the particle stream by the first gas stream flowing at a supersonic speed in the third section; d) applying the first particle stream to the carrier material to form a layer of a coating and the active material is introduced into the Laval nozzle as a second particle stream via the first section and the binding material as the first particle stream via the third section.

[0018] The above (non-exhaustive) classification of the process steps into a) to d) is primarily intended to serve as a distinction and does not enforce any order and / or dependency. The frequency of the process steps can also vary. It is also possible for process steps to overlap one another, at least partially. Most preferably, steps a) to d) take place at least temporarily in parallel. Steps b) to d) take place, in particular, after or simultaneously with step a).

[0019] The process uses only one Laval nozzle, meaning the gas and / or particle streams pass through only one Laval nozzle (at least partially). However, different Laval nozzles can be used for different coating layers, so that the entire coating is produced using different Laval nozzles.

[0020] A Laval nozzle is generally known. These typically comprise a converging first section, a second section with a smallest flow cross-section, and a diverging third section. The Laval nozzle has an inlet upstream of the first section and an outlet downstream of the third section. The Laval nozzle extends a total length between the inlet and outlet along the flow direction. The individual sections each extend a length.

[0021] The principle of the Laval nozzle is based on the different properties of gases flowing at subsonic and supersonic speeds. The velocity of a subsonic gas flow increases as the cross-sectional area becomes increasingly narrower, since the mass flow rate is constant. In particular, the gas flow through a Laval nozzle is isentropic (the gas entropy is nearly constant). In subsonic flow, sound propagates through the gas. In the second section, where the cross-sectional area or flow area is minimal, the gas velocity locally becomes sonic (Mach number = 1.0), a condition known as choked flow. When the cross-sectional area of ​​the Laval nozzle increases again in the third section, the gas begins to expand, and the gas flow increases to supersonic speeds.A Laval nozzle only creates a throttled flow if the pressure and mass flow through the nozzle are sufficient to reach sonic speeds. Otherwise, supersonic flow is not achieved, and the Laval nozzle behaves like a Venturi tube. With a Laval nozzle, the inlet pressure into the nozzle must always be significantly higher than the ambient pressure. Furthermore, the gas pressure at the outlet of the third section of a Laval nozzle should not be too low. In practice, the ambient pressure must not be higher than approximately twice the pressure in the supersonic gas stream at the outlet to allow supersonic flow to exit the nozzle.

[0022] In particular, a solvent-free coating of a substrate is proposed. Solvent-free coating with dry particles is an ideal alternative to the wet slurry process, as it eliminates the cost of the solvent as well as its removal and recycling. The proposed process allows the use of dry powder for coating, meaning no solvent is used. The coating is sprayed onto the substrate rather than applied by electrostatic discharge (using Venturi / aerosol techniques).

[0023] The Laval nozzle allows a supersonic velocity of the gas medium to be set at the Laval nozzle outlet. This means that the particles are accelerated to a very high speed, thus impacting the carrier material. Due to the high kinetic energy, the dry mixture adheres sufficiently strongly to the carrier material. Furthermore, the coating already has a high density immediately after coating, so calendering for (further) densification of the active material is not necessary.

[0024] During calendering, the coated substrate is passed through a roller arrangement, which may be temperature-controlled and thus can heat the coated substrate. The coating is compacted by the rollers. This typically results in an increase in the density of a coating layer of at least 20%.

[0025] In particular, a binder or binding material is only required in small quantities because the high kinetic energy bonds the active material in the coating together by solid-state welding.

[0026] The coating can be applied in multiple layers or comprise several layers applied consecutively. In particular, the last layer applied is heated and leveled using the well-known principle of striping (leveling). Each layer can have a different chemistry, density, and thickness. This allows desired properties to be achieved with regard to electrolyte diffusion, electrical conductivity, adhesion of the coating to the substrate, and solid-state welding of the particles to one another.

[0027] After coating, the resulting electrode foil can be subjected to a skin drawing process to adjust the final thickness of the electrode foil. Skin drawing involves compressing both sides of the coating or coated substrate, while strip drawing (leveling / smoothing) involves processing only one side of the coating.

[0028] A final manufacturing step involves notching, which takes place before winding. Here, the (uncoated) collector area or conductor is brought into its final shape using a punching process.

[0029] In particular, the carrier material is cut to the final dimension (width) intended for the electrode foil before step d), i.e., before coating. In particular, this allows a single Laval nozzle to coat a full width of the carrier material without requiring relative movement between the carrier material and the Laval nozzle in the width direction. However, if necessary, multiple Laval nozzles can be used to coat the carrier material together, i.e., with coating stripes arranged side by side along the width.

[0030] The main advantages of the proposed method are: After coating, no calendering is required, since the coating density required for use with the electrode foil is achieved by the high velocity of the deposited particles; the binding material is fed into the third section of the Laval nozzle; this means that at least some of the particles are not heated, but are only accelerated by the gas stream exiting the Laval nozzle; the Laval nozzle generates a supersonic velocity for particle deposition; for cost reasons, dry air or nitrogen (instead of helium) can be used for the gas stream.

[0031] In the present case, the Laval nozzle is designed in particular such that a pressure in the gas flow within the third section, preferably at the outlet of the Laval nozzle, corresponds to an ambient pressure or is slightly lower (e.g. up to 20% lower) than an ambient pressure.

[0032] When the first gas stream enters the first section, it moves at subsonic speed. Due to the converging first section down to the smallest flow cross-section, the gas stream accelerates. In the second section, where the flow cross-section is minimal, the gas stream velocity along the flow direction becomes sonic. Downstream of the smallest flow cross-section, i.e., in the diverging third section, the flow cross-section becomes increasingly larger. The gas in the gas stream expands, and the gas stream velocity increases increasingly into the supersonic range.

[0033] The first gas stream comprises at least one of nitrogen, helium, a mixture of nitrogen and helium, or air. The first gas stream can have a high purity with respect to the aforementioned components. For example, the first gas stream can contain at least 95% by volume of the respective component, i.e., nitrogen, helium, a mixture of nitrogen and helium, or air.

[0034] The gas stream is provided at the inlet of the Laval nozzle, i.e., upstream of the first section, in particular at a pressure of 2 to 15 bar, preferably 3 to 12 bar. The first gas stream there has a temperature of, in particular, at most 120 degrees Celsius, preferably at most 105 degrees Celsius. Particularly preferably, the first gas stream there has a temperature of at least 80 degrees Celsius, preferably at least 90 degrees Celsius.

[0035] At the outlet of the Laval nozzle, i.e., downstream of the third section, the gas flow has a pressure of 1 to 2 bar. The gas flow there has a temperature between 40 and 80 degrees Celsius, particularly between 50 and 70 degrees Celsius.

[0036] In particular, the first gas stream has a volume flow of 15 to 30 cubic meters per hour.

[0037] At the outlet, the first gas stream reaches in particular a Mach number of 1 to 5, preferably 1 to 3.

[0038] The distance between the carrier material and the outlet can be between 5 and 40 millimeters, in particular between 10 and 30 millimeters.

[0039] In particular, the velocity of the particles emerging from the outlet with the gas flow is (as an average) between 70 and 90% of the velocity of the (e.g. first) gas flow.

[0040] The particle stream exiting the Laval nozzle is directed towards the carrier material, creating an interaction between the particle stream and the carrier material.

[0041] For particle deposition on the substrate, the particles must move at a critical velocity. The critical velocity depends on the coating particle. If a particle velocity is lower than the critical velocity, the particle will bounce off the substrate. If the particle velocity is higher than the critical velocity, the particles will penetrate the substrate and destroy it. Particles whose velocity equals the critical velocity will be coated onto the substrate.

[0042] Therefore, a high critical velocity is required for the particles. In this process, the particles reach supersonic speed when accelerated by the initial gas stream. Temperature and pressure parameters can be varied to adjust the kinetic energy of the particles. In this process, the active material is highly compressed as a result of deposition via the Laval nozzle, allowing a high density to be achieved. This eliminates the need for subsequent compaction and / or calendering.

[0043] With conventional Venturi tube deposition processes, these high velocities are not achieved. The temperature of the gas stream has no effect. The velocity is only changed by pressure. The resulting densities of the carrier material are too low, so calendering is still necessary.

[0044] In particular, the substrate is thoroughly cleaned before coating to remove oil, grease, dirt, paint, and other foreign matter. In particular, the surface of the substrate is roughened to improve the interaction between the coating and the substrate and to reduce / remove the inherent oxide layer on the surface. Various methods are available for cleaning the surface, such as plasma jet cleaning, ultrasonic cleaning, or blasting.

[0045] The carrier material used consists in particular of 10 to 12 µm thick copper for the anode and 12 to 15 µm thick aluminum for the cathode.

[0046] After cleaning, the substrate is first cut to a smaller width, particularly by mechanical slitting, laser cutting, waterjet cutting, or ultrasonic cutting. Slitting is performed primarily before coating, so that deposition can be carried out on the final required width of the substrate. If the slitting or cutting of the substrate or coated substrate is performed after coating, layers of less dense powder may adhere to the cutting edge and the cutting surface.

[0047] In particular, the Laval nozzle can be used to produce different coating layers with different densities.

[0048] In particular, the material of the coating to be applied is powdered and solvent-free.

[0049] In particular, the material of the first particle stream is powdery and solvent-free.

[0050] In particular, it comprises at least one of conductive carbon black, NMC (lithium-nickel-cobalt-manganese as a lithium-storing active material), graphite (as a lithium-storing active material), CNT (carbon nanotubes), SBR (styrene-butadiene rubber as a binder), CMC (carboxymethyl cellulose polymer), PVDF (polyvinylidene fluoride), and porous graphite. The components of the material that are not binder materials are hereinafter referred to as the active material.

[0051] The material of the coating to be applied includes, for example, 2% conductive carbon black, 0.5% CNT, 2% porous graphite, PVDF and NMC for a cathode.

[0052] The material of the coating to be applied includes, for example, for an anode 2% conductive carbon black, 0.5% CNT, 2% porous graphite, 3 to 4% SBR, 1 to 2% CMC, and the remainder (non-porous) graphite.

[0053] The particle size, in particular the median of the particles of the at least one particle stream, is in particular between 5 and 100 µm in diameter.

[0054] By feeding the first particle stream into the third section, a higher temperature can be set for the first gas stream, for example, thus adjusting the gas flow velocity. This prevents at least partial melting of the particles in the first particle stream, e.g., the binding material, or undesirable agglomeration of particles in the first particle stream, e.g., conductive carbon black.

[0055] Agglomeration of the particles is detrimental to the flowability of the particle stream and can, for example, influence the achievable density of the coating.

[0056] Furthermore, clogging of the Laval nozzle in the second section can be prevented because at least part of the material of the coating to be applied is fed downstream of the second section.

[0057] Furthermore, laminar flow conditions prevail in the third section, compared to the more turbulent flow conditions in the second section. This causes less friction in the material intended for coating, allowing the material to be accelerated to higher speeds.

[0058] In particular, the first particle stream is mixed with a second gas stream before being introduced into the third section. In particular, the second gas stream is branched off from the first gas stream. However, a separate gas stream can also be generated. The second gas stream allows the first particle stream to be better introduced into the third section and distributed there.

[0059] The statements regarding the first gas stream are particularly applicable to the second (or third) gas stream and vice versa.

[0060] In particular, the first particle stream is introduced into the third section via a plurality of inlet openings. In particular, at least two, preferably at least three, and particularly preferably at least four inlet openings are provided.

[0061] In particular, at least two inlet openings are arranged at different distances from the smallest flow cross-section. In particular, the difference in the distances is at least 3 to 15 millimeters, preferably 3 to 8 millimeters. In particular, at least two inlet openings are arranged offset from one another along a circumferential direction running transversely to the flow direction. In particular, the inlet openings are arranged evenly distributed along the circumferential direction.

[0062] The generation of turbulence can be prevented by the plurality of inlet openings and their special arrangement if necessary.

[0063] According to the invention, the active material (in particular without binding material) is introduced into the Laval nozzle as a second particle stream via the first section, and the binding material (with or without active material) is introduced as the first particle stream via the third section. Each particle stream can be mixed with a second (or third) gas stream, in particular before being introduced into the respective section.

[0064] By feeding the binding material via the third section, melting of the binder particles can be prevented.

[0065] By feeding the active material through the first section, the temperature of the first gas stream set there can heat the active material, thereby softening the particles of the second particle stream. However, the melting temperature of the active material is not exceeded.

[0066] In particular, a third gas stream is introduced into the Laval nozzle via the third section. In particular, the third gas stream is introduced into the third section via a separate inlet opening. In particular, the third gas stream is fed to the third section alone (i.e., without a particle stream introduced via the same inlet opening).

[0067] In particular, the third gas stream serves to further mix the binding material supplied to the third section with the second particle stream supplied via the first section. The third gas stream is intended, in particular, to generate additional turbulence in the third section and thus improve the mixing of the particle streams. In particular, the supply of a particle stream and / or a gas stream to the Laval nozzle can be controlled via a controllable valve.

[0068] In particular, steps a) to d) are performed several times consecutively for the carrier material, so that the active material is applied in a plurality of layers. In particular, between the individual passes of steps a) to d), i.e., in particular after each applied layer of the coating, a thermal treatment, cooling or heating, of the coated carrier material and / or strip drawing of the surface of the coating takes place.

[0069] In particular, immediately after (each) coating of the carrier material, a cooling process takes place by which the coating is cooled.

[0070] In particular, immediately before drawing or striping, the coated carrier material is heated, in particular to a temperature between 100 and 140 degrees Celsius, preferably between 110 and 130 degrees Celsius.

[0071] In particular, a first (first applied) layer of the coating has a first thickness, and a second layer applied subsequently to the first layer has a second thickness, wherein the second thickness is greater than the first thickness. In particular, for example, the first thickness is between 5 and 20 µm and the second thickness is between 20 and 40 µm. Additional layers can each have thicknesses between 20 and 60 µm. In particular, a third layer is also thicker than the second layer.

[0072] In particular, a first (first applied) layer of the coating has a first density, and a second layer applied subsequently to the first layer has a second density, wherein the second density is lower than the first density. Further layers may each have different densities. In particular, a third layer also has a lower density than the second layer. The density of each layer can be adjusted, in particular, by regulating the pressure of the at least one gas stream (in particular the first gas stream).

[0073] In particular, each layer may have at least one of its own, possibly different, configuration with respect to at least one of the following parameters: density, thickness, composition.

[0074] In particular, a density of the at least one layer of the coating after step d) is further increased by at most 10%, preferably by at most 5%, particularly preferably by at most 2%.

[0075] A Laval nozzle, in particular, has a converging first section upstream in the flow direction and a diverging third section downstream. The properties of a Laval nozzle are determined by the contour and length of the diverging third section and additionally by the ratio of the outlet cross-section to the smallest flow cross-section (expansion ratio). The smallest flow cross-section is located in the second section or forms the second section. The Laval nozzles used here can be conical in the third section (constant angle of expansion) or bell-shaped (increasingly smaller angle of expansion along the length of the third section).

[0076] The bell-shaped contour of the third section enables, in particular, better application behavior of the particles to be applied. It is therefore particularly advantageous if the entire third section is bell-shaped. However, only part of the third section can be bell-shaped and the rest of the third section can be designed differently, e.g. as a cone or a cylinder. The beginning of the third section, i.e. the connection to the second section, should preferably be bell-shaped. The bell shape should extend along the flow direction for at least 30% or at least 50% of the length of the third section. After that, the remainder of the third section can transition into a different shape. An abrupt transition from the bell shape to a cone or to a cylinder should be avoided in particular. Abrupt transitions can disrupt the uniformity (laminar flow) of the gas flow or particle flow.

[0077] The length of the third section extends in particular along the flow direction between the smallest flow cross-section or the beginning of the diverging section and the outlet of the Laval nozzle.

[0078] The bell-shaped, diverging shape of the third section creates a particularly pronounced laminar flow of the gas stream or particle stream. This allows the highest velocity for the particles in the particle stream to be achieved, as friction is reduced to a minimum.

[0079] Favorable coating results can be achieved with Laval nozzles with an expansion ratio (exit diameter / minimum flow diameter) between 1 and 25. It is particularly advantageous if the Mach number of the gas stream and / or particles at the exit is between 1 and 5, depending on the particle size. Smaller particles require a higher Mach number velocity for a high-density coating.

[0080] In particular, the third section of the Laval nozzle can have one of the following shapes: Conical (tapered) shape; Conical (tapered) shape which transitions into a cylindrical shape in the direction of flow; the transition occurring after 30% or 50% of the length of the third section; Bell-shaped; Bell-shaped, wherein the bell-shaped shape transitions into a square or pyramidal shape in the direction of flow; the transition occurring after 30% or 50% of the length of the third section.

[0081] In particular, a diameter of the inlet of the Laval nozzle is between 5 and 30 millimeters, in particular from 10 to 20 millimeters. In particular, a diameter of the outlet of the Laval nozzle is between 15 and 60 millimeters, in particular from 20 to 50 millimeters. In particular, a diameter of the smallest flow cross-section is between 2 and 5 millimeters. In particular, a length of the first section along the flow direction is between 10 and 25 millimeters, in particular between 10 and 20 millimeters. In particular, a length of the third section along the flow direction is between 25 and 40 millimeters, in particular between 30 and 35 millimeters.

[0082] The shape of the Laval nozzle can be selected, particularly with regard to the desired density or thickness uniformity. A third section that initially begins as a bell and then transitions to a square shape is preferred, as this allows for a uniform coating thickness.

[0083] A battery cell is further proposed, comprising at least one housing and at least one electrode foil arranged therein, which is coated with at least one active material by the method described.

[0084] The battery cell comprises in particular a housing enclosing a volume and arranged in the volume at least one first electrode foil of a first electrode type, a second electrode foil of a second electrode type and a separator material arranged therebetween as well as a liquid electrolyte.

[0085] The battery cell is, in particular, a pouch cell (with a deformable housing consisting of a pouch film) or a prismatic cell (with a rigid housing). A pouch film is a well-known deformable housing component used as a housing for so-called pouch cells. It is a composite material, e.g., comprising a plastic and aluminum.

[0086] The battery cell is in particular a lithium-ion battery cell.

[0087] The individual foils of the plurality of electrode foils are arranged one on top of the other, particularly forming a stack. The electrode foils are each assigned to different electrode types, i.e., they are designed as an anode or a cathode. The anodes and cathodes are arranged alternately and separated from each other by the separator material.

[0088] A battery cell is an energy storage device used, for example, in a motor vehicle to store electrical energy. In particular, a motor vehicle, for example, has an electric motor for driving the vehicle (a traction drive), which can be driven by the electrical energy stored in the battery cell.

[0089] A motor vehicle is further proposed, at least comprising a traction drive and a battery with at least one of the described battery cells, wherein the traction drive can be supplied with energy by the at least one battery cell.

[0090] The method can be carried out in particular by a control unit that is equipped, configured or programmed to carry out the described method. The control unit can at least a feed of the carrier material relative to the at least one Laval nozzle; a control of the at least one gas flow; a control of the at least one particle flow; a control of the aforementioned parameters, e.g. pressure, temperature, volume flow.

[0091] In particular, a coating device is proposed which is particularly designed so that the method described above can be carried out therewith.

[0092] The coating device comprises in particular the control unit described above.

[0093] Furthermore, the method can also be carried out by a computer or with a processor of a control unit.

[0094] Accordingly, a data processing system is also proposed, which comprises a processor adapted / configured to carry out the method or part of the steps of the proposed method.

[0095] A computer-readable storage medium may be provided which comprises instructions which, when executed by a computer / processor, cause the computer / processor to carry out the method or at least some of the steps of the proposed method.

[0096] The statements regarding the method are particularly applicable to the battery cell, the motor vehicle, the coating device, the control unit and the computer-implemented method (i.e. the computer or processor, the data processing system, the computer-readable storage medium) and vice versa.

[0097] The use of indefinite articles ("a", "an", "an" and "another"), particularly in the patent claims and the description reproducing them, is to be understood as such and not as a numeral. Terms or components introduced accordingly are therefore to be understood as appearing at least once and, in particular, as being able to appear multiple times.

[0098] As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and therefore do not necessarily specify any interdependence and / or sequence of these objects, quantities, or processes. Should a dependence and / or sequence be required, this is explicitly stated here or will be obvious to the person skilled in the art upon studying the specifically described embodiment. To the extent that a component can occur multiple times ("at least one"), the description of one of these components may apply equally to all or part of the majority of these components, but this is not mandatory.

[0099] The invention and the technical environment are explained in more detail below with reference to the attached figures.

[0100] They show: Fig. 1: a coating device for carrying out a method not according to the invention according to a first embodiment variant; Fig. 2: a part of a coating device for carrying out a method not according to the invention according to a second embodiment variant; Fig. 3: a coating device for carrying out the method according to the invention according to a third embodiment variant; Fig. 4: a coating device for carrying out the method according to a fourth embodiment variant; Fig. 5: a first embodiment variant of a Laval nozzle in perspective view; Fig. 6: a second embodiment variant of a Laval nozzle in perspective view; Fig. 7: a third embodiment variant of a Laval nozzle in perspective view; Fig. 8: a fourth embodiment variant of a Laval nozzle in perspective view; and Fig. 9: a battery cell.

[0101] The Fig. 1shows a coating device 31 for carrying out the method according to a first embodiment. The coating device 31 comprises a Laval nozzle 5, which has a converging first section 7, a second section 8 with a smallest flow cross-section 9, and a diverging third section 10, arranged one after the other along a flow direction 6. The Laval nozzle 5 has an inlet 32 ​​upstream of the first section 7 and an outlet 33 downstream of the third section 10. The Laval nozzle 5 extends between the inlet 32 ​​and the outlet 33 along the flow direction 6 over an entire length. The individual sections 7, 8, 10 each extend over a length 25.

[0102] According to step a) of the method, a first gas stream 11 is introduced via the inlet 32 ​​into the first section 7 of the Laval nozzle 5. The first gas stream 11 is controlled by a valve 30. The first gas stream 11 has been compressed to a predetermined pressure by a compressor 27 and heated to a predetermined temperature by a heating device 28.

[0103] According to step b), a first particle stream 12, comprising at least the active material 2 and a binding material 13 for the active material 2, is introduced via the third section 10 into the Laval nozzle 5. The active material 2 and the binding material 13 are mixed together in a mixing device 29 and introduced as a common first particle stream 12 via an inlet opening 17 into the third section 10.

[0104] By feeding the first particle stream 12 into the third section 10, a higher temperature can be set for the first gas stream 11, thus allowing the velocity of the gas stream 11 to be adjusted. At least partial melting of the particles of the first particle stream 12, e.g., the binding material 13, or undesired agglomeration of particles of the active material 2, e.g., conductive carbon black, can thus be prevented.

[0105] Furthermore, clogging of the Laval nozzle 5 in the second section 8 can be prevented, since the material of the coating 15 to be applied is supplied downstream of the second section 8.

[0106] Furthermore, laminar flow conditions exist in the third section 10, compared to the more turbulent flow conditions in the second section 8. This causes less friction in the material intended for the coating 15 and the material can be accelerated to higher speeds.

[0107] The first particle stream 12 is mixed with a second gas stream 16 before being introduced into the third section 10. The second gas stream 16 is branched off from the first gas stream 11. The second gas stream 16 allows the first particle stream 12 to be better introduced into the third section 10 and distributed there.

[0108] According to step c), the first gas stream 11 and the first particle stream 12 are mixed in the third section 10 and the first particle stream 12 is accelerated by the first gas stream 11 flowing at a supersonic speed in the third section 10. According to step d), the carrier material 1 is subjected to the first particle stream 12 to form a layer 14, 23 of a coating 15. A distance 18 between the carrier material 1 and the outlet 33 can be between 5 and 40 millimeters.

[0109] Fig. 2shows part of a coating device 31 for carrying out the method according to a second embodiment. Reference is made to the explanations regarding the first embodiment.

[0110] In contrast to the first embodiment, the first particle stream 11 is introduced into the third section 10 via a plurality of inlet openings 17. Four inlet openings 17 are provided.

[0111] The inlet openings 17 are arranged at different distances 18 from the smallest flow cross-section 9.

[0112] In addition, the inlet openings 17 are arranged offset from one another along a circumferential direction 19 running transversely to the flow direction 6. The inlet openings 17 are evenly distributed along the circumferential direction 19, in this case offset from one another by 90 degrees.

[0113] The generation of turbulence in the third section 10 can be prevented by the plurality of inlet openings 17 and their special arrangement.

[0114] Fig. 3 shows a coating device 31 for carrying out the method according to the invention according to a third embodiment. Reference is made to the explanations regarding the first embodiment.

[0115] In contrast to the first embodiment, the active material 2 (without binding material 13) is introduced into the Laval nozzle 5 as a second particle stream 20 via the first section 7, and the binding material 13 is introduced as the first particle stream 12 via the third section 10. Each particle stream 12, 20 is mixed with a second gas stream 16 before being introduced into the respective section 7, 10. Separate mixing devices 29 are provided for the active material 2 and for the binding material 13.

[0116] By supplying the binding material 13 via the third section 10, melting of the binder particles can be prevented.

[0117] By supplying the active material 2 via the first section 7, the active material 2 can be heated via the temperature of the first gas stream 11 set there, thus softening the particles of the second particle stream 20. However, the melting temperature of the active material 2 is not exceeded.

[0118] The supply of gas streams 11, 16 and particle streams 12, 20 is each controlled by valves 30.

[0119] Fig. 4 shows a coating device 31 for carrying out the method according to a fourth embodiment. Reference is made to the explanations regarding the third embodiment.

[0120] In contrast to the third embodiment, a third gas stream 21 is introduced into the Laval nozzle 5 via the third section 10. The third gas stream 21 is introduced into the third section 10 via a separate inlet opening 17. The third gas stream 21 is fed to the third section 10 alone (i.e., without a particle stream 12, 20 introduced via the same inlet opening 17).

[0121] The third gas stream 21 serves for the additional mixing of the binding material 13 supplied to the third section 10 with the second particle stream 20 supplied via the first section 7. The third gas stream 21 is intended in particular to generate additional turbulence in the third section 10 and thus to bring about a better mixing of the particle streams 12, 20.

[0122] The supply of each particle stream 12, 20 and each gas stream 11, 16, 21 into the Laval nozzle 5 is controlled by a controllable valve 30.

[0123] Fig. 5shows a first embodiment of a Laval nozzle 5 in perspective view. The Laval nozzle 5 has a converging first section 7, a second section 8 with a smallest flow cross-section 9, and a diverging third section 10, arranged one after the other along a flow direction 6. The Laval nozzle 5 has an inlet 32 ​​upstream of the first section 7 and an outlet 33 downstream of the third section 10. The Laval nozzle 5 extends between the inlet 32 ​​and the outlet 33 along the flow direction 6 over an entire length. The individual sections 7, 8, 10 each extend over a length 25.

[0124] The properties of a Laval nozzle 5 are determined by the contour and length 25 of the diverging third section 10 and additionally by the ratio of the outlet cross-section to the smallest flow cross-section 9 (expansion ratio). The smallest flow cross-section 9 is located in the second section 8 or forms the second section 8.

[0125] The present Laval nozzle 5 is conical in the third section 10 (constant angle of expansion).

[0126] Fig. 6 shows a second variant of a Laval nozzle 5 in perspective view. Refer to the explanations for Fig. 5 is referred to.

[0127] In contrast to the first embodiment, this Laval nozzle 5 has a conical shape which transitions into a cylindrical shape in the flow direction 6; the transition occurs after approximately 50% of the length 25 of the third section 10.

[0128] Fig. 7 shows a third variant of a Laval nozzle 5 in perspective view. Refer to the explanations for Fig. 5 is referred to.

[0129] In contrast to the first embodiment, this Laval nozzle 5 has a bell-shaped contour of the third section 10.

[0130] Fig. 8 shows a fourth variant of a Laval nozzle 5 in perspective view. Refer to the explanations for Fig.7 is referred to.

[0131] In contrast to the third embodiment, in this Laval nozzle 5 only a part of the third section 10 is bell-shaped and the rest of the third section 10 is pyramidal or the bell-shaped part gradually changes to a square cross-section at the outlet 33.

[0132] The bell-shaped diverging shape of the third section 10 creates a particularly pronounced laminar flow of the gas stream 11, 16, 21 or particle stream 12, 20. This allows the highest speed for the particles in the particle stream 12, 20 to be achieved because friction is reduced to a minimum.

[0133] Fig. 9 shows a battery cell 4, comprising at least a housing 26 and arranged therein at least one electrode foil 3, which is coated with at least one active material 2 by the described method. The electrode foil 3 comprises a carrier material 1 with a coating 15 on both sides.

[0134] A first (first applied) layer 14 of the coating 15 has a first thickness 22 and a second layer 23 applied subsequent to the first layer 14 and onto this first layer 14 has a second thickness 24, wherein the second thickness 24 is greater than the first thickness 22. These statements apply to each of the coatings 15 applied to different sides of the carrier material 1. List of reference symbols

[0135] 1Carrier material 2Active material 3Electrode foil 4Battery cell 5Laval nozzle 6Flow direction 7First section 8Second section 9Flow cross-section 10Third section 11First gas stream 12First particle stream 13Binder 14First layer 15Coating 16Second gas stream 17Inlet opening 18Distance 19Circumferential direction 20Second particle stream 21Third gas stream 22First thickness 23Second layer 24Second thickness 25Length 26Housing 27Compressor 28Heater 29Mixing device 30Valve 31Coating device 32Inlet 33Exit

Claims

1. Method for coating a support material (1) with an active material (2) for producing an electrode foil (3) of a battery cell (4) with a Laval nozzle (5), wherein the Laval nozzle (5) has, arranged one after the other along a direction of throughflow (6), at least a converging first portion (7), a second portion (8), having a smallest throughflow cross section (9), and a diverging third portion (10); wherein the method has at least the following steps: a) introducing a first gas stream (11) into the Laval nozzle (5) via the first portion (7); b) introducing a first particle stream (12), at least comprising a binding material (13) for the active material (2), into the Laval nozzle (5) via the third portion (10); c) mixing the first gas stream (11) and the first particle stream (12) and accelerating the first particle stream (12) by means of the first gas stream (11) flowing at a supersonic speed in the third portion (10); d) subjecting the support material (1) to the first particle stream (12) to form a layer (14, 23) of a coating (15); characterized in that the active material (2) is introduced into the Laval nozzle (5) as a second particle stream (20) via the first portion (7) and the binding material (13) is introduced into said Laval nozzle as the first particle stream (12) via the third portion (10).

2. Method according to Claim 1, wherein the first gas stream (11) comprises at least one of the following: nitrogen, helium, a mixture of nitrogen and helium, or air.

3. Method according to either of the preceding claims, wherein the material of the first particle stream (12) is in powder form and solvent-free and comprises at least one of the following: conductive carbon black, NMC, graphite, CNT, SBR, CMC, PVDF and porous graphite.

4. Method according to one of the preceding claims, wherein the first particle stream (12) is mixed with a second gas stream (16) before being introduced into the third portion (10).

5. Method according to one of the preceding claims, wherein the first particle stream (12) is introduced into the third portion (10) via a plurality of inlet openings (17).

6. Method according to Claim 5, wherein at least two inlet openings (17) are arranged at different distances (18) from one another from the smallest throughflow cross section (9).

7. Method according to either of preceding Claims 5 and 6, wherein at least two inlet openings (17) are arranged offset from one another along a circumferential direction (19) running transversely to the direction of throughflow (6).

8. Method according to one of the preceding claims, wherein a third gas stream (21) is introduced into the Laval nozzle (5) via the third portion (10).

9. Method according to one of the preceding claims, wherein steps a) to d) are carried out several times one after the other for the support material (1), so that the active material (2) is applied in a plurality of layers (14, 23).

10. Method according to Claim 9, wherein a first layer (14) of the coating (15) has a first thickness (22) and a second layer (23), applied after the first layer (14), has a second thickness (24), wherein the second thickness (24) is greater than the first thickness (22).

11. Method according to either of preceding Claims 9 and 10, wherein a first layer (14) of the coating (15) has a first density and a second layer (23), applied after the first layer (14), has a second density, wherein the second density is lower than the first density.

12. Method according to one of the preceding claims, wherein, after step d), a density of the layer (14, 23) is increased by at most 10%.