Method for producing electrode mixtures and dry electrodes with the aid of a cooling vessel

Abstract

The present invention relates to a method for producing and conditioning an electrode mixture, which consists of active material, optionally additives, and a binder, the method comprising the steps of: 1) producing the electrode mixture in a mixing vessel of a mixer, wherein, during production, the mixture is heated to a temperature TH, where TH > 45°C; 2) transferring the electrode mixture into a cooling mixer having a cooling vessel, the walls of which are preferably cooled; 3) cooling the electrode mixture in the cooling vessel by at least ΔT = 5°C to a removal temperature TE, which is preferably < 35°C; and 4) removing the electrode mixture from the cooling vessel. The invention also relates to a method for producing dry electrodes from electrode mixtures.

Description

[0001] Maschinenfabrik Gustav Eirich GmbH & Co. KG

[0002] Our reference number: 240839WO

[0003] Method for producing electrode mixtures and dry electrodes using a cooling container

[0004] The present invention relates to a method for producing and conditioning dry electrode mixtures. Furthermore, the present invention relates to a method for producing dry electrodes from these electrode mixtures.

[0005] In recent years, battery technology, and in particular lithium-ion technology, has moved into the spotlight, as it is essential for the functionality of, for example, fully electric vehicles, but also for stationary energy storage systems. A long-lasting, high-capacity battery that is cost-effective to manufacture is a prerequisite for the acceptance of fully electric vehicles.

[0006] Currently, lithium-ion batteries are predominantly used. Within this category, several specific cell chemistries dominate, with the following being the most widespread cathode materials:

[0007] • Nickel-manganese-cobalt (NMC) electrode mixture: These cells use a mixture of nickel, manganese, and cobalt. The nickel ensures high energy density, manganese provides thermal stability, and cobalt stabilizes the structure.

[0008] • Nickel-cobalt-aluminum (NCA) electrode mixture: This mixture contains nickel, cobalt, and aluminum in the cathode. The aluminum content stabilizes the structure and improves the lifespan, while nickel maximizes the energy density.

[0009] • Lithium iron phosphate (LFP) electrode mixture: In this cobalt-free cell chemistry, lithium iron phosphate is used as the cathode material, which is less energy-dense but offers a longer lifespan and better thermal stability.

[0010] The anodes usually consist of graphite or silicon-graphite mixtures. For all these types, electrode mixtures are produced using polymeric binders, sometimes also with conductive additives, applied to conductive foils, and calendered during or after this process to optimize the structural integrity and density of the electrodes.

[0011] Furthermore, there are developments that could play a significant role in the future. Besides more cost-effective, but lower-performing, cobalt-free sodium-ion cell chemistries, intensive research is also being conducted on all-solid-state batteries with solid electrolytes. This technology theoretically offers an even higher energy density than conventional lithium-ion batteries and, due to the solid electrolyte, even greater safety. The production of all these batteries will likely continue to require calendered electrodes, which present various challenges in the calendering process.

[0012] In summary, the calendering of electrode mixtures will continue to play an important role in future battery technologies, as it optimizes the density, homogeneity, and mechanical properties of the electrodes. However, the specific materials that will be used will depend on advances in materials science and the requirements of electromobility.

[0013] A typical lithium-ion cell electrode consists of a copper foil acting as the anode and an aluminum foil acting as the cathode. The foils are usually coated on both sides with active material and, at least for the cathode, with additives.

[0014] The electrodes must meet high standards in order to produce a reliable, high-capacity lithium-ion battery.

[0015] The electrode layer must have a defined, constant thickness and a defined pore structure into which the electrolyte can penetrate to transport lithium ions to each particle of the active material. Ideally, the active material should be wetted by the electrolyte over as large an area as possible. Furthermore, the particles of the active material must be electrically connected to the metal foil—that is, in the described example, to the copper or aluminum foil—to ensure the transport of electrons to and from each particle of the active material.

[0016] Furthermore, the particles of the active material must be bound both to each other and to the metal foil, for which a binder is used. Finally, the layer thickness should be as uniform as possible across the width and length. To produce the layers, the starting materials—that is, the active material, the binder, and any additives—must be mixed together and dispersed into a so-called "slurry" (paste). Typically, a liquid solvent (e.g., water or N-methyl-2-pyrrolidone (NMP)) is added, which then has to be removed again in complex drying processes after the electrode mixture has been applied to the foil. The voids that form during the drying process are compressed to a defined porosity during the subsequent calendering process.

[0017] The predominant wet processing of electrodes is time-consuming and energy-intensive. Furthermore, the automated production of electrode mixtures usually requires bulky drying equipment.

[0018] There are already approaches to producing electrode mixtures dry, i.e., with little or even no solvent. However, this requires more intensive preparation during the mixing process to convert the polymeric binders, which are no longer soluble in a solvent, into a processable and bondable state. Especially when PTFE or PVDF is used as a binder, the mixture typically needs to be processed in successive steps at different temperatures. When using PTFE, the mixture is fibrillated by temperature activation and the application of shear energy at temperatures above 30°C. The nano- and microscale polymer fibers formed during fibrillation create a crumbly to plastic mass that is very difficult to remove from the mixer.Since the mixture then needs to be evenly dosed into a calender gap to produce the desired electrode film, the crumbly to plastic mass is often unusable. The mass must first be converted into a readily dosable agglomerate, granules, or powder.

[0019] Based on the described prior art, it is therefore an object of the present invention to provide a method for producing dry electrode mixtures which provides a readily processable electrode mixture of high quality.

[0020] This problem is solved by a method for producing and conditioning an electrode mixture, which consists of active material and binder and optionally additives, comprising the steps 1) producing the electrode mixture in a mixing vessel of a mixer, wherein during production the mixture is heated to a temperature TH, where TH > 45°C,

[0021] 2) Transferring the electrode mixture into a cooling mixer with a cooling vessel, the walls of which are preferably cooled,

[0022] 3) Cooling the electrode mixture in the cooling container by at least AT= 5°C to a withdrawal temperature TE, which is preferably TE < 35°C.

[0023] 4) Removal of the electrode mixture from the cooling container.

[0024] In this application, the term "mixer" means any device for producing a material mixture and / or for homogenizing, dispersing, kneading, plasticizing, or conveying a mixture, in which a relative movement is generated between the mixture and at least one boundary surface within a mixing chamber bounded by a wall. This relative movement can be effected by a mixing element arranged in the mixing chamber and / or by movement of the mixing vessel and / or by a gas flow; the movement can, in particular, include rotation or agitation. Operation can be continuous and / or discontinuous. Furthermore, the "mixer" can consist not only of a single machine but also of several machines connected in series, which provide the electrode mixture at the discharge of the last machine.Thus, the term "mixer" does not refer solely to machines that are marketed and offered as mixers, but also to machines for other basic process engineering operations such as mills, in which a mixing process is inextricably superimposed alongside the comminution or dispersing process when different raw materials are fed into the machine simultaneously or sequentially.

[0025] In this application, the term "mixing container" refers to the housing that defines the mixing or comminution space, regardless of its geometric design, including container-, trough-, pipe- or channel-shaped designs as well as linearly extended process spaces with inlet and outlet openings (in particular cylinders / housings of a screw machine, e.g. extruder cylinders).

[0026] The term "mixing element" encompasses dynamic and static elements that influence the flow or mixing, such as agitators, rotor / stator assemblies, and structures integrated into the wall. The mixing element can be a separate component or an integral part of the wall. A twin-screw extruder, for example, is a mixer within the meaning of this application; its mixing chamber forms the process channel (extruder cylinder / housing), and the mixing elements are the two screws, which may be co-rotating or counter-rotating, intermeshing or non-intermeshing. The mixing chamber itself can also produce the mixing action if its movement generates the relative motion, as in a V-mixer; a separate mixing element is then not required.

[0027] It has been shown that the quality of the electrode mixture can be significantly improved if the temperature of the mixture is considerably increased during the mixing process in the mixing vessel, i.e., raised to more than 45°C. This can be achieved, for example, by introducing high mechanical power using a stirrer to generate frictional heat. However, in the resulting plastic, elastic, and "sticky" state, the electrode mixture is difficult to remove from the vessel. Furthermore, its consistency does not allow for uniform dosing into a calender gap.

[0028] Improved processability of the optimally blended electrode mixture is achieved when it is cooled while simultaneously being agitated, for example, by a stirring or mixing tool. The plastic, cohesive mass then breaks down into a dosable bulk material. However, this is very time-consuming, as the container and its walls must be cooled, and heat dissipation through the cooled surface area of ​​the container walls is limited. Furthermore, the heat stored within the container itself must also be removed, which slows down the product cooling process. If the preparation takes place in a mixing vessel, the container must also be reheated after removal, as a high temperature is required for the subsequent production of the next batch.

[0029] According to the invention, the warm electrode mixture is transferred to a cooling vessel of a cooling mixer, with the walls of the cooling vessel preferably being cooled. To achieve the fastest and most uniform cooling of the electrode mixture in the cooling vessel, the electrode mixture is moved within the cooling vessel, for example by rotating the cooling vessel and / or by arranging a rotating mixing tool within the cooling vessel. The cooling mixer can be arranged in a cascade configuration, so that the warm electrode mixture falling out of the mixing vessel by gravity falls directly into the cooling vessel.

[0030] The mixing vessel is immediately ready for the next batch and does not need to be reheated. The inventive method thus saves considerable time and energy. In a preferred embodiment, the electrode mixture is cooled in the cooling vessel by at least 9°C and preferably to a withdrawal temperature TE < 19°C. Particularly when using PTFE as a binder, this stabilizes the electrode mixture during storage, transport, and dosing. In particular, the dosing of the electrode mixture into a calender gap is significantly improved by this cooling.

[0031] Alternatively, in step 3) the cooling does not take place below a withdrawal temperature TE > 24°C and in step 4) the electrode mixture is fed to a cooling device by means of which the electrode mixture is cooled by at least 4°C, preferably to a temperature TK < 19°C.

[0032] The conditioning of the electrode mixture thus takes place in several steps. After heating the mixture, during which the added binder and / or solid electrolyte, along with the other mixture components, is brought into a segregation-free state, the mixture is cooled in the next step in the cooling vessel by at least AT = 5°C and preferably to a withdrawal temperature TE < 35°C, but not below a withdrawal temperature TE = 24°C. This cooling, combined with slow agitation, transforms the rather plastic mixture into a bulk material. The electrode mixture can then be more easily removed from the cooling vessel. Depending on the raw material formulation, the electrode mixture may not yet be completely stable for storage and can be easily discharged from buffer tanks or silos.Due to the presence of oversize material, it is not yet fully suitable for being fed with high accuracy into a calender gap only a few dozen micrometers wide.

[0033] For example, ethylene carbonate (EC) is used as a material in all-solid-state batteries (ASSBs). EC is used as a solid electrolyte. By heating it to over 45°C, the EC, which is solid at room temperature, transitions into a liquid state and can thus form an agglomerate or granules together with the other powdered raw materials. Cooling in step 3) to below 35°C causes the granules to solidify, making them easy to remove from the cooling container. In principle, this production of melt granules is also possible with other meltable binders, electrolytes, or additives.

[0034] To ensure the electrode mixture is both stable for storage and easy to dose, it is removed from the cooling container and transferred to a separate cooling unit. The electrode mixture is thus only slightly cooled in the cooling container and removed while still warm. This has the advantage of reducing the time the cooling container is in contact with the material, allowing the container walls to cool down more quickly and thoroughly when empty. This results in a greater temperature difference between the empty container and the product being added from the mixing container, making it available for the next batch sooner. This can reduce the overall cycle time of the cascade and thus increase throughput.

[0035] The extracted electrode mixture is then cooled by at least 4°C and preferably to a temperature TK < 19°C using the cooling device. Particularly when using PTFE as a binder, this stabilizes the electrode mixture during storage, transport, and dosing. Ideally, the PTFE contained in the mixture is first cooled to a temperature < 35°C (still in a pseudohexagonal, very disordered phase), causing the mixture to decompose and thus allowing it to be more easily extracted from the container. The tendency of PTFE to fibrillate decreases with decreasing temperature due to changing crystal structures in two temperature ranges. Cooling preferably occurs below the transition temperature of PTFE of 30°C to the partially ordered hexagonal phase, or even better, below 19°C to the well-ordered triclinic phase.

[0036] Essentially, the cooling of the electrode mixture is carried out in two steps. In the first step, the mixture is cooled only to the point where it transitions into a structured bulk state, making it easier to remove from the cooling container. The further cooling required to bring the electrode mixture into a state that is as stable for storage and easy to dose as possible, so that it can be processed further in a calender, then takes place outside the cooling container. Because the cooling container no longer needs to be cooled as much, the cycle time can be significantly reduced.

[0037] The cooling system could, for example, consist of a third mixer arranged in a cascade configuration, the walls of which are also cooled. Alternatively, a cooled premixer could be installed upstream of the mixer for producing the electrode mixture. In this premixer, a powder mixture of the active material and one or more additives is produced. This powder mixture is then further processed in the mixer for producing the electrode mixture after the addition of the binder (usually a polymer). While this increases the number of machines and thus initially the costs, significantly shorter residence times in the heating and cooling mixers can lead to fewer machines overall and lower operating costs at high throughput rates.In a preferred embodiment, a conveying line of a pneumatic conveying system for extracting the electrode mixture from the cooling container is provided as a cooling device, which is operated with a gas preferably with a temperature TG < 19°C, wherein preferably in step 3), between steps 3) and 4) and / or during step 4) dry ice or a liquefied gas, e.g. liquid nitrogen, is introduced into the cooling container, wherein the gas produced by sublimation or evaporation is directed into the conveying line.

[0038] The pneumatic conveying system for removing an electrode mixture from the cooling container ensures that the mixture can be removed efficiently, cleanly and without segregation or significant change in the bulk properties or damage to the particles.

[0039] Pneumatic conveying includes, among other things, a pneumatic conveying unit, which usually consists of a blower or compressor that generates the necessary airflow, as well as a feed device, conveying lines which may additionally be equipped with a double jacket for cooling and / or insulation, and a material separator.

[0040] The feed device is installed in the cooling tank, for example in the form of a suction pipe, or at the outlet of the cooling tank, and transfers the mixture into the conveying line. The actual conveying can be carried out using a vacuum suction system or a pressure chamber, which gently introduces the electrode mixture into the line. Vacuum conveying is preferred. A cooling effect can be achieved if the transport gas used for pneumatic conveying is cooled or mixed with the exhaust gas produced by sublimation or evaporation from the liquid gas added to cool the mixture.

[0041] In a preferred embodiment, liquefied gas, such as liquid nitrogen or liquid carbon dioxide, or even in solid form as dry ice, is introduced into the mixture in the cooling container for cooling purposes. This significantly accelerates the cooling process. For example, 100 kg of plastic, fibrillated mass was cooled from 90 °C to below 20 °C in less than 3 minutes by adding 10 kg of dry ice. If cooling is achieved solely through a double-walled container, the cooling process requires a cooling time of more than 30 minutes. The amount of liquefied gas or dry ice added is preferably measured to ensure that the target temperature, i.e.,The cooling process must achieve a minimum temperature of 5°C through complete gasification or sublimation as quickly as possible, while simultaneously ensuring that the mixture is not cooled below the minimum extraction temperature of 24°C through gasification or sublimation. The faster the cooling process, the sooner the cooling mixer is ready to receive mixtures with a temperature above 45°C. In the case of long heating times in the heating mixer, this could even allow for the alternating feeding of several heating mixers. Simultaneous cooling of the double-walled container of the cooling mixer with a cooling medium reduces the required amount of liquid gas and the heating of the cooling container to a minimum.

[0042] If dry ice or liquid nitrogen is introduced into the cooling tank before extraction, the abrupt gas evolution during sublimation or evaporation leads to a pressure increase within the tank, which can assist the pneumatic conveying system's feed mechanism. Furthermore, the resulting gas has a very low temperature, so that when it flows into the conveying line and remains in contact with the electrode mixture for an extended period, it further cools the mixture. This effect is particularly pronounced in low-flow conveying (also known as continuous flow conveying) due to the large mass and heat exchange surfaces between the electrode mixture and the gas. To prevent the temperature from dropping too low, warmer gas, such as ambient air, can be mixed with the gas produced by evaporation or sublimation. This also prevents condensation effects on cold pipes.

[0043] At the end of the conveying line, the electrode material is separated from the gas in the material separator. A cyclone separator, a deflector separator, or a filter system can be used here to gently separate the material and transfer it, for example, to a buffer tank.

[0044] In a further preferred embodiment, the electrode mixture according to step 4) is transferred to a buffer tank, wherein the buffer tank is preferably temperature-controlled and used as a cooling device, wherein the buffer tank is preferably double-walled, with a cooling fluid able to flow between the two walls, and / or the buffer tank has thermal insulation, and wherein the electrode mixture is particularly preferably moved within the buffer tank. This can be achieved by an agitator, gas aeration via nozzles, or in the form of a fluidized bed or fluidized bed by means of a continuously flowing, appropriately temperature-controlled pressurized gas. The buffer tank can thus itself be used as a cooling device. A separate cooling device, such as the described pneumatic conveying with cooled transport gas, can be provided instead or additionally.To prevent the electrode mixture particles from sticking together and to facilitate discharge, a stirring tool may be present in the buffer tank, which stirs and loosens the mixture until it can be transferred to, for example, a calender.

[0045] In a preferred embodiment, the electrode mixture according to step 4) is applied to a sieve, and only the portion passing through the sieve is used as the conditioned electrode mixture for electrode production. The sieve can be located within or after the buffer storage tank. The sieve separates the electrode mixture into the portion passing through the sieve and the overflow, with the overflow collecting components that have a diameter larger than the sieve mesh size. The sieved portion, loosened by the sieving, can be dosed much more easily and uniformly, for example, into a calender gap.

[0046] The sieve preferably has a mesh size of less than 10 mm, and particularly preferably less than 5 mm, and most particularly preferably less than 2 mm.

[0047] In a preferred embodiment, the screen overflow is directed into the container, cooling tank, buffer tank, or conveying line. Alternatively, the screen overflow can also be directed into a comminution device, e.g., another mixer. This allows the screen overflow to be recycled. Preferably, it is returned to the buffer tank, or, if a pneumatic conveying line is provided for extracting the electrode mixture from the container, returned to this conveying line. Alternatively, the screen overflow can also be transferred to a feed tank or separator, which transfers the material as part of the electrode mixture into the container or cooling tank, so that it is brought to a temperature T together with fresh raw materials during the production of the electrode mixture. His heated to > 45°C and a homogeneous electrode mixture of new and recycled raw materials is produced, or is homogeneously incorporated into the electrode mixture in the cooling mixer during cooling by the mixing tool and cooled and crushed together with the electrode mixture.

[0048] In a further preferred embodiment, a friction screen or an eddy current screen is used, preferably in such a way that no screen overflow remains. By using a friction screen or an eddy current screen, a considerable force is exerted on the material, for example by a rotor, so that larger agglomerates are broken up and the screen overflow is significantly reduced. The forces are particularly preferably adjusted so that no screen overflow remains that would need to be recycled. Recycling can then be omitted.

[0049] Finally, a dry electrode can be produced from the electrode mixture prepared according to the invention. For this purpose, the electrode mixture is fed, for example, to a calender and calendered into a web, whereby any protruding edge strips of the web are then removed, for example, by cutting them off, to ensure a uniform web width. The removed edge strips are fed into the container, the buffer container, or the conveying line. If powder application processes are used to coat the electrode film before calendering, the excess powder can be returned to the process in the same form. The same applies to dusts that are stirred up and extracted during the handling of the electrode mixtures at the application points of the coating unit.

[0050] The calendering process plays a crucial role in shaping and compacting the electrodes to achieve the desired electrochemical properties.

[0051] During calendering, the electrode mixture is rolled or compacted into a film by a pair or series of rollers and then pressed onto a current collector (usually copper for the anode or aluminum for the cathode) at the end or even during this process. This forms the mixture into a uniform, dense layer with a defined thickness and structure. This process directly influences the porosity, thickness, and adhesion of the electrode mixture to the collector. Depending on the cell type being manufactured, the sandwich structure (electrode mixture and current collector) can then be either wound or stacked. In winding, anode and cathode strips are wound together with a separator into a spiral structure (typical for cylindrical or prismatic cells). In stacking, the electrodes and separators are placed on top of each other in layers (typical for pouch cells).

[0052] By returning the edge strips or excess material, material can be recycled, thereby reducing production costs. If the excess material is not in bulk but in the form of a compressed film, a further preferred embodiment provides a shredding device that divides the separated edge strips into smaller strip sections. The separated strip sections, usually in the form of an endless belt of varying width, could be continuously fed into the shredding device by means of a conveyor belt or a suction stream to make them available for reuse in the production process.

[0053] A batch mixer, for example, is suitable as a comminution device, in which both the screen overflow, if any, and the strip sections are collected or fed in batches. By briefly chopping the mixture, a conveyable, fine-grained product, such as an agglomerate or powder, can be produced, which has the same properties as the electrode mixture produced in the container.

[0054] This material can then preferably be pneumatically removed from the batch mixer and transferred to the buffer tank along with the fresh raw material. If sufficient height is available, as an alternative to pneumatic removal from the shredding mixer, the shredding mixer could be positioned above the buffer tank for pneumatic removal of the mixture from the main mixers and discharged directly into them by gravity via a bottom discharge device. Alternatively, the batch mixer could also be positioned above the cooling mixer and discharge the shredded edge strips or excess material into the cooling mixer, where they are, for example, mixed into a subsequent batch of fresh material during the cooling process.

[0055] Since both screen overflow and edge sections accumulate continuously, a preferred embodiment provides for the use of a continuous comminution device, e.g., a continuously operated mixer or mill, such as a pin mill or impact mill. The comminutioned end product can either fall directly into the buffer container at the discharge or be pneumatically lifted into the buffer container.

[0056] Alternatively, the edge strips can also be fed into the grating sieve.

[0057] Further advantages, features, and applications of the present invention will become clear with reference to the following description of preferred embodiments and the accompanying figures. These show:

[0058] Figure 1 shows an arrangement for carrying out a first embodiment of a conditioning procedure, Figure 2 shows an arrangement for carrying out a second embodiment of a conditioning procedure and

[0059] Figure 3 shows an arrangement for carrying out a first embodiment of the method according to the invention.

[0060] Figure 1 shows a schematic view of an arrangement for carrying out a first embodiment of a conditioning procedure.

[0061] In a container 1, the dry electrode mixture is produced preferably without the addition of solvents, such as low- or high-boiling solvents or water. However, it is also possible to add a small amount of low-boiling solvents to activate the binders superficially. The proportion of volatile, i.e., low-boiling, solvents in the mixture is less than 5%. In this embodiment, the container 1 is rotatable about the container axis 4, but can also be stationary. A mixing tool 2 is arranged inside the container 1 and is rotatable about the mixing tool axis. The container wall and bottom are double-walled, allowing a cooling or heating medium to be supplied between the two walls to heat or cool the container and thus the mixture contained within it.However, it is also possible that only the container wall or only the container bottom is double-walled and through which a cooling or heating medium flows. The mixing tool itself could also be double-walled and through which a heating or cooling medium flows.

[0062] A suction lance 3 is also provided, which is connected to a first pneumatic conveying line 11, through which the electrode mixture produced in the container 1 can be extracted by pneumatic conveying. A particle size sensor 8 is arranged in the first pneumatic conveying line, which provides feedback on the particle size within the first pneumatic conveying line. This information can be used to adjust the mixing process in the container 1, for example, by changing the rotational speed or mixing time.

[0063] The electrode mixture is produced in container 1, which necessitates heating the mixture to a temperature greater than 45 °C. To facilitate the removal of the electrode mixture, a cooling medium is introduced between the walls of the double wall of container 1. This cools the mixture by at least 5 °C, and in this example, to a temperature of less than 35 °C. The mixture is then transferred into a conveyable bulk material by moving the mixing tool 2. For example, cooling to 30 °C can be achieved. The still warm but now conveyable electrode mixture is then transferred via the suction lance 3 into the first pneumatic conveying line and introduced into a buffer container 7. In this embodiment, the buffer container 7 has at least a section of a double jacket, which allows the introduction of a cooling medium between the two walls of the double jacket.The electrode mixture is therefore cooled in the buffer tank by at least 4 °C and preferably to a temperature below 19 °C. A vacuum pump 19 is provided above the buffer tank 7 to assist the pneumatic conveying. A gas-solid separator 38 is located in the upper part of the buffer tank.

[0064] To assist with cooling and / or material discharge, the illustrated embodiment includes a gas aeration unit 36, through which gas can be blown into the electrode mixture contained in the buffer tank 7. A friction screen 12 with a rotor is arranged at the outlet of the buffer tank 7, and this screen is fed with the electrode mixture by means of a screw conveyor.

[0065] The friction screen is configured such that any oversize material present is broken up by mechanical force, preventing screen overflow. The material passing through the screen is then fed via a transfer unit 22 into a feed device 21. Load cells 23 determine the weight of the fed or discharged electrode mixture and control it accordingly. Additionally, the buffer hopper 7 can be equipped with load cells or other sensors for level control and metered material discharge. The discharge from the feed device 21 is directed onto a multi-roll calender 13, which forms the electrode mixture into a uniform web 14. Uneven strip sections at the edges of the web 14 are cut off by the cutting device 24, so that the strip sections 15 fall into a receiving device 16.The receiving device 16 is connected via a second pneumatic conveying line 10 to a separator 37, which is located above the mixer 1. To ensure pneumatic conveying, a conveying gas connection 25 is provided on the receiving device 16, and a vacuum pump or a correspondingly powerful blower is located above the separator 37. A Venturi nozzle 9 is provided in the second pneumatic conveying line 10. In the Venturi nozzle 9, an accelerated gas flow occurs due to a cross-sectional narrowing followed by a cross-sectional widening. This exerts high tensile forces on the strip sections 15, which are supplied as an endless belt, tearing this endless belt into smaller sections, ideally only a few centimeters in size. The Venturi nozzle 9 thus serves as a comminution device. The comminutioned edge strips 15 fall into the separator 37 and can be transferred to the container 1 via the metering device 6.The pieces of edge strips 15, temporarily stored in the separator 37, are preferably introduced into the mixer at the beginning of or during the fibrillation phase. This ensures that the edge strip sections are homogeneously incorporated into the electrode mixture. Particularly when the edge sections are added right at the beginning of the fibrillation phase, they act as inoculating nuclei, accelerating the fibrillation of the PTFE in the electrode mixture. For level monitoring and dosing control, the separator 37 can be equipped with load cells or level sensors. Additionally, a weighed buffer tank can be interposed between the dosing unit 6 and the mixing vessel 1 to allow for the weighing of a defined quantity of material for feeding into the mixing vessel.

[0066] Figure 2 shows a schematic representation of an arrangement with which a second embodiment of a conditioning process can be carried out. Where possible, the same reference numerals as in Figure 1 have been used to denote identical or nearly identical elements. Therefore, in the following, Figure 2 essentially only illustrates the difference from the setup in Figure 1. In Figure 2, a liquid gas supply 18 is arranged above the container 1. At the end of the mixing process for producing the electrode mixture at temperatures above 45 °C, the liquid gas 18, which is then introduced into the interior of the container 1, causes an abrupt cooling of the electrode mixture by a temperature difference of AT = 5 °C, preferably to a temperature below 35 °C, which facilitates the removal of the electrode mixture from the container 1. As soon as the liquid gas comes into contact with the warm mixture, it evaporates.The resulting cold gas is then also transferred via the suction lance 3 into the first pneumatic conveying line 11 and assists the pneumatic conveying. Due to the low temperature of the gas produced by evaporation, the electrode mixture is further cooled in the first pneumatic conveying line 11 by direct heat exchange between the mixture and the conveying gas. To support the cooling process, the conveying line 11 can be provided with a double jacket through which a cooling medium flows and / or with insulation. Further cooling can take place in the buffer tank 7 in the manner already described, if this has not already occurred in the first pneumatic conveying line 11. The conditioning, sieving, and metering of the electrode mixture are carried out in the device shown in Figure 2 in the same way as shown in Figure 1 and described in this context.

[0067] In contrast to Figure 1, the second pneumatic conveying line 10 is not connected to a separator located above the container 1, but is returned to the buffer container 7 via a Venturi nozzle, which serves to shred the edge strips 15. Alternatively or additionally, a shredding device 17, which here consists of a blade rotor, further shreds the sections of the edge strip 15 before the shredded edge strips 15 are returned to the buffer container 7. The essential difference between the embodiments shown in Figure 1 and Figure 2 is therefore that, firstly, cooling in the container 1 is achieved by supplying liquid gas 18, and secondly, the return of the resulting edge strips 15 does not take place in the container 1, but in the buffer container 7.It is understood that in other equally preferred embodiments, only one of the two described modifications compared to the embodiment of Figure 1 could be implemented. Cooling in the container 1 can also be achieved by a combination of wall cooling via the double jacket and evaporative cooling using liquid gas. If only a liquid gas is used as the cooling medium, the double jacket in the mixer 1 can be omitted.

[0068] Figure 3 shows an arrangement with which a first embodiment of the method according to the invention can be implemented. The mixing vessel 1 is again visible, but here it serves only as a supply point 34 for the heating medium, for supplying the heating medium into the double wall of the vessel 1. The medium supply and discharge 34 is effected by means of immersion tubes at different heights in an open channel on the outer wall of the rotating mixing vessel. The heating medium is circulated by means of a pump via a heat exchanger. In principle, the mixing vessel can also be designed without a double wall and without additional heating by means of heat transfer by radiation, induction, or hot gas flow, since the heat supply to the mixture can also occur exclusively via the frictional heat generated by the mixing tool during the mixing process. The electrode mixture is discharged here via a bottom drain 26 and a transfer.

[0069] 27 is transferred into a cooling mixer 28 arranged in a cascade below the container 1. The cooling mixer 28 has a coolant inlet and outlet 29, e.g. in the form of a rotary feedthrough, through which a cooling medium flows into the double wall of the cooling mixer container.

[0070] The still-warm electrode mixture can be supplied to and discharged from the cooling mixer 28. The mixture is first transferred to the cooling mixer 28, which serves as the cooling device, and then from the cooling mixer via the suction lance 3 into the first pneumatic conveying line 11 in the buffer tank 7. In addition to, or even as an alternative to, cooling via a double jacket, the mixture in the cooling mixer 28 can also be cooled by adding liquid gas or dry ice. In this embodiment, the buffer tank 7 has an agitator 35, which, via an agitator drive 30, can provide further movement and thus accelerated cooling of the electrode mixture in combination with the double-jacket cooling 20. A friction screen 12 is located at the outlet of the buffer tank 7.In this embodiment with a flat screen, however, less force is exerted on the particles, resulting in screen overflow, which is transferred to a discontinuous mixer that acts as a comminution device. Here, too, at the end of the calender, the edge strips 15 are separated from the uniform sheet by means of a cutting device 24. The edge strips 15 are also transferred via a conveyor belt 33 to the discontinuous mixer, which has an agitator equipped with knives that chops both the oversize material and the edge strips 15 into small particles. These are then transferred via a suction lance into the second pneumatic conveying line 10, where a Venturi nozzle 9 can be used to assist with further comminution.

[0071] In the arrangement shown in Figure 3, a particle size measuring device 8 is arranged in both the first and the second pneumatic conveying lines 10, 11. Particle size measurement can be performed, for example, using an optical measuring method and serves to detect deviations from a reference size distribution of the electrode mixture or of the bulk material returned via the second pneumatic conveying line 10. Using this information, a control loop can be implemented that adjusts the size distribution of the electrode mixture directly in the container 1 by adapting the tool speed, the mixture temperature, or the comminution time. Alternatively, or in combination, the temperature in the buffer container or the operating parameters of the friction screen 12 can also be adjusted. For temperature monitoring of the electrode mixture in the buffer container, the container is equipped with contact or non-contact temperature sensors.

[0072] To regulate the delivery gas temperature or delivery gas quantity, additional air 39 can be introduced into the delivery line 10. This air can be conditioned in terms of temperature and humidity via heat exchangers and / or absorbers.

[0073] The methods shown in Figures 1 and 2 and described here can also be used according to the invention if a corresponding cooling mixer is arranged below the mixer 1, as shown in Figure 3.

[0074] In the method shown in Figure 1, the suction lance 3 would then be positioned in the cooling container as shown in Figure 3. Otherwise, the method from Figure 1 can remain unchanged.

[0075] In the process shown in Figure 2, the suction lance 3 would also be positioned in the cooling vessel, as shown in Figure 3. Furthermore, the liquefied gas 18 would be fed into the cooling vessel instead of the mixing vessel. Otherwise, the process of Figure 1 can remain unchanged. The process according to the invention significantly simplifies the production of electrode mixtures and the production of dry electrodes from these mixtures by reducing the cycle time and significantly improving the quality. In addition, the amount of scrap is significantly reduced through the recycling of excess material.

[0076] Reference symbol list

[0077] 1 mixer with container

[0078] 2 Mixing tool

[0079] 3 suction lances

[0080] 4 Container rotation axis

[0081] 5 Mixing tool rotary axis

[0082] 6 Dosing unit

[0083] 7 buffer tanks

[0084] 8 Particle size measuring device

[0085] 9 Venturi nozzle

[0086] 10 second pneumatic conveying line

[0087] 11 first pneumatic conveying line

[0088] 12 grater

[0089] 13 multi-roll calenders

[0090] 14 lane

[0091] 15 edge strips

[0092] 16 Receiving device for pneumatic conveying

[0093] 17. Shredding device

[0094] 18 Liquefied petroleum gas

[0095] 19 Vacuum pump

[0096] 20 double jacket

[0097] 21 Feed device

[0098] 22 Transition

[0099] 23 load cells

[0100] 24 cutting device

[0101] 25 Propellant gas

[0102] 26. Bottom emptying

[0103] 27 Transition

[0104] 28 cooling mixers

[0105] 29 Coolant supply and discharge

[0106] 30 agitator drive

[0107] 31 Sieve overflow for oversize

[0108] 32 Discontinuous Mixer

[0109] 33 Conveyor belt

[0110] 34 Heating medium supply and discharge

[0111] 35 Buffer storage agitator

[0112] 36 Gas loosening

[0113] 37 separators

[0114] 38 Gas-solid separators

[0115] 39 Additional air

Claims

Patent claims 1. Method for the preparation and conditioning of an electrode mixture consisting of active material and binder, and optionally additives, comprising the steps 1) Producing the electrode mixture in a mixing vessel of a mixer, wherein during the production the mixture is heated to a temperature TH, where TH > 45°C, 2) Transferring the electrode mixture into a cooling mixer with a cooling vessel, the walls of which are preferably cooled, 3) Cooling the electrode mixture in the cooling container by at least AT= 5°C to a withdrawal temperature TE, which is preferably < 35° C. 4) Removal of the electrode mixture from the cooling container.

2. Method according to claim 1, characterized in that in step 3) the electrode mixture is cooled by at least 9°C and preferably to a withdrawal temperature TE < 19°C, preferably by introducing dry ice or liquid gas into the cooling container.

3. Method according to claim 1, characterized in that in step 3) the cooling does not take place below a withdrawal temperature TE > 24°C and in step 4) the electrode mixture is supplied to a cooling device by means of which the electrode mixture is cooled by at least 4°C, preferably to a temperature TK < 19°C.

4. Method according to claim 3, characterized in that a conveying line of a pneumatic conveying system for removing the electrode mixture from the cooling container, which is operated with a gas, preferably with a temperature TG < 19°C, is provided as a cooling device, wherein preferably in step 3), between steps 3) and 4) and / or during step 4) dry ice or liquid gas is introduced into the cooling container, and the gas produced by sublimation or evaporation is directed into the conveying line.

5. Method according to claim 3 or 4, characterized in that the electrode mixture according to step 4) is transferred to a buffer container, wherein the buffer container is preferably temperature-controlled and used as a cooling device, wherein the buffer container is preferably double-walled, wherein a cooling fluid can flow between the two walls, and / or the buffer container has thermal insulation. exhibits, wherein the electrode mixture is particularly preferably moved in the buffer container.

6. Method according to one of claims 2 to 5, characterized in that the electrode mixture according to step 4) is applied to a sieve and only sieve passage is used as conditioned electrode mixture, wherein preferably the sieve has a mesh size of less than 10 mm and particularly preferably of less than 5 mm and best of less than 2 mm.

7. Method according to claim 6, characterized in that the sieve overflow is directed into the container, the cooling mixer, the buffer container, a comminution device or into the conveying line.

8. Method according to claim 6, characterized in that a friction sieve or, more preferably, an eddy current sieve is used as the sieve, wherein the use is preferably carried out in such a way that no sieve overflow remains.

9. A method for producing dry electrodes from electrode mixtures produced by a method according to one of the preceding claims, characterized in that the electrode mixture is fed to a calender and calendered into a web, wherein the edge strips of the web or excess material are then cut off to ensure a uniform width of the web, and the cut-off edge strips or excess material are fed into the container, the cooling mixer, the buffer container or into the conveying line.

10. Method according to claim 9, characterized in that a comminution device is provided which divides the separated edge strips into smaller strip sections.

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