DE102023112620A1 - Method for producing electrode mixtures, and device therefor - Google Patents

Abstract

und $0\%\le p_{bk}\le 100\%-{\displaystyle {\sum }_{i=1}^{k-1}{p}_{bi}}$

ist.

Process for the production of electrode mixtures from different substances, namely from active material with a mass fraction w ₁ , optionally additives with a mass fraction w ₂ and binder with a mass fraction w ₃ , where w ₁ and w ₃ are each > 0%, w ₂ ≥ 0% and w ₁ , w ₂ and w ₃ are each < 100 %, with the steps
1) filling the active material and a first percentage p _a1 of the additives and/or a first percentage p _b1 of the binders into a container, where 0% ≤ p _α1 ≤ 100% and 0% ≤ p _b1 ≤ 100%, but either 0% < p _α1 or 0% < p _b1 ,
A) introducing a first mechanical power P ₁ into the substances contained in the container, by means of shear forces or impact forces,
2) Introducing a second percentage p _a2 of the additives and/or a further percentage p _b2 of the binders into the container, where 0% ≤ p _α2 ≤ 100% - p _α1 and 0% ≤ P _b2 ≤ 100% - P _b1 ,
B) introducing a second mechanical power P ₂ into the substances contained in the container, by means of shear forces or impact forces, during a second time interval T ₂ to produce a second mixture, where P ₂ > P ₁ , and
W) repeating steps A) and B) as long as binders and, if applicable, additives have not yet been completely introduced, whereby between steps A) and B) step K) is carried out to fill a further percentage portion p _ak of the additives and/or a further percentage portion p _bk of the binders into the container, whereby k=3 for the first repetition and k is increased by 1 after each repetition, and $0\%\le p_{ak}\le 100\%-{\displaystyle {\sum }_{i=1}^{k-1}{p}_{ai}}$

and $0\%\le p_{bk}\le 100\%-{\displaystyle {\sum }_{i=1}^{k-1}{p}_{bi}}$

is.

Description

The present invention relates to a method for producing electrode mixtures, a device for carrying out the method, the use of a device for carrying out the method and an electrode mixture which has been produced according to the method.

In recent years, battery technology, and in particular lithium-ion technology, has come into focus, as it is essential for the functionality of, for example, fully electric vehicles, but also for stationary power storage. A long-lasting battery with a high capacity that can be produced inexpensively is a prerequisite for the acceptance of fully electric vehicles.

Currently, Li-ion batteries are mainly used.

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

When charging the lithium-ion cell, lithium ions migrate from the cathode through an electrolyte to the anode and are held there by particles of the active material. The process described is reversible, so that the lithium ion current flow flows from the anode to the cathode when the battery is discharged.

High demands are placed on the electrodes in order to produce a reliable lithium-ion battery with high capacity.

The electrode layer must have pores into which the electrolyte can penetrate in order to transport lithium ions to each particle of the active material. Ideally, the active material must be wetted by the electrolyte over as large an area as possible. In addition, the particles of the active material must be electrically connected to the metal foil, i.e. in the example described, to the copper or aluminum foil, in order to ensure the transport of electrons to and from each particle of the active material.

Furthermore, the particles of the active material must be bound to each other and to the metal foil, for which a binder material is used. Finally, the layer thickness should be as uniform as possible.

To produce the layers, the reactants, i.e. the active material, the binder and, if necessary, the additives, must be mixed together and dispersed to form a so-called "slurry". A liquid solvent (e.g. water or N-methyl-2-pyrrolidone (NMP)) is usually added here, which then has to be removed again in a complex drying process after the electrode mixture has been applied to the film.

This is time-consuming and energy-intensive. In addition, voluminous drying facilities must be provided in the mechanical production of the electrode mixtures.

Based on the described prior art, it is therefore the object of the present invention to provide a method for producing electrode mixtures which reduces the amount of solvent required or, in the best case, even does not require any solvent at all and yet still provides an easily processable electrode mixture of high quality.

Furthermore, it is an object of the present invention to provide a device for carrying out the method.

• 1) Einfüllen des aktiven Materials sowie eines ersten prozentualen Anteils p_a1 der Additive und/oder eines ersten prozentualen Anteils p_b1 der Binder in einen Behälter, wobei 0% ≤ p_α1 ≤ 100% und 0%≤ p_b1 ≤ 100%, jedoch entweder 0% < p_α1 oder 0% < p_b1 ist,
  1. A) Einbringen einer ersten mechanischen Leistung P₁ in die im Behälter aufgenommen Substanzen, mittels Scherkräften oder Aufprallkräften, wobei Scherkräfte bevorzugt sind,
• 2) Einfüllen eines zweiten prozentualen Anteils p_a2 der Additive und/oder eines weiteren prozentualen Anteils p_b2 der Binder in den Behälter, wobei 0% ≤ p_a2 ≤ 100% - p_α1 und 0% ≤ P_b2 ≤ 100% - p_b1
  • B) Einbringen einer zweiten mechanischen Leistung P₂ in die im Behälter aufgenommen Substanzen, mittels Scherkräften oder Aufprallkräften, wobei Scherkräfte bevorzugt sind, während eines Zeitintervalls T₂, wobei P₂> P₁, und W) Wiederholen der Schritte A) und B) solange Binder und gegebenenfalls Additive noch nicht vollständig eingebracht sind, wobei vor Schritt A) und/oder zwischen Schritt A) und B) der Schritt
  • K) Einfüllen eines weiteren prozentualen Anteils p_ak der Additive und/oder eines weiteren prozentualen Anteils p_bk der Binder in den Behälter erfolgt, wobei bei der ersten Wiederholung k=3 ist und k nach jeder Wiederholung um 1 erhöht wird, sowie $0\%\le p_{ak}\le 100\%-{\displaystyle {\sum }_{i=1}^{k-1}{p}_{ai}}$
    
    und $0\%\le p_{bk}\le 100\%-{\displaystyle {\sum }_{i=1}^{k-1}{p}_{bi}}$
    

With regard to the method, this object is achieved by a method for producing electrode mixtures from different substances, namely from active material with a mass fraction w ₁ , optionally additives with a mass fraction w ₂ and binder with a mass fraction w ₃ , where w ₁ and w ₃ are each > 0%, w ₂ ≥ 0% and w ₁ , w ₂ and w ₃ are each < 100%, with the steps

• 1) filling the active material and a first percentage p _a1 of the additives and/or a first percentage p _b1 of the binders into a container, where 0% ≤ p _α1 ≤ 100% and 0% ≤ p _b1 ≤ 100%, but either 0% < p _α1 or 0% < p _b1 ,
  1. A) introducing a first mechanical power P ₁ into the substances contained in the container, by means of shear forces or impact forces, whereby shear forces are preferred,
• 2) Adding a second percentage p _a2 of the additives and/or a further percentage p _b2 of the binders into the container, where 0% ≤ p _a2 ≤ 100% - p _α1 and 0% ≤ P _b2 ≤ 100% - p _b1
  • B) introducing a second mechanical power P ₂ into the substances contained in the container, by means of shear forces or impact forces, whereby shear forces are preferred, during a time interval T ₂ , whereby P ₂ > P ₁ , and W) repeating steps A) and B) as long as binders and optionally additives have not yet been completely introduced, whereby before step A) and/or between steps A) and B) the step
  • K) adding a further percentage p _ak of the additives and/or a further percentage p _bk of the binders into the container, whereby k=3 for the first repetition and k is increased by 1 after each repetition, and $0\%\le p_{ak}\le 100\%-{\displaystyle {\sum }_{i=1}^{k-1}{p}_{ai}}$
    
    and $0\%\le p_{bk}\le 100\%-{\displaystyle {\sum }_{i=1}^{k-1}{p}_{bi}}$
    

If an electrode mixture is produced for a cathode, the active material used can be, for example, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate or other lithium or sodium metal oxides.

If an electrode mixture is produced for an anode, graphite, carbon such as activated carbon or graphene, or silicon-carbon composites can be used as the active material. The mass fraction w ₁ can be up to 99.9%, with w ₁ preferably being between 90 and 99.9%.

The additives used are usually conductive additives, such as conductive carbon black, which are particularly necessary when producing an electrode mixture for a cathode, since the active material is often only poorly electrically conductive. In addition to the conductive additives, for example, silicon or silicon compounds, solid electrolytes, nanoparticulate aerosils as well as oxalic acids, graphene, carbon nanotubes (CNT), styrene-butadiene rubber (SBR) or conductive graphite are used for electrode mixtures for anodes and cathodes, whereby the mass fraction w ₂ is preferably ≥ 0 and < 10%. In particular with silicon or silicon compounds or solid electrolytes, the mass fractions can also be significantly higher than 10%.

The mass fraction w ₃ of the binder is also between 0.1 and 10% in a preferred embodiment. Polymeric binders, such as fluorine-containing polymer binders such as PVDF and PTFE, are used as binders in particular. Alternatively, carboxymethylcelluloses (CMC) could also be used as a binder. Many polymer binders, and in particular PTFE, show the effect of fibrillation at a certain temperature and when energy, in particular shear energy, is introduced, which improves the processability of the electrode mixture.

Step A) can be performed simultaneously with step 1) or after step 1).

In step A), the components added to the container in step 1) are mixed dry, i.e. no solvent such as water is added. This produces a largely homogeneous mixture. This forms a particle composite structure, i.e. the particles of the active material are surrounded by the binder and/or the (conductive) additives.

After step A), step 2) is carried out, in which further amounts of additives and/or further amounts of binders are added. It is not necessary for any further amounts to be added in step 2). For example, if all amounts intended for step B) have already been added in step 1), no further amounts need to be added in step 2). The amounts p _a2 and p _b2 can therefore both be 0%. In other words, step 2) can be omitted.

In step B), which can be carried out either after step 2) or during step 2), a second mechanical power P ₂ is introduced into the mixture by means of shear forces, although impact forces could also be used instead, which is higher than the first mechanical power.

The mechanical powers in both steps A) and B) can be introduced, for example, using appropriately designed mixing tools in a mixing container. In step B), the speed is increased compared to the speed in step A). The mechanical powers P ₁ and P ₂ do not have to be constant, but can change during the respective step. For example, the speed of the mixing tool used can be kept constant during the individual steps. However, since the density and flowability of the mixture changes during the individual steps, the power introduced also changes. It is important, however, that the mechanical power introduced in step B) is greater than in step A).

Alternatively, the mechanical power could also be introduced in a continuous extruder. Different mechanical powers during successive time intervals can then be realized by different length zones along the mixing axis of the extruder and by different geometries of mixing elements in the respective zones.

A PTFE binder, for example, is initially present as an agglomerate, which consists of individual, ball-of-wool-shaped particles made of pearl-string-shaped polymer fibers. In step B), a thread-like/fiber-like structure is formed due to the adhesion of the polymer binder components to the surfaces of the active material, which forms a network, usually a spider web-like network, into which the previously formed particle composite structures are integrated. In other words, the active material is coated with the binder and, if necessary, the additives.

Depending on the application, the time interval T ₂ of step B) can be between 1 and 90 minutes, with the duration preferably being between 10 and 30 minutes.

If all the desired components of the electrode mixture to be produced have already been added before step B) is carried out, the process according to the invention can end here. However, if all the binders and optionally additives have not yet been completely added, steps A) and B) are repeated, with further portions of the additives and/or binders being added before step A) and/or between steps A) and B) of the repetition. Thus, portions of binders and/or additives added later also go through steps A) and B).

In particular, when producing electrode mixtures for cathodes, a preferred embodiment provides that w ₂ > 0%, p _a1 > 0% and p _b1 = 0%. In other words, in step 1), only a portion of the additives or the entire amount of additives and no binders are added. Binders are only added in step 2) or in step K), if steps A) and B) are repeated.

In a further preferred embodiment, at least in the last execution of step B) and preferably in all executions of step B), the power P ₂ is dimensioned such that in step B) the temperature of the substances held in the container increases and step B) is terminated as soon as the temperature of the substances held in the container reaches the predetermined temperature T _H .

The preferred T _H value is T _H > 50°C, particularly 50 °C < T _H < 80°C and most preferably 50 °C < T _H < 70°C. The temperature T _H should not be significantly exceeded.

The polymer binder, especially a PTFE binder, usually only shows fibrillation at significantly higher temperatures. Surprisingly, however, this is achieved at lower temperatures by introducing mechanical energy.

If in a specific application it turns out that the time interval in which step B) is carried out is too short because the temperature T _H is reached very quickly, it can be extended by cooling the container.

• Schritt C) Einbringen einer dritten mechanischen Leistung P₃ in die im Behälter aufgenommen Substanzen mittels Scherkräften oder Aufprallkräften, wobei Scherkräfte bevorzugt sind, während eines Zeitintervalls T₃, wobei P₃ < P₂ ist.

In a further preferred embodiment, after the last execution of step B) it is provided:

• Step C) introducing a third mechanical power P ₃ into the substances contained in the container by means of shear forces or impact forces, with shear forces being preferred, during a time interval T ₃ , where P ₃ < P ₂ .

If shear forces are introduced into the mixture via a mixing tool, the speed of the mixing tool can be reduced in step C).

To form an optimally structured dry mix, the mechanical power applied can be reduced in step C), which surprisingly improves the quality of the mix. It has been found that to form the network-like structure, a high mechanical power P ₂ only needs to be applied at the beginning. As soon as the fibrillation of the binder begins, the entire formation of the structure can also be completed with less power input.

As a rule, it is advantageous if the time interval T ₃ is shorter than the time interval T ₂ .

In a preferred embodiment, the energy required in step B) for the temperature increase to the predetermined temperature T _H is introduced completely or at least 80% by mechanical energy, ie by the shear forces.

Additional external heating is not absolutely necessary.

As soon as the temperature T _H is reached or exceeded, the mechanical power introduced into the mixture is reduced so that no further significant temperature increase occurs.

Essentially, the temperature of the mixture is kept constant and the mixture is simply agitated. This completes the fibrillation and produces what is known as a structured dry mixture, which is well suited for making an electrode.

In a preferred embodiment, in step C), the power is dimensioned such that the temperature of the substances accommodated in the container is maintained in an interval between 0.8 x T _H and 1.1 x T _H and preferably in an interval between 0.9 x T _H and 1.05 x T _H.

• D) Abkühlung der im Behälter aufgenommen Substanzen auf eine Temperatur T_L< T_H, während eine vierte mechanischen Leistung P₄ in die im Behälter aufgenommen Substanzen mittels Scherkräften eingebracht wird, wobei P₄ < P₂ und vorzugsweise P₄ < P₃ ist.

In a further preferred embodiment, after the last execution of step B) and if present after step C), the step follows:

• D) cooling the substances contained in the container to a temperature T _L < T _H , while a fourth mechanical power P ₄ is introduced into the substances contained in the container by means of shear forces, where P ₄ < P ₂ and preferably P ₄ < P ₃ .

Thus, at the end of step C), the mixture is cooled, while at the same time the mixture continues to be moved to ensure good mixing. In principle, it would also be possible to cool a stationary, non-moving mixture so that P4 = 0. Intermittent movement and resting of the mixture during cooling is also possible. The temperature T _L is preferably < 45°, particularly preferably < 40 °C and best of all < 35 °C.

Moving the mixture during cooling significantly changes the structure, i.e. the ability of the electrode mixture to be transported and dosed.

The cooling is advantageously supported by cooling, for example, the walls of a mixing container in which the mixture is held. Alternatively and/or additionally, the cooling can also be carried out by means of a cold gas stream and/or with the aid of liquid gases such as nitrogen or CO ₂ , e.g. also in the form of dry ice.

• E) Zerkleinerung der im Behälter aufgenommen Substanzen in eine Vielzahl von Agglomeraten durch Einbringen einer fünften mechanischen Leistung P₅ mit P₅ >P₄, wobei die Agglomerate vorzugsweise eine durchschnittliche Korngröße zwischen 0,05 und 5 mm aufweisen.

In a further preferred embodiment, step D) is followed by the step:

• E) comminution of the substances contained in the container into a plurality of agglomerates by introducing a fifth mechanical power P ₅ with P ₅ >P ₄ , wherein the agglomerates preferably have an average grain size between 0.05 and 5 mm.

This measure ensures that the so-called structured mixture is fine-grained, free-flowing and can therefore be easily removed from a mixing container as well as fed into further processing for the purpose of producing the electrode.

The process according to the invention does not require any addition of solvents.

The quality of the mixture can be further improved if the process is carried out in a protective gas atmosphere. This is particularly advantageous in step B). However, it is best to carry out all steps of the process in a protective gas atmosphere. The protective gas atmosphere can be, for example, specially conditioned dry air or an inert gas.

In a preferred embodiment, an electrode is produced by either rolling out an electrode mixture produced according to the described method and laminating it onto a conductive foil or pressing it onto a conductive foil.

The device for carrying out the described method has a mixing container with a mixing container wall and a mixing container bottom, a mixing tool arranged in the mixing container and a wall scraper, wherein the mixing tool is rotatable about a tool axis w and the mixing container about a container axis b, wherein the tool axis w and the container axis b are spaced apart from one another.

The device can therefore be used for all process steps. Both the mixing provided for in step A) and the later introduction of mechanical energy by means of shear forces in steps B) and C) can take place in the mixing container. In a preferred embodiment, the device has a heating and/or cooling device for tempering a mixed material arranged in the mixing container. For example, the mixing container can be designed with double walls in such a way that a tempering fluid, i.e. a cooling or heating fluid, can be passed between the two walls of the double wall. In particular, the cooling device can significantly reduce the duration of step C) or limit the temperature of the mixed material and/or the temperature increase in step A) and/or step B), which is a great advantage.

It is also particularly preferred that at least one section of the mixing container bottom is designed with double walls in such a way that a cooling or heating fluid can be passed between the two walls of the double wall.

It has been shown that the quality of the mixture is improved if the mixing tool and the mixing container are rotated in the same direction around the tool axis w or the container axis b while the device is in operation. If you look inside the mixing container at the bottom of the container, both the mixing container and the mixing tool are rotated clockwise or anti-clockwise. Mixing processes are known for other applications in which the mixing tool and the mixing container are rotated in opposite directions around the tool axis w or the container axis b, i.e. one of the elements, the mixing tool and the mixing container, is rotated clockwise around its axis while the other element is rotated anti-clockwise. However, when producing electrode mixtures, the movement of the mixing tool and the mixing container in the same direction has proven to be effective.

In a preferred embodiment, the wall scraper is also designed as a floor scraper, so that the scraper also prevents the permanent adhesion of mixed material to the mixing container floor, at least in sections.

In a further preferred embodiment, it is provided that the wall scraper is in contact with the mixing container wall and preferably also with the mixing container bottom and/or that the mixing tool is in contact with the mixing container bottom. This prevents a thin film of the electrode mixture from forming on the wall or bottom. Since direct contact can result in increased wear on the container wall, the container bottom or the wall scraper and mixing tool, it is provided in a preferred embodiment that the wall scraper and/or the mixing tool is made of a plastic, particularly preferably PTFE or polyamide, at least on a section in contact with the mixing container wall or the mixing container bottom. The mixing tool and/or wall scraper can be made entirely of plastic or only the area in contact with the mixing container wall or the mixing container bottom can be made of plastic.

The mixing tool used in the device can also be optimized for producing the electrode mixture. In a preferred embodiment, it is therefore provided that the mixing tool has a tool shaft and at least one mixing part that protrudes in the radial direction beyond the tool shaft, preferably several mixing parts that are arranged at a distance from one another in the axial direction, or the mixing part consists of a shearing element arranged within an imaginary circular ring and a rolling element that protrudes in the axial direction beyond the shearing element. The mixing part particularly preferably has more than one, e.g. two, rolling elements that protrude in the axial direction beyond the shearing element.

The mixing part can have blade-like elements directed radially outwards. It is also possible to design the mixing part as a plate with external teeth.

Due to the high tool speeds and sometimes abrasive raw material components, wear can occur on the mixing part. Therefore, in a preferred embodiment, these are particularly protected against wear on the surfaces in contact with the mixture. This can be done on the mixer shafts or on the stationary wall/floor scraper, for example, via spray coatings with hard metal or ceramic or alternatively with polyurethanes and other plastic materials, since copper and zinc-free processing is particularly required for battery electrodes. The surface of the mixing parts can also be protected against wear by coating, by manufacturing them from a ceramic or a powder metallurgical material or by welding on wear protection elements. The rolling elements protruding axially from the shear element can, for example, consist of a ceramic material or a powder metallurgically manufactured material, e.g. hard metal, or have elements made from them that are glued or soldered onto a steel holding element.

In a further preferred embodiment, a pneumatic conveying device is provided with which the mixed material can be conveyed out of the mixing container. For example, the pneumatic conveying device can be designed as a suction lance that is or can be arranged inside the mixing container. It can also be integrated into the wall scraper, for example. The suction lance preferably ends on the mixing container floor at the radially innermost lower corner of the wall scraper or in the corner formed by the mixing container and wall scraper on the wall in the direction of flow of the mixed material.

In this case, the container bottom does not need to have an emptying opening. The measure in step E) in particular makes the structured dry mixture free-flowing, so that it can be easily sucked out using the conveying device.

Alternatively, it is also possible for the bottom of the mixing container to have a closable emptying opening and for a pneumatic conveying line to be arranged under the emptying opening in such a way that mixed material emerging from the mixing container via the emptying opening falls into the pneumatic conveying line. Alternatively, a mechanical discharge device such as a belt or a vibrating chute or simply a collecting container can be arranged under the emptying opening.

The pneumatic conveying device can be operated with protective gas, whereby the protective gas is preferably conveyed in a closed circuit. The protective gas provides, for example, dry air to prevent moisture from being introduced during the process. The air can be specially conditioned to achieve a very low dew point.

• 1 eine erste Ausführungsform eines erfindungsgemäßen Mischers,
• 2 eine zweite Ausführungsform eines erfindungsgemäßen Mischers und
• 3 ein Ablaufdiagramm des erfindungsgemäßen Verfahrens.

Further advantages, features and application possibilities will become clear from the following description of a preferred embodiment and the associated figures. They show:

• 1 a first embodiment of a mixer according to the invention,
• 2 a second embodiment of a mixer according to the invention and
• 3 a flow chart of the method according to the invention.

In 1 a first embodiment of a device according to the invention for carrying out the method is shown. The device has a container with a container wall 1 and a container bottom 2. The mixing container is rotatable about the container axis b.

A mixing tool is arranged in the mixing container, which can be rotated around the mixing tool axis w with the help of a motor 4 and a drive belt 5. The container wall is double-walled and provided with a separating plate which divides the cavity formed in the double wall into an inner section 6 and an outer section 7. A tempering fluid, e.g. a cooling fluid in the embodiment shown, can be introduced into the inner section 6 via the fluid feed 8, so that the cooling fluid flows in the direction of the arrow along the base and the wall and reaches the outer area 7 and is drawn off again there. The fluid feed 8 is designed here as a rotary feedthrough which both supplies and removes the fluid and transfers the fluid from the stationary part to the rotating part of the container.

Alternatively, the separating plate can be omitted. In this case, a return channel should be arranged on the outer wall of the double jacket in order to be able to drain the tempering fluid.

With the help of the tempering fluid, the container and thus also the mixture contained in the container can be heated or cooled. The mixing tool 3 has several mixing parts 9, 10. The mixing parts 10, which are arranged in the upper part of the mixing tool 3, consist of a large number of circular rings arranged parallel to one another, which can have recesses on their peripheral surface (not shown) in order to increase the shear forces to be introduced.

The discs marked with the reference number 10 can, as in the embodiment in 1 shown only in the upper part of the mixing tool 3. However, they can also be distributed over the entire length of the mixing tool 3. The lower mixing part 9 can then be omitted.

In the embodiment shown in 1 the lower mixing part 9 is also circular, with a series of recesses (not shown) in the peripheral surface of the mixing part 9. Upper rolling elements 11 and lower rolling elements 12 extend perpendicular to the lower mixing part 9. The lower rolling elements 12 are in contact with the container bottom 2 or are at least positioned very close to the container bottom. The distance to the container bottom should be less than 1 mm. The lower rolling elements 12 prevent part of the mixture from settling on the bottom. The upper rolling elements 11 ensure that the entire mixture moves in the mixer. The upper mixing parts 10 could also be omitted. In this case, it would be advantageous if the upper rolling elements 11 extended further upwards in order to reduce the space in which no mixing or rolling movement takes place.

Furthermore, a wall scraper 13 is provided which is in contact with the container wall 1 and with a circular area of the container bottom 2 in order to prevent adhesion of the electrode mixture to the container wall and the bottom areas not swept over by the lower rolling elements 12.

To remove the finished mixture, a suction lance 14 can be introduced into the mixing container or moved back and forth from a raised position in which the suction lance is not immersed in the mixture and a lower position in which the suction lance is immersed in the mixture.

In 1 the lower position is shown, while the upper position is only indicated by dashed lines.

The finished mixture can be sucked out via the suction lance 14. In this embodiment, the suction lance 14 is also double-walled, whereby conveying gas can be fed through the hollow space of the double wall via a feed 15. The mixed material is sucked out via the suction lance 14 and separated from the conveying gas in the separator or filter 16. The conveying gas can be completely fed back into the container via the feed 15 and can be designed as a protective gas, e.g. as dry air, in order to prevent undesirable moistening of the mixed material. The mixed material separated from the conveying gas in the filter 16 can be discharged at the lower end of the filter via a flap or lock system (not shown).

In 2 A second embodiment of the device according to the invention is shown. Where possible, the same reference numbers have been used for similar elements as in the embodiment of 1 shown, used.

In the following, only the differences to the embodiment of 1 shown.

The mixing tool 3 here has significantly more of the circular mixing parts 10. The lower mixing part 9 has only rolling elements 12 directed downwards. The rolling element directed upwards 11 is missing. The mixing container has an opening in the container bottom 2, which can be opened by means of a spherical segment-like closure 17 to empty the container. The mixed material falling out of the emptying opening falls into the collecting trough 18 of a conveyor device, which is pneumatically operated in the embodiment shown. The mixed material is transported by the conveying fluid along the line 19 into the separator 16. The conveying fluid is then fed back into the mixing container via the line 20 and back into the trough 18 via the line 21. The system can be essentially hermetically sealed so that a protective gas atmosphere can be maintained.

Since the container base 2 now has a drain opening, the cooling and heating device is constructed somewhat differently. Tempering fluid is supplied via the supply and discharge 8 of the cooling device via a line 22 that extends into the double wall of the container base 2 and is sucked out again via a line 23 that extends just below the fill level of the tempering fluid. The tempering fluid is circulated by means of a pump and the heat released from the double jacket is discharged to an external, second cooling circuit via a heat exchanger. By conveying the tempering fluid in the circuit, the fill level in the double jacket is automatically kept constant.

Alternatively, only the side wall of the mixing container can be provided with a double jacket so that the feed line 22 ends near the bottom of the container.

In a particularly preferred embodiment of the method according to the invention, the 3 outlined procedure is used.

In step 1), an additive, e.g. a conductive additive, which is to be used to produce the electrode mixture, is divided into several parts, e.g. two parts. The first part is then mixed with the active material in step A). The aim of this step is for the active material to be coated with the additive part.

Only then is another portion (in the example the remaining portion) of the additives added in step 2) and the active materials and the additives are mixed together in step B). This measure enables a better coating of the active materials with the additives.

If, instead, the entire amount of additives is added at the same time, much more care must be taken in the mixing step, as the additives themselves can tend to form agglomerates and separate from the active materials. If a rotating mixing tool is used, the peripheral speed of the mixing tool in step B) should be 10 to 80 m/s, preferably between 20 and 50 m/s and most preferably between 25 and 35 m/s. In step A), a lower peripheral speed can be selected.

In step W, it is checked whether all the desired components have already been fully added. If so, the process continues with step C. If not, and in the example described no binder has been added yet, steps K), A), K), B) are repeated until all the desired components have been fully added.

In the preferred embodiment, all binder components are added with steps K), A), K), B).

In the second step A) (after step K)), the reactants of the electrode mixture are mixed together. After a further step K), a further step B) follows in which a second mechanical power P ₂ is introduced into the substances held in the container by means of shear forces.

In particular, step B) but also all other steps can be carried out, for example, using sharp-edged, rapidly rotating mixing tools or in appropriately designed mixers with such mixing tools. During this step, heating occurs due to the mechanical power P ₂ introduced, which can optionally be increased by corresponding thermal energy from the outside or reduced by heat dissipation to the outside. The temperature reached in the mixture remains below 70 °C according to the invention, since this is surprisingly sufficient to ensure that the polymers of the plastic binder adhere to the particle surface and are drawn into thread-like structures, so that a network structure is formed in which the previously formed particle composite structure is integrated. At 70 °C, the temperature is surprisingly well below the temperature required for fibrillation. of PTFE, temperatures of 80 - 120°C are considered optimal. However, this temperature has proven to be completely sufficient for optimum adhesion of the polymers to the particle surfaces. Due to the intensive and targeted fibrillation and the associated formation of a network structure, masses ranging from lumpy to plastic, dough-like masses are created in the mixer, which evade simple emptying, subsequent material transport and ultimately precise and uniform dosing onto the metallic foil.

In order not to destroy and thus shorten the fibrils or polymer fibers formed and to promote adhesion to particle surfaces or linking and stretching to form ever finer and thinner fibers, the mechanical power P ₃ is finally reduced in step C) compared to the mechanical power P _2. A further increase in temperature and comminution of the fiber length formed is thus avoided. Cooling should also be avoided as far as possible in order to allow the mass to mature at an almost constant temperature level. The fibrillated mass plasticizes more and more and, depending on the binder content, forms a dough-like, easily moldable mass.

If step B) has already produced a sufficiently malleable plastic mass that cannot or can hardly be further improved by the maturation in step C), step C) can be reduced to a few seconds or skipped altogether.

In order to therefore transfer these lumpy to plastic masses into a form so that they can be easily removed from the mixer and transported between the mixer and the downstream processing process without any problems, ideally over distances of several meters, and above all, can be easily dosed, step D) follows, in which the mixture is cooled to a temperature T _L of, for example, 45 °C, while a fourth mechanical power P ₄ is introduced into the material, which is also lower than the second mechanical power P _2. The fourth mechanical power P ₄ can also be selected to be lower than the third mechanical power P _3. If a mixing tool is used, the peripheral speed can be reduced to, for example, 5 m/s or less.

During cooling, the plastic mass "solidifies" and is broken down into a lumpy to crumbly structure with a very broad particle size distribution by the movement of the mixing tool and the rotating mixing container. The lower the temperature of the mixture, the more crumbly the mixture becomes. At this point, the mixture is easy to transport but is still difficult to dose due to the broad particle size distribution, especially if dosing is to be carried out uniformly over a wider dosing cross-section.

In order to further improve the dosing capability, the mixture is crushed in a further step E) after cooling has taken place, which can be achieved, for example, by the mixing tool used, which is operated at a significantly increased second mixing speed, thereby introducing a fifth mechanical power P _5. If a mixing tool is used, the peripheral speed of the mixing tool can be increased, for example, to 5 to 20 m/s.

This produces agglomerates that have an average grain size of between 0.05 and 5 mm and can therefore be gravimetrically dosed very well over wide dosing cross-sections. This produces the corresponding electrode mixture. This can be rolled out in step F) and laminated onto a conductive foil to produce an electrode.

Preferred embodiments are given below: No. 1 2 3 4 5 6 7 Active material Lithium-nickel-manganese-cobalt oxides (NCM) NCM NCM graphite graphite NCM graphite additive soot soot soot - silicon soot soot binder PTFE PVDF PVDF PTFE PTFE PTFE PTFE p _b1 = 0%? No No Yes Yes Yes Yes Yes Step C)? possible No No possible possible possible possible Step D)? Yes No No Yes Yes Yes Yes Step E)? possible No No possible possible possible possible

In embodiment 4, no additive is used. In embodiments 1 and 2, binder is added in step A). In all other embodiments, it is only added in step B) or in the last step B) or in the first step K). Steps C) to E) are omitted in the 2nd and 3rd embodiments. While step D) is carried out in the 1st embodiment and embodiments 4-7, this is optional for steps C and E.

It has been shown that at least the last step B) is carried out for a period of 3-30 minutes and preferably for a period of 3-10 minutes. The temperature at the end of step B) should be less than 70°C and preferably between 50°C and 70°C.

Step C) is preferably carried out for a period of between 1 and 10 minutes, during which the temperature of the absorbed substances is kept almost constant. If necessary, step C) can also be carried out for longer in order to achieve a noticeable improvement in the network structure.

During step D), cooling and coarse grinding take place at the same time. This step should take place for a period of between 3 and 90 minutes and particularly preferably between 3 and 30 minutes, with the temperature falling below 45 °C, preferably below 40 °C and most preferably below 35 °C.

Step E) should only be carried out for a short period of time between 5 and 60 seconds and preferably between 5 seconds and 30 seconds. During this time the temperature should not rise again or at least should only change slightly.

list of reference symbols

1

container wall 1

2

container bottom 2

3

mixing tool

4

Motor

5

drive belt

6

inner section in the double wall

7

outer section in the double wall

8

fluid supply and discharge

9, 10

mixing part

11, 12

rolling element

13

wall scraper

14

suction lance

15

feeding

16

separator

17

spherical segment-like closure

18

drip tray

19, 20, 21, 22, 23

Line

Claims (23)

Method for producing electrode mixtures from different substances, namely from active material with a mass fraction w ₁ , optionally additives with a mass fraction w ₂ and binders with a mass fraction w ₃ , where w ₁ and w ₃ are each > 0%, w ₂ ≥ 0% and w ₁ , w ₂ and w ₃ are each < 100%, with the steps 1) filling the active material and a first percentage proportion p _a1 of the additives and/or a first percentage proportion p _b1 of the binders into a container, where 0% ≤ p _α1 ≤ 100% and 0% ≤ p _b1 ≤ 100%, but either 0% < p _α1 or 0% < p _b1 , A) introducing a first mechanical power P ₁ into the substances contained in the container by means of shear forces or impact forces, with shear forces being preferred, 2) filling a second percentage p _a2 of the additives and/or a further percentage p _b2 of the binders into the container, where 0% ≤ p _a2 ≤ 100% - p _a1 and 0% ≤ p _b2 ≤ 100% - p _b1 B) introducing a second mechanical power P ₂ into the substances contained in the container, by means of shear forces or impact forces, shear forces being preferred, during a second time interval T ₂ in order to produce a second mixture, where P ₂ > P ₁ , and W) repeating steps A) and B) as long as binders and optionally additives have not yet been completely introduced, where between steps A) and B) the step K) filling a further percentage p _ak of the additives and/or a further percentage p _bk of the binders into the container takes place, where k=3 for the first repetition and k is increased by 1 after each repetition will, as well as $0\%\le p_{ak}\le 100\%-{\displaystyle {\sum }_{i=1}^{k-1}{p}_{ai}}$

and $0\%\le p_{bk}\le 100\%-{\displaystyle {\sum }_{i=1}^{k-1}{p}_{bi}}$

$$

is. procedure according to claim 1 , characterized in that w ₂ > 0%, p _a1 >0% and p _b1 = 0%. Method according to one of the preceding claims, characterized in that at least during the last implementation of step B) and preferably during all implementations of step B) care is taken that the temperature of the substances accommodated in the container does not exceed a predetermined temperature T _H , wherein preferably T _H > 40° C , particularly preferably 40° C < T _H < 80° C and most preferably 50° C < T _H < 70° C. Method according to one of the preceding claims, characterized in that at least during the last execution of step B) and preferably during all executions of step B), the power P ₂ is dimensioned such that in step B) the temperature of the substances received in the container increases and step B) is terminated as soon as the temperature of the substances received in the container reaches the predetermined temperature T _H . Method according to one of the preceding claims, characterized in that after the last execution of step B) follows: step C) introducing a third mechanical power P ₃ into the substances received in the container by means of shear forces or impact forces, shear forces being preferred, during a third time interval T 3 , where P ₃ < P ₂ . procedure according to claim 5 , characterized in that T ₃ < T ₂ . procedure according to claim 5 or 6 , characterized in that in step C) the power is dimensioned such that the temperature of the substances accommodated in the container is maintained in an interval between 0.8 x T _H and 1.1 x T _H and preferably in an interval between 0.9 x T _H and 1.05 x T _H. Method according to one of the preceding claims, characterized in that after the last implementation of step B) and if present after step C) follows: D) cooling the substances received in the container to a temperature T _L < T _H , while a fourth mechanical power P ₄ is introduced into the substances received in the container by means of shear forces or impact forces, shear forces being preferred, where P ₄ < P ₂ . procedure according to claim 8 , characterized in that after step D) follows: E) comminution of the substances received in the container into a plurality of agglomerates by introducing a fifth mechanical power P ₅ with P ₅ >P ₄ , wherein the agglomerates preferably have an average grain size between 0.05 and 5 mm. Method according to one of the preceding claims, characterized in that at least during the last execution of step B), this step B) and preferably all steps of the method are carried out in a protective gas atmosphere. Method according to one of the preceding claims, characterized in that a polymer binder, preferably PTFE or PVDF, is used as binder, with PTFE being particularly preferred. A method for producing an electrode, wherein an electrode mixture is produced by means of a method according to one of the preceding claims and the electrode mixture is either rolled out and laminated onto a conductive foil or pressed onto the conductive foil. Device for carrying out a method according to one of the Claims 1 until 11 , wherein the device comprises a mixing container with a mixing container wall and a mixing container bottom, a mixing tool arranged in the mixing container and a wall scraper, wherein the mixing tool is rotatable about a tool axis w and the mixing container about a container axis b, wherein the tool axis w and the container axis b are spaced apart from one another. device according to claim 13 , characterized in that a heating and/or cooling device is provided for cooling a mixed material arranged in the mixing container, wherein the mixing container is preferably designed with double walls in such a way that a cooling or heating fluid can be passed between the two walls of the double wall, wherein particularly preferably at least one section of the mixing container bottom is also designed with double walls in such a way that a cooling or heating fluid can be passed between the two walls of the double wall. device according to claim 13 or 14 , characterized in that during operation of the device the mixing tool and the mixing container are rotated in the same direction about the tool axis w or the container axis b. Device according to one of the Claims 13 until 15 , characterized in that the wall scraper is in contact with the mixing container wall and/or that the mixing tool is in contact with the mixing container bottom, wherein preferably the wall scraper and/or the mixing tool is made of a plastic, particularly preferably of PTFE or polyamide, at least on a section in contact with the mixing container wall or mixing container bottom. Device according to one of the Claims 13 until 16 , characterized in that the mixing tool has a tool shaft and at least one mixing part protruding in the radial direction beyond the tool shaft, wherein the mixing tool preferably has a plurality of mixing parts which are arranged spaced apart from one another in the axial direction and/or the mixing part consists of a shearing element arranged within an imaginary circular ring and a rolling element protruding in the radial direction beyond the shearing element. Device according to one of the Claims 13 until 16 , characterized in that a pneumatic conveying device is provided with which the mixed material can be conveyed out of the mixing container. device according to claim 18 , characterized in that the pneumatic conveying device is designed as a suction lance which is or can be arranged in the interior of the mixing container, wherein preferably the suction lance is integrated into the wall scraper. device according to claim 18 , characterized in that the mixing container bottom has a closable emptying opening and a pneumatic conveying line is arranged below the emptying opening in such a way that mixed material emerging from the mixing container via the emptying opening falls into the pneumatic conveying line. Device according to one of the Claims 19 until 20 , characterized in that the pneumatic conveying device is operated with protective gas, wherein the protective gas is preferably conveyed in a closed circuit. Use of a device according to one of the Claims 13 until 21 for carrying out a procedure according to one of the Claims 1 until 11 . Electrode mixture which is prepared by a process according to one of the Claims 1 until 11 is manufactured.

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