Method for producing electrode mixtures and device therefor

Abstract

The invention relates to a method for producing electrode mixtures from various substances, specifically from active material with a mass fraction wi, optionally additives with a mass fraction w2 and binders with a mass fraction w3, where w1 and w3 are each > 0%, w2 is ≥ 0% and w1, w2 and w3 are each < 100 %, said method having the following steps: 1) filling the active material and a first percentage fraction pai of the additives and / or a first percentage fraction pbi of the binders into a container, where 0% ≤ P a1 ≤ 100% and 0% ≤ P b1 ≤ 100%, however where either 0% < P a1 or 0% < P b1 , A) introducing a first mechanical power P1 into the substances received in the container, by means of shearing forces or impact forces, 2) filling a second percentage fraction P a2 of the additives and / or a further percentage fraction 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 P2 into the substances received in the container, by means of shearing forces or impact forces, during a second time interval T2 in order to create a second mixture, where P2 > P1. and W) repeating steps A) and B) as long as binders and optionally additives have not yet been fully introduced, wherein between step A) and B), step K) filling a further percentage fraction pak of the additives and / or a further percentage fraction pbk of the binders into the container is carried out, wherein in the first repetition k=3 and after each repetition k is increased by 1, and (I) and (II).

Description

[0001] Process for the production of electrode mixtures and device therefor

[0002] 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 produced by the method.

[0003] In recent years, battery technology, and in particular lithium-ion technology, has come into focus, as it is essential for the functionality of fully electric vehicles, for example, as well as for stationary power storage systems. A long-lasting, high-capacity battery that can be produced cost-effectively is a prerequisite for the acceptance of fully electric vehicles.

[0004] Currently, Li-ion batteries are mainly used.

[0005] 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 typically coated on both sides with active material and, at least for the production of a cathode, with additives.

[0006] During charging of a lithium-ion cell, lithium ions migrate from the cathode through an electrolyte to the anode, where they are held by particles of the active material. This process is reversible, so the lithium-ion current flows from the anode to the cathode when the battery is discharged.

[0007] High demands are placed on the electrodes in order to produce a reliable lithium-ion battery with high capacity.

[0008] The electrode layer must have pores into which the electrolyte can penetrate 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. Furthermore, the particles of the active material must be electrically connected to the metal foil—in the example described, the copper or aluminum foil—to ensure the transport of electrons to and from each particle of the active material.

[0009] Furthermore, the particles of the active material must be bonded both 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.

[0010] To produce the layers, the reactants—the active material, the binder, and any additives—must be mixed together and dispersed into a so-called "slurry." Typically, a liquid solvent (e.g., water or N-methyl-2-pyrrolidone (NMP)) is added, which then has to be removed again in a complex drying process after the electrode mixture has been applied to the foil.

[0011] This is time-consuming and energy-intensive. Furthermore, the mechanical production of electrode mixtures requires the provision of bulky drying equipment.

[0012] Based on the described prior art, it is therefore an object of the present invention to provide a process for producing electrode mixtures which reduces the amount of solvent required or, in the best case, even does without solvent altogether and yet still provides an easily processable electrode mixture of high quality.

[0013] Furthermore, it is an object of the present invention to provide a device for carrying out the method.

[0014] With regard to the method, this object is achieved by a method for producing electrode mixtures from various substances, namely from active material with a mass fraction wi, optionally additives with a mass fraction W2 and binder with a mass fraction W3, where wi and W3 are each > 0%, W2 ^ 0% and wi, W2 and W3 are each < 100%, with the steps

[0015] 1 ) Filling of the active material and a first percentage p ai of the additives and / or a first percentage p M the binder in a container, where 0% < p al < 100% and 0% < p bl < 100%, but either 0% < Pai or 0% < p bl is, A) introducing a first mechanical power Pi into the substances contained in the container, by means of shear forces or impact forces, with shear forces being preferred,

[0016] 2) Filling a second percentage portion p a 2 of the additives and / or a further percentage pb2 of the binders into the container, where 0% < p a2 < 100% - p al and 0% < p b2 < 100% - p bl

[0017] B) introducing a second mechanical power P2 into the substances contained in the container, by means of shear forces or impact forces, shear forces being preferred, during a time interval T2, where P2> Pi, and

[0018] W) Repeating steps A) and B) as long as the binder and, if applicable, additives have not yet been completely introduced, whereby before step A) and / or between steps A) and B) the step

[0019] K) Adding a further percentage share p a k of the additives and / or a further percentage pbk of the binder into the container, where k=3 for the first repetition and k is increased by 1 after each repetition, and 0% < p ak < 100% - Si=i Pai and 0% < p bk < 100% - l 'i PiH-

[0020] 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.

[0021] When producing an electrode mixture for an anode, the active material used can be graphite, carbon such as activated carbon or graphene, or silicon-carbon composites. The mass fraction w can be up to 99.9%, with w preferably being between 90 and 99.9%.

[0022] The additives used are usually conductive additives, such as conductive carbon black, which are particularly necessary in the production of an electrode mixture for a cathode, since the active material often has poor electrical conductivity. In addition to the conductive additives, materials used in electrode mixtures for anodes and cathodes include silicon or silicon compounds, solid electrolytes, nanoparticulate aerosils, oxalic acids, graphenes, carbon nanotubes (CNTs), styrene-butadiene rubber (SBR), or conductive graphites, with the mass fraction W2 preferably being 0 and < 10%. Especially with silicon or silicon compounds or solid electrolytes, the mass fractions can be significantly higher than 10%.

[0023] The mass fraction W3 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 particularly used as binders. Alternatively, carboxymethylcellulose (CMC) could also be used as a binder. Many polymer binders, and especially PTFE, exhibit fibrillation at a certain temperature and upon application of energy, particularly shear energy, which improves the processability of the electrode mixture.

[0024] Step A) can be performed simultaneously with step 1) or after step 1).

[0025] In step A), the components added to the container in step 1) are mixed dry, meaning no solvent, such as water, is added. This produces a largely homogeneous mixture. A particle composite structure forms, meaning the particles of the active material are surrounded by the binder and / or the (conductive) additives.

[0026] After step A), step 2) is carried out, in which further portions of the additives and / or further portions of the binder are added. It is not necessary for any further portions to be added in step 2). For example, if all the portions required for step B) have already been added in step 1), no further portions need to be added in step 2. The portions p a 2 and pb2 can therefore both be 0%. In other words, step 2) can be omitted.

[0027] In step B), which can be carried out either after step 2) or during step 2), a second mechanical power P2 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.

[0028] The mechanical power input in both steps A) and B) can be achieved, 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 Pi and P2 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 change during the individual steps, the power input also changes. It is important, however, that the mechanical power input in step B) is greater than in step A).

[0029] Alternatively, the mechanical power could also be applied in a continuous extruder. Different mechanical power levels during successive time intervals can then be achieved by varying the length of the zones along the extruder's mixing axis and by varying the geometries of the mixing elements in the respective zones.

[0030] A PTFE binder, for example, initially exists as an agglomerate consisting of individual, wool-ball-like particles of pearl-string-like polymer fibers. In step B), the adhesion of the polymeric binder components to the surfaces of the active material creates a thread-like / fiber-like structure, which then forms a network, usually a spider-web-like network, into which the previously formed particle composite structures are embedded. In other words, the active material is coated with the binder and, if applicable, the additives.

[0031] Depending on the application, the time interval T2 of step B) can be between 1 and 90 minutes, with the duration preferably being between 10 and 30 minutes.

[0032] If all desired components of the electrode mixture to be produced have already been added before step B), the process according to the invention can end here. However, if not all binders and, if applicable, additives have been completely added, steps A) and B) are repeated, with additional 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 binder and / or additives added later also pass through steps A) and B).

[0033] In particular, in the production of electrode mixtures for cathodes, a preferred embodiment provides that W2 > 0%, p ai>0% and pbi = 0%. In other words, in step 1) only a part of the additives or the complete amount of additives and no binder at all is added. Only in step 2) or in step K) if steps A) and B) are repeated, is binder added. In a further preferred embodiment, at least in the last implementation of step B) and preferably in all implementations of step B), the power P2 is dimensioned such that in step B) the temperature of the substances held in the container increases and step B) is ended as soon as the temperature of the substances held in the container reaches the predetermined temperature TH.

[0034] The preferred TH is TH > 50 °C, particularly 50 °C < TH < 80 °C, and ideally 50 °C < TH < 70 °C. The temperature Tn should not be significantly exceeded.

[0035] The polymeric binder, especially a PTFE binder, typically only exhibits fibrillation at significantly higher temperatures. Surprisingly, however, this can be achieved even at lower temperatures by applying mechanical energy.

[0036] 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 TH is reached very quickly, it can be extended by cooling the container.

[0037] In a further preferred embodiment, after the last execution of step

[0038] B) provided:

[0039] Step C) Introducing a third mechanical power P3 into the substances contained in the container by means of shear forces or impact forces, with shear forces being preferred, during a time interval T3, where P3 < P2.

[0040] If shear forces are introduced into the mixture via a mixing tool, in step

[0041] C) the speed of the mixing tool is reduced.

[0042] To form an optimally structured dry mix, the mechanical power applied in step C) can be reduced, which surprisingly improves the quality of the mix. It has been shown that high mechanical power P2 is only required at the beginning to form the network-like structure. Once the binder fibrillation begins, the entire formation of the structure can be completed with lower power input.

[0043] As a rule, it is advantageous if the time interval T3 is shorter than the time interval T2. In a preferred embodiment, the energy required in step B) for the temperature increase to the predetermined temperature TH is provided entirely or at least 80% by mechanical energy, i.e., by shear forces.

[0044] Additional external heating is not absolutely necessary.

[0045] As soon as the temperature TH is reached or exceeded, the mechanical power introduced into the mixture is reduced so that no further significant temperature increase occurs.

[0046] Essentially, the temperature of the mixture is kept constant and the mixture is simply agitated. This completes the fibrillation process and produces a so-called structured dry mix, which is well suited for electrode production.

[0047] In a preferred embodiment, in step C), the power is dimensioned such that the temperature of the substances contained in the container is maintained in an interval between 0.8 x TH and 1.1 x TH and preferably in an interval between 0.9 x TH and 1.05 x TH.

[0048] In a further preferred embodiment, after the last execution of step B) and if present after step C), the step follows:

[0049] D) Cooling of the substances contained in the container to a temperature TL < TH, while a fourth mechanical power P4 is introduced into the substances contained in the container by means of shear forces, where P4< P2 and preferably P4< P3.

[0050] Thus, at the end of step C), the mixture is cooled while simultaneously continuing to agitate to ensure thorough mixing. In principle, it would also be possible to cool a static, non-agitated mixture so that P4 = 0. Intermittent agitation and resting of the mixture during cooling is also possible. The temperature TL is preferably < 45°C, more preferably < 40°C, and most preferably < 35°C.

[0051] Moving the mixture during cooling significantly changes the structure, ie the ability of the electrode mixture to be transported and dosed.

[0052] Cooling is advantageously assisted by cooling, for example, the walls of a mixing vessel in which the mixture is held. Alternatively and / or additionally, cooling can also be carried out using a cold gas stream and / or with the aid of liquefied gases such as nitrogen or CO2, e.g., in the form of dry ice.

[0053] In a further preferred embodiment, step D) is followed by the step:

[0054] E) Comminution of the substances contained in the container into a plurality of agglomerates by introducing a fifth mechanical power P5 with P5 >P4, wherein the agglomerates preferably have an average grain size between 0.05 and 5 mm.

[0055] 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 creating the electrode.

[0056] The process according to the invention does not require any addition of solvents.

[0057] 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.

[0058] 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.

[0059] The device for carrying out the described method 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.

[0060] The device can therefore be used for all process steps. Both the mixing provided for in step A) and the subsequent 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 mixture arranged in the mixing container. For example, the mixing container can be designed with double walls such 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 mixture and / or the temperature rise in step A) and / or step B), which is a great advantage.

[0061] It is also particularly preferred that at least one section of the mixing container base is designed with a double wall such that a cooling or heating fluid can be passed between the two walls of the double wall.

[0062] It has been shown that the quality of the mixture improves if the mixing tool and mixing container are rotated in the same direction about 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 counterclockwise. Mixing processes are known for other applications in which the mixing tool and mixing container are rotated in opposite directions about the tool axis w or the container axis b, i.e. one of the elements, the mixing tool and mixing container, is rotated clockwise about its axis, while the other element is rotated counterclockwise. However, the same direction of movement of the mixing tool and mixing container has proven to be effective in the production of electrode mixtures.

[0063] 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 bottom of the mixing container, at least in sections.

[0064] 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 the 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 that is 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 section that is in contact with the mixing container wall or the mixing container bottom.The area in contact with the bottom of the mixing container must be made of plastic.

[0065] The mixing tool used in the device can also be optimized for producing the electrode mixture. In a preferred embodiment, the mixing tool has a tool shaft and at least one mixing part protruding radially beyond the tool shaft, preferably comprising a plurality of mixing parts arranged spaced apart from one another in the axial direction, or the mixing part consisting of a shearing element arranged within an imaginary circular ring and a rolling element protruding axially beyond the shearing element. Particularly preferably, the mixing part has more than one, e.g. two, rolling elements protruding axially beyond the shearing element.

[0066] The mixing part can have blade-like elements directed radially outward. It is also possible to design the mixing part as a plate with external teeth.

[0067] Due to the high tool speeds and sometimes abrasive raw material components, wear can occur on the mixing part. Therefore, in a preferred embodiment, the surfaces that come into contact with the mixture are specially protected against wear. This can be done on the mixer shafts or on the stationary wall / bottom scraper, for example, by 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 that protrude axially from the shearing element can, for example, be made from a ceramic material or a powder metallurgically produced material, e.g.consist of a hard metal or have elements made from it that are glued or soldered onto a steel holding element.

[0068] 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 at the bottom of the mixing container at the radially innermost lower corner of the wall scraper or at the corner formed by the mixing container and wall scraper on the wall in the direction of flow of the mixed material.

[0069] In this case, the container bottom does not need to have a discharge opening. The measure in step E) in particular makes the structured dry mix free-flowing, allowing it to be easily vacuumed off using the conveying device.

[0070] Alternatively, the mixing tank floor can have a closable discharge opening and a pneumatic conveying line arranged below the discharge opening so that the mix exiting the mixing tank through the discharge opening falls into the pneumatic conveying line. Alternatively, a mechanical discharge device such as a belt or vibrating chute, or simply a collecting container, can be arranged below the discharge opening.

[0071] The pneumatic conveying system can be operated with inert gas, preferably in a closed circuit. The inert gas can, for example, provide dry air to prevent moisture from being introduced during the process. The air can be specially conditioned to achieve a very low dew point.

[0072] Further advantages, features, and possible applications will become clear from the following description of a preferred embodiment and the accompanying figures. They show:

[0073] Figure 1 shows a first embodiment of a mixer according to the invention, Figure 2 shows a second embodiment of a mixer according to the invention and Figure 3 shows a flow diagram of the method according to the invention.

[0074] Figure 1 shows a first embodiment of an apparatus according to the invention for carrying out the method. The apparatus comprises a container with a container wall 1 and a container bottom 2. The mixing container is rotatable about the container axis b.

[0075] A mixing tool is arranged in the mixing container and can be rotated about the mixing tool axis w with the aid of a motor 4 and a drive belt 5. The container wall is double-walled and provided with a dividing 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 supply 8, so that the cooling fluid flows in the direction of the arrow along the bottom and the wall and reaches the outer region 7, where it is drawn off again. The fluid supply 8 is designed here as a rotary union which handles both the supply and removal of the fluid and transfers the fluid from the stationary part to the rotating part of the container.

[0076] Alternatively, the baffle plate can be omitted. In this case, a return channel should be arranged on the outer wall of the double jacket to allow the temperature control fluid to be removed.

[0077] With the help of the temperature control 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 plurality of circular rings arranged parallel to one another, which may have recesses on their circumferential surface (not shown) to increase the shear forces to be applied.

[0078] The discs designated with the reference number 10 can, as shown in the embodiment in Figure 1, be arranged 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.

[0079] In the embodiment shown in Figure 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 any 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.

[0080] 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 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 inserted into the mixing container or moved back and forth from a raised position, in which the suction lance is not immersed in the mixture, to a lower position, in which the suction lance is immersed in the mixture.

[0081] In Figure 1 the lower position is shown, while the upper position is only indicated by dashed lines.

[0082] The finished mixture can be sucked off via the suction lance 14. In this embodiment, the suction lance 14 is also double-walled, with conveying gas being fed through the hollow space of the double wall via an inlet 15. The mixed material is sucked off via the suction lance 14 and separated from the conveying gas in the separator or filter 16. The conveying gas can be reintroduced entirely into the container via the inlet 15 and can be designed as a protective gas, e.g., as dry air, to prevent undesired 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).

[0083] Figure 2 shows a second embodiment of the device according to the invention. Where possible, the same reference numerals have been used for similar elements as shown in the embodiment of Figure 1.

[0084] Therefore, only the differences to the embodiment of Figure 1 are shown below.

[0085] The mixing tool 3 here has significantly more of the circular mixing parts 10. The lower mixing part 9 only has rolling elements 12 directed downwards. The rolling element 11 directed upwards is missing. The mixing container has an opening in the container base 2 which can be opened by means of a spherical segment-like closure 17 to empty the container. The mixed material falling from the emptying opening falls into the collecting trough 18 of a conveying device which, in the embodiment shown, is pneumatically operated. The mixed material is transported by the conveying fluid along line 19 into the separator 16. The conveying fluid is then fed back into the mixing container via line 20 and then back into the trough 18 via 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 an emptying opening, the cooling orThe heating device is constructed somewhat differently. The cooling device's supply and discharge line 8 feeds the tempering fluid through a line 22 extending into the double wall of the vessel bottom 2, and it is then extracted again through a line 23 extending just below the fill level of the tempering fluid. The tempering fluid is circulated by a pump, and the heat dissipated from the double wall is dissipated to a second, external cooling circuit via a heat exchanger. By pumping the tempering fluid through the circuit, the fill level in the double wall is automatically maintained constant.

[0086] 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 container bottom.

[0087] In a particularly preferred embodiment of the method according to the invention, the sequence outlined in Figure 3 is used.

[0088] In step 1), an additive, e.g., a conductive additive, 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 goal of this step is to envelop or coat the active material with the additive portion.

[0089] Only then is another portion (in the example, the remaining portion) of the additives added in step 2), and the active materials and additives are mixed together in step B. This measure allows for a better coating of the active materials with the additives.

[0090] If, instead, the entire amount of additives is added simultaneously, significantly more care must be taken during 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 ideally between 25 and 35 m / s. A lower peripheral speed can be selected in step A).

[0091] In step W, a check is made to determine whether all desired components have been fully added. If so, the process continues with step C. If not, and in the example described, no binder has yet been added, steps K), A), K), B) are repeated until all desired components have been fully added. In the preferred embodiment, all binder components are added with steps K), A), K), B).

[0092] 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 force P2 is applied to the substances contained in the container by means of shear forces.

[0093] 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 introduced mechanical power P2, which can optionally be amplified by corresponding thermal energy from the outside or reduced by heat dissipation to the outside. According to the invention, the temperature reached in the mixture remains below 70°C, as 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, forming a network structure in which the previously formed particle composite structure is integrated. At 70°C, the temperature is surprisingly well below the temperatures of 80 - 120°C considered optimal for the fibrillation of PTFE.However, this temperature has proven to be entirely sufficient for optimal adhesion of the polymers to the particle surfaces. Due to the intensive and targeted fibrillation and the associated formation of a network structure, the masses formed in the mixer vary from lumpy to plastic, dough-like, which evade easy emptying, subsequent material transport, and ultimately precise and uniform dosing onto the metallic foil.

[0094] In order to prevent the fibrils or polymer fibers formed from being destroyed and thus shortened, and to promote adhesion to particle surfaces or interlinking and stretching to form increasingly finer and thinner fibers, the mechanical power P3 is finally reduced in step C) compared to the mechanical power P2. This prevents further temperature increases and comminution of the formed fiber length. Cooling should also be avoided as far as possible in order to allow the mass to mature at a nearly constant temperature level. The fibrillated mass plasticizes increasingly and, depending on the binder content, forms a dough-like, easily moldable mass. If step B) has already produced a sufficiently moldable, 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 entirely.

[0095] In order to transfer these lumpy to plastic masses into a shape so that they can be easily removed from the mixer and transported between the mixer and the downstream processing step without any problems, ideally over distances of several meters, and above all, so that they can be easily dosed, step D) follows, in which the mixture is cooled to a temperature TL of, for example, 45 °C, while a fourth mechanical power P4 is introduced into the material, which is also lower than the second mechanical power P2. The fourth mechanical power P4 can also be selected to be lower than the third mechanical power P3. If a mixing tool is used, the peripheral speed can be reduced to, for example, 5 m / s or less.

[0096] During cooling, the plastic mass "solidifies" and, due to the movement through the mixing tool and the rotating mixing vessel, is broken down into a lumpy to crumbly structure with a very broad particle size distribution. The lower the mix temperature, the more crumbly the mix becomes. At this point, the mix is ​​easy to transport but still difficult to meter due to the broad particle size distribution, especially if uniform metering is required across a wider metering cross-section.

[0097] To further improve dosing capability, the mixture is comminuted in a further step E) after cooling. This can be achieved, for example, by using the mixing tool, which operates at a significantly increased second mixing speed, thereby introducing a fifth mechanical power P5. If a mixing tool is used, the peripheral speed of the mixing tool can be increased, for example, to 5 to 20 m / s.

[0098] This produces agglomerates with an average grain size between 0.05 and 5 mm, making them ideal for gravimetric dosing over wide dosing cross-sections. This produces the corresponding electrode mixture. This mixture can be rolled out in step F) and laminated onto a conductive foil to produce an electrode. Preferred embodiments are given below:

[0099] In embodiment 4, no additive is used. In embodiments 1 and 2, binder is added in step A). ​​In all other embodiments, it is added only in step B), in the last step B, or in the first step K). Steps C to E are omitted in embodiments 2 and 3. While step D) is performed in embodiment 1 and embodiments 4-7, it is optional for steps C and E.

[0100] It has been shown that at least the last step (B) should be carried out for a duration of 3-30 minutes, and ideally for a duration of 3-10 minutes. The temperature at the end of step (B) should be less than 70°C, and ideally between 50°C and 70°C.

[0101] 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 nearly constant. If necessary, step C) can also be carried out for a longer period to achieve a noticeable improvement in the network structure.

[0102] During step D), cooling and simultaneous coarse comminution occur. This step should take place for a period of between 3 and 90 minutes, and particularly preferably between 3 and 30 minutes, during which the temperature drops below 45°C, preferably below 40°C, and most preferably below 35°C. Step E) should only take place for a short period of between 5 and 60 seconds, and preferably between 5 and 30 seconds. During this time, the temperature should not rise again or should at least change only slightly.

[0103] List of reference symbols

[0104] Container wall 1

[0105] Container bottom 2

[0106] Mixing tool

[0107] Motor

[0108] Drive belt inner section in the double wall outer section in the double wall Fluid supply and discharge , 10 Mixing section 1, 12 Rolling element 3 Wall scraper 4 Suction lance 5 Feed 6 Separator 7 Ball segment-like closure 8 Collecting tray 9, 20,21,22, 23 Line

Claims

Patent claims 1 . A method for producing electrode mixtures from various substances, namely active material with a mass fraction wi, optionally additives with a mass fraction W2 and binder with a mass fraction W3, where wi and W3 are each > 0%, W2 0% and wi, W2 and W3 are each < 100%, comprising the steps 1 ) Filling of the active material and a first percentage p ai of the additives and / or a first percentage p M the binder in a container, where 0% < p al < 100% and 0% < p bl < 100%, but either 0% < Pai or 0% < p bl is, A) introducing a first mechanical power Pi 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 portion p a2 of the additives and / or a further percentage p b2 the binder in the container, where 0% < p a2 < 100% - p al and 0% < p b2 < 100% - p bl B) introducing a second mechanical power P2 into the substances contained in the container, by means of shear forces or impact forces, shear forces being preferred, during a second time interval T2, in order to produce a second mixture, where P2 > Pi, and W) Repeat steps A) and B) as long as the binder and, if applicable, additives have not yet been completely introduced, whereby between steps A) and B) the step K) Adding a further percentage share p a k of the additives and / or a further percentage p b k the binder is added to the container, with k=3 for the first repetition and k being increased by 1 after each repetition, and 0% < p ak < 100% — .i=i Pai and 0% < is.

2. Method according to claim 1, characterized in that W2 > 0%, p a i>0% and p bi = 0%.

3. 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) it is ensured that the temperature of the substances held in the container does not exceed a predetermined temperature TH exceeds, preferably T H > 40°C , particularly preferably 40°C < T H < 80°C and preferably 50°C < T H < 70° C is 4. 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 P2 is dimensioned such that in step B) the temperature of the substances held in the container increases and step B) is ended as soon as the temperature of the substances held in the container reaches the predetermined temperature TH.

5. 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 P3 into the substances contained in the container by means of shear forces or impact forces, with shear forces being preferred, during a third time interval T3, where P3 < P2.

6. Method according to claim 5, characterized in that T3 < T2.

7. Method 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 TH and 1.1 x TH and preferably in an interval between 0.9 x TH and 1.05 x TH.

8. Method according to one of the preceding claims, characterized in that after the last execution of step B) and if present after step C) follows: D) Cooling the substances contained in the container to a temperature TL < TH, while a fourth mechanical power P4 is introduced into the substances contained in the container by means of shear forces or impact forces, with shear forces being preferred, where P4 < P2 .

9. Method according to claim 8, characterized in that after step D) follows: E) Crushing of the substances contained in the container into a multitude of agglomerates by introducing a fifth mechanical power P5 with P5>P4, wherein the agglomerates preferably have an average grain size between 0.05 and 5 mm.

10. Method according to one of the preceding claims, characterized in that at least during the last implementation of step B), this step B) and preferably all steps of the method are carried out in a protective gas atmosphere.

11. Method according to one of the preceding claims, characterized in that a polymer binder, preferably PTFE or PVDF, is used as the binder, with PTFE being particularly preferred.

12. A method for producing an electrode, wherein an electrode mixture is produced by a method according to any 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.

13. Device for carrying out a method according to one of claims 1 to 11, wherein the device 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.

14. Device according to claim 13, characterized in that a heating and / or cooling device is provided for cooling a mixture arranged in the mixing container, wherein the mixing container is preferably designed with a double wall such that a cooling or heating fluid can be passed between the two walls of the double wall, wherein particularly preferably at least a section of the mixing container base is also designed with a double wall such that a cooling or heating fluid can be passed between the two walls of the double wall.

15. 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 and the container axis b, respectively.

16. Device according to one of claims 13 to 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 the wall scraper and / or the mixing tool is preferably 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.

17. Device according to one of claims 13 to 16, characterized in that the mixing tool has a tool shaft and at least one mixing part projecting in the radial direction beyond the tool shaft, wherein the mixing tool preferably has a plurality of mixing parts 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 projecting in the radial direction beyond the shearing element.

18. Device according to one of claims 13 to 16, characterized in that a pneumatic conveying device is provided with which the mixed material can be conveyed out of the mixing container.

19. 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 the suction lance is preferably integrated into the wall scraper.

20. 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.

21. Device according to one of claims 19 to 20, characterized in that the pneumatic conveying device is operated with protective gas, wherein the protective gas is preferably conveyed in a closed circuit.

22. Use of a device according to one of claims 13 to 21 for carrying out a method according to one of claims 1 to 11.

23. An electrode mixture produced by a process according to any one of claims 1 to 11.

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