Method for producing electrode mixture and device for carrying out method

Abstract

The invention relates to a method for producing an electrode mixture consisting of a plurality of substances, i.e. An active material in a mass ratio w1, optionally an additive in a mass ratio w2 and a binder in a mass ratio w3, where w1 and w3 are both gt; 0%, w2 > = 0%, and w1, w2 and w3 are lt, respectively; the percentage is 100%; the method comprises the following steps: 1) filling a container with an active material and a first percentage pa1 of an additive and / or a first percentage pb1 of a binder, in which, but or, A) a first mechanical power P1 is introduced into the substance contained in the container by means of a shear force or impact force, and a second mechanical power P2 is introduced into the substance contained in the container by means of a second shear force or impact force; 2) filling the container with a second percentage pa2 of an additive and / or a further percentage pb2 of a binder, and wherein, B) during a second time interval T2, by means of a shear or impact force, a second mechanical power P2 is introduced into the substance contained in the container to produce a second mixture, where P2gt; the method is characterized in that the method comprises the following steps: (1) adding a binder and optional additives to the container, (2) adding the binder to the container, (3) adding the binder to the container, (3) adding the binder to the container, (3) adding the binder to the container, (3) adding the binder to the container, (4) adding the binder to the container, (3) adding the binder to the container, (3) adding the binder to the container, (4) adding the binder to the container, (4) adding the binder to the container, (5) adding the binder to the container, and (5) adding the binder to the container, and (5) adding the binder to the container.

Description

[0001] The present invention relates to a method for producing an electrode mixture, a device for carrying out the method, the use of a device for carrying out the method, and an electrode mixture produced according to the method.

[0002] In recent years, battery technology, in particular lithium-ion technology, has received increasing attention, since this technology is of great importance both for the functioning of, for example, purely electric vehicles and for stationary power stores. Batteries with high capacity, low manufacturing costs and long service life are a prerequisite for the acceptance of purely electric vehicles.

[0003] At present, mainly lithium-ion batteries are used.

[0004] The electrodes of a typical lithium-ion battery have a copper foil as anode and an aluminum foil as cathode. The foils are usually coated on both sides with active material and, at least for the production of the cathode, also with additives.

[0005] During charging of a lithium-ion battery, lithium ions move from the cathode through the electrolyte to the anode and are fixed there by the particles of the active material. The described process is reversible, so that when the battery is discharged, a current of lithium ions flows from the anode to the cathode.

[0006] In order that reliable lithium-ion batteries with high capacity can be produced, high demands are placed on the electrodes.

[0007] The electrode layer must have pores through which the electrolyte can penetrate, so that lithium ions can be transported to every 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, i.e. in the described example either the copper foil or the aluminum foil, in order to ensure that electrons are transferred to and from every particle of the active material.

[0008] Furthermore, the particles of the active material must not only be bound to one another, but also to the metal foil, for which a binder material is used. Finally, the layer thickness should be formed as uniformly as possible.

[0009] In order to produce these layers, the reactants, i.e. the active material, the binder and optionally additives, need to be mixed with one another and dispersed into a so-called "paste" (English: Paste, suspension). Usually, a liquid solvent (for example, water or N-methyl-2-pyrrolidone (NMP)) is added here, which then, after the electrode mixture has been introduced onto the foil, has to be removed again in a complex drying process.

[0010] This is both time-consuming and energy-intensive. Furthermore, in the machine production of electrode mixtures, voluminous drying equipment has to be provided.

[0011] Therefore, starting from the described prior art, the task of the present application is to provide a method for producing an electrode mixture which reduces the amount of solvent required or, in the best case, even completely dispenses with a solvent and still provides an electrode mixture of high quality and easy to process.

[0012] Furthermore, the task of the present application is to provide a device for carrying out the method.

[0013] The task is achieved in methodic terms by a method for producing an electrode mixture, which consists of a plurality of substances, namely of an active material in a mass fraction of w1, optionally an additive in a mass fraction of w2 and a binder in a mass fraction of w3, wherein w1 and w3 are each > 0%, w2 ≥ 0% and w1, w2 and w3 are each < 100%, the method comprising the following steps: 1) filling an active material as well as a first percentage p a1 of an additive and / or a first percentage p b1 of a binder into a container, wherein and but or , A) introducing a first mechanical power P1 into the substances contained in the container by means of a shear force or an impact force, wherein a shear force is preferred, 2) filling a second percentage p a2 of an additive and / or a further percentage p b2 of a binder into the container, wherein and , B) introducing a second mechanical power P2 into the substances contained in the container by means of a shear force or an impact force during a second time interval T2, wherein P2 > P1, wherein a shear force is preferred, and W) repeating steps A) and B) as long as the binder and optionally the additive have not been completely introduced, wherein before step A) and / or between steps A) and B) the following step is carried out: K) filling a further percentage p ak of an additive and / or a further percentage p bk of a binder into the container, wherein k = 3 at the first repetition and k is increased by 1 after each repetition, and

[0014] ​If an electrode mixture for a cathode is prepared, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate or other lithium metal oxides or sodium metal oxides can be used as active material, for example.

[0015] If an electrode mixture for an anode is prepared, graphite, carbon (e.g. activated carbon or graphene) or silicon-carbon composites can be used as active material, for example. In this case, the mass fraction w1 can be up to 99.9%, wherein preferably w1 is between 90% and 99.9%.

[0016] The additives used are mostly conductive additives, such as conductive carbon black, which are particularly necessary when preparing an electrode mixture for a cathode, since the active material is usually poorly conductive. In addition to the conductive additives, the electrode mixtures for the anode and the cathode also use, for example, silicon or silicon compounds, solid electrolytes, nanoparticulate aerosols and oxalic acid, graphene, carbon nanotubes (CNT), styrene butadiene rubber (SBR) or conductive graphite, wherein preferably the mass fraction w2 > 0 and < 10%. In particular, in the case of silicon or silicon compounds or solid electrolytes, the mass fraction can also be significantly higher than 10%.

[0017] In a preferred embodiment, the mass fraction w3 of the binder is also between 0.1% and 10%. In particular, polymer binders, such as fluoropolymer binders (e.g. PVDF and PTFE), are used as binders. Alternatively, carboxymethyl cellulose (CMC) can also be used as a binder. Many polymer binders, in particular PTFE, exhibit a fibrillation effect at certain temperatures and when energy, in particular shear energy, is introduced, which improves the processability of the electrode mixture.

[0018] Step A) can be carried out simultaneously with step 1) or can be carried out after step 1).

[0019] In step A), the components added to the container in step 1) are dry mixed, i.e. without the addition of any solvent (e.g. water). In the process, a substantially homogeneous mixture is prepared. During this, a particle composite structure is formed, i.e. the particles of the active material are surrounded by the binder and / or the (conductive) additives.

[0020] After step A), step 2) is carried out, in which further fractions of additives and / or further fractions of binders are introduced. In the process, it is not necessarily necessary to introduce further fractions in step 2). For example, if all the fractions provided for step B) have already been introduced in step 1), it is not necessary to introduce further fractions in step 2). Thus, the fractions p a2 and p b2Both can be 0%. In other words, step 2) can be omitted.

[0021] In step B), which can be carried out after step 2) or during step 2), a second mechanical power P2 is introduced into the mixture by means of a shearing force, wherein a percussion force can also be used instead of a shearing force, the second mechanical power being higher than the first mechanical power.

[0022] The introduction of the mechanical power in steps A) and B) can be effected, for example, by means of correspondingly designed mixing tools in the mixing vessel. In this case, the rotational speed in step B) is increased compared to the rotational speed in step A). The mechanical powers PI and P2 do not have to be constant, but can change during the execution of the respective step. Thus, for example, the rotational speed of the mixing tools used can remain constant during the execution of the individual steps. However, since the density and flowability of the mixture change during the execution of the individual steps, the power introduced also changes. It is important, however, that the mechanical power introduced in step B) is greater than the mechanical power introduced in step A).

[0023] Alternatively, the mechanical power can also be introduced into a continuous extruder. The different mechanical powers during the continuous time interval can then be realized by different length regions along the mixing axis of the extruder and by different geometries of the mixing elements in the respective regions.

[0024] For example, the PTFE binder initially exists in the form of agglomerates, which consist of individual, fluffy granules of bead-chain-like polymer fibers. In step B), due to the adhesion of the polymer binder component to the surface of the active material, a filamentous / fibrous structure is formed, which develops into a network, in particular typically into a spiderweb-like network, into which the previously formed granular composite structure is embedded. In other words, the active material is coated with binder and optional additives.

[0025] Depending on the application, the step B) time interval T2 can be between 1 minute and 90 minutes, wherein the duration is preferably chosen to be between 10 minutes and 30 minutes.

[0026] If all the required components of the electrode mixture to be prepared have been filled in before the execution of step B), the method according to the application can end here. However, if not all the binder and optional additives have been added completely, steps A) and B) are repeated, wherein, before the repeated step A) and / or between steps A) and B), further fractions of additives and / or binder are filled in. The subsequently added fractions of binder and / or additives are thus also subjected to steps A) and B).

[0027] In particular when preparing an electrode mixture for a cathode, it is provided in a preferred embodiment that w2>0%,p a1 >0% and p b1 =0%. In other words, in step 1) only part of the additives or all of the additives are added without supplying the binder. If steps A) and B) are to be repeated, the binder is added only in step 2) or step K).

[0028] In another preferred embodiment, at least in the last execution of step B) and preferably in all executions of step B), the power P2 is adjusted such that in step B) the temperature of the substance contained in the container is increased and as soon as the temperature of the substance contained in the container reaches a predetermined temperature T H , step B) is terminated.

[0029] In this case, for T H , preferably T H > 50°C, particularly preferably 50°C < T H < 80°C, and optimally 50°C < T H < 70°C. The temperature T H should not be significantly exceeded.

[0030] Polymeric binders, in particular PTFE binders, generally exhibit fibrillation only at significantly higher temperatures. Surprisingly, however, this can be achieved even at lower temperatures by the introduction of mechanical energy.

[0031] If it is found in the specific application case that the time interval in which step B) is executed is too short because the temperature T H is reached very quickly, the time interval can be extended by cooling the container.

[0032] In another preferred embodiment, the following step C) is specified after the last execution of step B): During the time interval T3, a third mechanical power P3 is introduced into the substance contained in the container by means of a shear force or an impact force, with P3 < P2, wherein a shear force is preferred.

[0033] If the shear force is introduced into the mixture by means of a mixing tool, the speed of the mixing tool can be reduced in step C).

[0034] In order to form an optimally structured dry mixture, the mechanical power introduced in step C) can be reduced, which surprisingly improves the quality of the mixture. It turns out that in order to form a network structure, only a high mechanical power P2 needs to be introduced at the beginning. Once the fibrillation of the binder has started, the complete formation of the structure can be completed with a lower power input.

[0035] Generally, it is advantageous if the time interval T3 is shorter than the time interval T2.

[0036] In a preferred embodiment, in step B) the temperature is increased to a predetermined temperature T H The required energy is introduced completely or at least 80% by mechanical energy (i.e. shear forces).

[0037] Additional external heating is not absolutely necessary.

[0038] Once the temperature T H is reached or exceeded, the mechanical power introduced into the mixture is reduced so that no further significant temperature increase is caused.

[0039] Basically, the temperature of the mixture remains constant and the mixture simply moves. Thereby, the fibrillation is completed and a so-called structured dry mixture is obtained which is very suitable for the production of electrodes.

[0040] In a preferred embodiment, in step C) the power is adjusted so that the temperature of the substance contained in the container is kept within an interval of 0.8 x T H and 1.1 x T H and preferably within an interval of 0.9 x T H and 1.05 x T H .

[0041] In another preferred embodiment, after the last execution of step B) and, if step C) exists, after step C), the following step D) is executed: cooling the substance contained in the container to a temperature T L < T H , while a fourth mechanical power P4 is introduced into the substance contained in the container by means of shear forces, wherein P4 < P2 and preferably P4 < P3.

[0042] Thus, at the end of step C) the mixture is cooled, wherein at the same time the movement of the mixture is continued to ensure a good mixing. In principle, it is also possible to cool a stationary, not moving mixture, thus P4 = 0. During the cooling, an intermittent movement and a standstill of the mixture are also possible. Preferably, the temperature T L < 45°C, particularly preferably < 40°C and optimally < 35°C.

[0043] During the cooling, the movement of the mixture will change the structure significantly, i.e. the further transportability of the electrode mixture can be further distributed metered.

[0044] The cooling is advantageously supported by refrigeration, for example by keeping the walls of the mixing container of the mixture. Alternatively and / or additionally, the cooling can also be accomplished by means of a cold gas stream and / or by means of a liquefied gas (for example nitrogen or CO2, for example also in the form of dry ice).

[0045] In a further preferred embodiment, it is provided that after step D) the following step E) is carried out: By introducing a fifth mechanical power P5, the substance contained in the container is comminuted into a plurality of agglomerates, wherein P5 > P4, wherein the agglomerates preferably have an average particle size of between 0.05 and 5 mm.

[0046] This measure ensures that the so-called structured mixture is fine-grained, flowable and can thus be easily removed from the mixing container and further processed to produce an electrode.

[0047] The method according to the application does not require the addition of a solvent at all.

[0048] If the method is carried out in a protective gas atmosphere, the quality of the mixture can be further improved. This is particularly advantageous in step B). However, all steps of the method are preferably carried out in a protective gas atmosphere. It can be provided, for example, that specially conditioned dry air or an inert gas is used as the protective gas atmosphere.

[0049] In a preferred embodiment, the electrode is produced by calendering and laminating or pressing the electrode mixture produced according to the method onto a conductive foil.

[0050] The device for carrying out the 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 is rotatable about a container axis b, wherein the tool axis w and the container axis b are spaced apart from one another.

[0051] The device can thus be used for all method steps. Thus, the mixing provided in step A) as well as the introduction of mechanical energy by means of shear forces in the subsequent steps B) and C) can be carried out in the mixing container. In a preferred embodiment, the device has a heating and / or cooling device for tempering the mixture arranged in the mixing container. For example, the mixing container can be designed as a double-walled so that a tempering fluid, i.e. a cooling fluid or a heating fluid, can be conducted between the two walls of the double-walled. In particular, the cooling device can significantly reduce the duration of step C) or limit the temperature and / or the temperature increase of the mixture in step A) and / or step B), which is very advantageous.

[0052] It is also particularly preferred that at least a portion of the bottom of the mixing container is designed to be double-walled, so that cooling fluid or heating fluid can flow between the two walls of the double-walled container.

[0053] It has been found that the quality of the mixture is improved when the mixing tool and mixing container rotate in the same direction about the tool axis w or the container axis b during operation of the apparatus. When the bottom of the container is observed from inside, the mixing container and mixing tool thus appear to rotate clockwise or counterclockwise. For other applications, mixing methods are known in which the mixing tool and mixing container rotate in opposite directions along the tool axis w or the container axis b; that is, one element (mixing tool and mixing container) rotates clockwise about its axis while the other rotates counterclockwise. However, in the preparation of electrode mixtures, the co-directional movement of the mixing tool and mixing container has proven useful.

[0054] In a preferred embodiment, the wall scraper is also designed as a bottom scraper, so that the scraper also prevents the mixture from permanently adhering to the bottom of the mixing container, at least in some areas.

[0055] In another preferred embodiment, the scraper contacts the wall of the mixing container and preferably also the bottom of the mixing container, and / or the mixing tool contacts the bottom of the mixing container. This prevents the electrode mixture from forming a film on the wall or bottom. Since direct contact can lead to increased wear on the container wall, container bottom, or the scraper and mixing tool, in a preferred embodiment, the scraper and / or mixing tool are made of plastic, particularly preferably PTFE or polyamide, at least in the portions contacting the mixing container wall or bottom. In this case, the mixing tool and / or scraper can be made entirely of plastic, or only in the areas contacting the mixing container wall or bottom.

[0056] The mixing tool used in this apparatus can also be optimized for the preparation of electrode mixtures. Therefore, in a preferred embodiment, the mixing tool is specified to have a tool shaft and at least one mixing component extending radially beyond the tool shaft. Preferably, the mixing tool has a plurality of mixing components arranged spaced apart from each other in the axial direction, or the mixing component consists of a shearing element arranged within an imaginary ring and a rolling element extending axially beyond the shearing element. Particularly preferably, the mixing component has one or more (e.g., two) rolling elements that extend axially beyond the shearing element.

[0057] The hybrid component can have radially outward-oriented blade-like elements. Alternatively, the hybrid component can be designed as a plate with external teeth.

[0058] Due to the high tool speed and the abrasive nature of some raw material components, the mixing components may experience wear. Therefore, in a preferred embodiment, the mixing components are protected, particularly from wear, on the surfaces that come into contact with the mixture. This can be achieved, for example, by spraying carbide or ceramic onto the mixer shaft or a fixed scraper / scraper, or alternatively by spraying polyurethane and other plastic materials, as copper- and zinc-free treatment is particularly required in battery electrodes. The surface of the mixing components can also be protected from wear by coating, by preparation of ceramic or powder metallurgy materials, or by wear-protective elements. The rolling elements extending axially from the shearing element can be made, for example, of ceramic or powder metallurgy materials (e.g., carbide), or have elements made of these materials that are glued or welded to a retaining element made of steel.

[0059] In another preferred embodiment, a pneumatic conveying device is provided to transport the mixture from the mixing container. For example, the pneumatic conveying device can be designed as a suction pipe, which is arranged inside the mixing container. Alternatively, the suction pipe can be integrated into a wall scraper. The suction pipe preferably terminates at the radially innermost lower corner of the wall scraper at the bottom of the mixing container, or at an angle formed by the walls of the mixing container and the wall scraper in the direction of material flow.

[0060] In this case, the container does not need to have a drain opening at the bottom. In particular, through the measures in step E), the structured dry mixture becomes flowable, allowing it to be easily drawn out by means of a conveying device.

[0061] Alternatively, the bottom of the mixing container may also have a closable vent opening, and a pneumatic conveying pipe may be arranged below the vent opening, so that the mixture discharged from the mixing container falls into the pneumatic conveying pipe through the vent opening. Alternatively, a mechanical unloading device (e.g., a conveyor belt or vibrating trough, or a simple collection container) may also be arranged below the vent opening.

[0062] In this case, the pneumatic conveying device can be operated using a protective gas, preferably delivered in a closed loop. For example, the protective gas provides dry air to prevent moisture from entering during the process. The air can be specially conditioned to achieve an extremely low dew point.

[0063] Further advantages, features, and application possibilities will become clear based on the following description of preferred embodiments and the accompanying drawings. In the drawings: Figure 1 A first embodiment of the mixer according to the invention is shown. Figure 2 A second embodiment of the mixer according to the invention is shown, and Figure 3 A flowchart of the method according to the present invention is shown.

[0064] Figure 1 A first embodiment of an apparatus according to the invention for performing the method is shown. The apparatus includes a container having a container wall 1 and a container bottom 2. The mixing container is rotatable about a container axis b.

[0065] A mixing tool is arranged within the mixing container, which can rotate about its axis w by means of a motor 4 and a drive belt 5. The container wall is designed as a double-walled structure and is equipped with a partition that divides the cavity formed in the double-walled structure into an inner section 6 and an outer section 7. A temperature-regulating fluid (e.g., a cooling fluid in the illustrated embodiment) is introduced into the inner section 6 via a fluid supply device 8, causing the cooling fluid to flow along the bottom and wall in the direction of the arrow, reach the outer section 7, and be extracted again in the outer section. Here, the fluid supply device 8 is designed as a rotary joint that enables the supply and discharge of fluid and transfers fluid from the fixed part of the container to the rotating part.

[0066] Alternatively, the partition can be omitted. Therefore, the reflux channel should be arranged on the outer wall of the double jacket so that the temperature-regulating fluid can be extracted.

[0067] Therefore, the container and the mixture contained therein can be heated or cooled by means of a temperature-regulating fluid. The mixing tool 3 has a plurality of mixing components 9, 10. The mixing component 10 arranged on the upper part of the mixing tool 3 consists of a plurality of rings arranged parallel to each other, which may have notches (not shown) on their circumferential surfaces to increase the shear force to be introduced.

[0068] like Figure 1 As shown in the embodiment, the disc with reference numeral 10 can be arranged only on the upper part of the mixing tool 3. However, the disc can also be distributed along the entire length of the mixing tool 3. In that case, the lower mixing component 9 can be omitted.

[0069] exist Figure 1In the illustrated embodiment, the lower mixing component 9 is also circular, with a series of notches (not shown) on its circumferential surface. The upper roller element 11 and the lower roller element 12 extend vertically toward the lower mixing component 9. The lower roller element 12 contacts the container bottom 2, or is positioned at least very close to the container bottom. The distance from the container bottom should be less than 1 mm. The lower roller element 12 prevents some of the mixture from depositing on the bottom. The upper roller element 11 ensures that all the mixture moves within the mixer. The upper mixing component 10 can also be omitted. In this case, it would be advantageous if the upper roller element 11 extended further upward to reduce the space where mixing or rolling motion does not occur.

[0070] In addition, a wall scraper 13 is provided, which contacts the annular area of ​​the container wall 1 and the container bottom 2 to prevent the electrode mixture from adhering to the container wall and the bottom area not swept by the lower roller element 12.

[0071] To remove the mixture, the suction pipe 14 can be introduced into the mixing container, or moved back and forth between an elevated position (where the suction pipe is not immersed in the mixture) and a lower position (where the suction pipe is immersed in the mixture).

[0072] Figure 1 The lower position is shown, while the upper position is indicated only by a dashed line.

[0073] The resulting mixture can be drawn out through the suction pipe 14. In this embodiment, the suction pipe 14 is also designed with double walls, through which the transport gas can be supplied via the supply device 15. The mixture is drawn out through the suction pipe 14 and separated from the transport gas in a separator or filter 16. The transport gas can be completely returned to the container via the supply device 15 and can be designed as a protective gas, such as dry air, to prevent unwanted moisture absorption of the mixture. The mixture separated from the transport gas in the filter 16 can be discharged from the lower end of the filter via a flap system or a gate system (not shown).

[0074] Figure 2 A second embodiment of the device according to the invention is shown. Where possible, the same reference numerals are used in conjunction with... Figure 1 The same type of elements shown in the embodiments.

[0075] Therefore, only those related to [other technologies] are shown below. Figure 1 The differences in the implementation methods.

[0076] Here, the mixing tool 3 has significantly more circular mixing components 10. The lower mixing component 9 has only downward-oriented roller elements 12. There are no upward-oriented roller elements 11. The mixing container has an opening in the bottom 2 of the container, which can be opened by means of a spherical segmental closure 17 to empty the container. The mixture falling from the venting opening falls into the collection tray 18 of the conveying device, which, in the illustrated embodiment, is pneumatically operated. The mixture is conveyed by a conveying fluid along pipe 19 to the separator 16. The conveying fluid is then guided back to the mixing container via pipe 20 and back to the tray 18 via pipe 21. The system can be substantially hermetically sealed, thereby maintaining a protective gas atmosphere.

[0077] Because the bottom 2 of the container now has a drain opening, the structure of the cooling or heating device is slightly different. The temperature-regulating fluid is supplied via pipe 22 extending into the double wall of the container bottom 2 through the supply and discharge device 8 of the cooling device, and is drawn back out via pipe 23 extending only slightly below the liquid level of the temperature-regulating fluid. The temperature-regulating fluid is guided in the loop by means of a pump, and the heat discharged from the double jacket is transferred to the external second cooling loop via a heat exchanger. By supplying the temperature-regulating fluid in the loop, the liquid level in the double jacket is automatically kept constant.

[0078] Alternatively, the sidewalls of the mixing container may be provided with a double jacket, so that the supply pipe 22 terminates near the bottom of the container.

[0079] In a particularly preferred embodiment of the method according to the invention, using Figure 3 The process is shown below.

[0080] In step 1), the additives (e.g., conductive additives) used to prepare the electrode mixture are divided into multiple portions (e.g., two portions). Then, in step A), the first portion is mixed with the active material. The purpose of this step is to encapsulate or coat the active material with a portion of the additive.

[0081] Only after this is another portion of the additive (the remaining portion in this example) added in step 2), and the active material and the additive mixed together in step B). This measure allows the active material to be better encapsulated / coated by the additive.

[0082] Conversely, if the entire amount of additive is added simultaneously, greater care must be taken during the mixing step, as the additive itself may tend to form aggregates and separate from the active material. If a rotary mixing tool is used, the circumferential speed of the mixing tool in step B) should be between 10 m / s and 80 m / s, preferably between 20 m / s and 50 m / s, and optimally between 25 m / s and 35 m / s. In step A), a lower circumferential speed can be selected.

[0083] In step W, check if all required components have been fully added. If yes, proceed to step C. If no, and in the described example, no adhesive has been added yet, repeat steps K), A), K), and B) until all required components have been fully added.

[0084] Therefore, in a preferred embodiment, all adhesive components are added via steps K), A), K), and B).

[0085] In the second step A) (after step K), the reactants in the electrode mixture are mixed together. Following the further step K), there is a further step B), in which the second mechanical power P2 is reintroduced into the substance contained in the container by means of shear force.

[0086] Specifically, step B) and all other steps can be carried out, for example, by a sharp-edged, rapidly rotating mixing tool or in a mixer of a corresponding design equipped with such a tool. In this step, the temperature rises due to the introduced mechanical power P2, which can be enhanced as needed by appropriate external heat energy or reduced by heat dissipation to the outside. According to the invention, the temperature reached in the mixture is maintained below 70°C, as this is surprisingly sufficient to allow the polymer of the plastic binder to adhere to the particle surface and be stretched into a fibrous structure, thereby forming a network structure in which the previously formed particle composite structure is embedded. Surprisingly, the temperature of 70°C is far below the temperature considered optimal for PTFE fibrillation, 80°C-120°C. However, this temperature has proven perfectly sufficient to allow the polymer to optimally adhere to the particle surface. Due to the intense and targeted fibrillation and the resulting network structure, partially agglomerated or even plastic, doughy substances are produced in the mixer, which are difficult to simply evacuate, subsequently transport the material, and ultimately accurately and uniformly dispense and meter on the metal foil.

[0087] To avoid damaging the formed fibrils or polymer fibers (causing them to shorten), and to promote their adhesion to the particle surface or their interconnection and stretching to form increasingly finer and thinner fibers, the mechanical power P3 is ultimately reduced relative to the mechanical power P2 in step C). This avoids further increases in temperature and shortening of the already formed fibers. Cooling should also be avoided as much as possible to allow the material to mature at a nearly constant temperature level. During this process, the fibrillated material becomes increasingly plasticized and, depending on the binder content, forms a dough-like, easily moldable substance.

[0088] If a sufficiently malleable plastic material has been obtained in step B), and the material cannot be further improved or can hardly be improved further by the curing in step C), then step C) can be shortened to a few seconds or even skipped entirely.

[0089] Therefore, in order to transform these agglomerated and even plastic materials into a form that can be easily removed from the mixer and transported without problems between the mixer and downstream processing, ideally over distances of several meters, and most importantly, accurately metered, followed by step D), where the mixture is cooled to, for example, a temperature T of 45ºC. L Simultaneously, a fourth mechanical power P4 is introduced into the material, which is also lower than the second mechanical power P2. Alternatively, the fourth mechanical power P4 can be lower than the third mechanical power P3. If a hybrid tool is used, the circumferential speed can be reduced to, for example, 5 m / s or lower.

[0090] During cooling, the plastic material "solidifies" and is broken down by the movement of the mixing tools and rotary mixing containers into agglomerates and even flaky structures with very wide particle size distributions. The lower the temperature of the mixture, the more flaky it becomes. At this point, although the mixture is transportable, it remains difficult to meter due to its wide particle size distribution, especially when uniform metering is required across a wide metering cross-section.

[0091] To further improve metering capacity, after cooling, the mixture is pulverized in a further step E), which can be achieved, for example, by using a mixing tool that operates at a significantly increased second mixing speed, thereby introducing a fifth mechanical power P5. If a mixing tool is used, the circumferential speed of the mixing tool can be increased to, for example, 5 m / s to 20 m / s.

[0092] During this process, agglomerates are generated with an average particle size between 0.05 mm and 5 mm, thus enabling excellent gravity measurement over a wide metering cross-section. The corresponding electrode mixture is then prepared. In step F), this electrode mixture can be calendered and laminated onto a conductive foil to prepare an electrode.

[0093] Preferred embodiments are given below:

[0094] No additives are used in Example 4. In Examples 1 and 2, the adhesive has already been added in step A). ​​In all other examples, the adhesive is added only in step B), or in the last performed step B), or in the first step K). Steps C) through E) are omitted in Examples 2 and 3. Although step D) is performed in Example 1 and Examples 4-7, steps C and E are optional.

[0095] It has been shown that at least the last step B) should be performed over a duration of 3–30 minutes, and preferably over a duration of 3–10 minutes. The temperature at the end of step B) should be below 70°C, and preferably between 50°C and 70°C.

[0096] Preferably, step C) is performed for a duration of 1 to 10 minutes, during which the temperature of the contained material remains almost constant. If desired, step C) can also be performed for a longer period to significantly improve the network structure.

[0097] During step D), cooling and coarse grinding are carried out simultaneously. This step should be performed for a duration of 3 to 90 minutes, and particularly preferably for a duration of 3 to 30 minutes, wherein the temperature drops to below 45°C, preferably below 40°C, and most preferably below 35°C.

[0098] Step E) should be performed only for a short duration between 5 and 60 seconds, preferably between 5 and 30 seconds. During this process, the temperature should not rise again, or at least change only slightly. Reference tag list

[0099] 1 container wall 1 2 Container bottom 2 3 Mixing Tools 4 motors 5. Transmission belt 6 internal sections of double-walled 7. External section of double-walled structure 8. Fluid supply and discharge devices 9 and 10 are mixed components 11 and 12 roller pressing elements 13 Wall Scraper 14 Suction Tube 15 Supply Units 16 Separators 17. Spherical segmental closure 18 Collection Discs Pipes 19, 20, 21, 22, and 23.

Claims

1. A method for preparing an electrode mixture, said electrode mixture comprising multiple substances, namely, an active material in a mass percentage of w1, an additive optionally in a mass percentage of w2, and a binder in a mass percentage of w3, wherein, w1 and w3 are each > 0%, w2 ≥ 0%, and w1, w2, and w3 are each < 100%, and the method comprises the following steps: 1) The active material and the first percentage p a1 The additives and / or the first percentage p b1 The adhesive is filled into the container, wherein, and ,but or , A) Introduce a first mechanical power P1 into the substance contained in the container by means of shear forces or impact forces, wherein shear forces are preferred. 2) The second percentage p a2 The additives and / or additional percentages p b2 The adhesive is filled into the container, wherein and , B) During a second time interval T2, introduce a second mechanical power P2 into the substance contained in the container by means of shear forces or impact forces to generate a second mixture, wherein P2 > P1, wherein shear forces are preferred, and W) Repeat steps A) and B) as long as the binder and optional additives have not been fully introduced, wherein between steps A) and B), the following step is carried out: K) will add another percentage p ak The additives and / or additional percentages p bk The adhesive is filled into the container, wherein k=3 in the first repetition and k increases by 1 after each repetition, and .

2. The method according to claim 1, characterized in that, w2>0%, p a1 >0% and p b1 =0%.

3. The method according to any one of the preceding claims, characterized in that, At least in the last execution of step B), and preferably in all executions of step B), ensure that the temperature of the substance contained in the container does not exceed a predetermined temperature T. H Preferably, T H >40ºC, particularly preferably, 40ºC <T H <80ºC, and ideally, 50ºC <T H <70ºC.

4. The method according to any one of the preceding claims, characterized in that, At least in the last execution of step B), and preferably in all executions of step B), the power P2 is adjusted such that in step B), the temperature of the substance contained in the container rises, and once the temperature of the substance contained in the container reaches a predetermined temperature T... H Then terminate step B).

5. The method according to any one of the preceding claims, characterized in that, Carry out the following step C) after the last execution of step B): During a third time interval T3, introduce a third mechanical power P3 into the substance contained in the container by means of shear forces or impact forces, wherein P3 < P2, wherein shear forces are preferred.

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

7. The method according to claim 5 or 6, characterized in that, In step C), the power is adjusted such that the temperature of the substance contained in the container is maintained at 0.8 × T. H and 1.1×T H Within the range between, and preferably maintained at 0.9×T H and 1.05×T H Within the range between.

8. The method according to any one of the preceding claims, characterized in that, After the last execution of step B), and if step C) exists, carry out the following step D) after step C): Cool the substance contained in the container to a temperature T L <T H , and at the same time, introduce a fourth mechanical power P4 into the substance contained in the container by means of a shearing force or an impact force, where P4 < P2, and the shearing force is preferred.

9. The method according to claim 8, characterized in that, Carry out the following step E) after step D): Reduce the substance contained in the container to a plurality of agglomerates by introducing a fifth mechanical power P5, wherein P5 > P4, and wherein the agglomerates preferably have an average particle size between 0.05 mm and 5 mm.

10. The method according to any one of the preceding claims, characterized in that, At least in the last execution of step B), step B) and preferably all steps of the method are carried out in a protective gas atmosphere.

11. The method according to any one of the preceding claims, characterized in that, A polymer binder, preferably PTFE or PVDF, is used as the binder, wherein PTFE is particularly preferred.

12. A method for preparing an electrode, wherein, Prepare an electrode mixture by means of the method according to any one of the preceding claims, and calender and laminate the electrode mixture onto a conductive foil, or press it onto the conductive foil.

13. An apparatus for performing the method according to any one of claims 1 to 11, wherein, The device comprises: a mixing container having 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 capable of rotating about a tool axis w, and the mixing container is capable of rotating about a container axis b, and wherein the tool axis w and the container axis b are spaced apart from each other.

14. The apparatus according to claim 13, characterized in that, Heating and / or cooling means are provided for cooling the mixing material arranged in the mixing container, wherein preferably the mixing container is designed to be double-walled such that a cooling or heating fluid can be conducted between the two walls of the double wall, and wherein particularly preferably at least a part of the mixing container bottom is also designed to be double-walled such that a cooling or heating fluid can be conducted between the two walls of the double wall.

15. The apparatus according to claim 13 or 14, characterized in that, During operation of the device, the mixing tool and the mixing container rotate in the same direction about the tool axis w or the container axis b.

16. The apparatus according to any one of claims 13 to 15, characterized in that, The wall scraper contacts the mixing container wall, and / or the mixing tool contacts the mixing container bottom, wherein preferably the wall scraper and / or the mixing tool are at least partly made of plastic in the part contacting the mixing container wall or the mixing container bottom, particularly preferably made of PTFE or polyamide.

17. The apparatus according to any one of claims 13 to 16, characterized in that, The mixing tool has a tool shaft and at least one mixing component extending radially beyond the tool shaft. Preferably, the mixing tool has a plurality of mixing components arranged spaced apart from each other in the axial direction, and / or the mixing component consists of a shearing element arranged within an imaginary ring and a rolling element extending radially beyond the shearing element.

18. The apparatus according to any one of claims 13 to 16, characterized in that, A pneumatic conveying device is provided, which can be used to transport the mixture from the mixing container.

19. The apparatus according to claim 18, characterized in that, The pneumatic conveying device is designed as a suction pipe, which is arranged inside the mixing container or can be arranged inside the mixing container, wherein preferably, the suction pipe is integrated into the wall scraper.

20. The apparatus according to claim 18, characterized in that, The mixing container has a closable vent opening at the bottom, and a pneumatic conveying pipe is arranged below the vent opening, so that the mixture discharged from the mixing container falls into the pneumatic conveying pipe through the vent opening.

21. The apparatus according to any one of claims 19 to 20, characterized in that, The pneumatic conveying device is operated using a protective gas, wherein preferably, the protective gas is conveyed in a closed loop.

22. Use of an apparatus for performing the method according to any one of claims 1 to 11, as claimed in any one of claims 13 to 21.

23. An electrode mixture prepared by the method according to any one of claims 1 to 11.

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