Mixer for producing electrode mixtures

Abstract

The application relates to a mixer for producing an electrode mixture. The application relates to a mixer for producing an electrode mixture, comprising a mixing vessel which is rotatable about a mixing vessel axis and has a rotationally symmetrical and preferably circular vessel base and a vessel wall, a scraping device which is movable relative to the mixing vessel and which contacts the vessel base or is at a distance of less than 2 mm from the vessel base, and a pressure-based conveying device for removing the electrode mixture from the mixing vessel, wherein the pressure-based conveying device comprises a conveying channel which is arranged on or in the scraping device, the conveying channel having an inlet and an outlet, the inlet being arranged in the vicinity of the vessel base.

Description

Technical Field

[0001] This invention relates to a mixer for producing electrode mixtures, the mixer having a mixing container that is rotatable about a mixing container axis and having a rotationally symmetrical and preferably circular container bottom and container walls. Background Technology

[0002] Such mixers are generally known. However, these mixers can only be used in a limited way to produce electrode mixtures. The reason for this is that, in the production of electrode mixtures, especially dry electrode mixtures, the mixture typically needs to be heated and cooled as quickly as possible. This can only be achieved in a simple way if the container walls and the entire bottom of the mixing vessel have a double jacket for receiving cooling and / or heating fluids, and therefore the discharge closure at the bottom of the vessel must be omitted. This makes it difficult to remove the finished mixture from the mixing vessel because the mixture typically has a viscous, clay-like consistency.

[0003] For example, electrode mixtures are used in the production of batteries.

[0004] In recent years, focus has been placed on battery technology, particularly lithium-ion technology, as it is crucial not only for the functionality of vehicles such as all-electric vehicles but also for stationary batteries. A typical lithium-ion battery has a copper foil as the anode and an aluminum foil as the cathode. The foil is typically coated with active materials on both sides, and at least for the production of the cathode, it is coated with additives. Furthermore, the particles of the active material must be bonded together and attached to the metal foil, for which a binder material is used. To produce these layers, the reactants—the active materials, binder, and, if necessary, additives—must be mixed and dispersed into a slurry. Typically, a liquid solvent, such as water, is added here, and this liquid solvent must be removed again in a complex drying process after the electrode mixture is applied to the foil.

[0005] Because this process is very time-consuming and energy-intensive, there is a need to produce dry electrode mixtures of sufficient quality for the production of dry electrodes. Due to the complex properties of the active materials used (PTFE is often employed here), the electrode mixture must be heated during the mixing process, typically to above 45°C. To process PTFE, additional shear forces are usually applied to fiberize it, i.e., break it down into numerous fine fibers or filaments. However, removing the electrode mixture from the mixing container while heated is not easy, as the mixture has a highly adhesive, clay-like consistency. Cooling the electrode mixture can improve its removability, but this is also time-consuming, especially since the mixing container must be immediately reheated after removal to process the next batch. Utility Model Content

[0006] Therefore, the purpose of this invention is to provide a mixer for producing electrode mixtures that enables early removal of the electrode mixtures even under difficult conditions.

[0007] According to the present invention, this objective is achieved by providing a scraping device that is movable relative to a mixing container and contacts the bottom of the container or is less than 2 mm away from the bottom of the container; and providing a pressure-based conveying device for removing the electrode mixture from the mixing container.

[0008] Pressure-based conveying devices are equipment used to convey fluid or solid materials through a conveying channel (e.g., pipes or hoses) by creating a target pressure difference between the inlet and outlet. This pressure difference results in the continuous transport of the material, where, depending on the design of the equipment, a gas, liquid, or the material to be conveyed itself is used as the conveying medium. The pressure difference can be achieved by creating overpressure (pressure conveying) or underpressure (vacuum conveying). In particular, pressure-based conveying devices include:

[0009] - Pneumatic conveying devices: These use gas (usually air) as the conveying medium and are particularly suitable for conveying solid particles, such as powders or granules. Material is drawn in or conveyed by pressure within the conveying element through the flow of the conveying gas.

[0010] - Hydraulic conveying devices: These use liquid as the conveying medium and are typically used to transfer liquids or liquid mixtures, such as emulsions or suspensions. Material moves within the conveying element through the flow of the liquid.

[0011] These conveying devices are capable of transporting materials in various forms, such as liquid media, suspensions, powders, or granular solids. These devices are designed to transport materials safely and efficiently through flow generated by pressure differentials.

[0012] This invention was developed for the production of dry electrode mixtures. This is also the preferred application of the mixer according to this invention. However, the mixer can also be used for wet electrode mixtures. The invention will now be described based on the production of dry electrode mixtures. However, it should be understood that all the described features can also be used for wet electrode mixtures.

[0013] According to this invention, the pressure-based conveying device has a conveying channel arranged on or within a scraping device, having an inlet and an outlet, the inlet being located near the bottom of the container. Typically, the scraping device is fixedly arranged and, for example, fixed from above in a top-opening mixing container, which rotates about its axis. On one hand, the scraping device has the task of supporting the mixing process, i.e., picking up the mixture components adhering to the bottom of the container and possibly to the container walls, and returning these components to the actual mixing process. On the other hand, according to this invention, the conveying channel, arranged on or preferably within the scraping device, can be connected, for example, to a vacuum source to draw away the dried electrode mixture via the inlet of the conveying channel. The pressure differential required for conveying is generated only as needed, typically at the end of the mixing process.

[0014] Preferably, the cross-section of the conveying channel is selected such that, under a maximum pressure differential of 1 bar and a mass fraction of 0.3 kg / l to 2.6 kg / l of the mixture (Mischgut), the discharge rate can be at least 10 l / min, preferably at least 50 l / min, and particularly preferably at least 100 l / min.

[0015] To improve the mixing process, in a preferred embodiment, a mixing tool rotatable about its axis is arranged within the mixing container. The distance between the mixing container axis and the mixing tool axis is a ≥ 0, and they are arranged parallel to each other. When a = 0, the mixing tool axis will be exactly on the container axis. This is possible in principle, but in the preferred embodiment, a > 0 is specified. When a = 0, the mixing container is preferably designed to be fixed rather than rotatable.

[0016] In a preferred embodiment, the scraping device is further specified to have a first end and a second end, the first end contacting or being less than 2 mm from the container wall, and the second end being farther from the container wall than the first end. The inlet of the conveying channel is then closer to the second end than the first end, preferably at least twice the distance between the inlet and the first end, and particularly preferably at least four times the distance between the inlet and the second end. Therefore, by further moving the inlet towards the center of the bottom of the mixing container, it is ensured that the electrode mixture is always first removed from the particularly well-mixed area of ​​the mixing container.

[0017] The conveying channel can then extend vertically upward from the first end of the scraping device out of the mixing container. However, in a preferred embodiment, the scraping device also includes a wall section extending from the bottom of the container along the container wall, which contacts or is less than 2 mm from the container wall. The conveying channel can then be guided through or arranged on this wall section.

[0018] This also allows the mixture adhering to the mixing container to be removed from the walls and returned to the mixing process. Therefore, the scraping device functions as both a bottom scraper and a wall scraper. Furthermore, the conveying channels can be directed near the bottom of the mixing container to prevent damage from the mixture. Moreover, the absence of individual channels (immersed in the mixture) on the wall and bottom scrapers would hinder the uniform movement of the mixture, thus deteriorating the mixing results.

[0019] By integrating the conveying channels into the wall scraper and bottom scraper, the mixture is subjected to almost no additional disturbance during material circulation, which results in the reliable and complete removal of the mixture.

[0020] Because the scraping device and the mixing container move relative to each other, the scraping device has an inflow side to which the dried electrode mixture flows during operation due to the rotation direction of the mixing container. In a preferred embodiment, the inlet of the conveying channel is arranged on the inflow side, and preferably also on the side of the scraping device facing the bottom of the container. This ensures that the dried electrode mixture is removed very efficiently through the conveying channel of the pressure-based removal device.

[0021] In another preferred embodiment, the scraping device has a guide lip on its side facing the bottom of the container. This guide lip is preferably made of a plastic material and is arranged and configured such that, during mixer operation, it guides the dry electrode mixture at the bottom of the container toward the inlet of the delivery channel. Thus, for example, the guide lip may surround the inlet of the delivery channel on the side facing the bottom of the container, at least on the side opposite to the inflow side. Therefore, during the rotational movement of the mixing container, the guide lip can hold the dry electrode mixture directly in front of the delivery channel inlet, thereby guiding the electrode mixture into the delivery channel. In a preferred embodiment, the guide lip has a curved section in the portion contacting or less than 2 mm from the bottom of the container.

[0022] Preferably, the conveying channel has a circular cross-section. Advantageously, the scraping device is convexly curved on its side away from the bottom of the container, or is either a gable roof or a single-gable roof. It is important here that even when the filling height of the mixture is low, the mixture components are not allowed to remain on the top side of the scraping device, but rather these mixture components are returned to the mixing process as completely as possible.

[0023] The outlet of the delivery channel can be connected to a vacuum source (i.e., a corresponding pump) so that when the dried electrode mixture is to be removed from the mixing container, the dried electrode mixture can be drawn in through the inlet of the delivery channel and removed from the channel through the outlet.

[0024] In another preferred embodiment, the distance 'a' between the container axis and the mixing tool axis is greater than zero, and the mixing tool has at least one stirring element that contacts the bottom of the container or is less than 2 mm away from the bottom. Similar to a scraper, this stirring element is configured to loosen any mixture that may adhere to the bottom of the container and reintroduce it into the mixing process. As the mixing tool rotates about its axis (spaced apart from the container axis), the stirring element traces a cycloid on the bottom of the container. Here, the stirring element never contacts the container wall, resulting in a circular bottom with an outer ring into which the stirring element never enters. To ensure optimal mixing also occurs within this outer ring, the second end of the scraper should extend at least to the inner edge of the outer ring. Particularly preferably, the inlet of the conveying channel also extends at least to the inner edge of the ring. In a preferred embodiment, the stirring element is arranged such that the axis of rotation of the mixing container lies on the circle traversed by the stirring element as the mixing tool rotates. In another advantageous design, the stirring element is shaped such that, during the rotational motion of the mixing tool, it conveys the mixture outwards to the container wall, where it can be captured by the guide lip of the scraper and guided to the inlet of the conveying channel. This allows for almost complete evacuation of the mixer, even at the center of the mixing container. Here, the stirring element is geometrically designed such that when it contacts the mixture, it deflects most of the mixture radially outwards in the direction of rotation. In a top view, the stirring element may, for example, have a triangular, rhomboid, or trapezoidal cross-section, or consist of inclined cubes.

[0025] Furthermore, it has been shown that it is advantageous for the scraping device to be arranged not entirely radially relative to the container wall. It is also advantageous if the angle α formed by the encirclement of the imaginary line extending through the first and second ends at the point where the imaginary line intersects the circular circumference of the container bottom and the tangent at the circular container bottom is less than 90°. The angle α is preferably between 30° and 60°, and most preferably between 40° and 50°.

[0026] As mentioned above, due to the strong adhesion of the mixture to each other, it has proven advantageous to supply additional air or gas (e.g., dry nitrogen) via a supply channel with an outlet. Here, it is advantageous if the outlet is arranged such that the supplied air flowing out of the outlet points towards the inlet of the conveying channel or towards the inflow-side region located upstream of the inlet of the conveying channel. This allows the dry electrode mixture to be mixed with air (so-called dummy air), further fluidizing it and thus facilitating transport. Therefore, the risk of large clumps of electrode mixture being sucked into the conveying channel and clogging it can be significantly reduced. Attached Figure Description

[0027] Other advantages, features, and possible applications of this invention will become clear from the following description and accompanying drawings of preferred embodiments. In the drawings:

[0028] Figure 1 A schematic cross-sectional view of the first embodiment of the present invention is shown.

[0029] Figure 2 It shows Figure 1 Detailed view of the scraping device according to the embodiment,

[0030] Figure 3 It shows Figure 2 Detailed enlarged image of the scraping equipment.

[0031] Figure 4 Detailed views of alternative implementations of the scraping device are shown, as well as

[0032] Figure 5 A schematic diagram of the mixing container of the mixer according to the present invention, viewed from above, is shown. Detailed Implementation

[0033] Figure 1A schematic cross-sectional view of a first embodiment of the mixer 1 according to the present invention is shown. The mixer 1 includes a mixing container 2 having a circular bottom and a hollow cylinder connected to the bottom and forming the container wall. The container 2 is mounted on a support leg 3 via a rotary bearing 4 and is rotatable about a mixing container axis 5. A mixing tool 17 is arranged inside the mixing container 2, having a series of arms 9 and a downward-pointing stirring element 10 at the lowest arm. In the illustrated embodiment, the stirring element 10 is placed directly on the bottom of the mixing container 2. The mixing tool 17 can be rotated about a mixing tool axis 6 by means of a motor 7 driving a drive belt 8. The mixing tool axis 6 and the mixing container axis 5 are spaced apart by a distance a. When the mixing container 2 and the mixing tool 17 rotate, the mixture (i.e., the dry electrode mixture) can be mixed very uniformly within the mixing container. Removal is achieved by means of a pressure-based conveying device. A conveying device is arranged within a scraping device 11, which extends horizontally from a first end against the container wall to a second end further inward in the radial direction. Furthermore, the scraping device extends upward from the bottom of the container along the container wall in the axial direction of the container. The scraping device has a guide lip 12, which is made of plastic material and rests against the bottom or wall of the container, or at a distance of only 1 / 100 mm, and at most 1 / 10 mm, from the mixing container. Since the guide lip 12 is subjected to high mechanical stress due to direct contact with the bottom of the metal container and / or through material adhering to the container wall and bottom, and is related to the rotational movement of the container, the guide lip 12 is preferably designed as a rigid molded part to avoid bending and tearing of the elastic guide lip. To prevent material from adhering in the gap below the deflector and the mixing container, the guide lip 12 is preferably arranged on the inflow side of the scraping device.

[0034] Here, the entire rotatable container 2 is arranged within a housing 20 fixedly connected to the support legs 3. Preferably, the mixing container has rounded corners at the lower corners where the walls and bottom meet to prevent material from accumulating in the corners.

[0035] Figure 2 A detailed view of the scraping device 11 is shown. A guide lip 12 made of plastic extending along the container wall and bottom can also be seen here. If the mixing container has rounded corners at the lower corners as shown in this embodiment, the guide lip 12 is designed to have corresponding rounded corners at the corners. The guide lip 12 can preferably be designed as a single piece, but it can also be designed as a multi-piece piece. The guide lip is preferably made of a rigid, solid plastic / hard plastic, such as sheet-like PA, UHMW, or PTFE.

[0036] A conveying channel 21 based on pressure is arranged within the scraping device. The conveying channel 21 has an inlet 13 and an outlet 22. The inlet 13 is located on the lower side of the scraping device 11, i.e., the side facing the bottom of the container, and the outlet 22 is located on the side away from the bottom of the container. Furthermore, the inlet 13 is spaced apart from the container wall and is located in the radially innermost section of the scraping device. The outlet 22 is preferably located in the radially outermost section of the scraping device. Specifically, from... Figure 3 The enlarged view shows that the guide lip 12 at the radially inner end of the scraping device 11 is guided rearward from the inflow side and surrounds the inlet 13 at the outflow side and the radially innermost section of the scraping device 11. The annular section at the front of the guide lip 12 is marked with reference numeral 12a. Furthermore, an air supply passage 14 with an outlet 16 can be seen, which supplies air or gas to the area directly in front of the inlet of the conveying channel as needed. In the example shown, the front section 12a of the guide lip 12 has three openings 15. These openings can be, for example, through-holes through which the mixture retained in the annular section 12a of the guide lip 12 can pass during the mixing process, provided that the mixture is not intended to be removed via the inlet 13 of the conveying channel 21, so as to resupply the mixture to the mixing process. Alternatively, the openings 15 can also be additional outlet passages of the air supply passage 14 for mixing air into the mixture to fluidize it, thereby making it easier to draw the mixture away via the inlet 13 of the conveying channel 21.

[0037] but Figure 3 The embodiment shown is not well-suited for certain electrode mixtures because the unmixed mixture is captured in the front section 12a of the guide lip 12 and remains there until it is drawn away, thus this section is not uniformly mixed.

[0038] therefore, Figure 4 Alternative embodiments are shown. Here, the guide lip 12' also surrounds the inlet 13' of the conveying channel with its front section 12a', but the guide lip 12' has a downward-facing opening, i.e., a downward-facing opening on both the side facing the bottom of the container and the inflow side. Figure 3 The embodiments shown and Figure 4 In the embodiments shown, it is also conceivable to omit or shorten the front section 12a or 12a' of the guide lip 12 or 12'.

[0039] Figure 5A schematic top view of the mixing container or its bottom is shown. A mixing tool 17 and a downward-pointing stirring element 10 are visible. The mixing tool 17 rotates about a mixing tool axis spaced apart from the container's axis of rotation. This causes the stirring element 10 to trace so-called cycloidal curves on the bottom of the mixing container, indicated by dashed lines 18. In the illustrated embodiment, as the mixing tool 17 rotates about its tool axis 6, the stirring element 10 extends exactly through the axis of rotation 5 of the mixing container 2.

[0040] As can be seen, an outer ring 19 remains at the bottom of the container, which is not swept by the stirring element 10 of the mixing tool 17. This area is covered by a scraping device 11, which has a first end and a second end. The first end rests against the container wall via a guide lip 12, and the inlet 13 of the conveying channel is arranged in the second end. It can be seen that the scraping device 11 does not extend directly radially inward from the container wall, but is arranged at an angle. Figure 5 An angle α can be seen, which is formed by an imaginary line extending from the first end to the second end of the scraping device 11 and a tangent at the point where the imaginary line intersects the container wall. In the illustrated embodiment, this angle is approximately 45°.

[0041] In principle, the use of the pressure-based conveying device according to this invention is not limited to removing dry electrode mixtures, but can in principle be used for all powdery mixtures. The conveying device can also be used to remove all types of agglomerated or granular bulk materials, provided these materials have sufficiently good flowability. Furthermore, the conveying device can also be used to remove liquids and suspensions, such as battery electrode suspensions, from mixing containers. In this case, air can be omitted. The suspension is then drawn from the mixer by means of a pump connected to the settling tank, or preferably a vacuum pump.

[0042] Reference tag list

[0043] 1. Mixer

[0044] 2 containers

[0045] 3 legs

[0046] 4. Rotary bearings

[0047] 5. Mixing container axis

[0048] 6 Mixed tool axis

[0049] 7 motors

[0050] 8. Transmission belt

[0051] 9. Arm

[0052] 10. Stirring element

[0053] 11 Scraping equipment

[0054] 12, 12' guide lip

[0055] 12a, 12a' Anterior section of guide lip

[0056] 13. Entrance to the conveyor channel

[0057] 14 Gas supply channels

[0058] 15 Openings

[0059] 16. Gas supply channel outlet

[0060] 17. Mixed Tools

[0061] 18. Cycloidal Curve

[0062] 19 Outer Ring

[0063] 20. Outer shell

[0064] 21 Conveying Channel

[0065] 22. Exit of the conveyor channel.

Claims

1. A mixer for producing an electrode mixture, the mixer comprising: A mixing container, the mixing container being rotatable about a mixing container axis, and the mixing container having a rotationally symmetrical container bottom and container walls; A scraping device, movable relative to the mixing container and contacting or at a distance of less than 2 mm from the bottom of the container; and a pressure-based conveying device for removing the electrode mixture from the mixing container. Its features are, The pressure-based conveying device has a conveying channel arranged on or within the scraping device, the conveying channel having an inlet and an outlet, the inlet being arranged near the bottom of the container.

2. The mixer according to claim 1, characterized in that, The bottom of the container is round.

3. The mixer according to claim 1 or 2, characterized in that, A mixing tool is disposed in the mixing container, the mixing tool being rotatable about a mixing tool axis, wherein the mixing container axis and the mixing tool axis are spaced apart by a distance a ≥ 0 and are arranged parallel to each other.

4. The mixer according to claim 1 or 2, characterized in that, The scraping device has a first end and a second end, the first end being in contact with or at a distance of less than 2 mm from the container wall, and the second end being farther from the container wall than the first end, wherein the inlet of the conveying channel is arranged closer to the second end than the first end.

5. The mixer according to claim 4, characterized in that, The distance between the entrance and the first end is at least twice the distance between the entrance and the second end.

6. The mixer according to claim 5, characterized in that, The distance between the entrance and the first end is at least four times the distance between the entrance and the second end.

7. The mixer according to any one of claims 1-2 and 5-6, characterized in that, The scraping device includes a wall section extending from the bottom of the container along the container wall, the wall section contacting the container wall or at a distance of less than 2 mm from the container wall.

8. The mixer according to any one of claims 1-2 and 5-6, characterized in that, The scraping device has an inflow side to which the electrode mixture flows during operation due to the rotation direction of the mixing container, wherein the inlet is arranged on the inflow side and also on the side facing the bottom of the container.

9. The mixer according to any one of claims 1-2 and 5-6, characterized in that, The scraping device has a guide lip on its side facing the bottom of the container. The guide lip is made of plastic and is arranged and configured such that during operation of the mixer, the guide lip guides the electrode mixture at the bottom of the container toward the inlet.

10. The mixer according to claim 8, characterized in that, The scraping device has a guide lip on its side facing the bottom of the container. The guide lip is made of plastic and is arranged and configured such that during operation of the mixer, the guide lip guides the electrode mixture at the bottom of the container toward the inlet.

11. The mixer according to claim 10, characterized in that, The guide lip surrounds the inlet on the side facing the bottom of the container and at least on the side opposite to the inflow side.

12. The mixer according to any one of claims 1-2, 5-6 and 10-11, characterized in that, The conveying channel has a circular cross-section.

13. The mixer according to any one of claims 1-2, 5-6 and 10-11, characterized in that, The scraping device is configured as a convex bend, or a double-sloped roof shape or a single-sloped roof shape on the side opposite to the bottom of the container.

14. The mixer according to any one of claims 1-2, 5-6 and 10-11, characterized in that, The outlet is connected to a vacuum source.

15. The mixer according to claim 4, characterized in that, A mixing tool is disposed in the mixing container, the mixing tool being rotatable about its axis, wherein the distance a between the axis of the mixing container and the axis of the mixing tool is greater than 0 and they are arranged parallel to each other, and the mixing tool has at least one stirring element that contacts the bottom of the container or is at a distance of less than 2 mm from the bottom of the container, wherein during the rotational movement of the mixing container and the rotational movement of the mixing tool, the stirring element never enters the outer ring of the bottom of the container, and the second end extends at least to the inner edge of the ring, wherein the inlet extends at least to the inner edge of the ring.

16. The mixer according to claim 4, characterized in that, An imaginary line extending through the first end and the second end intersects the circular circumference of the bottom of the container at the point where the imaginary line intersects with the tangent at the circular bottom of the container, forming an angle α, the angle α being less than 90°.

17. The mixer according to claim 16, characterized in that, The angle α is between 30° and 60°.

18. The mixer according to claim 17, characterized in that, The angle α is between 40° and 50°.

19. The mixer according to any one of claims 1-2, 5-6, 10-11 and 15-18, characterized in that, It is equipped with a gas supply channel with an air outlet.

20. The mixer according to claim 19, characterized in that, The air outlet is arranged such that the supply air flowing out of the air outlet is directed toward the inlet of the conveying channel or toward an inflow-side region located upstream of the inlet of the conveying channel.

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