High shear mixing device

Abstract

The present invention provides a high-shear mixing device comprising a first screw kneader and a second screw kneader, each of which rotates in the opposite direction with its blade overlapping the other screw kneader, and wherein one of three blades provided in each of the first and second screw kneaders is an open-type blade having a through-hole formed in the center except for the outer periphery of the surface in the direction of rotation, and the remaining two blades are closed-type blades with the surface in the direction of rotation closed without a through-hole, and the open-type blade provided in the first screw kneader overlaps between two closed-type blades provided in the second screw kneader, and the open-type blade provided in the second screw kneader overlaps between two closed-type blades provided in the first screw kneader.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0098953 filed on July 28, 2023, and all the contents disclosed in the corresponding Korean patent application are included as part of this specification.

[0002] The present invention relates to a high-shear mixing device, particularly a high-shear mixing device used for manufacturing dry electrodes for secondary batteries.

Background Art

[0003] Agitation devices are used for manufacturing various pastes and for finely mixing various chemical raw materials such as inks, pigments, paints, cosmetics, pharmaceuticals, and coatings, as well as various coating agents, abrasives, ceramics, or metal powders, or various electronic materials (PZT, dielectrics, MLCC, ferrite, display materials), etc. As such agitation devices, particularly, planetary mixers that use blades and rotors to agitate highly viscous substances in a container are widely used.

[0004] Such planetary mixers are also used in manufacturing electrodes for secondary batteries. That is, with the expansion and development of the applications of secondary batteries, improvements in reducing the resistance, increasing the capacity, and improving the mechanical properties and productivity of electrodes have been continuously required. Along with this, the need for high-shear mixing for electrode manufacturing mixtures has also been increasing.

[0005] Specifically, recently, a technology for manufacturing a dry electrode film by mixing an active material, a binder, and a conductive material without a liquid medium such as a solvent or a dispersion medium and then passing the powder mixture through a rolling roll has been actively developed, and high-shear mixing is applied to such electrode manufacturing.

[0006] In other words, the above-mentioned method uses a binder called a "fibrillizable binder" or "fibril-forming binder." When high-shear mixing is applied to a mixture containing the binder, the binder is micro-fibrillated to bind the active material and the conductive material together.

[0007] However, in such high-shear mixing processes, the fibrillated polymer becomes like chewing gum, placing a heavy load on the high-shear mixing equipment, which often leads to damage to the equipment. On the other hand, if the shear force is reduced to prevent such damage to the equipment, the fibrillated polymer does not form fibers properly. Therefore, due to these problems, it is extremely difficult to construct high-shear mixing equipment as a large-capacity mass production device for manufacturing dry electrodes for secondary batteries. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Korean Published Patent No. 10-2011-0117902 [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention was devised to solve the aforementioned problems of the prior art, and aims to provide a high-shear mixing device that can efficiently mix materials without generating an overload when mixing materials under high shear force.

[0010] In particular, the objective is to provide a high-shear mixing apparatus that can efficiently microfiberize a mixture for manufacturing dry electrodes containing a fibrillated polymer as a binder without causing overload during high-shear mixing. [Means for solving the problem]

[0011] To achieve the above objective, the present invention, First screw kneader and second screw kneader, A first rotation drive device for rotating the first screw kneader and a second rotation drive device for rotating the second screw kneader, The first rotation drive device and the second rotation drive device are installed in a rotational drive device, The drive unit body on which the aforementioned orbital drive device is installed, Mixing tank and Includes, Each of the first and second screw kneaders includes a shaft, one end of which is connected to the respective self-rotating drive device, and three blades, one end of which is fixed to the shaft and which have bodies that are spirally bent along the longitudinal direction of the shaft. Each of the aforementioned screw kneaders rotates in opposite directions to each other, with the blades of the other screw kneaders overlapping each other. Of the three blades provided in each of the first and second screw kneaders, one blade is an open-type blade with a through hole formed in the center of the rotation direction surface, excluding the outer circumference, while the remaining two blades are all closed-type blades with the rotation direction surface closed without a through hole. The open blades of the first screw kneader overlap between the two closed blades of the second screw kneader, and the open blades of the second screw kneader overlap between the two closed blades of the first screw kneader, providing a high-shear mixing device.

[0012] In one embodiment of the present invention, the high-shear mixing apparatus is characterized in that the screw kneader rotates on its own axis by the rotation drive device and revolves around an orbit by the orbit drive device.

[0013] In one aspect of the present invention, the through holes formed in each blade can be formed to extend to the outer peripheral surface of the shaft.

[0014] In one aspect of the present invention, the rotational direction end portions of the blades provided in the first screw kneader and the second screw kneader may rotate while maintaining a separation distance of 1 mm to 10 mm from other screw kneaders.

[0015] In one aspect of the present invention, the high-shear mixing device can be used for high-shear mixing of a mixture for manufacturing a dry electrode containing a fibrillated polymer as a binder, and can be used for the purpose of microfibrillating the fibrillated polymer.

Effects of the Invention

[0016] The high-shear mixing device according to one aspect of the present invention provides an effect that it is possible to efficiently mix substances without generating an overload when mixing substances by a high-shear force. Further, due to such an effect, damage to the device is minimized, and thus the device can be configured with a large capacity.

[0017] In particular, the high-shear mixing device according to one aspect of the present invention provides an effect that it is possible to efficiently microfibrillate the polymer without generating an overload when performing high-shear mixing of a mixture for manufacturing a dry electrode containing a fibrillated polymer as a binder.

Brief Description of the Drawings

[0018] [Figure 1] It is a perspective view showing an embodiment of the high-shear mixing device of the present invention. [Figure 2] It is a perspective view showing an embodiment of the screw kneader provided in the high-shear mixing device of the present invention. [Figure 3] It is a diagram showing a simplified overlapping shape of the screw kneader shown in FIG. 2. [Figure 4]It is a perspective view showing an overlapping shape of a screw feeder of a comparative example having an overlapping structure different from that of the screw feeder of the present invention. [Figure 5] It is a diagram showing a simplified overlapping shape of the screw feeder shown in FIG. 4.

Mode for Carrying Out the Invention

[0019] Hereinafter, for the convenience of those with ordinary knowledge in the technical field to which the present invention pertains to easily implement, embodiments of this invention will be described in detail with reference to the attached drawings. However, the present invention can be embodied in various different forms and is not limited to the embodiments described herein. Throughout the specification, similar parts are denoted by the same reference numerals.

[0020] FIG. 1 is a perspective view showing an embodiment of a high-shear mixing device 100 of the present invention, FIG. 2 is a perspective view showing an embodiment of a screw feeder provided in the high-shear mixing device of the present invention, and FIG. 3 is a diagram showing a simplified overlapping shape of the screw feeder shown in FIG. 2.

[0021] A high-shear mixing apparatus 100 according to one embodiment of the present invention, as shown in Figure 1, includes a first screw kneader 10 and a second screw kneader 10', a first rotation drive device 21 for rotating the first screw kneader 10 and a second rotation drive device 21' for rotating the second screw kneader 10', a revolution drive device 23 on which the first rotation drive device 21 and the second rotation drive device 21' are installed to rotate, a drive device body 20 on which the revolution drive device 23 is installed, and a mixing tank 30. Each of the first screw kneader 10 and the second screw kneader 10' includes a shaft 13, 13' with one end connected to the rotation drive devices 21, 21', and three blades 15, 15' with one end fixed to the shaft and having a body that is spirally bent along the longitudinal direction of the shaft. Each of the aforementioned screw kneaders 10, 10' rotates in opposite directions to the other screw kneaders, with their blades 15, 15' overlapping each other, as shown in Figure 2.

[0022] As shown in Figures 2 and 3, one of the three blades provided on each of the first screw kneader 10 and the second screw kneader 10' is an open-type blade with through holes 18, 18' formed in the center of the rotation direction surface excluding the outer circumference, while the remaining two blades are all closed-type blades with the rotation direction surface closed without through holes. The open-type blade provided on the first screw kneader 10 overlaps with the two closed-type blades provided on the second screw kneader 10', as shown in Figures 2 and 3, and the open-type blade provided on the second screw kneader 10' overlaps with the two closed-type blades provided on the first screw kneader 10.

[0023] Furthermore, when the screw kneader rotates on its own axis and engages with the surrounding components, it has the characteristic of revolving in the opposite direction to the direction in which the mixture is discharged.

[0024] The high-shear mixing apparatus 100 of the present invention is particularly suitable for use in the manufacture of dry electrodes for secondary batteries. Specifically, in the manufacture of dry electrodes for secondary batteries, a mixture containing an active material, a conductive material, and a fibrillated binder such as PTFE is mixed under high shear to fibrousize the binder, and the mixture thus produced is manufactured into a free-standing electrode through a rolling process. In such a high-shear mixing process, the fibrillated polymer becomes like chewing gum, placing a large load on the high-shear mixing apparatus, which often causes damage to the apparatus. On the other hand, if the shear force is reduced to prevent such damage to the apparatus, the fibrillated polymer does not fibrousize properly. Therefore, due to these problems, it is very difficult to construct a high-shear mixing apparatus as a large-capacity mass production apparatus for the manufacture of dry electrodes for secondary batteries.

[0025] However, when using the high-shear mixing apparatus of the present invention, the dispersibility of the mixture is greatly improved, and the fibrillated polymer is effectively microfibrillated without placing a heavy load on the apparatus. Therefore, the high-shear mixing apparatus of the present invention can be suitably used for high-shear mixing in the manufacture of dry electrodes for secondary batteries, and it is possible to construct it as a large-capacity mass production apparatus.

[0026] When using the high-shear mixing apparatus of the present invention, it is possible to continuously apply a high shear force of 10 to 500 N·m to a mixture containing the active material, conductive material, and a fibrillated binder such as PTFE, while producing a mixture for freestanding electrodes of excellent quality without damaging the apparatus. Furthermore, when such a mixture is rolled, a freestanding electrode with excellent tensile strength is produced, and when such electrodes are used to construct a battery, the battery life is greatly improved.

[0027] In particular, the inventors discovered that, as shown in Figures 4 and 5, when the open blades provided in the first screw kneader 10 overlap with the open blades and closed blades provided in the second screw kneader 10', and when the open blades provided in the second screw kneader 10' overlap with the open blades and closed blades provided in the first screw kneader 10, the open blades overlap with each other, and the through holes 18, 18' overlap with each other, and the material to be mixed passes through the through holes 18, 18' without being subjected to shear force, the high shear mixing effect is reduced, and the inventors completed the present invention to improve this.

[0028] In other words, the inventors discovered that when the open blades provided in the first screw kneader 10 overlap between the two closed blades provided in the second screw kneader 10', as shown in Figures 2 and 3, and the open blades provided in the second screw kneader 10' overlap between the two closed blades provided in the first screw kneader 10, the high shear mixing effect increases, and as a result, when electrodes are manufactured using the mixture produced by the high shear mixing device, the life characteristics of the lithium secondary battery are improved, thus completing the present invention.

[0029] In one embodiment of the present invention, the blades 15 and 15' have one end of their body connected to the shaft in a longitudinal spiral manner, and the body surface in the rotational direction may have a shape that is spirally bent along the longitudinal direction of the shaft to match this.

[0030] In one embodiment of the present invention, the bodies of the blades 15, 15' may be circular plates with one end cut off, elliptical plates with one end cut off, or polygonal plates, which are spirally bent along the longitudinal direction of the shafts 13, 13'. In the case of the circular and elliptical shapes, the cut portion may be spirally connected to the shaft in the longitudinal direction, and in the case of the polygonal shape, one side may be spirally connected to the shaft in the longitudinal direction. Furthermore, the bodies may be partially modified versions of the exemplified shapes to be advantageous for high-shear mixing. In the case of polygons, they may be triangular, quadrilateral, pentagonal, hexagonal, or other polygonal shapes, and are not particularly limited. However, quadrilateral shapes can be used more preferably.

[0031] In one embodiment of the present invention, the high-shear mixing device 100 is characterized in that the screw kneaders 10, 10' rotate on their own axis by the rotation drive devices 21, 21' and revolve on their own axis by the revolving drive device 23. Furthermore, when the screw kneaders rotate and engage with each other, they revolve in the opposite direction to the direction in which the mixture is discharged. As described above, when the rotation and revolving of the screw kneaders occur simultaneously, the mixture can be mixed more uniformly and high-shear mixing can be performed more efficiently, which is preferable.

[0032] The through holes 18, 18' formed in the blades 15, 15' of the first screw kneader 10 and the second screw kneader 10' shown in Figure 2 represent a configuration in which the through holes are formed in the center of the blade excluding the outer circumference of the rotational direction surface, and in particular, a configuration in which the through holes are formed extending to the outer circumference of the shaft.

[0033] In one embodiment of the present invention, the area of ​​the through-holes 18, 18' can be formed to be 40-80%, more preferably 50-70%, of the total area of ​​the rotational direction surface of the blade body. When through-holes are formed within this range, it is preferable because the mixture can be effectively mixed without placing a high load on the apparatus. In particular, within the above range, the fibrillated polymer can also be effectively microfibrillated.

[0034] When the high-shear mixing apparatus includes a first screw kneader 10 and a second screw kneader 10' in the configurations shown in Figures 2 and 3, the dispersibility of the mixture is greatly improved, and the fiberization of fibrillated polymers such as PTFE can be effectively achieved. Furthermore, the apparatus is not subjected to a large load during the fiberization process of fibrillated polymers such as PTFE. Therefore, the high-shear mixing apparatus of the present invention having the above-described structure can be suitably used for high-shear mixing for the manufacture of dry electrodes for secondary batteries, and it is possible to construct a large-capacity mass production apparatus.

[0035] In particular, when a mixture containing an active material, a conductive material, and a fibrillated binder such as PTFE is mixed under high shear, and the mixed mixture is rolled to produce a dry freestanding electrode, the tensile strength of the freestanding electrode is greatly improved, and such a dry freestanding electrode has the effect of greatly improving the lifespan of a secondary battery.

[0036] In one embodiment of the present invention, it is preferable that the rotational ends of the blades provided in the first screw kneader 10 and the second screw kneader 10' rotate while maintaining a separation distance of 1 mm to 10 mm, preferably 1 mm to 5 mm, and more preferably 1 mm to 3 mm from other screw kneaders. With such a separation distance, the fibrillated polymer such as PTFE is effectively fiberized, and a large load that could damage the high-shear mixing apparatus is not placed on it, making it possible to efficiently manufacture freestanding electrodes of excellent quality.

[0037] In one embodiment of the present invention, the rotational speed of the first screw kneader 10 and the second screw kneader 10' may more preferably be 10 rpm to 500 rpm, preferably 10 rpm to 300 rpm, and more preferably 10 rpm to 150 rpm. When high-shear mixing is performed at such speeds, the fibrillated polymer such as PTFE is effectively fiberized, and the high-shear mixing apparatus is not subjected to a large load that could damage the apparatus, making it possible to efficiently manufacture freestanding electrodes of excellent quality. The orbital speed may also be 5 rpm to 100 rpm, preferably 10 rpm to 50 rpm, and more preferably 10 rpm to 30 rpm.

[0038] The present invention will be described in detail below with reference to examples. However, the examples of the present invention can be modified in various different forms, and the scope of the present invention should not be construed as being limited to the examples detailed below. The examples of the present invention are provided to give a more complete explanation of the present invention to a person of average knowledge in the industry.

[0039] Example 1: Manufacturing of free-standing electrodes using a high-shear mixing apparatus A mixture for a free-standing electrode was prepared by mixing 95.5% or 97% by weight of NCM powder (product name: GL80, LG Chem), which is a positive electrode active material particle with an average particle size of 10 μm, 1.5% by weight of Li250 (Denka) as a conductive material, and PTFE (1.5% or 3% by weight) as a binder.

[0040] The high-shear mixing apparatus of the present invention was configured as shown in Table 1 below, and the mixture was subjected to high-shear mixing for 2 minutes by applying a shear force of 100 N·m at 90°C, with rotation at 30 rpm and revolution at 15 rpm.

[0041] Next, the kneaded secondary mixture produced as described above was manufactured into a 200 μm thick freestanding film using a two-roll mill (MR-3, Inoue Co.) at 100°C.

[0042] Subsequently, the freestanding film was placed on one surface of a 20 μm thick primer-coated aluminum foil (manufactured by Dongwon Systems) current collector and bonded via a lamination roll maintained at 120°C to produce the positive electrode.

[0043] [Table 1]

[0044] (Note) Overlap: The rotational ends of the blades on the first and second screw kneaders maintain a 3mm separation from the other screw kneader.

[0045] Experimental Example 1: Measurement of Tensile Strength of Freestanding Electrodes The tensile strength of the freestanding electrodes manufactured in Examples 1-2 and Comparative Examples 1-2 was measured using a LLOYD UTM device with a 180-degree peel test method at a rate of 50 mm / min. During the measurement, the maximum force applied up to the point where the film did not break was evaluated as the strength of the freestanding film, and the measurement results are shown in Table 2 below.

[0046] [Table 2]

[0047] Experimental Example 2: Evaluation of Battery Life Characteristics (1) Manufacturing of lithium secondary batteries A coin-type half-cell was manufactured using the positive electrodes produced in Examples 1-2 and Comparative Examples 1-2, lithium metal as the counter electrode, and an electrolyte containing 1M LiPF6 in a solvent of EC:DMC:DEC (volume ratio of 1:2:1).

[0048] (2) Evaluation of the capacity retention rate of lithium secondary batteries The coin-type half-cell manufactured as described above was subjected to 100 charge-discharge cycles at 25°C under voltage ranges of 3 to 4.3V and current conditions of 0.33C rate. The capacity retention rate for 100 discharge cycles relative to the discharge capacity was then calculated, and the results are shown in Table 3 below.

[0049] [Table 3]

[0050] Although the present invention has been described in relation to the preferred embodiments mentioned above, various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the appended claims include such modifications and variations insofar as they fall within the spirit of the invention. [Explanation of Symbols]

[0051] 10: First Screw Kneader 10': Second screw kneader 13, 13': Shaft 15, 15': Blade 18,18': Through hole 20: Drive unit body 21: First rotation drive device 21': Second rotation drive unit 23: Orbital drive mechanism 30: Mixing tank

Claims

1. First screw kneader and second screw kneader, A first rotation drive device for rotating the first screw kneader and a second rotation drive device for rotating the second screw kneader, The first rotation drive device and the second rotation drive device are installed in a rotational drive device, The drive unit body on which the aforementioned orbital drive device is installed, Mixing tank and Includes, Each of the first and second screw kneaders includes a shaft, one end of which is connected to each of the self-rotating drive devices, and three blades, one end of which is fixed to the shaft and which have bodies that are spirally bent along the longitudinal direction of the shaft. Each screw kneader rotates in opposite directions to the other screw kneaders, with their blades overlapping each other. Of the three blades provided in each of the first and second screw kneaders, one blade is an open-type blade with a through hole formed in the center of the rotation direction surface excluding the outer circumference, while the remaining two blades are all closed-type blades with the rotation direction surface closed without a through hole. A high-shear mixing device in which the open blades of the first screw kneader overlap between the two closed blades of the second screw kneader, and the open blades of the second screw kneader overlap between the two closed blades of the first screw kneader.

2. The high-shear mixing apparatus according to claim 1, characterized in that the first screw kneader and the second screw kneader rotate on their own axis by the first rotation drive device and the second rotation drive device, respectively, and revolve by the revolving drive device.

3. The high-shear mixing apparatus according to claim 1, characterized in that the through-holes formed in each blade extend to the outer circumferential surface of the shaft.

4. The high-shear mixing apparatus according to claim 1, characterized in that the rotational ends of the blades provided in the first screw kneader and the second screw kneader rotate while maintaining a separation distance of 1 mm to 10 mm from other screw kneaders.

5. A high-shear mixing apparatus according to any one of claims 1 to 4, characterized in that it is used for high-shear mixing of a dry electrode manufacturing mixture containing a fibrillated polymer as a binder, and is used for the purpose of microfiberizing the fibrillated polymer.

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