High Shear Mixing Equipment

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 contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a high shear mixing device, and more particularly to a high shear mixing device used in the manufacture of dry electrodes for secondary batteries. [Background technology]

[0003] Mixing devices are used in various paste manufacturing equipment and to finely mix chemical raw materials such as inks, pigments, paints, cosmetics, pharmaceuticals, and coating materials, as well as various coating agents, abrasives, ceramic or metal powders, and various electronic materials (PZT, dielectrics, MLCC, Ferrite, display materials), etc. Planetary mixers, which use blades and rotors to mix high-viscosity materials in a container, are particularly commonly used as mixers for mixing high-viscosity materials.

[0004] The planetary mixer is also used in the production of electrodes for secondary batteries. That is, with the expansion and development of the applications of secondary batteries, there is a continuous demand for improvements in electrodes, such as lower resistance, higher capacity, improved mechanical properties, and improved productivity, and accordingly, there is an increasing need for high-shear mixing for electrode production mixtures.

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

[0006] That is, in the above-mentioned method, binders called "fibrillizable binders" or "fibril-forming binders" are used, and when a mixture containing the binder is subjected to high shear mixing, the binder is microfibrillated to bind the active material and the conductive material.

[0007] However, during this high-shear mixing process, the fibrillated polymer becomes like chewing gum, placing a heavy load on the high-shear mixer, which often results in damage to the mixer. Meanwhile, if the shear force is reduced to prevent damage to the mixer, the fibrillated polymer is not properly fibrillated. Therefore, due to these issues, it is extremely difficult to build a high-shear mixer as a large-capacity mass-production device for the manufacture of dry electrodes for secondary batteries. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-2011-0117902 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been devised to solve the above-mentioned problems of the prior art, and aims to provide a high shear mixer that can efficiently mix materials without causing overload when mixing materials with high shear force.

[0010] In particular, the object of the present invention is to provide a high-shear mixing device that can efficiently microfiberize a polymer without generating an overload when high-shear mixing a mixture for manufacturing a dry electrode containing a fibrillating polymer as a binder. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides a first screw kneader and a second screw kneader; a first rotation drive device that rotates the first screw kneader and a second rotation drive device that rotates the second screw kneader; a revolution drive device on which the first rotation drive device and the second rotation drive device are rotatably installed; a drive unit main body in which the revolution drive unit is installed; A mixing tank; Including, Each of the first screw kneader and the second screw kneader includes a shaft, one end of which is connected to each of the rotation drive devices, and three blades, one end of which is fixed to the shaft and has a body bent in a spiral shape along the longitudinal direction of the shaft; The screw kneaders rotate in opposite directions to each other with their blades overlapping each other, One of the 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 rotation direction surface, and the remaining two blades are closed-type blades having a closed rotation direction surface without a through-hole, The open-type blade of the first screw kneader overlaps between two closed-type blades of the second screw kneader, and the open-type blade of the second screw kneader overlaps between two closed-type blades of the first screw kneader, thereby providing a high-shear mixing device.

[0012] In one aspect of the present invention, the high shear mixing device has a feature in which the screw kneader rotates on its axis by the rotation drive device and simultaneously revolves by the revolution drive device.

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

[0014] In one embodiment of the present invention, the ends of the blades in the rotation direction of the first and second screw kneaders may rotate while maintaining a distance of 1 mm to 10 mm from the other screw kneaders.

[0015] In one aspect of the present invention, the high shear mixing device is used for high shear mixing of a mixture for manufacturing a dry electrode containing a fibrillating polymer as a binder, and can be used to microfiberize the fibrillating polymer. [Effects of the Invention]

[0016] The high shear mixer according to one aspect of the present invention provides the advantage of being able to efficiently mix materials without overloading when mixing materials using high shear force, and also minimizes damage to the device, allowing for a large capacity configuration.

[0017] In particular, the high shear mixing device according to one aspect of the present invention provides the effect of efficiently microfibrillating the polymer without generating overload during high shear mixing of a mixture for manufacturing a dry electrode containing a fibrillating polymer as a binder. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view showing one embodiment of the high shear mixing device of the present invention. FIG. [Figure 2] FIG. 1 is a perspective view showing one embodiment of a screw kneader provided in the high shear mixing apparatus of the present invention. [Figure 3] FIG. 3 is a simplified diagram showing the overlapping shape of the screw kneader shown in FIG. 2. [Figure 4]FIG. 2 is a perspective view showing the overlap shape of a screw kneader of a comparative example having an overlap structure different from that of the screw kneader of the present invention. [Figure 5] FIG. 5 is a simplified diagram showing the overlapping shape of the screw kneader shown in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Like reference numerals are used throughout the specification to refer to like parts.

[0020] FIG. 1 is a perspective view showing one embodiment of the high shear mixing apparatus 100 of the present invention, FIG. 2 is a perspective view showing one embodiment of a screw kneader provided in the high shear mixing apparatus of the present invention, and FIG. 3 is a simplified view showing the overlapping shape of the screw kneader shown in FIG. 2.

[0021] 1, a high shear mixer 100 according to one embodiment of the present invention includes a first screw kneader 10 and a second screw kneader 10', a first rotation drive 21 for rotating the first screw kneader 10 and a second rotation drive 21' for rotating the second screw kneader 10', a revolution drive 23 on which the first rotation drive 21 and the second rotation drive 21' are rotatably installed, a drive unit body 20 on which the revolution drive 23 is installed, and a mixing tank 30. The first screw kneader 10 and the second screw kneader 10' each include a shaft 13, 13' connected at one end to the rotation drive 21, 21', and three blades 15, 15' fixed at one end to the shaft and having a body spirally curved along the longitudinal direction of the shaft. As shown in FIG. 2, the screw kneaders 10, 10' rotate in opposite directions to each other with the blades 15, 15' overlapping with the other screw kneaders.

[0022] As shown in FIGS. 2 and 3, one of the three blades provided in each of the first screw kneader 10 and the second screw kneader 10′ is an open-type blade having a through-hole 18, 18′ 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 having a closed surface in the direction of rotation without a through-hole. As shown in FIGS. 2 and 3, the open-type blade provided in the first screw kneader 10 overlaps between the two closed-type blades provided in the second screw kneader 10′, and the open-type blade provided in the second screw kneader 10′ overlaps between the two closed-type blades provided in the first screw kneader 10.

[0023] Furthermore, when the screw kneader rotates and engages with the rotating members, it revolves in the opposite direction to the direction in which the mixture is discharged.

[0024] The high-shear mixer 100 of the present invention is particularly suitable for use in the manufacture of dry electrodes for secondary batteries. That is, during the manufacture of dry electrodes for secondary batteries, a mixture containing an active material, a conductive material, and a fibrillating binder such as PTFE is subjected to high-shear mixing to fiberize the binder, and the resulting mixture is then rolled to form a free-standing electrode. During this high-shear mixing process, the fibrillated polymer becomes like chewing gum, placing a heavy load on the high-shear mixer, often resulting in damage to the mixer. Meanwhile, reducing the shear force to prevent damage to the mixer results in poor fiberization of the fibrillated polymer. Therefore, due to these issues, it is extremely difficult to build a high-shear mixer as a large-capacity mass-production device for the manufacture of dry electrodes for secondary batteries.

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

[0026] Using the high-shear mixer of the present invention, a high shear force of 10 to 500 N·m can be continuously applied to a mixture containing the active material, conductive material, and a fibrillating binder such as PTFE, while producing a high-quality mixture for a free-standing electrode without damaging the mixer. Furthermore, when such a mixture is rolled, a free-standing electrode with excellent tensile strength is produced, and when such an electrode is used to construct a battery, the battery's lifespan is significantly improved.

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

[0028] That is, the inventors discovered that when the open-type blades of the first screw kneader 10 overlap between the two closed-type blades of the second screw kneader 10' as shown in Figures 2 and 3, and the open-type blades of the second screw kneader 10' overlap between the two closed-type blades of the first screw kneader 10, the high shear mixing effect is increased, and therefore, when an electrode is manufactured using the mixture produced in the high shear mixer, the life characteristics of the lithium secondary battery are improved, thereby completing the present invention.

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

[0030] In one embodiment of the present invention, the body of the blade 15, 15' may be a circular plate with one end cut, an oval plate with one end cut, or a polygonal plate, bent in a spiral shape along the longitudinal direction of the shaft 13, 13'. In the case of the circular and oval shapes, the cut portion may be connected to the shaft in a spiral shape in the longitudinal direction, and in the case of the polygonal shape, one side may be connected to the shaft in a spiral shape in the longitudinal direction. The body may also be a shape that is partially modified from the above-mentioned shapes to be advantageous for high-shear mixing. The polygonal shape may be a triangle, square, pentagon, hexagon, or other polygonal shape, but is not limited thereto. However, a square shape is more preferable.

[0031] In one embodiment of the present invention, the high shear mixer 100 has a feature in which the screw kneaders 10, 10' rotate on their axes by the rotation drivers 21, 21' and simultaneously revolve by the revolution driver 23. Furthermore, when the screw kneaders rotate on their axes and engage with each other, they revolve in the opposite direction to the direction in which the mixture is discharged. When the screw kneaders simultaneously rotate and revolve as described above, the mixture is 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 FIG. 2 are formed in the center of the blade in the direction of rotation, excluding the outer periphery, and in particular, the through holes are formed extending to the outer periphery of the shaft.

[0033] In one embodiment of the present invention, the area of ​​the through-holes 18, 18' may be 40 to 80%, more preferably 50 to 70%, of the total area of ​​the surface of the blade body in the direction of rotation. Forming through-holes within this range is preferred because the mixture is effectively mixed without placing a heavy load on the device. In particular, within this range, the fibrillating polymer can be effectively microfibrillated.

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

[0035] In particular, when a dry freestanding electrode is manufactured by subjecting a mixture containing an active material, a conductive material, and a fibrillating binder such as PTFE to high shear mixing and then rolling the mixed mixture, the tensile strength of the freestanding electrode is significantly improved, and such a dry freestanding electrode provides the effect of significantly improving the lifespan of a secondary battery.

[0036] In one embodiment of the present invention, the ends of the blades in the first screw kneader 10 and the second screw kneader 10' in the direction of rotation are preferably spaced apart from the other screw kneaders by 1 mm to 10 mm, preferably 1 mm to 5 mm, and more preferably 1 mm to 3 mm. This distance ensures effective fiberization of fibrillating polymers such as PTFE, and prevents the high-shear mixer from being subjected to a large load that could damage the device, making it possible to efficiently produce high-quality freestanding electrodes.

[0037] In one embodiment of the present invention, the rotation speed of the first screw kneader 10 and the second screw kneader 10' may 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 these speeds, fibrillation of a fibrillating polymer such as PTFE is effectively achieved, and a large load that could damage the high-shear mixing device is not applied, making it possible to efficiently produce high-quality freestanding electrodes. Furthermore, the revolution speed may be 5 rpm to 100 rpm, preferably 10 rpm to 50 rpm, and more preferably 10 rpm to 30 rpm.

[0038] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples according to 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 more completely explain the present invention to those skilled in the art.

[0039] Example 1: Fabrication of free-standing electrodes using a high shear mixing device A mixture for a freestanding electrode was prepared by mixing 95.5 wt % or 97 wt % 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 wt % of Li250 (Denka) as a conductive material, and 1.5 wt % or 3 wt % of PTFE as a binder.

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

[0041] Next, the kneaded secondary mixture prepared above was processed into a free-standing film having a thickness of 200 μm using a two-roll mill (MR-3, Inoue Co., Ltd.) at 100° C.

[0042] Then, the free-standing film was placed on one side of a 20 μm-thick primer-coated aluminum foil (manufactured by Dongwon Systems Co., Ltd.) current collector and bonded via a lamination roll maintained at 120° C. to prepare a positive electrode.

[0043] [Table 1]

[0044] (Note) Overlap: The ends of the blades in the first and second screw kneaders in the direction of rotation are kept 3 mm apart from the other screw kneaders.

[0045] Experimental Example 1: Measurement of the tensile strength of a free-standing electrode The tensile strength of the free-standing electrodes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was measured using a LLOYD UTM device at 50 mm / min using a 180° peel test method. The maximum force applied until the film did not break during the test was evaluated as the strength of the free-standing film, and the measurement results are shown in Table 2 below.

[0046] [Table 2]

[0047] Experimental example 2: Battery life characteristic evaluation (1) Manufacture of lithium secondary batteries Coin-type half-cells were fabricated using the positive electrodes prepared in Examples 1 and 2 and Comparative Examples 1 and 2, lithium metal as a counter electrode, and an electrolyte containing 1M LiPF in a solvent of EC:DMC:DEC (volume ratio 1:2:1).

[0048] (2) Capacity retention rate evaluation of lithium secondary batteries The prepared coin-type half battery was charged and discharged 100 times at 25°C under the conditions of a voltage range of 3 to 4.3 V and a current rate of 0.33 C, and then the capacity retention rate after 100 discharges relative to the capacity of one discharge was calculated, and the results are shown in Table 3 below.

[0049] [Table 3]

[0050] Although the present invention has been described in connection with the preferred embodiments set forth above, various modifications and variations can be made thereto without departing from the spirit and scope of the invention, and it is therefore intended by the appended claims to cover all such modifications and variations as fall within the spirit and scope 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 device 23: Revolution drive unit 30: Mixing tank

Claims

1. a first screw kneader and a second screw kneader; a first rotation drive device that rotates the first screw kneader and a second rotation drive device that rotates the second screw kneader; a revolution drive device on which the first rotation drive device and the second rotation drive device are rotatably installed; a drive unit main body in which the revolution drive unit is installed; A mixing tank; Including, Each of the first screw kneader and the second screw kneader includes a shaft, one end of which is connected to each rotation drive device, and three blades, one end of which is fixed to the shaft and has a body bent in a spiral shape along the longitudinal direction of the shaft; Each screw kneader rotates in the opposite direction to the other screw kneaders with its blades overlapping each other. One of the 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 a surface in the direction of rotation, and the remaining two blades are closed-type blades having a surface in the direction of rotation closed without a through-hole, A high shear mixing device in which the open-type blade of the first screw kneader overlaps between two closed-type blades of the second screw kneader, and the open-type blade of the second screw kneader overlaps between two closed-type blades of the first screw kneader.

2. 2. The high shear mixer according to claim 1, wherein the first screw kneader and the second screw kneader rotate on their axes by the first rotation drive device and the second rotation drive device, respectively, and simultaneously revolve by the revolution drive device.

3. 2. The high shear mixer according to claim 1, wherein the through holes formed in each blade extend to the outer circumferential surface of the shaft.

4. 2. The high shear mixer according to claim 1, wherein the ends of the blades of the first and second screw kneaders rotate at a distance of 1 mm to 10 mm from each other.

5. 5. The high shear mixing device according to claim 1, wherein the high shear mixing device is used for high shear mixing of a mixture for producing a dry electrode containing a fibrillating polymer as a binder, and for microfibrillating the fibrillating polymer.

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