High-shear mixing apparatus

Abstract

The present invention provides a high-shear mixing apparatus having a first screw kneader and a second screw kneader, wherein the respective screw kneaders rotate in opposite directions while a blade thereof overlaps that of the other screw kneader, and, from among three blades provided in each of the first screw kneader and the second screw kneader, one is an open blade having a through-hole formed in a central portion that excludes the outer peripheral portions of the sides thereof in the rotational direction and the other two blades all are closed blades of which the sides in the rotational direction are closed without a through-hole, wherein the open blade provided in the first screw kneader overlaps between the two closed blades provided in the second screw kneader and the open blade provided in the second screw kneader overlaps between the two closed blades provided in the first screw kneader.

Description

high shear mixing device

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0098953, filed July 28, 2023, the entire contents of which 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.

[0003] Stirring devices are used to finely mix various paste manufacturing equipment and chemical raw materials, such as ink, pigments, paints, cosmetics, pharmaceuticals, and coatings, various coating agents, abrasives, ceramic or metal powders, or various electronic materials (PZT, dielectrics, MLCC, Ferrite, display materials). In particular, planetary mixers, which use blades and rotors to stir high-viscosity substances in a container, are widely used as equipment for stirring high-viscosity substances.

[0004] Planetary mixers like the above are also used in the manufacture of secondary battery electrodes. As the applications and development of secondary batteries expand, there is a continuous demand for improvements in electrode resistance, higher capacity, mechanical properties, and productivity. Consequently, the need for high-shear mixing of electrode manufacturing mixtures is also increasing.

[0005] Specifically, 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 dispersion medium and then passing the powder mixture through a rolling roll has been actively developed recently, and high-shear mixing is being applied to the manufacturing of such electrodes.

[0006] That is, in the above method, a binder called a “fibrillizable binder” or a “fibril-forming binder” is used, and when high-shear mixing is applied to a mixture including the binder, the binder becomes microfibrillated and binds the active material and the conductive material.

[0007] However, during this high-shear mixing process, the fiberizable polymer becomes like chewing gum, placing a large load on the high-shear mixing device, which often results in damage to the high-shear mixing device. Furthermore, when the shear force is lowered to prevent damage to the device, the fiberizable polymer does not fiberize properly. Consequently, due to these issues, it is extremely difficult to build a high-shear mixing device into a large-scale mass-production device for the manufacture of dry electrodes for secondary batteries.

[0008] [Prior Art Literature]

[0009] [Patent Document]

[0010] Republic of Korea Publication Patent No. 10-2011-0117902

[0011]

[0012] The present invention has been devised to solve the above-mentioned problems of the prior art, and aims to provide a high-shear mixing device capable of efficiently mixing materials without causing overload when mixing materials using high-shear force.

[0013] In particular, the purpose of the present invention is to provide a high-shear mixing device capable of efficiently microfibrillating a polymer without overload during high-shear mixing of a mixture for manufacturing a dry electrode including a fiberizable polymer as a binder.

[0014] In order to achieve the above purpose, the present invention

[0015] First screw kneader and second screw kneader;

[0016] A first rotational driving device for rotating the first screw kneader and a second rotational driving device for rotating the second screw kneader;

[0017] An idle drive device in which the first and second rotational drive devices are installed so as to be able to rotate;

[0018] A driving device body having the above-mentioned idle drive device installed; and

[0019] including mixed group;

[0020] Each of the first screw kneader and the second screw kneader includes a shaft having one end connected to the rotational driving device; and three blades having bodies that are fixed at one end to the shaft and are helically curved along the longitudinal direction of the shaft;

[0021] Each of the above screw kneaders rotates in opposite directions with the blades of the other screw kneader overlapping each other.

[0022] Among the three blades provided in each of the first screw kneader and the second screw kneader, one blade is an open blade having a through hole formed in the center except for the outer periphery of the rotational direction surface, and the other two blades are both closed blades having a rotational direction surface closed without a through hole.

[0023] A high-shear mixing device in which an open blade provided in the first screw kneader overlaps between two closed blades provided in the second screw kneader, and an open blade provided in the second screw kneader overlaps between two closed blades provided in the first screw kneader.

[0024] In one embodiment of the present invention, the high-shear mixing device may be characterized in that the screw kneaders rotate by the rotational drive devices while rotating by the rotational drive devices.

[0025] In one embodiment of the present invention, the through hole formed in each blade may be formed to extend to the outer circumferential surface of the shaft.

[0026] In one embodiment of the present invention, the rotational end portions of the blades provided in the first screw kneader and the second screw kneader can rotate while maintaining a distance of 1 mm to 10 mm from the other screw kneader.

[0027] In one embodiment of the present invention, the high-shear mixing device can be used for high-shear mixing of a mixture for manufacturing a dry electrode including a fiberizable polymer as a binder to form microfibrils from the fiberizable polymer.

[0028] The high-shear mixing device of the present invention provides the effect of efficiently mixing materials without overload when mixing materials using high shear forces. Furthermore, since damage to the device is minimized due to this effect, it has the characteristic of enabling the device to be configured for large-capacity use.

[0029] In particular, the high-shear mixing device of the present invention provides an effect of efficiently microfibrillating the polymer without overload during high-shear mixing of a mixture for manufacturing a dry electrode including a fiberizable polymer as a binder.

[0030]

[0031] FIG. 1 is a perspective view showing one embodiment of a high-shear mixing device of the present invention.

[0032] Figure 2 is a perspective view showing one embodiment of a screw kneader provided in a high-shear mixing device of the present invention.

[0033] Figure 3 is a simplified drawing showing the overlap shape of the screw kneader shown in Figure 2 above.

[0034] Figure 4 is a perspective view showing the overlap shape of a comparative screw kneader having a different overlap structure from the screw kneader of the present invention.

[0035] Figure 5 is a simplified drawing showing the overlap shape of the screw kneader shown in Figure 4.

[0036]

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. Like reference numerals designate similar parts throughout the specification.

[0038] FIG. 1 is a perspective view illustrating one embodiment of a high-shear mixing device (100) of the present invention, FIG. 2 is a perspective view illustrating one embodiment of a screw kneader provided in the high-shear mixing device of the present invention, and FIG. 3 is a drawing illustrating a simplified overlapping form of the screw kneader illustrated in FIG. 2.

[0039] The high-shear mixing device (100) of the present invention, as shown in FIG. 1,

[0040] It comprises a first screw kneader (10) and a second screw kneader (10'); a first rotation drive device (21) for rotating the first screw kneader and a second rotation drive device (21') for rotating the second screw kneader; an orbital drive device (23) in which the first rotation drive device (21) and the second rotation drive device (21') are installed to be rotatable; a drive device body (20) in which the orbital drive device (23) is installed; and a mixing tank (30);

[0041] Each of the first screw kneader (10) and the second screw kneader (10') includes a shaft (13, 13') having one end connected to the rotational driving device (21, 21'); and three blades (15, 15') having one end fixed to the shaft and having a body helically curved along the longitudinal direction of the shaft;

[0042] As shown in Fig. 2, each of the above screw kneaders (10, 10') rotates in opposite directions with the other screw kneader and blade (15, 15') overlapping each other.

[0043] As shown in FIGS. 2 and 3, among the three blades provided in each of the first screw kneader (10) and the second screw kneader (10'), one blade is an open blade having a through hole (18, 18') formed in the center except for the outer periphery of the rotational direction surface, and the other two blades are both closed blades having a rotational direction surface closed without a through hole.

[0044] The open blade provided in the first screw kneader has the characteristic of overlapping between two closed blades provided in the second screw kneader, as shown in FIGS. 2 and 3, and the open blade provided in the second screw kneader has the characteristic of overlapping between two closed blades provided in the first screw kneader.

[0045] Additionally, when the screw kneader rotates and engages with the feeder, the mixture can rotate in the opposite direction to the discharge direction.

[0046] The high-shear mixing device (100) of the present invention can be particularly preferably used in the manufacture of dry electrodes for secondary batteries. That is, when manufacturing dry electrodes for secondary batteries, a mixture including an active material, a conductive material, and a fiberizable binder such as PTFE as a binder is mixed at high shear to fiberize the binder, and the mixture thus manufactured is manufactured into a free-standing electrode through a rolling process. During this high-shear mixing process, the fiberizable polymer becomes like chewing gum, which places a large load on the high-shear mixing device, often resulting in damage to the equipment. On the other hand, when the shear force is lowered to prevent such damage to the equipment, the fiberizable polymer is not properly fiberized. Therefore, due to these problems, it is very difficult to build a high-shear mixing device into a large-capacity mass-production device for the manufacture of dry electrodes for secondary batteries.

[0047] However, when using the high-shear mixing device of the present invention, the dispersibility of the mixture is significantly improved, and the microfibrillation of the fiberizable polymer is effectively achieved without placing a large load on the device. Therefore, the high-shear mixing device of the present invention can be preferably used for high-shear mixing for the production of dry electrodes for secondary batteries, and enables construction as large-capacity mass-production equipment.

[0048] When using the high-shear mixing device of the present invention, it is possible to continuously apply a high shear force of 10 to 500 N·m to a mixture comprising the active material, the conductive material, and a fiberizable binder such as PTFE as a binder, while producing a mixture for a free-standing electrode of excellent quality without damaging the equipment. Furthermore, when this mixture is rolled, a free-standing electrode having excellent tensile strength is produced, and when a battery is composed of this electrode, the lifespan of the battery is also significantly improved.

[0049] In particular, the inventors of the present invention have discovered that, as shown in FIGS. 4 and 5, when the open blade provided in the first screw kneader overlaps between the open blade and the closed blade provided in the second screw kneader, and the open blade provided in the second screw kneader overlaps between the open blade and the closed blade provided in the first screw kneader, the open blades overlap each other, the through holes (18, 18') overlap each other, and the mixing material passes through the through holes (18, 18') without being subjected to a shear force, thereby reducing the high-shear mixing effect, and have completed the present invention to improve this.

[0050] That is, the inventors of the present invention have discovered that when the open blade provided in the first screw kneader overlaps between two closed blades provided in the second screw kneader, as shown in FIGS. 2 and 3, and the open blade provided in the second screw kneader overlaps between two closed blades provided in the first screw kneader, the load of the mixing device can be reduced while the high-shear mixing effect can be maximized, and accordingly, when an electrode is manufactured using a mixture manufactured by the high-shear mixing device, the life characteristics of a lithium secondary battery are improved, thereby completing the present invention.

[0051]

[0052] In one embodiment of the present invention, the blade (15, 15') may have one end of the body helically connected to the shaft in the longitudinal direction, and accordingly, the body surface in the rotational direction may have a shape in which it is helically bent along the longitudinal direction of the shaft.

[0053] In the present invention, the blade (15, 15') body may be a circular plate with one end cut off, an oval plate with one end cut off, or a polygonal plate-shaped body that is spirally bent along the longitudinal direction of the shaft (13, 13'). In this case, in the case of the cut circular and oval shapes, the cut portion may be spirally coupled to the shaft in the longitudinal direction, and in the case of the polygon, one side may be spirally coupled to the shaft in the longitudinal direction. In addition, the body may be a shape that is partially modified from the above-described shape to be advantageous for high-shear mixing. In the case of the polygon, it may be a polygonal shape such as a triangle, a square, a pentagon, a hexagon, etc., and is not particularly limited. However, a square shape may be more preferably used.

[0054] In one embodiment of the present invention, the high-shear mixing device (100) has a feature that the screw kneaders (10, 10') rotate by the rotation driving devices (21) and revolve by the rotation driving device (23) at the same time. In addition, the screw kneader has a feature that, when it rotates and meshes with each other, it revolves in the opposite direction to the direction in which the mixture is discharged. As described above, when the rotation and revolution of the screw kneader are performed simultaneously, the mixture is mixed more uniformly, and high-shear mixing can also be performed more efficiently, which is preferable.

[0055] The through holes (18, 18') formed in the blades (15, 15') of the first screw kneader (10) and the second screw kneader (10') illustrated in Fig. 2 represent a form in which the through holes are formed in the center excluding the outer periphery of the rotational direction surface of the blades, and in particular, a form in which the through holes are formed by extending to the outer periphery of the shaft.

[0056] In one embodiment of the present invention, the area of ​​the through-hole (18, 18') may be formed to be 40 to 80%, more preferably 50 to 70%, of the total area of ​​the rotational direction surface of the blade body. When the through-hole is formed within the above range, the mixture is effectively mixed without applying a high load to the device, which is preferable. In particular, the microfibrillation of the fiberizable polymer can also be effectively achieved within the above range.

[0057]

[0058] When the high-shear mixing device includes the first screw kneader (10) and the second screw kneader (10') of the types illustrated in FIGS. 2 and 3, the dispersibility of the mixture is greatly improved, and the fiberization of a fiberizable polymer such as PTFE is effectively achieved. In addition, the device does not have a large load during the fiberization process of a fiberizable polymer such as PTFE. Therefore, the high-shear mixing device of the present invention having the above-described structure can be suitably used for high-shear mixing for the production of dry electrodes for secondary batteries, and enables the construction of large-capacity mass production equipment.

[0059] In particular, when a mixture including an active material, a conductive material, and a fiberizable binder such as PTFE is mixed at high shear and the mixed mixture is rolled to manufacture a dry free-standing electrode, the tensile strength of the free-standing electrode is greatly improved, and such a dry free-standing electrode provides the effect of greatly improving the lifespan of a secondary battery.

[0060] In one embodiment of the present invention, it may be preferable that the rotational distal ends of the blades provided in the first screw kneader and the second screw kneader rotate while maintaining a distance of 1 mm to 10 mm, preferably 1 mm to 5 mm, and more preferably 1 mm to 3 mm from the other screw kneader. When the distance is as described above, fiberization of a fiberizable polymer such as PTFE is effectively performed, and since a large load that may damage the high-shear mixing device is not applied, it is possible to efficiently manufacture a freestanding electrode of excellent quality.

[0061] In one embodiment of the present invention, the rotation speed of the first screw kneader and the second screw kneader may be more preferably 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 the above speed, fiberization of a fiberizable polymer such as PTFE is effectively performed, and since a large load that may damage the high-shear mixing device is not applied to the device, it is possible to efficiently manufacture a free-standing electrode of excellent quality. In addition, the rotation speed may be 5 rpm to 100 rpm, preferably 10 rpm to 50 rpm, and more preferably 10 rpm to 30 rpm.

[0062] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the present invention. However, the examples according to the present invention may be modified in various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more completely explain the present invention to those of average skill in the art.

[0063]

[0064] Example 1: Preparation of freestanding electrodes using a high-shear mixing device

[0065] A mixture for a pre-stranded electrode was prepared by mixing 95.5 wt% or 97 wt% of NCM powder (trade name: GL80, LG Chemical Co., Ltd.), which is a positive electrode active material particle with an average particle diameter of 10 μm, 1.5 wt% of Li250 (Denka Co., Ltd.) as a conductive material, and 1.5 wt% or 3 wt% of PTFE as a binder.

[0066] 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 by applying a shear force of 100 N·m at a rotation speed of 30 rpm and an revolution speed of 15 rpm at 90°C.

[0067] Next, the secondary mixture in the form of dough prepared above was prepared into a free-standing film having a thickness of 200 μm using a two-roll mill (MR-3, Inoue Co.) at 100°C.

[0068] Afterwards, the above free-standing film was placed on one side of a current collector made of Primer Coated Aluminum Foil (manufactured by Dongwon Systems) having a thickness of 20 μm, and bonded using a lamination roll maintained at 120°C to manufacture a positive electrode.

[0069] High shear mixing device configuration Binder content (wt%) Screw kneader configuration First and second screw blade arrangement Screw kneader rotation Mixing volume Example 1 First screw kneader First blade open type (through hole formation) Second and third blades closed Types of Figures 2 and 3 Overlap Revolution + rotation 1.5 L 1.5 Second screw kneader First blade open type (through hole formation) Second and third blades closed Types of Figures 2 and 3 Overlap Revolution + rotation 1.5 L 3.0 Second screw kneader First blade open type (through hole formation) Second and third blades closed Types of Figures 2 and 3 Overlap Revolution + rotation 1.5 L 3.0 Second screw kneader First blade open type (through hole formation) Second and third blades closed Types of Comparative Example 1 First screw kneader First blade open type (through hole formation) Second and third blades closed Types of Figures 4 and 5 Shape Overlap Revolution + Rotation 1.5 L 1.5 Second Screw Kneader First blade open type (through hole formation) Second and third blades closed type Comparative Example 2 First Screw Kneader First blade open type (through hole formation) Second and third blades closed type Figures 4 and 5 Shape Overlap Revolution + Rotation 1.5 L 3.0 Second Screw Kneader First blade open type (through hole formation) Second and third blades closed type

[0070] Overlap Co., Ltd.: The rotational ends of the blades provided in the first screw kneader and the second screw kneader maintain a distance of 3 mm from the other screw kneader.

[0071]

[0072] Experimental Example 1: Measurement of tensile strength of a freestanding electrode

[0073] The tensile strength of the free-standing electrodes manufactured in Examples 1 and 2 and Comparative Examples 1 and 2 was measured at 50 mm / min using a 180-degree peel measurement method using a LLOYD UTM device. The maximum value of the force applied until the film did not break during the measurement was evaluated as the strength of the free-standing film, and the measurement results are shown in Table 2 below.

[0074] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Tensile Strength (MPa) 6.86 7.34 6.47 6.98

[0075]

[0076] Experimental Example 2: Evaluation of Battery Life Characteristics

[0077] (1) Manufacturing of lithium secondary batteries

[0078] Coin-type half-cells were manufactured using the positive electrodes manufactured in Examples 1 to 2 and Comparative Examples 1 to 2, lithium metal as a counter electrode, and an electrolyte containing 1 M LiPF6 in a solvent of EC: DMC: DEC (volume ratio of 1:2:1).

[0079]

[0080] (2) Evaluation of capacity retention rate of lithium secondary batteries

[0081] The coin-type half-cell manufactured above was charged and discharged 100 times at 25°C under the voltage range of 3 to 4.3 V and current conditions of 0.33 C-rate. The 100-cycle discharge capacity retention rate was calculated relative to the 1-cycle discharge capacity, and the results are shown in Table 3 below.

[0082] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Capacity Retention Rate 0.33 / 0.33C, Room Temperature Life (Capa. Efficiency, %@100th cycle) 98.5 97.7 96.8 96.1

[0083] Although the present invention has been described in connection with the preferred embodiments mentioned above,

[0084] Various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the appended claims shall encompass such modifications and variations as long as they fall within the spirit and scope of the present invention.

[0085]

[0086] [Explanation of symbols]

[0087] 10: 1st screw kneader 10': 2nd screw kneader

[0088] 13, 13': Shaft 15, 15': Blade

[0089] 18,18': Through hole 20: Drive unit body

[0090] 21: First bicycle drive device 21': Second bicycle drive device

[0091] 23: Idle drive device 30: Mixing tank

Claims

1. First screw kneader and second screw kneader; A first rotational driving device for rotating the first screw kneader and a second rotational driving device for rotating the second screw kneader; An idle drive device in which the first and second rotational drive devices are installed so as to be able to rotate; A driving device body having the above-mentioned idle drive device installed; and including mixed media; Each of the first screw kneader and the second screw kneader includes a shaft having one end connected to the rotational driving device; and three blades having bodies that are fixed at one end to the shaft and are helically curved along the longitudinal direction of the shaft; Each of the above screw kneaders rotates in opposite directions with the blades of the other screw kneader overlapping each other. Among the three blades provided in each of the first screw kneader and the second screw kneader, one blade is an open blade having a through hole formed in the center except for the outer periphery of the rotational direction surface, and the other two blades are both closed blades having a rotational direction surface closed without a through hole. A high-shear mixing device in which an open blade provided in the first screw kneader overlaps between two closed blades provided in the second screw kneader, and an open blade provided in the second screw kneader overlaps between two closed blades provided in the first screw kneader.

2. In paragraph 1, The high-shear mixing device is characterized in that the screw kneaders rotate by the rotational driving devices and revolve by the rotational driving device at the same time.

3. In paragraph 1, A high-shear mixing device characterized in that the through holes formed in each of the above blades extend to the outer surface of the shaft.

4. In paragraph 1, A high-shear mixing device characterized in that the rotational end portions of the blades provided in the first screw kneader and the second screw kneader rotate while maintaining a distance of 1 mm to 10 mm from the other screw kneader.

5. In paragraph 1, A high-shear mixing device characterized in that it is used for high-shear mixing of a mixture for manufacturing a dry electrode including a fiberizable polymer as a binder, and is used for the purpose of microfibrillating the fiberizable polymer.

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