Method for producing secondary battery electrode slurry

Abstract

To control a dispersion status of materials to be kneaded by adjusting the number of revolutions using a two-screw continuous kneader, thereby producing a slurry having an appropriate viscosity.SOLUTION: In a process where, by using a two-screw continuous kneader 1 that includes a cylindrical housing 10 having an exhaust port and at least one supply port, a pair of two rotary shafts 8 arranged in parallel inside the housing 10, and a plurality of stirring blades axially mounted to the rotary shafts 8, graphite as an active material, a styrene-butadiene rubber (SBR) aqueous solution as a binder, and powder or an aqueous solution of carboxymethyl-cellulose (CMC) as a thickener are fed through the supply port of the housing, and a slurry is produced by rotating the pair of two rotary shafts 8, the viscosity of products (slurry) after kneading discharged through the exhaust port is checked timely, and the number of revolutions is changed to adjust the viscosity.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a secondary battery electrode slurry. [Background technology]

[0002] The slurry is a suspension with a relatively high viscosity obtained by kneading a powder and a liquid. Conventionally, a batch-type kneader such as a planetary mixer has been used to produce the secondary battery electrode slurry.

[0003] A method for producing an electrode composite material is known in which an active material, an electronically conductive material, and an ionically conductive material are mixed and kneaded using a kneader equipped with a screw to form a composite (see, for example, Patent Document 1). In this method, the ionically conductive material is heated during kneading to convert it into a glass ceramic, thereby producing an electrode composite material for an all-solid-state secondary battery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6764677 Summary of the Invention [Problem to be solved by the invention]

[0005] It is important that the viscosity of the slurry is adjusted to an appropriate level for easy application to the substrate in the coating process. If the viscosity is too low or too high, problems such as inability to apply to the desired thickness arise, and if the viscosity is too high, problems such as the slurry being too hard and clumping at the entrance of the coating device making it impossible to apply arise. In addition, if the materials in the slurry are not mixed uniformly and aggregates are present, for example, a smooth electrode surface cannot be obtained, and the aggregates may peel off, adversely affecting battery performance.

[0006] In recent years, there has been a trend to reduce energy consumption in the subsequent drying process by setting the solid content of the slurry high, but conventional batch-type kneaders were unable to sufficiently disperse the materials when the solid content was high, and were unable to reduce the viscosity of the slurry to the desired level, which meant that viscosity adjustment was required in a separate device as a post-treatment.

[0007] The present invention has been made in consideration of these points, and its object is to make it possible to produce secondary battery electrode slurry with a viscosity suitable for the coating process using a single device by improving the dispersibility without changing the composition of the electrode material. [Means for solving the problem]

[0008] In order to achieve the above object, in this invention, a twin-screw continuous kneader is used and the rotation speed is adjusted to control the dispersion state of the materials being kneaded, thereby making the slurry viscosity appropriate.

[0009] Specifically, in the method for producing a secondary battery electrode slurry according to the first aspect of the present invention, a cylindrical housing having an outlet and at least one inlet; A pair of rotating shafts arranged in parallel inside the housing; A twin-shaft continuous mixer having a plurality of stirring blades axially attached to the rotating shaft is used, Graphite as an active material, a styrene butadiene rubber (SBR) aqueous solution as a binder, and a carboxymethyl cellulose (CMC) powder or aqueous solution as a thickener are charged from the supply port of the housing, In the process of producing a slurry by rotating the pair of rotating shafts, the viscosity of the kneaded product (slurry) discharged from the discharge outlet is checked as needed, and the rotation speed is changed to adjust the viscosity.

[0010] According to the above configuration, the twin-shaft continuous kneader can apply high shear force to the material, and by gradually increasing the rotation speed of the rotating shaft while applying a shear force appropriate to the material and improving the dispersion state of the material, a secondary battery electrode slurry with a viscosity appropriate for the subsequent coating process can be discharged from the discharge outlet.

[0011] In the second invention, in the first invention, 46% by weight or more and 99% by weight or less of graphite as a first active material; 0% by weight or more and 50% by weight or less of graphite as a second active material, As a thickener, a CMC powder or a CMC aqueous solution having a CMC content of 0.5% by weight to 2.0% by weight is used. An aqueous solution of SBR with a solid content of 0.5% by weight to 2.0% by weight as a binder is added. Each is fed through the supply port.

[0012] Within the above composition range, by adjusting the rotation conditions, a secondary battery electrode slurry having an appropriate viscosity can be obtained that is easy to apply to a substrate in the application step.

[0013] In a third aspect of the present invention, in the first or second aspect of the present invention, A secondary battery electrode slurry is produced while keeping the temperature lower than room temperature by circulating cooling water through a jacket provided inside the housing.

[0014] According to the above configuration, the inside of the housing can be efficiently cooled from the jacket of the housing, so that the temperature of the product can be kept low, suppressing damage to the material caused by heat generated during kneading, and secondary battery electrode slurry of stable quality can be obtained. Depending on the size of the device, the material inside the device may be cooled by passing cooling water through the rotating shaft as well. These cooling mechanisms can suppress damage to the material caused by heat generated during kneading. Effect of the Invention

[0015] As described above, according to the present invention, a secondary battery electrode slurry having a viscosity suitable for the coating process can be produced in one device without changing the composition of the electrode material. Therefore, it is not necessary to provide a separate device for adjusting the viscosity of the secondary battery electrode slurry before the coating process, which shortens the process and saves the installation space of the separate device. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a plan view showing a twin-screw continuous kneader. [Diagram 2] 1 is a graph showing the relationship between the rotation speed and the viscosity at two different discharge amounts of secondary battery electrode slurry per hour when CMC is supplied in the form of an aqueous solution by the manufacturing method for secondary battery electrode slurry according to the present invention. [Diagram 3] 1 is a graph showing the relationship between the rotation speed and the viscosity at two different discharge amounts of secondary battery electrode slurry per hour when CMC is supplied as a powder by the manufacturing method of secondary battery electrode slurry according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] - Configuration of twin-shaft continuous kneader - FIG. 1 shows a twin-shaft continuous mixer 1 according to an embodiment of the present invention. For example, this twin-shaft continuous mixer 1 includes a base 2 that is placed on the ground of a factory or the like, and a drive unit 3 and a body unit 4 that are each provided at fixed positions on the base 2.

[0019] The drive unit 3 includes, for example, an electric motor 5 and a gear box 6 to which the driving force of the electric motor 5 is transmitted via an input shaft 6b. In this embodiment, a pair of output shafts 6a extend from the gear box 6, and a rotating shaft 8 is connected to each output shaft 6a via a joint 7.

[0020] The twin-shaft continuous mixer 1 is provided with a cylindrical housing 10 having a discharge port (not shown) and at least one supply port 11 in a body portion 4. The discharge port is provided in the lower portion of the housing 10. In addition to the supply port 11 shown in the figure, one or more supply ports for supplying, for example, a diluent are provided downstream. A pair of rotating shafts 8 are supported in parallel inside the housing 10. A plurality of stirring blades are attached to each rotating shaft 8 in the axial direction.

[0021] Although not shown in detail, it is possible to provide a feed zone, a solidification zone, a mixing zone, and a dilution zone within the housing 10, adjust the length of each zone, and attach stirring blades of different shapes to each zone.

[0022] -Method for manufacturing secondary battery electrode slurry- Using the twin-screw continuous kneader 1 as described above, electrode materials such as an active material, a binder, a thickener, and a diluting solvent are charged from the supply port 11 of the housing 10.

[0023] The electrode material is continuously supplied to the twin-shaft continuous kneader 1 from the supply port 11, and the electrode material is kneaded by rotating the pair of rotating shafts 8. The viscosity of the kneaded product discharged from the discharge port is checked, and the rotation is adjusted so as to obtain a desired viscosity, thereby adjusting the viscosity.

[0024] At this time, the secondary battery electrode slurry is produced while keeping the temperature lower than room temperature by circulating cooling water through a jacket provided inside the housing 10 and a rotary joint incorporated in the shaft. This allows the secondary battery electrode slurry to be produced with stable quality without the material being damaged by heat generated by kneading.

[0025] The method described above provides a secondary battery electrode slurry with an appropriate viscosity that can be easily applied to a substrate in the coating process. This secondary battery electrode slurry with an appropriate viscosity is applied to an electrode current collector as a substrate in the coating process. Because the viscosity is kept optimal, problems such as the viscosity being too low or too high to be able to coat the desired width do not occur, and problems such as the viscosity being too high to be able to make the slurry hard and harden the entrance of the coating device, making it impossible to coat, do not occur.

[0026] In this way, the twin-shaft continuous kneader 1 can apply high shear force to the material, and by gradually increasing the rotation speed of its rotating shaft 8, it can apply a shear force appropriate to the material and improve the dispersion state of the material, thereby discharging secondary battery electrode slurry with a viscosity suitable for the subsequent coating process from the outlet.

[0027] --Example-- The twin-shaft continuous mixer 1 used had a mixer section such as an agitator blade having a diameter of 50 mm and a length of approximately 660 mm, and the rotation speed was adjustable from 60 rpm to 600 rpm and 1200 rpm. Cooling water at 8° C. was circulated in the jacket of the housing 10.

[0028] After being fed from the feed port 11, the solid content in the kneading zone is set to 63% by weight to effectively disperse the material, and then the material is diluted in the dilution zone and discharged at a solid content of 56% by weight.

[0029] As an example, 85% by weight or more and 90% by weight or less of graphite was used as the first active material, 7.5% by weight or more and 12.5% ​​by weight or less of graphite was used as the second active material, 0.5% by weight to 2.0% by weight of CMC aqueous solution (about 1% concentration) was used as a thickener, and 0.5% by weight to 2.0% by weight of SBR aqueous solution was used as a binder, and the rotation speed was changed from 600 rpm to 1200 rpm. Figure 2 shows the case where the weight of the secondary battery electrode slurry per hour was set to 40 kg and the case where it was set to 60 kg.

[0030] As shown in this figure, when the rotation speed of the rotating shaft 8 is gradually increased, the viscosity gradually decreases almost linearly from 24.3 Pa·s to 8.3 Pa·s when the discharge rate is 40 kg per hour, and from 28.5 Pa·s to 13.6 Pa·s when the discharge rate is 60 kg per hour. This was the same whether the weight of the secondary battery electrode slurry discharged per hour was 40 kg or 60 kg.

[0031] As another example, FIG. 3 shows a case where 0.5% by weight to 2.0% by weight of CMC as powder is fed from the supply port 11 as a thickener, instead of an aqueous CMC solution.

[0032] In this case too, it can be seen that as the rotation speed of the rotating shaft 8 is gradually increased, the viscosity gradually decreases almost linearly from 22.1 Pa·s to 5.2 Pa·s in the case of a discharge rate of 40 kg per hour, and from 28.0 Pa·s to 12.2 Pa·s in the case of a discharge rate of 60 kg per hour.

[0033] From these results, it was found that a secondary battery electrode slurry with an appropriate viscosity can be obtained by gradually increasing the rotation speed of the twin-screw continuous kneader 1 between a low speed of 600 rpm and a high speed of 1200 rpm to reduce the viscosity of the discharged secondary battery electrode slurry.

[0034] Therefore, according to the method for producing secondary battery electrode slurry according to this embodiment, secondary battery electrode slurry having a viscosity suitable for the coating process can be produced in a single device.

[0035] This eliminates the need to provide a separate device for adjusting the viscosity of the secondary battery electrode slurry during the coating process, shortening the process and saving space for installing the separate device.

[0036] It should be noted that the above-described embodiments are essentially preferred examples, and are not intended to limit the scope of the present invention, its applications, or uses. [Explanation of symbols]

[0037] Single-shaft continuous mixer 2. Bass 3 Drive unit 4. Body 5 Electric motor 6 Gearbox 6a Output shaft 6b Input shaft 7. Joints 8 Rotating Shaft 10. Housing 11 Supply inlet

Claims

1. a cylindrical housing having an outlet and at least one inlet; A pair of rotating shafts arranged in parallel inside the housing; A twin-shaft continuous mixer having a plurality of stirring blades axially attached to the rotating shaft is used, Graphite as an active material, an aqueous solution of styrene butadiene rubber (SBR) as a binder, and a powder or aqueous solution of carboxymethyl cellulose (CMC) as a thickener are charged from a supply port of the housing, In the process of producing a slurry by rotating the pair of rotating shafts, the viscosity of the kneaded product (slurry) discharged from the discharge port is checked at appropriate times, and the rotation speed is changed to adjust the viscosity. A method for producing a secondary battery electrode slurry comprising the steps of:

2. 46% by weight or more and 99% by weight or less of graphite as a first active material, 0% by weight or more and 50% by weight or less of graphite as a second active material, As a thickener, a CMC powder or a CMC aqueous solution having a CMC content of 0.5% by weight to 2.0% by weight is added. An aqueous solution of SBR having a solid content of 0.5% by weight to 2.0% by weight as a binder is added. Each is fed from the supply port.

2. The method for producing a secondary battery electrode slurry according to claim 1.

3. A secondary battery electrode slurry is produced while keeping the temperature lower than room temperature by circulating cooling water through a jacket provided inside the housing.

3. The method for producing a secondary battery electrode slurry according to claim 1 or 2.

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