JP7036620B2 - Press equipment and electrode manufacturing method - Google Patents

Description

The present invention relates to a press device having excellent productivity and a method for manufacturing an electrode having excellent productivity.

Electrodes of non-aqueous secondary batteries such as lithium ion secondary batteries usually have a structure having an active material layer containing an active material and a binder on one or both sides of a current collector made of a metal foil or the like. It is used. Such an electrode is, for example, a paint for forming an active material-containing composition (paint for forming an active material layer) containing an active material, a binder, a solvent, etc. on the surface of the current collector drawn from a roll around which the current collector is wound. ) Is applied and dried to form an active material layer, and then a pressing process is performed to adjust the density of the active material layer. In the pressing process, pressure is applied to the active material layer by a roll called a press roll, but at that time, a part of the active material layer may be peeled off from the roll and attached to the roll to become dirty. If the pressing process is continued with the stains attached, the stains may be further attached and increased, the electrodes may be defective in pressing, and the characteristics of the battery may be adversely affected.

Therefore, Patent Document 1 discloses a technique of attaching a non-woven fabric and cleaning the roll in order to remove foreign matter adhering to the surface of the roll.

Patent Document 2 discloses that the dew point environment at the time of pressing the negative electrode for a non-aqueous electrolyte secondary battery is set to -10 ° C or lower, and the binder contained in the active material mixture is less likely to adhere to the press roll surface. Has been done.

JP-A-2015-76230 Japanese Unexamined Patent Publication No. 2008-204863

By the way, in the method of Patent Document 2, it is difficult for the press roll to get dirty in the pressing process, but it is difficult to completely prevent the press roll from getting dirty. In any case, when the dirt adheres, the surface of the roll is cleaned. Is required. Further, if the pressing process is performed without making it difficult to get dirty, the dirt adheres to the roll more and it takes time and effort to clean.

Therefore, by transporting the electrodes under the dew point environment adjustment before the press process, dirt adheres to the press roll during the press process, and if a cleaning process is performed to clean the press roll after the press process, the production is highly productive. It can be said that it is a method. However, in the case of water-based electrodes such as the negative electrode of a lithium-ion secondary battery, the cleaning process uses water as a solvent to wipe off the cleaning liquid, so the water content affects the dew point environment and maintains a specific dew point environment. It will be difficult.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a press device having excellent productivity and a method for manufacturing an electrode having excellent productivity.

The press device of the present invention that has achieved the above object is a roll press device for pressing an electrode provided with an active material layer on a strip-shaped metal foil, and is arranged at a position in contact with the surface of the active material layer. The roll is placed in contact with the roll that rotates during transportation of the electrode and the surface of the roll, and the roll comes into contact with the cleaning portion for cleaning the surface of the roll with water and the surface of the active material layer. The dew point adjustment mechanism that adjusts the dew point of the dew point environment adjustment area including at least a part of the upstream side in the electrode transport direction from the position where the electrode is transported, and the dew point environment adjustment area have a positive pressure as compared with the downstream side of the dew point environment adjustment area. It is characterized by being provided with a pressure adjusting mechanism.

Further, the method for manufacturing an electrode of the present invention is characterized in that an electrode is manufactured by using the roll press device.

According to the present invention, it is possible to provide a press device having excellent productivity and a method for manufacturing an electrode having excellent productivity.

It is a figure which shows typically the press device of this invention.

The press device of the present invention is a roll press device for pressing an electrode provided on a strip-shaped metal foil. A schematic diagram of an example of the configuration of the roll press device of the present invention is shown in FIG. The roll press device 1 shown in FIG. 1 includes rolls 2A and 2B for pressing an electrode 10 having an active material layer 12 on a strip-shaped metal foil 11, and a cleaning unit 4A for cleaning the roll surface with a cleaning liquid using water as a solvent. 4B, a dew point adjustment mechanism 3 for adjusting the dew point of the dew point environment adjustment area 30, a dew point environment adjustment area 30 and cleaning units 4A, 4B, which are arranged downstream of the dew point environment adjustment area 30 in the transport direction of the electrode. It is provided with a pressure adjusting mechanism 5 that makes the pressure positive compared to the downstream side in the electrode transport direction from the dew point environment adjusting area.

This makes it possible to provide a highly productive press roll device. That is, by making the dew point environment adjustment area a positive pressure compared to the downstream side in the electrode transport direction, air containing water derived from a cleaning liquid using water as a solvent used in the cleaning unit does not flow to the dew point environment adjustment area. This makes it easy to maintain the dew point environment in the dew point environment adjustment area. Therefore, the dew point adjustment, the pressing process, and the cleaning process can be continuously and simultaneously performed without stopping the roll press device in the cleaning process.

The electrode to be pressed in the roll press device of the present invention is a water-soluble polymer having a viscosity adjusting function represented by CMC, the flexibility of the electrode represented by SBR, and a binder for binding active material particles to each other. The effect of the present invention can be obtained if the electrode is composed of an emulsion (aqueous dispersion of polymer particles) or the like. Specifically, it is a positive electrode or a negative electrode of an alkaline electrolyte battery (nickel-metal hydride battery, a nicad battery, etc.), a negative electrode of a lithium ion secondary battery, or the like, and each electrode can take a known material and configuration. ..

Taking the negative electrode of a lithium ion secondary battery as an example, the negative electrode active material includes graphite, thermally decomposed carbons, cokes, glassy carbons, calcined organic polymer compounds, MCMB, carbon fibers, activated carbon and the like. One or more of carbon materials; metals that can be alloyed with lithium (Si, Sn, etc.), materials containing these metals (alloys, etc.), and the like can be used. Styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC) and the like are preferably used as the binder. A copper or copper alloy foil can be used as the strip-shaped metal foil as the negative electrode current collector.

For the negative electrode of a lithium ion secondary battery, a negative electrode active material and a binder are dispersed in water to prepare an active material-containing composition, which is applied onto a negative electrode current collector and dried to prepare a negative electrode before pressing. .. The coating means for coating the active material-containing composition on the negative electrode current collector is not particularly limited, and is known as a coating method used in conventional production (a method using a gravure coat, a die coat, a dam coater, etc.) and the like. The same method can be adopted.

More specifically, the roll press apparatus of the present invention will be described with reference to FIG. The rolls 2A and 2B rotate in the directions of RA and RB, respectively, while being transported in the transport direction TD of the electrode 10, and apply pressure in the PA and PB directions while contacting the surface of the active material layer 12 (pressing step). There is a dew point environment adjustment area 30 (a part surrounded by a broken line in FIG. 1) on the upstream side in the electrode transport direction at a position where the rolls 2A and 2B come into contact with the active material layer 12. In the dew point environment adjustment area 30, the dew point adjustment mechanism 3 performs dew point adjustment. In FIG. 1, the dew point environment adjustment area 30 includes the positions where the rolls 2A and 2B come into contact with the active material layer 12, but this is not always necessary, and the dew point environment adjustment area 30 is partly upstream of the electrode transport direction TD. If the above is included, the effect of preventing the adhesion of dirt to the rolls 2A and 2B can be obtained. The dew point adjusting mechanism 3 for adjusting the dew point of the dew point environment adjusting area 30 can use a mechanism such as sending cold air to the dew point environment adjusting area, but is not limited thereto.

When pressing the negative electrode of the lithium ion secondary battery, it is preferable to adjust the dew point of the dew point environment adjusting area 30 to −10 ° C. or lower. Within this range, it is possible to preferably prevent dirt from adhering to the roll.

The rolls 2A and 2B are arranged so as to sandwich the strip-shaped electrode 10, and rotate with respect to the electrode transport direction TD as shown in FIG. 1, respectively. The electrodes pressed by the rotating rolls 2A and 2B are continuously conveyed.

If the electrode has passed through the dew point environment adjustment area 30, it is difficult for the rolls 2A and 2B to get dirty in the pressing process. Since the cleaning portions 4A and 4B are provided on the downstream side of RA and RB, the soiled parts of the rolls 2A and 2B are cleaned, and the stains are removed when the parts come into contact with the active material layer next time. Will be.

In the cleaning units 4A and 4B, the surfaces of the rolls 2A and 2B are cleaned with a cleaning liquid containing water. The cleaning liquid containing water (cleaning liquid using water as a solvent) is water, a liquid in which water and alcohol are mixed, an aqueous solution containing a surface active material, or the like. The cleaning units 4A and 4B can be, for example, a non-woven fabric impregnated with a cleaning liquid containing water. Further, the cleaning units 4A and 4B may be connected to a cleaning liquid supply mechanism (not shown) that constantly supplies a cleaning liquid containing water.

The roll press device of the present invention includes a pressure adjusting mechanism 5. The pressure adjusting mechanism 5 adjusts the dew point environment adjusting area 30 so as to have a positive pressure as compared with the downstream side in the electrode transport direction from the dew point environment adjusting area 30. The pressure adjusting mechanism 5 is, for example, an air adjusting duct, and there is a means for adjusting the air volume with the air adjusting duct to realize a positive pressure in the dew point environment adjusting area 30.

Further, in FIG. 1, the pressure adjusting mechanism 5 is arranged in the dew point environment adjusting area 30 and is adjusted so that the area becomes higher than the air pressure, but the present invention is not limited to this. For example, the pressure adjusting mechanism 5 may be arranged by demarcating the downstream side in the electrode transport direction from the dew point environment adjusting area 30, and the air pressure in the dew point environment adjusting area may be adjusted to be lower than the air pressure by pumping out the air. ..

The roll press device of FIG. 1 includes partitions 6A and 6B that partition the dew point environment adjustment area 30 and the cleaning portions 4A and 4B downstream of the dew point environment adjustment area 30 in the electrode transport direction TD. As a result, the influence of the moisture used in the cleaning units 4A and 4B on the dew point environment adjusting area 30 can be further reduced, and the dew point environment can be more easily maintained in the dew point environment adjusting area 30.

The partitions 6A and 6B can take various forms. For example, cloth curtains, partitions, and walls may be constructed. For example, a material in which a moisture adsorbent is arranged on the wall surface on the cleaning portions 4A and 4B can also be used.

Further, if the electrode is manufactured by using such a roll press device, a highly productive manufacturing method can be obtained.

The present invention is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented within a range that does not deviate from the gist thereof.

Claims (5)

A roll press device that presses an electrode with an active material layer on a strip-shaped metal foil.
A roll arranged at a position in contact with the surface of the active material layer and rotating during transportation of the electrode,
A cleaning unit located at a position in contact with the surface of the roll and on the downstream side in the roll rotation direction from the position where the roll contacts the surface of the active material layer, and cleans the surface of the roll with a cleaning liquid using water as a solvent. When,
A dew point adjustment mechanism that adjusts the dew point of the dew point environment adjustment area including at least a part of the upstream side in the electrode transport direction from the position where the roll contacts the surface of the active material layer.
A pressure adjusting mechanism that makes the dew point environment adjusting area positive pressure as compared with the downstream side in the electrode transport direction from the dew point environment adjusting area.
Equipped with
A roll press device in which the dew point in the dew point environment adjustment area is adjusted to −10 ° C. or lower . The roll press device according to claim 1, which is arranged on the downstream side in the transport direction from the dew point environment adjustment area and includes a partition for partitioning the dew point environment adjustment area and the cleaning unit. The roll press device according to claim 1 or 2, wherein the dew point environment adjusting area includes a position where the roll comes into contact with the surface of the active material layer. The roll press device according to any one of claims 1 to 3, wherein the electrode is a negative electrode of a lithium ion secondary battery. It is a manufacturing method of electrodes.
A manufacturing method for manufacturing an electrode using the roll press device according to claim 1 or 2.

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