JP2024020798A - Manufacturing method of electrode sheet - Google Patents

Abstract

A main object of the present disclosure is to provide a method for manufacturing an electrode sheet that can suppress deterioration in electrode quality. The present disclosure includes a preparation step of preparing a coated sheet in which a coated portion coated with an electrode material is arranged on a first surface of a current collector sheet having a longitudinal direction in a first direction. , a drying step of drying the coated area by irradiating the coated sheet with a laser beam while conveying the coated sheet in the first direction, and in the drying step, a constant rate drying section. The above-mentioned problem is solved by providing a method for manufacturing an electrode sheet in which the above-mentioned pulsed wave laser light is irradiated in the lapse rate drying section. [Selection diagram] Figure 3

Description

The present disclosure relates to a method for manufacturing an electrode sheet.

As a technology related to the manufacturing method of electrode sheets used for manufacturing batteries such as lithium ion secondary batteries, electrode material is applied to the current collector sheet being transported to form a coated area, and the coated area is dried. A method for obtaining an electrode layer is known.

For example, Patent Document 1 describes a coating process in which an active material mixture is applied to a long metal foil to be transported to form a coated part of the active material mixture, and a coating process that is performed before the coating process. A first irradiation of irradiating a laser onto an irradiation position of the long metal foil located upstream in the transport direction of the long metal foil from both ends of the mixture application location along the transverse direction of the long metal foil. a second irradiation step that is executed after the first irradiation step and irradiates both edges in the transverse direction of the coated portion formed by the coating step; and a second irradiation step that is executed after the second irradiation step; A method of manufacturing an electrode is disclosed, which includes a drying step of drying a coated part.

JP2019-029256A

As a technique for drying a coated sheet having a coated portion coated with an electrode material, a technique of irradiating laser light as a heat source has been proposed. In this case, when the laser beam is continuously irradiated, the temperature of the coated sheet tends to become high. Therefore, the quality of the electrode may be affected.

The present disclosure has been made in view of the above circumstances, and its main purpose is to provide a method for manufacturing an electrode sheet that can suppress deterioration in quality.

[1]
a preparation step of preparing a coated sheet in which a coated part coated with an electrode material is arranged on a first surface of a current collector sheet having a longitudinal direction in a first direction;
a drying step of drying the coated area by irradiating the coated sheet with a laser beam while conveying the coated sheet in the first direction;
In the drying step, the pulsed laser beam is irradiated in the constant rate drying section and the decreasing rate drying section.

According to the method for manufacturing an electrode sheet in the present disclosure, deterioration in quality can be suppressed.

FIG. 2 is a schematic plan view and a schematic cross-sectional view illustrating a drying process in the present disclosure. FIG. 2 is a schematic diagram illustrating changes over time in the solvent content rate in the coated part and the surface temperature of the coated part in the drying step in the present disclosure. A schematic diagram illustrating the change over time in the surface temperature of the coated part when irradiated with pulsed wave laser light, a schematic diagram illustrating the change over time in the output of the laser light when irradiated with pulsed wave laser light, and a continuous diagram. FIG. 3 is a schematic diagram illustrating a change over time in the output of a laser beam when a wave laser beam is irradiated.

Hereinafter, a method for manufacturing an electrode sheet according to the present disclosure will be described in detail using the drawings. Each figure shown below is shown schematically, and the size and shape of each part are appropriately exaggerated for easy understanding. In addition, in this specification, when expressing the manner in which another member is arranged with respect to a certain member, when it is simply expressed as "above" or "below", unless otherwise specified, the term "above" or "below" refers to the arrangement of another member in contact with a certain member. This includes both a case where another member is placed directly above or below a certain member, and a case where another member is placed above or below a certain member via another member.

FIG. 1 is a schematic plan view and a cross-sectional view illustrating a drying process in the present disclosure, and FIG. 1(b) is a cross-sectional view taken along line AA in FIG. 1(a). As shown in FIGS. 1(a) and 1(b), the coated sheet 10 prepared in the preparation process has an electrode material coated on the first surface S1 of the current collector sheet 1 having the longitudinal direction in the first direction D1. It has a coated part 2 that has been polished. Further, the coated sheet 10 may have an uncoated portion 3 on which the electrode material is not coated. As shown in FIGS. 1A and 1B, in the drying step, the coated sheet 10 is irradiated with laser light from the laser irradiation device L while the coated sheet 10 is being conveyed in the first direction D1. Thereby, the coated part 2 is dried and an electrode layer is obtained.

Here, when the coated sheet 10 is continuously irradiated with laser, the coated part 2 and the current collector sheet 1 in the area where the coated part 2 does not exist (for example, the uncoated part 3) tend to become high temperature. . Therefore, the peel strength between the electrode layer and the current collector sheet decreases, which may lead to deterioration in the quality of the end portion of the electrode layer, such as peeling of the electrode layer. Furthermore, the current collector sheet may be oxidized, resulting in a decrease in battery performance.

FIG. 2 is a schematic diagram illustrating changes over time in the solvent content in the coated part and the surface temperature of the coated part in the drying process. As shown in FIG. 2, the drying process can be roughly divided into three sections. That is, they are a preheating section, a constant rate drying section, and a lapse rate drying section. In the preheating section, the surface temperature of the coated part increases. In the constant rate drying section, the surface temperature of the coated part becomes approximately constant. In the lapse rate drying section, the surface temperature of the coated area rises again.

FIG. 3(a) is a schematic diagram illustrating the change over time in the surface temperature of the coated part when irradiated with pulsed wave laser light, and FIG. 3(b) is a schematic diagram illustrating the change over time in the surface temperature of the coated part when irradiated with pulsed wave laser light. FIG. 3 is a schematic diagram illustrating changes over time in the output of laser light. As shown in FIGS. 3A and 3B, when irradiating pulsed laser light, there is an ON time and an OFF time. While the surface temperature of the coated part increases during the ON time, the surface temperature of the coated part decreases during the OFF time.

In the present disclosure, in the drying process, pulsed wave laser light is irradiated in the constant rate drying section and the decreasing rate drying section. During the OFF time, it is possible to suppress the coated portion and the current collector sheet in the area where the coated portion is not present from becoming high temperature. Further, most of the drying process is a constant rate drying section and a decreasing rate drying section. Furthermore, the temperature of the coated area increases as the constant rate drying zone changes to the decreasing rate drying zone. Therefore, by irradiating pulsed laser light in these sections, temperature rise can be effectively suppressed. Therefore, excessive drying of the coated area can be suppressed. Therefore, it is possible to produce an electrode sheet in which deterioration in peel strength between the electrode layer and the current collector sheet is suppressed. In addition, oxidation caused by the current collector sheet being heated to a high temperature can be suppressed.

Generally, the drying time is determined by the output of the laser light. Therefore, if the output per unit time is the same, the drying time will be the same regardless of whether the laser light is a pulse wave or a continuous wave. For example, as shown in FIG. 3(b), when the laser beam is a pulse wave, when the output is 200 W, and the ON time and OFF time are each 0.5 seconds, the output per second is 100 W. Therefore, in this case, the drying time is the same as when the laser beam is a continuous wave and the output per second is 100 W, as shown in FIG. 3(c), for example. Therefore, by irradiating the pulsed laser beam, the coated area can be dried while maintaining the quality of the electrode sheet without increasing the drying time.

1. Preparation Step As shown in FIG. 1, the preparation step in the present disclosure includes disposing a coating portion 2 coated with an electrode material on a first surface S1 of a current collector sheet having a longitudinal direction in a first direction D1. This is a step of preparing a coated sheet 10.

The current collector sheet has a longitudinal direction in the first direction. The current collector sheet has a first surface S1, which is one surface in the thickness direction, and a second surface S2, which is the back surface of the first surface S1. The current collector sheet is preferably used as a current collector such as a negative electrode current collector, a positive electrode current collector, and a bipolar current collector. As the current collector sheet, for example, metal foil such as aluminum, copper, SUS, nickel, etc. is used. The thickness of the current collector sheet is, for example, 0.1 μm or more, and may be 1 μm or more. On the other hand, the thickness of the current collector sheet is, for example, 1 mm or less, and may be 100 μm or less.

The electrode material may be a negative electrode material (material of the negative electrode active material layer). The negative electrode material includes, for example, a negative electrode active material, a conductive material, a binder, and a solvent. Further, the electrode material may be a positive electrode material (material of the positive electrode active material layer). The positive electrode material includes, for example, a positive electrode active material, a conductive material, a binder, and a solvent. These materials are not particularly limited, and known materials can be used.

As shown in FIG. 1(a), the coated sheet 10 may have an uncoated portion 3 on which the electrode material is not coated. For example, the coated portion is disposed at the center of the current collector sheet in the transverse direction, and the uncoated portions are disposed at both ends of the current collector sheet across the coated portion in the transverse direction. Further, when applying the electrode material intermittently as described below, the coated sheet may have intermittent portions where the electrode material is not applied.

The method for preparing the coated sheet is not particularly limited, but for example, the electrode material may be coated on the first surface of the current collector sheet by the coating means while the current collector sheet is conveyed in the first direction by the conveying means. It can be manufactured by forming a section. At this time, the electrode material may be applied continuously or intermittently. Further, it is preferable that the coating machine is disposed upstream of the laser irradiation machine in the conveyance direction, and that this process and the drying process described below are performed continuously.

2. Drying Step The drying step in the present disclosure is a step of drying the coated portion by irradiating the coated sheet with laser light while conveying the coated sheet in the first direction. In this step, pulsed wave laser light is irradiated in the constant rate drying section and the decreasing rate drying section.

The conveyance speed of the coated sheet is, for example, constant. As shown in FIG. 1, the coating sheet 10 is irradiated with laser light from a laser irradiator L, for example. The laser irradiation machine has a laser head. A laser head usually includes an optical lens having a predetermined curvature. The laser head is oscillated by a laser oscillator and irradiates the coated sheet with laser light through an optical lens.

The laser irradiation machine may have multiple laser heads. In this case, it is preferable that the plurality of laser heads are arranged above the coated sheet being conveyed in a row at intervals along the first direction. The above-mentioned interval (distance between adjacent laser heads) may be the same or different.

In this step, pulsed wave laser light is irradiated in the constant rate drying section and the decreasing rate drying section. The irradiation conditions of the pulsed laser beam are not particularly limited. The energy density of the laser beam is, for example, 0.1 W/cm ² or more, and may be 0.2 W/cm ² or more. On the other hand, the energy density may be, for example, 2.0 W/cm ² or less, 1.0 W/cm ² or less, or 0.5 W/cm ² or less. For example, when the energy density is 2.0 W/cm ² , the ON time is, for example, 2 seconds or less. By setting the ON time within the above range, overheating can be suppressed. The OFF time is not particularly limited. By adjusting the pulse width and pulse interval (period) of the laser beam, the ON time and OFF time can be adjusted.

Further, in this step, in the preheating section, pulsed wave laser light may be irradiated, or continuous wave laser light may be irradiated.

Here, the "preheating section" is a section in which the surface temperature of the coated part increases. The "constant rate drying section" is a section in which the surface temperature of the coated area is approximately constant. The "declining rate drying section" is a section in which the surface temperature of the coated area increases again after the constant rate drying section. The preheating section, constant rate drying section, and decreasing rate drying section can be confirmed, for example, by measuring the change in the weight of the coated sheet over time, or by measuring the change in the surface temperature of the coated part over time. For example, a radiation thermometer can be used to measure the surface temperature of the coated part. The change in weight of the coated sheet over time may be measured in advance to prepare a curve showing the change in weight over time, and the time of each section may be determined from the curve. Alternatively, the time-dependent change in the surface temperature of the coated portion may be measured in advance, a curve showing the time-dependent change in the surface temperature may be prepared, and the time of each section may be determined from the curve.

3. Other Steps The method for manufacturing an electrode sheet in the present disclosure may include a coating step of forming a coated portion coated with an electrode material on the second surface of the current collector sheet. In this case, it is preferable to form the coated part on the second surface at a position overlapping with the coated part on the first surface in plan view. Furthermore, after the coating step, a drying step may be included to dry the coated portion on the second surface. In this case, it is preferable to irradiate the second surface side of the current collector sheet with pulsed laser light in the constant rate drying section and the lapse rate drying section, similarly to the first surface side.

The method for manufacturing an electrode sheet in the present disclosure may include a pressing step of pressing the electrode sheet in the thickness direction. Through the pressurizing process, the electrode layer is brought into pressure contact with the current collector sheet.

4. Electrode Sheet The electrode sheet manufactured in the present disclosure includes a current collector sheet and an electrode layer formed on the first surface of the current collector sheet. Further, the electrode sheet may also have an electrode layer on the second surface of the current collector sheet. That is, the electrode sheet may have electrode layers on both the first and second surfaces of the current collector sheet. The electrode layer formed on the first surface of the current collector sheet may be a positive electrode active material layer or a negative electrode active material layer. The electrode layer formed on the first surface and the electrode layer formed on the second surface of the current collector sheet may both be positive electrode active material layers, both may be negative electrode active material layers, and one One may be a positive electrode active material layer and the other may be a negative electrode active material layer.

Although the type of battery in which the electrode body is used is not particularly limited, examples include lithium ion secondary batteries. Applications of batteries include, for example, power sources for vehicles such as hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), electric vehicles (BEV), gasoline vehicles, and diesel vehicles. In particular, it is preferably used as a power source for driving a hybrid vehicle (HEV), plug-in hybrid vehicle (PHEV), or electric vehicle (BEV). Batteries may also be used as a power source for moving objects other than vehicles (for example, trains, ships, and airplanes), and may be used as a power source for electrical products such as information processing devices.

Hereinafter, the present disclosure will be further explained by showing examples.

First, we determined the irradiation conditions for pulsed laser light. (1) First, the relationship between the energy density of continuous wave laser light and drying time was determined. (2) Next, a target drying time was set. (3) From the relationship between the energy density of the continuous wave laser beam and the drying time, the energy density for the target drying time was determined. For example, when the target drying time was 150 seconds, the energy density was 1.0 W/cm ² . (4) Next, the ON time and OFF time when irradiating pulse wave laser light were determined. For example, the ON time was 0.5 seconds and the OFF time was 0.5 seconds. (5) Next, we determined the conditions under which the above (3) and (4) are compatible. For example, if the energy density is 2.0 W/cm ² , the ON time is 0.5 seconds, and the OFF time is 0.5 seconds, the energy density per second is 1.0 W/cm ² , and the above (3). It will be the same as the energy density.

Next, in the preheating section, continuous wave laser light is irradiated with an energy density of 1.0 W/cm ² , and in the constant rate drying section and the lapse rate drying section, the energy density is 2.0 W/cm ² , ON time is 0.5 seconds, and OFF is applied. Pulse wave laser light was irradiated for 0.5 seconds.

The present disclosure is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any configuration that has substantially the same technical idea as the claims of the present disclosure and provides similar effects is the present invention. within the technical scope of the disclosure.

1... Current collector sheet 2... Coated section 3... Uncoated section 10... Coated sheet

Claims (1)

a preparation step of preparing a coated sheet in which a coated part coated with an electrode material is arranged on a first surface of a current collector sheet having a longitudinal direction in a first direction;
a drying step of drying the coated area by irradiating the coated sheet with a laser beam while conveying the coated sheet in the first direction,
In the drying step, the pulsed laser beam is irradiated in the constant rate drying section and the decreasing rate drying section.

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