Method for manufacturing electrode sheets

Abstract

To provide a method for manufacturing an electrode sheet which can prevent cracking of an electrode layer.SOLUTION: The present disclosure provides a method for manufacturing an electrode sheet including: a preparation step of preparing an application sheet having an application unit on which an electrode material is applied, on a first surface of a collector sheet having a longer direction in a first direction; a preheating step of heating the application unit to a first temperature by a laser beam radiated from a laser head while conveying the application sheet in the first direction; and a dry step of drying the application unit which has been heated to the first temperature, by hot wind or infrared light, while conveying the application sheet in the first direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an electrode sheet.

Background Art

[0002] As a technique related to a method for manufacturing an electrode sheet used in manufacturing a battery such as a lithium-ion secondary battery, a method is known in which an electrode material is applied to a conveyed current collector sheet to form a coating portion, and the coating portion is dried to obtain an electrode layer.

[0003] For example, in Patent Document 1, an application step of applying an active material mixture to a conveyed long metal foil to form a coating portion of the active material mixture, and a first irradiation step of irradiating a laser to an irradiation position of the long metal foil located upstream in the conveyance direction of the long metal foil from both ends of the mixture application location along the short side direction of the long metal foil, which is performed before the application step, and a second irradiation step of irradiating a laser to both edge portions in the short side direction in the coating portion formed by the application step, which is performed after the first irradiation step, are disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a method for drying a coated sheet having a coating portion coated with an electrode material, a method of irradiating laser light as a heat source has been proposed. On the other hand, as will be described later, when drying is performed only by irradiating laser light, there is a risk that cracks will occur in the obtained electrode layer.

[0006] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide a method for manufacturing an electrode sheet that can prevent cracks in the electrode layer. [Means for solving the problem]

[0007] [1] A method for manufacturing an electrode sheet, comprising: a preparation step of preparing a coated sheet having a coated portion on a first surface of a current collector sheet having a longitudinal direction in the first direction, wherein an electrode material is coated thereon; a preheating step of heating the coated portion to a first temperature with laser light irradiated from a laser head while conveying the coated sheet in the first direction; and a drying step of drying the coated portion that has reached the first temperature with hot air or infrared rays while conveying the coated sheet in the first direction. [Effects of the Invention]

[0008] This disclosure offers the advantage of being able to manufacture electrode sheets while preventing cracking of the electrode layer. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram illustrates the crack prevention mechanism in this disclosure. [Figure 2] These are schematic plan views and schematic cross-sectional views illustrating the coated sheet in this disclosure. [Figure 3] This is a schematic diagram illustrating the preheating and drying processes in this disclosure. [Modes for carrying out the invention]

[0010] The method for manufacturing the electrode sheet described in this disclosure will be explained in detail below.

[0011] In the electrode sheet manufacturing method described herein, first, a coated sheet is prepared having a coated portion coated with electrode material on the first surface of a current collector sheet having a longitudinal direction in the first direction (preparation step). Next, while conveying the coated sheet in the first direction, the coated portion is heated to a first temperature by laser light irradiated from a laser head (preheating step). Then, while conveying the coated sheet in the first direction, the coated portion that has reached the first temperature is dried with hot air or infrared rays (drying step).

[0012] As mentioned above, it is known that laser light is used to dry the coating layer. Laser light has the advantage of being able to raise the temperature of the coating layer in a shorter time, thus shortening the coating time. As shown in Figures 1(a) and (b), the coating layer 2 contains solid components 2a such as active material and liquid components 2b such as solvent. Generally, the liquid component 2b evaporates in the order of the surface side of the coating layer 2 (the side opposite to the current collector sheet 1 in the thickness direction T) and then the side of the current collector sheet 1. Also, as shown in Figure 1(b), as drying progresses, the vapor from the evaporation of the liquid component becomes more difficult to release to the outside of the coating layer because the solid component acts as a barrier. Therefore, if the drying process is carried out using only high-energy laser light, there will be a large amount of vapor even in the later stages of drying when vapor release becomes difficult, and as a result, internal pressure may be generated and cracking may occur.

[0013] In contrast, the electrode sheet manufacturing method described in this disclosure suppresses cracking by using hot air or infrared (IR), which dries more slowly than laser light (generating less steam), after irradiation with laser light. Furthermore, since the temperature can be raised to a predetermined first temperature in a short time using laser light, the advantage of laser light, which shortens the drying time, can also be enjoyed.

[0014] 1. Preparation process FIG. 2(a) is a schematic plan view illustrating a coating sheet prepared in the preparation step in the present disclosure, and FIG. 2(b) is a cross-sectional view taken along line A-A of FIG. 2(a). As shown in FIGS. 2(a) and 2(b), the preparation step in the present disclosure is a step of preparing a coating sheet 10 having 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.

[0015] 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 not particularly limited as long as it is a material used as a current collector such as a negative electrode current collector, a positive electrode current collector, or a bipolar current collector.

[0016] The electrode material may be a negative electrode material (material for 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 for 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 are used.

[0017] The method for preparing the coating sheet is not particularly limited. For example, it can be produced by transporting the current collector sheet in the first direction by a conveyor and coating the electrode material on the first surface of the current collector sheet by a coater to form a coating portion. At this time, the electrode material may be continuously coated or intermittently coated.

[0018] 2. Preheating step As shown in FIG. 3(a), the preheating step in the present disclosure is a step of heating the coating portion ۲ to a first temperature by laser light irradiated from a laser head 20 while transporting the coating sheet 10 in the first direction D1.

[0019] The first temperature can be appropriately set according to the situation such as the temperature of the coating layer before preheating, the composition of the electrode material, and the thickness of the coating layer. The first temperature is, for example, 25°C or higher and 100°C or lower.

[0020] The energy density of the laser light and the irradiation time of the laser light can be appropriately adjusted according to the situation such as the first temperature, the size of the coating layer, etc. The energy density of the laser light is, for example, 0.1 W / cm , , ,

[0026] or more and 1.0 W / cm 2 or less. The irradiation time of the laser light is, for example, 10 seconds or more and 3 minutes or less.

[0021] 3. Drying process The drying process in the present disclosure is a process of drying the coating portion that has reached the first temperature with hot air or infrared rays while transporting the coating sheet in the first direction.

[0022] As shown in FIG. 3(b), it is preferable that the preheating process and the drying process are continuous processes. Also, as shown in FIG. 3(b), in the drying process, for example, the electrode sheet 10 after the preheating process is transported to the drying furnace 30, and the coating layer 2 is dried by a hot air supply device or an infrared irradiation device provided in the drying furnace 30.

[0023] The temperature of the hot air may be the same as or different from the first temperature described above. In the latter case, the temperature of the hot air may be lower or higher than the first temperature. The temperature of the hot air is, for example, 50°C or more and 140°C or less.

[0024] The wavelength of the infrared rays is not particularly limited and can be appropriately adjusted.

[0025] The drying process is preferably carried out, for example, until the moisture content in the coating layer becomes a predetermined value or less. The moisture content is, for example, 5000 ppm or less, may be 3000 ppm or less, or may be 1000 ppm or less.

[0026] 4. Electrode sheet The electrode sheet manufactured in this disclosure comprises a current collector sheet and an electrode layer formed on a first surface of the current collector sheet. Multiple electrode layers may be formed intermittently on the current collector sheet. In the electrode sheet, the electrode layers may be formed on the first surface of the current collector sheet and on a second surface facing the first surface, respectively.

[0027] The electrode sheet is used in the manufacture of a battery and may be either a positive electrode sheet or a negative electrode sheet. In other words, the current collector sheet and electrode layer may be either a positive electrode current collector and a positive electrode active material layer, or a negative electrode current collector and a negative electrode active material layer. When the electrode sheet in this disclosure is a positive electrode sheet, it is combined with a negative electrode sheet and a separator to form an electrode body. Similarly, when the electrode sheet in this disclosure is a negative electrode sheet, it is combined with a positive electrode sheet and a separator to form an electrode body.

[0028] The type of battery using electrode sheets is not particularly limited, but lithium-ion secondary batteries are an example. Applications of the battery include powering vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline cars, and diesel cars. It is particularly preferable for the battery to be used as a power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). The battery may also be used as a power source for mobile devices other than vehicles (e.g., trains, ships, aircraft), or as a power source for electrical products such as information processing devices.

[0029] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Explanation of symbols]

[0030] 1 ... Current collection sheet 2 ... Coating section 10 ...Coated sheet 20… Laser head 30...Drying oven

Claims

[Claim 1] Preparation step: Prepare a coated sheet having a coated portion on the first surface of a current collector sheet having a longitudinal direction in the first direction, wherein an electrode material is coated on the first surface of the current collector sheet. While the coated sheet is being transported in the first direction, the coated area is irradiated from a laser head with an energy density of 0.1 W / cm². ２ 1.0W / cm or more ２ A preheating step is performed by irradiating the following laser light for 10 seconds to 3 minutes to heat it to a first temperature of 100°C or less. The process includes a drying step in which the coated sheet is conveyed in the first direction, and the coated portion that has reached the first temperature is dried with hot air or infrared rays. The preheating step is a step in which the coating portion is first heated after the preparation step, A method for manufacturing an electrode sheet, wherein the temperature of the hot air in the drying step is 50°C or higher and 140°C or lower.

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