Method for manufacturing electrode sheet

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 technology]

[0002] 2. Description of the Related Art Known technology relating to a manufacturing method of an electrode sheet used in manufacturing batteries such as lithium-ion secondary batteries is a method in which an electrode material is applied to a conveyed current collector sheet to form a coated portion, and the coated portion is dried to obtain an electrode layer.

[0003] For example, Patent Document 1 discloses a method for manufacturing an electrode, which includes a coating step in which an active material mixture is applied to a long metal foil being transported to form a coated portion of the active material mixture, a first irradiation step that is performed prior to the coating step in which a laser is irradiated to an irradiation position on the long metal foil that is located upstream in the transport direction of the long metal foil from both ends of the mixture application location along the short side of the long metal foil, and a second irradiation step that is performed after the first irradiation step in which a laser is irradiated to both edges in the short side of the coated portion formed by the coating step. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-029256 A Summary of the Invention [Problem to be solved by the invention]

[0005] As a method for drying a coated sheet having a coated portion coated with an electrode material, a method of irradiating a laser beam as a heat source has been proposed. However, as described below, when drying is performed only by irradiating a laser beam, there is a risk of cracks occurring in the obtained electrode layer.

[0006] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide a manufacturing method for an electrode sheet that can prevent cracking of 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 coated with an electrode material on a first surface of a current collecting sheet having a longitudinal direction in a first direction; a preheating step of heating the coated portion to a first temperature by laser light irradiated from a laser head while transporting the coated sheet in the first direction; and a drying step of drying the coated portion that has reached the first temperature by hot air or infrared rays while transporting the coated sheet in the first direction. Effect of the Invention

[0008] The present disclosure has an effect of enabling the production of an electrode sheet while preventing cracks in the electrode layer. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram illustrating a mechanism for preventing cracking in the present disclosure. [Diagram 2] 1A and 1B are a schematic plan view and a schematic cross-sectional view illustrating a coated sheet according to the present disclosure. [Diagram 3] FIG. 2 is a schematic diagram illustrating a preheating step and a drying step in the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The method for producing an electrode sheet according to the present disclosure will be described in detail below.

[0011] In the manufacturing method of an electrode sheet according to the present disclosure, first, a coated sheet having a coated portion coated with an electrode material on a first surface of a current collecting sheet having a longitudinal direction in a first direction is prepared (preparation step). Next, while the coated sheet is transported 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 the coated sheet is transported in the first direction, the coated portion that has reached the first temperature is dried by hot air or infrared rays (drying step).

[0012] As mentioned above, it is known to use laser light for drying the coating layer. Laser light has the advantage that the coating layer can be heated in a shorter time, and the coating time can be shortened. As shown in Figures 1(a) and (b), the coating layer 2 contains solid components 2a such as active materials and liquid components 2b such as solvents. In general, the liquid components 2b evaporate from the surface side of the coating layer 2 (the surface opposite to the current collector sheet 1 in the thickness direction T) and then from the current collector sheet 1 side. Also, as shown in Figure 1(b), as the drying progresses, the solid components act as a barrier and the vapor resulting from the evaporation of the liquid components becomes more difficult to be discharged to the outside of the coating layer. Therefore, if the drying process is performed using only high-energy laser light, the amount of vapor is large even in the latter half of the drying process when the vapor is more difficult to be discharged, which may result in internal pressure and cracks.

[0013] In contrast, in the manufacturing method of the electrode sheet in the present disclosure, after irradiation with the laser light, hot air or infrared rays (IR) that can dry more slowly (generate less steam) than the laser light are used, thereby making it possible to suppress cracking. In addition, by using the laser light, it is possible to raise the temperature to the predetermined first temperature in a short time, so that it is possible to enjoy the advantage of the laser light that the drying time can be shortened.

[0014] 1. Preparation process Fig. 2(a) is a schematic plan view illustrating a coated sheet prepared in the preparation step of the present disclosure, and Fig. 2(b) is a cross-sectional view taken along line AA of Fig. 2(a). As shown in Fig. 2(a) and (b), the preparation step of the present disclosure is a step of preparing a coated sheet 10 having a coated portion 2 coated with an electrode material on a first surface S1 of a current collecting sheet having a longitudinal direction in a first direction D1.

[0015] The current collecting sheet has a longitudinal direction in a first direction. The current collecting sheet has a first surface S1 which is one surface in the thickness direction, and a second surface S2 which is the reverse surface of the first surface S1. The current collecting sheet is not particularly limited as long as it is made of a material that can be 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 (a material for a 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. The electrode material may be a positive electrode material (a material for a 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 coated sheet is not particularly limited, but for example, the coated sheet can be prepared by conveying the current collecting sheet in a first direction with a conveyor while applying the electrode material to the first surface of the current collecting sheet with a coater to form a coated portion. At this time, the electrode material may be applied continuously or intermittently.

[0018] 2. Preheating process As shown in FIG. 3(a), the preheating process in the present disclosure is a process in which the coated section 2 is heated to a first temperature by laser light irradiated from the laser head 20 while the coated sheet 10 is transported in a first direction D1.

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

[0020] The energy density of the laser beam and the irradiation time of the laser beam can be appropriately adjusted depending on the conditions such as the first temperature and the size of the coating layer. The energy density of the laser beam is, for example, 0.1 W / cm 2 More than 1.0W / cm 2 The irradiation time of the laser light is, for example, not less than 10 seconds and not more than 3 minutes.

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

[0022] As shown in Fig. 3(b), the preheating step and the drying step are preferably continuous steps. Also, as shown in Fig. 3(b), in the drying step, for example, the electrode sheet 10 after the preheating step is transported to a drying furnace 30, and the coating layer 2 is dried by a hot air supplier or an infrared ray irradiator provided in the drying furnace 30.

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

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

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

[0026] 4. Electrode sheet The electrode sheet manufactured in the present disclosure has a current collector sheet and an electrode layer formed on a first surface of the current collector sheet. A plurality of 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 opposite to the first surface.

[0027] The electrode sheet is used in the manufacture of a battery and may be a positive electrode sheet or a negative electrode sheet. That is, the current collector sheet and the electrode layer may be a positive electrode collector and a positive electrode active material layer, or a negative electrode collector and a negative electrode active material layer. When the electrode sheet in the present 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 the present 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 in which the electrode sheet is used is not particularly limited, and may be, for example, a lithium ion secondary battery. Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline automobiles, and diesel automobiles. In particular, the battery is preferably used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for moving objects other than vehicles (for example, railways, ships, and aircraft), and may also be used as a power source for electrical appliances such as information processing devices.

[0029] The present disclosure is not limited to the above-described embodiment. The above-described embodiment is merely an example, and any configuration that is substantially the same as the technical idea described in the claims of the present disclosure and that exhibits similar effects is included in the technical scope of the present disclosure. [Explanation of symbols]

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

Claims

[Claim 1] a preparation step of preparing a coated sheet having a coated portion coated with an electrode material on a first surface of a current collecting sheet having a longitudinal direction in a first direction; a preheating step of heating the coated portion to a first temperature by laser light irradiated from a laser head while transporting the coated sheet in the first direction; a drying step of drying the coated portion that has reached the first temperature with hot air or infrared rays while transporting the coated sheet in the first direction.

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