Electrode manufacturing method

Abstract

To an electrode manufacturing method capable of suppressing edge cracking of the coating portion in an intermittent coating type electrode.SOLUTION: The electrode manufacturing method includes: a coating step of intermittently applying electrode mixture slurry onto the current collector foil to form a coated area where the electrode composite layer is formed and an uncoated area where the electrode layer is not formed; and a drying step of drying the electrode mixture slurry. The uncoated area is cooled in the drying step.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2021-044096) discloses a method of processing an end portion of an electrode sheet formed by wet powder film formation with a squeegee blade provided on a conveyance path to form an end portion with high linearity.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As an electrode sheet often adopted in a high energy density battery, an intermittent coating type electrode sheet in which a formed portion (coating portion) of an active material layer and an unformed portion (uncoated portion) alternately exist on a current collector foil is known.

[0005] [[ID=三十九]]However, in the production of an intermittent coating type electrode sheet, when drying the electrode composite material slurry coated on the current collector foil, the temperature of the uncoated portion tends to increase, and there is a risk of end cracking in the coating portion.

[0006] An object of the present disclosure is to suppress end cracking in a coating portion of an intermittent coating type electrode.

Means for Solving the Problems

[0007] 〔1〕A coating step of intermittently coating an electrode composite material slurry on a current collector foil to form a coating portion where an electrode composite material layer is formed and an uncoated portion where the electrode composite material layer is not formed, A drying step of drying the electrode composite material slurry, A method for manufacturing an electrode, wherein the uncoated portion is cooled during the drying step.

[0008] Compared to the uncoated portion, the coated portion is less susceptible to temperature rise due to latent heat, as the solvent contained in the electrode mixture slurry does not evaporate easily. Focusing on this point, the inventors of this disclosure have found that by cooling the uncoated portion, the temperature rise of the uncoated portion can be suppressed, thereby suppressing cracking at the edges of the coated portion.

[0009] [2] The method for manufacturing an electrode according to [1], wherein the uncoated portion is cooled by bringing it into contact with a roll.

[0010] [3] The method for manufacturing an electrode according to [1] or [2], wherein the uncoated portion is cooled from the back surface of the current collector foil.

[0011] [4] The method for manufacturing an electrode according to any one of [1] to [3], wherein the entire uncoated portion is cooled during the drying step. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic flowchart of the electrode manufacturing method in this embodiment. [Figure 2] Figure 2 is a conceptual diagram showing an example of a cooling method for the uncoated portion in this embodiment. [Figure 3] Figure 3 is a conceptual diagram showing another example of a cooling method for the uncoated portion in this embodiment. [Modes for carrying out the invention]

[0013] Embodiments of the present disclosure (hereinafter abbreviated as "Embodiments") and examples of the present disclosure (hereinafter abbreviated as "Examples") are described below. However, these embodiments and examples do not limit the technical scope of the present disclosure. In this specification, "positive electrode" and "negative electrode" are collectively referred to as "electrodes."

[0014] <Method of manufacturing electrodes> Figure 1 is a schematic flowchart of the electrode manufacturing method according to this embodiment. As shown in Figure 1, the electrode manufacturing method according to this embodiment comprises at least (a) a coating step and (b) a drying step. In the drying step, the uncoated portion is cooled. The electrode manufacturing method according to this embodiment may also include (c) a pressing step.

[0015] The electrodes manufactured in this embodiment may be positive electrodes, negative electrodes, or bipolar electrodes. The electrodes manufactured in this embodiment may be used in liquid-based batteries, polymer batteries, or all-solid-state batteries. The electrodes obtained by the manufacturing method of this disclosure are suitable for obtaining large-area electrodes (for example, 1000 mm × 1000 mm).

[0016] (a) Coating process In the coating process, electrode mixture slurry is intermittently applied to the current collector foil, creating coated areas where the electrode mixture layer is formed and uncoated areas where the electrode mixture layer is not formed.

[0017] (Current collector foil) The current collector foil may have a thickness of, for example, 5 μm to 100 μm. The current collector foil is conductive. Examples of current collector foils include aluminum (Al) foil, Al alloy foil, copper (Cu) foil, Cu alloy foil, nickel (Ni) foil, Ni alloy foil, titanium (Ti) foil, and Ti alloy foil. When the electrode is the positive electrode, the current collector foil is, for example, Al foil. When the electrode is the negative electrode, the current collector foil is, for example, Cu foil.

[0018] The surface of the current collector foil may be coated with carbon (C-coat treatment). There are no particular restrictions on the type of carbon used; examples include graphite, easily graphitizable carbon, and poorly graphitizable carbon.

[0019] (Electrode mixture slurry) The electrode composite slurry contains an electrode active material. The electrode active material may be a positive electrode active material or a negative electrode active material. When the electrode active material is a positive electrode active material, the electrode material is a positive electrode material. When the electrode active material is a negative electrode active material, the electrode material is a negative electrode material.

[0020] Examples of the positive electrode active material include lithium-containing metal oxides, lithium-containing phosphates, etc. Examples of the lithium-containing metal oxides include Li(NiCoMn)O2, Li(NiCoAl)O2, etc. Examples of the lithium-containing phosphates include LiFePO4, etc.

[0021] Examples of the negative electrode active material include carbon-based negative electrode active materials such as graphite, graphitizable carbon, non-graphitizable carbon, etc., alloy-based negative electrode active materials containing silicon (Si), tin (Sn), etc.

[0022] The electrode composite slurry contains a solvent. Examples of the solvent include aqueous solvents, organic solvents, etc. The aqueous solvent means water or a mixed solvent containing water and a polar organic solvent.

[0023] Examples of the aqueous solvent include water (ion-exchanged water), etc. Examples of the polar organic solvents that can be used in the mixed solvent include alcohols such as methanol, ethanol, isopropyl alcohol, etc., ketones such as acetone, etc., ethers such as tetrahydrofuran, etc. Examples of the organic solvent include N-methyl-2-pyrrolidone (NMP), etc.

[0024] The electrode composite slurry may further contain a conductive material. Examples of the conductive material include acetylene black (AB), vapor-grown carbon fiber (VGCF), carbon nanotube (CNT), etc.

[0025] The electrode material may further contain a binder. Examples of the binder include carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), etc.

[0026] The amount of conductive material and binder may be, for example, 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of electrode active material.

[0027] (Coating) In this process, electrode mixture slurry is applied to the surface of the current collector foil using any coating device. For example, a die coater or roll coater may be used as the coating device. The electrode mixture slurry may be applied to only one side (front) of the current collector foil. Alternatively, the electrode mixture slurry may be applied to both the front and back surfaces of the current collector foil. The electrode mixture slurry is applied to the current collector foil intermittently.

[0028] 《(b) Drying process》 In the drying process, the electrode mixture slurry coated onto the current collector foil is dried. For example, the electrode mixture slurry may be dried by a hot air drying oven or laser irradiation. From the viewpoint of carbon dioxide emissions, drying by laser irradiation is preferred.

[0029] The laser may be a semiconductor laser. Semiconductor lasers have the advantages of a large irradiation area, compact equipment, and high conversion efficiency, making them suitable for laser drying of slurries. The wavelength of the semiconductor laser may be, for example, 450 to 1600 nm or 800 to 1200 nm. If the surface of the current collector foil is treated with a C-coat, absorption by the semiconductor laser is increased, making it suitable for use.

[0030] The laser output is not particularly limited as long as it can vaporize the solvent without altering the constituent materials (solids) of the active material layer contained in the electrode mixture slurry. For example, the laser output is between 0.5W and 1000W. The drying time is determined by the laser power density (W / cm²). 2 The settings can be adjusted. For example, the temperature of the electrode (slurry) surface may be monitored using an infrared thermometer, and laser drying may be performed while adjusting the laser output.

[0031] The laser may be a continuous-wave (CW) laser or a pulsed laser.

[0032] The slurry temperature during laser drying is, for example, 20 to 100°C. Air blowing may or may not be performed during laser drying. If air blowing is performed, the air temperature is, for example, 80 to 120°C, and the air velocity is, for example, 1 to 20 m / s.

[0033] (cooling) In this process, the uncoated portion is cooled. By cooling the uncoated portion in this process, the temperature rise of the uncoated portion is suppressed, and cracking at the boundary between the coated portion and the uncoated portion (edge ​​cracking of the coated portion) can be suppressed. Figure 2 is a conceptual diagram showing one example of the cooling method for the uncoated portion in this embodiment, and Figure 3 is a conceptual diagram showing another example of the cooling method for the uncoated portion in this embodiment. The cooling method for the uncoated portion in this process will be explained below with reference to Figures 2 and 3.

[0034] There are no particular restrictions on the cooling method, but examples include cooling with a roll 3 (see Figure 2) and cooling with a blower 4 (see Figure 3). As a cooling method, cooling with a roll 3 is preferred from the viewpoint of being able to cool the entire uncoated area 2 evenly.

[0035] The roll 3 is preferably made of a material with high thermal conductivity. This allows for efficient cooling of the uncoated portion 2. Examples of materials with high thermal conductivity include metals such as silver, copper, aluminum, and silicon. The surface of the roll 3 may be made of a material with high thermal conductivity, or the entire roll 3 may be made of a material with high thermal conductivity.

[0036] It is preferable that the height of the roll 3 is equal to or greater than the length of the electrode (labeled "D" in Figure 2). It is also preferable that the circumference of the roll 3 is approximately the same as the width of the uncoated portion 2 (labeled "W" in Figure 2). By using such a roll 3, the uncoated portion 2 can be cooled efficiently.

[0037] The uncoated portion 2 is preferably cooled by contacting the roll 3. This allows for efficient cooling of the uncoated portion 2. The force (load) applied by the roll 3 to the uncoated portion 2 is, for example, 5N or less.

[0038] Roll 3 is cooled by any method. Roll 3 may be cooled by, for example, a blower 4. The air temperature of the blower 4 should be adjusted as appropriate so that it is above the temperature of the coated portion 1 and below the temperature of the uncoated portion 2. The air temperature of the blower 4 may be, for example, between 100°C and 180°C. The air velocity of the blower 4 should be adjusted as appropriate so that the temperature of the roller 3 reaches the above set temperature. However, if the air velocity of the blower 4 is slow, the uncoated portion 2 may not be sufficiently cooled, and if the air velocity of the blower 4 is fast, undulations may occur in the coated portion 2, or cracks may occur at the edges of the coated portion 2. For this reason, the air velocity of the blower 4 may be, for example, 1 to 12 m / s or 1 to 8 m / s.

[0039] Cooling is preferably performed from the back surface of the current collector foil 10, that is, from the surface of the current collector foil 10 where the coating portion 1 is not formed. For example, when drying an electrode mixture slurry by laser irradiation, the laser irradiation is performed from the front surface of the current collector foil. Since the laser device used for laser irradiation has filters, piping, etc., it is preferable to perform cooling from the back surface of the current collector foil 10 so as not to interfere with these.

[0040] The uncoated portion 2 may be partially cooled or the entire portion may be cooled. From the viewpoint of suppressing cracking at the edges of the coated portion 1, it is preferable that the entire uncoated portion 2 be cooled.

[0041] (c) Pressing process In the pressing process, the coated portion 1, which has been dried in the drying process, is pressed to form an active material layer. That is, an electrode with an active material layer formed on the current collector foil is manufactured. The pressure can be adjusted as appropriate according to the thickness of the active material layer after pressing. [Examples]

[0042] The following describes this embodiment using examples, but this embodiment is not limited to these examples.

[0043] (Example 1) C-coated current collector foil and electrode composite slurry were prepared. The electrode composite slurry was intermittently coated onto the surface of the current collector foil, forming coated areas (1200 mm x 1600 mm) and uncoated areas. The coated and uncoated areas were dried using a semiconductor laser. During drying, the uncoated areas were cooled by pressing a roller against the back surface of the current collector foil. The roller was made of silver and was large enough to cool the entire uncoated area. During cooling, the roller was cooled with a blower. After drying, the electrodes of Example 1 were manufactured by pressing.

[0044] (Comparative Example 1) In Comparative Example 1, cooling of the uncoated area was not performed. That is, the same material as in Example 1 was prepared. The electrode mixture slurry was intermittently coated onto the surface of the current collector foil, forming a coated area (1200 mm x 1600 mm) and an uncoated area. The coated and uncoated areas were dried with a semiconductor laser. After drying, the electrode of Comparative Example 1 was manufactured by pressing.

[0045] <Rating> In the above-described Example 1 and Comparative Example 1, cracks at the edges of the coated portion of each electrode were visually confirmed.

[0046] <Result> In Example 1, no cracking was observed at the edges of the coated area. On the other hand, in Comparative Example 1, cracking was observed at the edges of the coated area.

[0047] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims and not by the foregoing description, and all modifications are intended to be in the sense and scope equivalent to the claims. [Explanation of Symbols]

[0048] 1. Coated section, 2. Uncoated section, 3. Roll, 4. Blower, 10. Current collector foil.

Claims

1. A coating step in which an electrode mixture slurry is intermittently applied to a current collector foil to form a coated area where an electrode mixture layer is formed and an uncoated area where the electrode mixture layer is not formed, The process includes a drying step for drying the electrode mixture slurry, The drying process is carried out by laser irradiation. A method for manufacturing an electrode, wherein, in the drying step, the uncoated portion is cooled in the region where drying is taking place.

2. The method for manufacturing an electrode according to claim 1, wherein the uncoated portion is cooled by contacting it with a roll.

3. The method for manufacturing an electrode according to claim 1, wherein the uncoated portion is cooled from the back surface of the current collector foil.

4. The method for manufacturing an electrode according to claim 1, wherein the entire uncoated portion is cooled during the drying step.

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