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 technology]

[0002] Patent Document 1 (JP 2021-044096 A) discloses a method of processing the ends of an electrode sheet formed by wet powder deposition using a scraping blade installed on the transport path to form ends with high linearity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-044096 Summary of the Invention [Problem to be solved by the invention]

[0004] An intermittently coated electrode sheet, in which formed areas (coated areas) and unformed areas (uncoated areas) of the active material layer exist alternately on a current collector foil, is known as an electrode sheet that is often used in high energy density batteries.

[0005] However, in producing an intermittently coated electrode sheet, when the electrode mixture slurry coated on the current collector foil is dried, the temperature of the uncoated area is likely to become high, which may cause cracks at the edges of the coated area.

[0006] An object of the present disclosure is to suppress edge cracking of a coated portion in an intermittently coated electrode. [Means for solving the problem]

[0007] [1] a coating step of intermittently coating an electrode mixture slurry on a current collector foil to form a coated portion having an electrode mixture layer and an uncoated portion having no electrode mixture layer; A drying step of drying the electrode mixture slurry, The method for producing an electrode, wherein the uncoated portion is cooled in the drying step.

[0008] Compared to the uncoated portion, the temperature of the coated portion is less likely to rise due to the influence of latent heat until the solvent contained in the electrode mixture slurry evaporates. The inventors of the present disclosure have focused on this point and discovered that by cooling the uncoated portion, it is possible to suppress the temperature rise of the uncoated portion and suppress edge cracking of the coated portion.

[0009] [2] The method for producing an electrode according to [1], wherein the uncoated portion is cooled by contacting it 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 collecting foil.

[0011] [4] The method for producing an electrode according to any one of [1] to [3], wherein the uncoated portion is entirely cooled in the drying step. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a flow chart showing an outline of the method for producing an electrode in this embodiment. [Diagram 2] FIG. 2 is a conceptual diagram showing an example of a method for cooling an uncoated portion in this embodiment. [Diagram 3] FIG. 3 is a conceptual diagram showing another example of a method for cooling an uncoated portion in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present disclosure (hereinafter may be abbreviated as "the present embodiment") and an example of the present disclosure (hereinafter may be abbreviated as "the present embodiment") will be described. However, the present embodiment and the present embodiment do not limit the technical scope of the present disclosure. In this specification, the "positive electrode" and the "negative electrode" are collectively referred to as "electrodes".

[0014] <Electrode manufacturing method> Fig. 1 is a flow chart showing an outline of a method for producing an electrode according to the present embodiment. As shown in Fig. 1, the method for producing an electrode according to the present embodiment includes at least (a) a coating step and (b) a drying step. In the drying step, the uncoated portion is cooled. The method for producing an electrode according to the present embodiment may also include (c) a pressing step.

[0015] The electrode manufactured in this embodiment may be a positive electrode, a negative electrode, or a bipolar electrode. The electrode manufactured in this embodiment may be used in any of liquid batteries, polymer batteries, and all-solid-state batteries. The electrode obtained by the manufacturing method of the present disclosure is suitable for obtaining an electrode with a large area (for example, 1000 mm x 1000 mm).

[0016] (a) Coating process In the coating step, the electrode mixture slurry is intermittently coated onto the current collector foil to form a coated portion where an electrode mixture layer is formed and an uncoated portion where no electrode mixture layer is formed.

[0017] (current collecting foil) The current collecting foil may have a thickness of, for example, 5 μm or more and 100 μm or less. The current collecting foil is conductive. Examples of the current collecting foil 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 a positive electrode, the current collecting foil is, for example, an Al foil. When the electrode is a negative electrode, the current collecting foil is, for example, a Cu foil.

[0018] The surface of the current collector foil may be coated with carbon (C-coat treatment). The carbon is not particularly limited, and examples thereof include graphite, graphitizable carbon, and non-graphitizable carbon.

[0019] (Electrode mixture slurry) The electrode mixture 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 and lithium-containing phosphates. Examples of the lithium-containing metal oxides include Li(NiCoMn)O2 and Li(NiCoAl)O2. Examples of the lithium-containing phosphates include LiFePO4.

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

[0022] The electrode mixture slurry contains a solvent. Examples of the solvent include an aqueous solvent, an organic solvent, etc. The aqueous solvent refers to water or a mixed solvent containing water and a polar organic solvent.

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

[0024] The electrode mixture slurry may further contain a conductive material, such as acetylene black (AB), vapor grown carbon fiber (VGCF), carbon nanotube (CNT), etc.

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

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

[0027] (Coating) In this step, the electrode mixture slurry is applied to the surface of the current collecting foil by an arbitrary coating device. For example, a die coater, a roll coater, or the like may be used as the coating device. The electrode mixture slurry may be applied to only one side (front side) of the current collecting foil. The electrode mixture slurry may be applied to both the front and back sides of the current collecting foil. The electrode mixture slurry is intermittently applied to the current collecting foil.

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

[0029] The laser may be a semiconductor laser. A semiconductor laser has the features of a large irradiation area, small equipment, and high conversion efficiency, and therefore can be suitably used for laser drying of a slurry. The wavelength of the semiconductor laser may be, for example, 450 to 1600 nm or 800 to 1200 nm. When the surface of the current collecting foil is C-coated, the absorption by the semiconductor laser is high, and therefore the current collecting foil can be suitably used.

[0030] The output of the laser is not particularly limited as long as it can evaporate the solvent without causing deterioration of the constituent material (solid content) of the active material layer contained in the electrode mixture slurry. The output of the laser is, for example, 0.5 W or more and 1000 W or less. The drying time is determined by the laser output density (W / cm 2 For example, the temperature of the electrode (slurry) surface may be monitored by a radiation thermometer and the laser output may be adjusted while performing laser drying.

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

[0032] The temperature of the slurry during laser drying is, for example, 20 to 100° C. During laser drying, air may or may not be blown. When air is blown, the temperature of the air is, for example, 80 to 120° C., and the air speed 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 can be suppressed, and cracks at the boundary between the coated portion and the uncoated portion (edge ​​cracks of the coated portion) can be suppressed. FIG. 2 is a conceptual diagram showing an example of a method for cooling the uncoated portion in this embodiment, and FIG. 3 is a conceptual diagram showing another example of a method for cooling the uncoated portion in this embodiment. Hereinafter, the cooling method of the uncoated portion in this process will be described with reference to FIGS. 2 and 3.

[0034] The cooling method is not particularly limited, and examples thereof include cooling with a roll 3 (see FIG. 2) and cooling with a blower 4 (see FIG. 3). As a cooling method, cooling with a roll 3 is preferred from the viewpoint of being able to uniformly cool the entire uncoated portion 2.

[0035] The roll 3 is preferably made of a material having high thermal conductivity. In this way, the uncoated portion 2 can be cooled efficiently. Examples of materials having high thermal conductivity include metals such as silver, copper, aluminum, and silicon. The surface of the roll 3 may be made of a material having high thermal conductivity, or the entire roll 3 may be made of a material having high thermal conductivity.

[0036] The height of the roll 3 is preferably equal to or greater than the length of the electrode ("D" in FIG. 2). The circumference of the roll 3 is preferably approximately the same as the width of the uncoated portion 2 ("W" in FIG. 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 it with the roll 3. In this way, it is possible to efficiently cool the uncoated portion 2. The force (load) applied by the roll 3 to contact the uncoated portion 2 is, for example, 5 N or less.

[0038] The roll 3 is cooled by any method. The roll 3 may be cooled by, for example, a blower 4. The temperature of the blower 4 may be appropriately adjusted so that it is equal to or higher than the temperature of the coated part 1 and equal to or lower than the temperature of the uncoated part 2. The temperature of the blower 4 may be, for example, 100°C or higher and 180°C or lower. The wind speed of the blower 4 may be appropriately adjusted so that the temperature of the roller 3 is the above-mentioned set temperature. However, if the wind speed of the blower 4 is slow, the uncoated part 2 may not be sufficiently cooled, and if the wind speed of the blower 4 is fast, the coated part 2 may be undulated or the edge cracks of the coated part 2 may occur. Therefore, the wind speed 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 collecting foil 10, i.e., the surface of the current collecting foil 10 on which the coating portion 1 is not formed. For example, when drying the electrode mixture slurry by laser irradiation, the laser is irradiated from the front surface of the current collecting foil. Since the laser device used for laser irradiation has filters, piping, and the like, it is preferable to cool the current collecting foil 10 from the back surface so as not to be hindered by these.

[0040] The uncoated portion 2 may be cooled partially or entirely. From the viewpoint of preventing edge cracks in the coated portion 1, it is preferable that the uncoated portion 2 is cooled entirely.

[0041] (c) Pressing process In the pressing step, the coated portion 1 dried in the drying step is pressed to form an active material layer. That is, an electrode is produced in which an active material layer is formed on a current collector foil. The pressure can be appropriately adjusted depending on the thickness of the active material layer after pressing. EXAMPLES

[0042] The present embodiment will be described below using examples, but the present embodiment is not limited to these.

[0043] Example 1 A C-coated current collecting foil and an electrode mixture slurry were prepared. The electrode mixture slurry was intermittently applied to the surface of the current collecting foil to form a coated portion (1200 mm x 1600 mm) and an uncoated portion. The coated portion and the uncoated portion were dried by a semiconductor laser. During drying, the uncoated portion was cooled by pressing a roller against the back surface of the current collecting foil. The roller was made of silver and had a size that could cool the entire uncoated portion. During cooling, the roller was cooled by a blower. After drying, the electrode of Example 1 was produced by pressing.

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

[0045] <Evaluation> In the above-mentioned Example 1 and Comparative Example 1, the edge cracks in the coated portion of each electrode were visually confirmed.

[0046] <Result> No edge cracking of the coated portion was observed in Example 1. On the other hand, edge cracking of the coated portion was observed in Comparative Example 1.

[0047] The embodiments and examples disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0048] 1 coated section, 2 uncoated section, 3 roll, 4 blower, 10 current collecting foil.

Claims

1. a coating step of intermittently coating an electrode mixture slurry onto a current collector foil to form a coated portion having an electrode mixture layer and an uncoated portion having no electrode mixture layer formed thereon; A drying step of drying the electrode mixture slurry, The method for producing an electrode, wherein the uncoated portion is cooled in the drying step.

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

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

4. The method for producing an electrode according to claim 1 , wherein the uncoated portion is entirely cooled in the drying step.

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