Method for manufacturing electrode

Abstract

To provide a method for manufacturing an electrode capable of suppressing deterioration of a metal foil in a region where an active material composite is not coated.SOLUTION: The present invention relates to a method for manufacturing an electrode including the step of radiatively heating an active material composite on a conveyed metal foil. In the heating step, the metal foil is heated in a bent state such that an uncoated portion of the metal foil, where the active material composite is not applied, is kept away from the radiant heat.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Various techniques have been proposed for manufacturing electrodes such as those disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-235975 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a technique for using a laser to heat a metal foil coated with an active material mixture. In the conventional technique, the temperature of the metal foil in the uncoated portion of the active material mixture may rise excessively during heating, which may cause deterioration such as surface oxidation.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and has as its main object to provide a method for manufacturing an electrode that can suppress deterioration of the metal foil in the portion not coated with the active material mixture. [Means for solving the problem]

[0006] That is, the present disclosure includes the following aspects. <1> A method for manufacturing an electrode, comprising a heating step of radiating heat to an active material mixture on a transported metal foil, The method for manufacturing an electrode, wherein the heating step comprises heating an uncoated portion of the metal foil that is not coated with the active material mixture while the uncoated portion is folded away from the radiant heating. [Effects of the Invention]

[0007] The method for manufacturing an electrode according to the present disclosure can suppress deterioration of the metal foil in the portion not coated with the active material mixture. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an example of the heating step of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of the schematic diagram shown in FIG. 1 viewed from the front in the conveying direction. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of electrodes that do not characterize the present disclosure) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field. The dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships. The drawings also show the directions of a three-dimensional Cartesian coordinate system. Here, the xy plane is the horizontal plane, the z-axis direction is the vertical direction, and the larger dimension in the z-axis direction is considered to be the top. Furthermore, in this specification, when describing the arrangement of another component relative to a component, the terms "above" or "below" simply refer to both the case where the other component is arranged directly above or below the component so as to be in contact with the component, and the case where the other component is arranged above or below the component via another component, unless otherwise specified.

[0010] The present disclosure provides a method for manufacturing an electrode, which includes a heating step of radiantly heating an active material mixture on a transported metal foil, The present invention provides a method for manufacturing an electrode, wherein the heating step involves heating an uncoated portion of the metal foil that is not coated with the active material mixture while the uncoated portion is folded away from the radiant heating.

[0011] When heating an electrode, there is a trade-off between wanting to rapidly heat the active material mixture and preventing the uncoated metal foil from overheating. If the active material mixture is rapidly heated during electrode heating, the uncoated metal foil on the outer periphery of the active material mixture will overheat, causing degradation such as surface oxidation. Deterioration of the metal foil will lead to poor sealing and poor conductivity in subsequent processes. According to the present disclosure, by heating the uncoated portion of the active material mixture while covering it with a self-propelled device, deterioration of the metal foil in the uncoated portion of the active material mixture can be suppressed.

[0012] The method for manufacturing an electrode according to the present disclosure includes a heating step. The heating step is a step of radiating heat to the active material mixture on the transported metal foil, and may involve completely drying the active material mixture to remove moisture of the order of several hundred ppm, for example, 500 ppm or less. The conveying speed of the metal foil may be, for example, 30 m / min or more. The drying time of the active material mixture in the heating step can be appropriately set depending on the drying temperature of the active material mixture and the like. In the heating step, the active material mixture may be dried by radiant heating at a temperature of 100° C. to 200° C. for 10 to 15 seconds. The active material mixture is dried in a heating step to form an electrode layer, thereby obtaining an electrode of the present disclosure that includes a metal foil as a current collector and an electrode layer disposed on the metal foil.

[0013] The metal foil may have a carbon coating on the surface. The metal foil (current collector) may be a negative electrode current collector foil, a positive electrode current collector foil, a bipolar current collector foil, etc. Examples of materials for the current collector foil include metals such as aluminum, copper, SUS, and nickel. The thickness of the current collector foil is, for example, 0.1 μm or more and 100 μm or less.

[0014] The active material mixture can be prepared by mixing electrode materials including an active material, a binder, a conductive material, an electrolyte, a thickener, etc., together with a solvent. The active material mixture may be a positive electrode active material mixture or a negative electrode active material mixture. The active material mixture may contain water of about 10,000 ppm or less.

[0015] The active material may be a positive electrode active material. Examples of the positive electrode active material include oxide active materials. Examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li(Ni 0.5 Mn 1.5 )O4, and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCuPO4.

[0016] The active material may be a negative electrode active material. Examples of the negative electrode active material include carbon active materials, oxide active materials, and metal active materials. Examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of the oxide active material include Nb2O5, Li4Ti5O 12 and SiO. Examples of the metal active material include In, Al, Si, and Sn.

[0017] Examples of binders include fluorine-containing binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), rubber-based binders such as butadiene rubber, and acrylic-based binders.

[0018] Examples of conductive materials include carbon materials, metal particles, conductive polymers, etc. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF).

[0019] Examples of thickeners include polysaccharides such as carboxymethyl cellulose and methyl cellulose.

[0020] Examples of the electrolyte include solid electrolytes such as sulfide solid electrolytes and oxide solid electrolytes. Examples of the sulfide solid electrolyte include solid electrolytes containing Li, X (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. The sulfide solid electrolyte may further contain at least one of O and a halogen element. Examples of the halogen element include F, Cl, Br, and I.

[0021] Examples of oxide solid electrolytes include Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, and Li 1.3 Al 0.3 Ti 0.7 (PO4)3, Li5La3Ta2O 12 , Li7La3Zr2O 12 , Li6BaLa2Ta2O 12 , Li 3.6 Si 0.6 P 0.4 O4, Li4SiO4, Li3PO4, Li3PO 4-3 / 2x N x (x≦1).

[0022] Examples of the solvent include aqueous solvents and organic solvents. An aqueous solvent refers to water or a mixed solvent containing water and a polar organic solvent. For example, an appropriate dispersion medium can be selected depending on the types of active material, binder, etc. As the aqueous solvent, water is preferably used because of its ease of handling. Examples of polar organic solvents 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. The organic solvent may, for example, be N-methyl-2-pyrrolidone (NMP).

[0023] Examples of the heat source for radiating heat to the active material mixture include an IR (infrared) device, a laser device, etc. The heat source may be a laser device because it can narrow the irradiation range and has good controllability.

[0024] In the heating step, the metal foil is heated in a state where the uncoated portion, which is not coated with the active material mixture, of the metal foil is folded away from the radiant heating. When the electrode passes through the radiant heating area, the uncoated portion of the metal foil, where the active material mixture is not coated, is bent so that it is positioned lower in the Z direction than the coated portion, where the active material mixture is coated. This prevents oxidation of the metal foil in the uncoated portion. This ensures good bonding strength when joining a resin sealant or metal tab to the metal foil in subsequent processes. Examples of the folding device for bending the uncoated portion of the active material composite include rollers. Examples of the roller include free rollers and servo-driven rollers. For example, rollers may be arranged on both sides of the electrode in the conveyance direction so as to come into contact with the metal foil of the uncoated portion of the active material composite, and the metal foil of the uncoated portion of the active material composite may be folded. The rollers serving as folding devices may be provided so as to come into contact with the metal foil of the uncoated portion of the active material composite at a total of four locations: on both sides of the workpiece in the conveyance direction upstream of the radiant heating region in the heating step, and on both sides of the workpiece in the conveyance direction downstream of the radiant heating region. In the bending region of the heating step, second rollers for suppressing deflection may be provided on both sides of the active material mixture coated portion in the conveyance direction below the Z direction so as to come into contact with the metal foil of the active material mixture coated portion.

[0025] FIG. 1 is a schematic diagram showing an example of the heating step of the present disclosure. FIG. 2 is a schematic diagram of the schematic diagram shown in FIG. 1 viewed from the front in the conveying direction. As shown in FIG. 1, in the heating process, a workpiece 1 including an active material composite coated portion 2 in which an active material composite is coated on a metal foil and an active material composite uncoated portion 3 in which an active material composite is not coated on a metal foil is transported in a transport direction. The roller 21, which serves as a folding processing device, is arranged so as to come into contact with the metal foil of the uncoated portion 3 of the active material composite at a total of four locations: on both sides of the workpiece 1 in the conveying direction upstream of the radiant heating area during the heating process, and on both sides of the workpiece 1 in the conveying direction downstream of the radiant heating area. As shown in Figure 2, in the folding processing area of ​​the active material composite uncoated portion 3, second rollers 22 are provided on both sides of the active material composite coated portion 2 in the conveying direction on the lower side in the Z direction so as to come into contact with the metal foil of the active material composite coated portion 2, thereby suppressing deflection of the active material composite in the active material composite coated portion 2. While the active material mixture uncoated portion 3 is bent downward in the Z direction by the roller 21, the active material mixture in the active material mixture coated portion 2 is radiated with a laser 12 emitted from a laser device 11 and heated by radiation. By bending the active material mixture uncoated portion 3 downward in the Z direction by the roller 21, the side below the active material mixture coated portion 2 in the Z direction is further away from the focus of the laser 12, and the radiation heat is weakened. This suppresses the transfer of radiation heat to the active material mixture uncoated portion 3, while uniformly heating the active material mixture in the active material mixture coated portion 2, suppressing excessive heating of the metal foil in the active material mixture uncoated portion 3 and preventing deterioration of the metal foil in the active material mixture uncoated portion 3.

[0026] The electrode obtained by the manufacturing method of the present disclosure includes an electrode layer and a current collector foil. The electrode layer may be a positive electrode layer or a negative electrode layer. The electrode layer may contain one of a positive electrode active material and a negative electrode active material, as well as a binder, a conductive material, an electrolyte, etc. These materials are as described above. The current collecting foil may be a negative electrode current collecting foil, a positive electrode current collecting foil, a bipolar current collecting foil, etc. The material, thickness and shape of the current collecting foil are as described above.

[0027] The electrodes of the present disclosure are typically used in the manufacture of batteries. The electrodes may be positive or negative electrodes. The type of battery in which the electrode is used is not particularly limited, but examples thereof include lithium ion secondary batteries. The battery may be a primary battery or a secondary battery. The battery may be a liquid battery using an electrolytic solution as an electrolyte, or may be a solid-state battery. In the present disclosure, a solid-state battery refers to a battery containing a solid electrolyte. The solid-state battery may be a semi-solid battery, which is a solid battery containing a solid electrolyte and a liquid-based material, or an all-solid-state battery, which is a solid battery containing no liquid-based material. 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-powered vehicles, and diesel-powered vehicles. In particular, the battery may be 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 mobile objects other than vehicles (e.g., railways, ships, and aircraft), or as a power source for electrical appliances such as information processing devices. [Explanation of symbols]

[0028] 1. Work 2. Active material mixture coating section 3. Uncoated area of ​​active material mixture 11. Laser equipment 12. Laser 21. Laura 22. Second Roller

Claims

[Claim 1] A method for manufacturing an electrode, comprising a heating step of radiating heat to an active material mixture on a transported metal foil, The method for manufacturing an electrode, wherein the heating step comprises heating an uncoated portion of the metal foil that is not coated with the active material mixture while the uncoated portion is folded away from the radiant heating.

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