JP7736050B2 - Electrode assembly manufacturing method - Google Patents

Description

This disclosure relates to a method for manufacturing an electrode assembly.

Various technologies have been proposed for manufacturing electrode bodies such as those disclosed in Patent Document 1.

Japanese Patent Application Laid-Open No. 2019-029256

In conventional technology, when drying electrode material while transporting it with a laser, heat tends to accumulate in the current collector, which is an intermittent area where the electrode material is not coated. Therefore, if the laser is irradiated on the intermittent area at the same time, there is a risk that the electrode material-coated area near the intermittent area will dry out more than necessary. Furthermore, when drying is performed using hot air or IR instead of a laser, it is difficult to control the irradiation width.

This disclosure was made in consideration of the above-mentioned circumstances, and its primary objective is to provide a method for manufacturing an electrode assembly that reduces the occurrence of cracks.

That is, the present disclosure includes the following aspects.
<1> A method for manufacturing an electrode assembly,
a drying step of drying the electrode material by a laser while transporting a workpiece having an electrode material coated on at least one surface of a current collector;
A method for manufacturing an electrode body, wherein in the drying step, the laser is irradiated onto the workpiece so that the irradiation range of the laser is inclined with respect to the transport direction of the workpiece when viewed in a plane.

<2> In a plan view of the workpiece, the width direction of the electrode material is perpendicular to the conveyance direction of the workpiece,
The method for manufacturing an electrode body according to <1>, wherein an inclination angle of the laser irradiation range with respect to the width direction of the electrode material is 10° or more and 60° or less.

The electrode assembly manufacturing method disclosed herein can reduce the occurrence of cracks.

FIG. 1 is a schematic diagram showing an example of a conventional drying process. FIG. 2 is a schematic diagram showing an example of the drying step of the present disclosure.

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 the electrode body 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.
Furthermore, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships.

The present disclosure provides a method for manufacturing an electrode assembly, comprising:
a drying step of drying the electrode material by a laser while transporting a workpiece having an electrode material coated on at least one surface of a current collector;
In the drying step, the laser is irradiated onto the workpiece so that the irradiation range of the laser is inclined with respect to the conveying direction of the workpiece in a plan view of the workpiece.

FIG. 1 is a schematic diagram showing an example of a conventional drying process.
As shown in Figure 1, the workpiece 1 has an electrode material 2 coated on a current collector, and has intermittent portions 3 that are uncoated portions of the electrode material 2. The workpiece 1 is transported in the transport direction, and a laser is irradiated parallel to the width direction of the electrode material 2 (perpendicular to the transport direction) in a plan view. Therefore, heat is simultaneously stored in the intermittent portions 3, and the amount of heat transferred to the coated portions of the electrode material 2 increases, making the electrode material 2 prone to cracking.

FIG. 2 is a schematic diagram showing an example of the drying step of the present disclosure.
As shown in Figure 2, by irradiating the workpiece 1 with a laser at an inclined angle relative to the width direction of the electrode material 2 in a plan view, heat is less likely to accumulate in the intermittent portion 3, the amount of heat transferred to the coated portion of the electrode material 2 is reduced, and cracks are less likely to occur in the electrode material 2.

In this disclosure, by tilting the laser irradiation range relative to the workpiece transport direction, heat does not accumulate in a concentrated manner on the current collector, which is the gap where the electrode material is not coated. This allows the electrode material to dry under favorable conditions, reducing the occurrence of cracks in the resulting electrode body. Furthermore, by equalizing the drying time for the gap and the electrode material-coated area, high-speed drying is possible. Furthermore, binder segregation, which causes battery resistance, can be suppressed, and the amount of binder added to the electrode material can be reduced, thereby improving the performance of batteries using the resulting electrode body.

(drying process)
The method for manufacturing an electrode assembly according to the present disclosure includes a drying step.
The drying step is a step of drying the electrode material by a laser while transporting a workpiece having a current collector coated on at least one surface thereof.
In the drying step, a laser device may be used to dry the electrode material. In addition to the laser device, a conventionally known device capable of drying the electrode material, such as a hot air device or an IR (infrared) device, may be used as the drying device. In the drying step, the electrode material may be completely dried until the moisture content is several hundred ppm or less.
In the drying step, the electrode material may be dried in a drying furnace. In the drying step, the workpiece may be transported on a transport body. The transport speed may be, for example, 30 m/min or more.
The drying temperature of the electrode material may be 100°C to 200°C.
The drying time of the electrode material is not particularly limited.
After the drying step, the electrode material becomes an electrode layer, and an electrode body including a current collector and an electrode layer formed on at least one surface of the current collector is obtained.

In the drying process, the workpiece is irradiated with a laser so that the irradiation range of the laser is inclined with respect to the conveying direction of the workpiece when viewed from above.
In a plan view of the workpiece, the width direction of the electrode material may be perpendicular to the workpiece transport direction, and the inclination angle of the laser irradiation range with respect to the width direction of the electrode material may be more than 0° and less than 90°, may be 5° or more and 80° or less, or may be 10° or more and 60° or less. In other words, the inclination angle of the laser irradiation range with respect to the workpiece transport direction may be more than 0° and less than 90°, may be 10° or more and 85° or less, or may be 30° or more and 80° or less.
Methods for setting the tilt angle of the laser irradiation range include, for example, tilting the laser head body, placing multiple laser heads, using a vertical cavity surface emitting laser (VCSEL), and installing a shielding plate.
The laser energy density may be 2 W/cm ² or more.

The workpiece includes a current collector and an electrode material coated on at least one surface of the current collector.
The workpiece may be for a bipolar electrode in which electrode materials are coated on both sides of a current collector, where the electrode material coated on one side of the current collector is a positive electrode material and the electrode material coated on the other side of the current collector is a negative electrode material.

The current collector may be a negative electrode current collector, a positive electrode current collector, a bipolar current collector, etc. Examples of materials for the current collector include metals such as aluminum, copper, SUS, and nickel. The thickness of the current collector is, for example, 0.1 μm or more and 100 μm or less. The shape of the current collector may be a sheet, etc.

The electrode material is applied to at least one of the first surfaces of the current collector. The electrode material may be applied only to the first surface of the current collector, or may be applied to both the first surface and a second surface opposite to the first surface of the current collector.
The method for applying the electrode material is not particularly limited, and any conventionally known method can be used.
The electrode material can be prepared by mixing a mixture containing an active material, a binder, a conductive material, an electrolyte, a thickener, etc., with a solvent. The electrode material may be a positive electrode material or a negative electrode material. The electrode material may contain moisture of about 10,000 ppm or less.
The width of the electrode material is not particularly limited and may be 1000 mm or more.

The active material may be a positive electrode active material. Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include rock salt layer-type active materials such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , and LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , spinel-type active materials such as LiMn ₂ O ₄ and Li(Ni _0.5 Mn _1.5 )O ₄ , and olivine-type active materials such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , and LiCuPO ₄ .

The active material may be a negative electrode active material. Examples of the negative electrode active material include a carbon active material, an oxide active material, and a metal active material. Examples of the carbon active material include graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of the oxide active material include Nb ₂ O ₅ , Li ₄ Ti ₅ O ₁₂ , and SiO. Examples of the metal active material include In, Al, Si, and Sn.

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

Conductive materials include, for example, carbon materials, metal particles, and conductive polymers. Carbon materials include, for example, particulate carbon materials such as acetylene black (AB) and ketjen black (KB); and fibrous carbon materials such as carbon fiber, carbon nanotubes (CNT), and carbon nanofibers (CNF).

Thickeners include polysaccharides such as carboxymethyl cellulose (CMC) and methyl cellulose.

Examples of the electrolyte include solid electrolytes such as sulfide solid electrolytes and oxide solid electrolytes. Examples of sulfide solid electrolytes include solid electrolytes containing Li, X (where 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 halogen elements include F, Cl, Br, and I.

Examples of oxide solid electrolytes include Li ₂ O—B ₂ O ₃ —P ₂ O ₅ , Li ₂ O—SiO ₂ , Li ₂ O—B ₂ O ₃ , Li _1.3 Al _0.3 Ti _0.7 (PO ₄ ) ₃ , Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li _3.6 Si _0.6 P _0.4 O ₄ , Li ₄ SiO ₄ , Li ₃ PO ₄ , and Li ₃ PO _4-3/2x N _x (x≦1).

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 solvent 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).

The electrode assembly obtained by the manufacturing method of the present disclosure includes a current collector and an electrode layer formed by drying an electrode material coated on at least one surface of the current collector.
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 collector may be a negative electrode current collector, a positive electrode current collector, a bipolar current collector, etc. The material of the current collector, the thickness of the current collector, and the shape of the current collector are as described above.

The electrode assembly of the present disclosure is typically used in the manufacture of batteries. The electrode assembly may be a positive electrode, a negative electrode, or a bipolar electrode. A bipolar electrode comprises a positive electrode layer on one side of a current collector and a negative electrode layer on the other side of the current collector.
The type of battery in which the electrode body is used is not particularly limited, and examples thereof include lithium-ion secondary batteries. The battery may be a liquid-based battery using an electrolytic solution as the electrolyte, or a solid-state battery using a solid electrolyte as the electrolyte. 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.

(Examples 1 to 6, Comparative Example 1)
The electrode material used was a negative electrode material containing graphite as a negative electrode active material, CMC as a thickener, and SBR as a binder. The width of the electrode material was 1000 mm.
A workpiece was prepared by coating one surface of a current collector with an electrode material, and the workpiece was irradiated with a laser to dry the electrode material, thereby obtaining an electrode body.
The laser energy density was 2 W/cm ² , and the laser irradiation range was 1200 mm×300 mm.
As shown in Table 1, in each of the Examples and Comparative Examples, the quality of the coated edge was evaluated when the inclination angle of the laser irradiation range relative to the width direction of the electrode material was changed.
The quality was evaluated by visually checking whether the electrode body had any cracks. The results are shown in Table 1.

As shown in Table 1, it has been demonstrated that the electrode assembly obtained using the manufacturing method disclosed herein can reduce the occurrence of cracks.

1. Workpiece 2. Electrode material 3. Intermittent part

Claims (2)

A method for manufacturing an electrode assembly,
a drying step of drying the electrode material by a laser while transporting a workpiece having an electrode material coated on at least one surface of a current collector;
A method for manufacturing an electrode body, wherein in the drying step, the laser is irradiated onto the workpiece so that the irradiation range of the laser is inclined with respect to the transport direction of the workpiece when viewed in a plane. In a plan view of the workpiece, a width direction of the electrode material is perpendicular to a transport direction of the workpiece,
The method for manufacturing an electrode body according to claim 1 , wherein an inclination angle of the laser irradiation range with respect to the width direction of the electrode material is 10° or more and 60° or less.