JP7806772B2 - 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. 2020-145034

When drying an electrode assembly for a bipolar battery, in which positive and negative electrode composites are coated on both sides of a current collector, different heating conditions may be required for the top and bottom surfaces of the electrode composite. For example, if the electrode assembly is dried under bone-dry conditions for the positive electrode composite, the negative electrode composite on the back side may become brittle and crack. A drying method suitable for such cases is needed.

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 can suppress the occurrence of cracks in the electrode assembly.

That is, the present disclosure includes the following aspects.
<1> A method for manufacturing a bipolar electrode assembly including a current collector, a positive electrode layer disposed on a first surface of the current collector, and a negative electrode layer disposed on a second surface of the current collector,
a preparation step of applying a positive electrode composite material to the first surface of the current collector and applying a negative electrode composite material to the second surface of the current collector to prepare a workpiece including the current collector, the positive electrode composite material, and the negative electrode composite material;
a drying step of drying the workpiece while transporting it,
In the drying step, one surface of the workpiece is heated by radiant heat and the other surface of the workpiece is heated by hot air, thereby drying the workpiece.

<2> The method for manufacturing an electrode assembly described in <1>, wherein the temperature of the hot air is lower than the temperature of the radiant heat.

<3> The method for manufacturing an electrode assembly described in <1>, wherein, in the drying step, one side of the workpiece is heated by the radiant heat and the hot air, and the other side of the workpiece is heated by the hot air.

<4> The method for manufacturing an electrode assembly described in <3>, wherein, in the drying step, the temperature of the hot air used to heat one side of the workpiece is higher than the temperature of the hot air used to heat the other side of the workpiece.

<5> The method for manufacturing an electrode assembly described in <3>, wherein, in the drying step, the dew point of the hot air heating one side of the workpiece is lower than the dew point of the hot air heating the other side of the workpiece.

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

FIG. 2 is a schematic diagram illustrating an example of a drying step according to the present disclosure. FIG. 2 is a schematic diagram showing an example of a workpiece, a laser, and hot air in the drying furnace shown in FIG. 1 . FIG. 2 is a schematic diagram showing another 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 a bipolar electrode assembly including a current collector, a positive electrode layer disposed on a first surface of the current collector, and a negative electrode layer disposed on a second surface of the current collector, the method comprising:
a preparation step of applying a positive electrode composite material to the first surface of the current collector and applying a negative electrode composite material to the second surface of the current collector to prepare a workpiece including the current collector, the positive electrode composite material, and the negative electrode composite material;
a drying step of drying the workpiece while transporting it,
In the drying step, one surface of the workpiece is heated by radiant heat and the other surface of the workpiece is heated by hot air, thereby drying the workpiece.

In the present disclosure, during the drying process, the side of the workpiece where more moisture needs to be removed is heated intensively using radiant heat from a laser or the like, while the side where gentler heating is required is heated using hot air. This allows for different heating conditions on the front and back of the workpiece, thereby preventing cracks from occurring in the electrode body.

The manufacturing method of the electrode assembly disclosed herein includes (1) a preparation process and (2) a drying process.

(1) Preparation Step The preparation step is a step of applying a positive electrode composite to the first surface of the current collector and applying a negative electrode composite to the second surface of the current collector to prepare a workpiece including the current collector, the positive electrode composite, and the negative electrode composite.

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 current collector may be in the form of a sheet, etc.

The positive electrode mixture can be prepared by applying it to a first surface of a current collector.
The positive electrode mixture may be a positive electrode paste prepared by mixing positive electrode materials including a positive electrode active material, a binder, a conductive material, an electrolyte, a thickener, and the like together with a solvent such as water.
The negative electrode mixture can be prepared by applying it to the second surface, which is the surface opposite to the first surface, of the current collector.
The negative electrode mixture may be a negative electrode paste prepared by mixing negative electrode materials including a negative electrode active material, a binder, a conductive material, an electrolyte, a thickener, and the like, together with a solvent such as water.
The amount of the positive electrode paste and the negative electrode paste applied to the current collector may be, for example, 30 to 80 mg/cm ² .
The viscosity of the positive electrode paste and the negative electrode paste may be, for example, 5,000 to 50,000 mPa·S.
The positive electrode paste and the negative electrode paste may contain moisture of about 10,000 ppm or less.

Examples of the positive electrode active material include oxide active materials, such as rock salt layer-type active materials such as _LiCoO2 , _LiMnO2 , _LiNiO2 , _LiVO2 , and LiNi1 _/3Co1 / _{3Mn1 /3O2} , spinel-type active materials such as _{LiMn2O4 and Li} ( _Ni0.5Mn1.5 ) _O4 , and olivine-type active materials such as _LiFePO4 , _LiMnPO4 , _LiNiPO4 , _{and LiCuPO4} .

Examples of negative electrode active materials include carbon active materials, oxide active materials, and metal active materials. Examples of carbon active materials include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of oxide active materials include Nb ₂ O ₅ , Li ₄ Ti ₅ O ₁₂ , and SiO. Examples of metal active materials 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 butadiene rubber, 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 and methyl cellulose.

Examples of electrolytes include inorganic 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. Furthermore, sulfide solid electrolytes 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 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).

(2) Drying Process The drying process is a process in which the workpiece is dried while being transported.
In the drying step, one side of the workpiece is heated by radiant heat and the other side of the workpiece is heated by hot air, thereby drying the workpiece.
In the drying step, for example, the positive electrode mixture, which requires more moisture removal than the negative electrode mixture, may be dried by radiant heating, and the negative electrode mixture, which is more likely to become embrittled by heating, may be dried by hot air.
Regarding the drying conditions, the temperature of the hot air may be lower than the temperature of the radiant heat. By creating a temperature gradient in the thickness direction of the workpiece by radiant heat heating from one side (front side) of the workpiece and hot air from the other side (back side) of the workpiece, it is possible to perform drying suitable for bipolar electrode bodies, which have different desirable heating conditions on the front and back sides of the workpiece.

In the drying step, one side of the workpiece may be heated by the radiant heat and the hot air, and the other side of the workpiece may be heated by the hot air, which makes it easier to control the temperature and dew point in the drying step and allows the workpiece to be dried efficiently.
In the drying step, the temperature of the hot air that heats one side of the workpiece may be higher than the temperature of the hot air that heats the other side of the workpiece.
In the drying step, the dew point of the hot air that heats one side of the workpiece may be lower than the dew point of the hot air that heats the other side of the workpiece.

In the drying step, the positive electrode mixture and the negative electrode mixture may be completely dried until the moisture content is reduced to several hundred ppm or less, for example, 500 ppm or less.
The positive electrode mixture becomes a positive electrode layer through a drying process, and the negative electrode mixture becomes a negative electrode layer through a drying process.
The drying device that heats by radiant heat may be a laser device, an IR (infrared) device, or the like.
The drying device that heats with hot air can be a hot air device such as an air nozzle.

In the drying step, the workpiece may be dried in a drying furnace while being transported on a transport body. The transport speed may be, for example, 30 m/min or more.
The shape of the carrier may be a roll or a plate.
A laser device or IR device may be installed above the workpiece in the drying furnace, and an air nozzle may be installed below the workpiece. An air nozzle may also be installed above the workpiece in the drying furnace. The hot air from the air nozzle above the workpiece may have a higher temperature and a lower dew point than the hot air from the air nozzle below the workpiece. To facilitate temperature control and dew point control, exhaust holes may be provided corresponding to the air nozzle above the workpiece and the air nozzle below the workpiece. A partition may be provided inside the drying furnace to separate the spaces above and below the workpiece.
In the coating and drying process in the preparation step (1) above, if it is desired to create a temperature gradient above and below the workpiece or a humidity gradient above and below the workpiece, a similar drying furnace may be provided.
In the drying step, the heating temperature of the workpiece may be 100°C to 200°C.
In the drying step, the drying time of the workpiece can be set appropriately depending on the dew point and temperature in the drying furnace, the heating temperature of the workpiece, etc.

FIG. 1 is a schematic diagram showing an example of the drying process of the present disclosure.
FIG. 2 is a schematic diagram showing an example of the workpiece, laser, and hot air in the drying furnace shown in FIG.
In the drying process shown in FIG. 1, the workpiece 1 is transported in the transport direction.
As shown in FIG. 2 , the workpiece 1 includes a current collector 2, a positive electrode composite 3, and a negative electrode composite 4, with the positive electrode composite 3 being applied to a first surface, which is the upper surface of the current collector 2, and the negative electrode composite 4 being applied to a second surface, which is the lower surface of the current collector 2.
As shown in Figure 1, the upper surface of the workpiece 1 is heated by a laser 12 irradiated by a laser device 11 in a drying furnace 10, and the lower surface of the workpiece 1 is heated by hot air 22 supplied into the drying furnace 10 by a hot air device 21 (air nozzle) in the drying furnace 10.
For the drying process, the temperature of the hot air 22 may be lower than the temperature of the laser 12 .
In the drying step, an IR device or the like may be used instead of the laser device 11 .
In the drying process, a partition may be provided to separate the work 1 from the top and bottom.

FIG. 3 is a schematic diagram showing another example of the drying step of the present disclosure.
In the drying process shown in Figure 3, the inside of the drying furnace 10 is divided by an upper and lower partition 50 that separates the workpiece 1 from the top and bottom, and a laser device 11, an upper hot air device 41, and an upper exhaust hole 43 are provided in the space above the workpiece 1, and a lower hot air device 31 (air nozzle) and a lower exhaust hole 33 are provided in the space below the workpiece 1.
The upper surface of the workpiece 1 is heated by a laser 12 irradiated by a laser device 11 in the drying furnace 10 and upper hot air 42 supplied into the drying furnace 10 by an upper hot air device 41 (air nozzle), and the lower surface of the workpiece 1 is heated by lower hot air 32 supplied into the drying furnace 10 by a lower hot air device 31 in the drying furnace 10.
In the drying process, the temperature of the upper hot air 42 may be higher than the temperature of the lower hot air 32 .
In the drying process, the dew point of the upper hot air 42 may be lower than the dew point of the lower hot air 32 .

The electrode body obtained by the manufacturing method of the present disclosure has a bipolar structure including a current collector, a positive electrode layer disposed on a first surface of the current collector, and a negative electrode layer disposed on a second surface of the current collector.
The positive electrode layer is disposed on the first surface of the current collector.
The positive electrode layer contains the above-mentioned positive electrode active material, binder, conductive material, electrolyte, thickener, and the like.
The negative electrode layer is disposed on the second surface of the current collector, which is opposite to the first surface.
The negative electrode layer contains the above-mentioned negative electrode active material, binder, conductive material, electrolyte, thickener, and the like.

The electrode assemblies of the present disclosure are typically used in the manufacture of batteries.
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.

1. Workpiece 2. Current collector 3. Positive electrode composite 4. Negative electrode composite 10. Drying furnace 11. Laser device 12. Laser 21. Hot air device (air nozzle)
22. Hot air 31. Lower hot air device (air nozzle)
32. Lower hot air 33. Lower heat exhaust vent 41. Upper hot air device (air nozzle)
42. Upper hot air 43. Upper heat exhaust vent 50. Upper and lower partition

Claims (5)

A method for manufacturing a bipolar electrode assembly including a current collector, a positive electrode layer disposed on a first surface of the current collector, and a negative electrode layer disposed on a second surface of the current collector,
a preparation step of applying a positive electrode composite material to the first surface of the current collector and applying a negative electrode composite material to the second surface of the current collector to prepare a workpiece including the current collector, the positive electrode composite material, and the negative electrode composite material;
a drying step of drying the workpiece while transporting it,
In the drying step, one surface of the workpiece is heated by radiant heat and the other surface of the workpiece is heated by hot air, thereby drying the workpiece. The method for manufacturing an electrode assembly according to claim 1, wherein the temperature of the hot air is lower than the temperature of the radiant heat. The method for manufacturing an electrode assembly according to claim 1, wherein, in the drying step, one side of the workpiece is heated by the radiant heat and the hot air, and the other side of the workpiece is heated by the hot air. The method for manufacturing an electrode assembly according to claim 3, wherein, in the drying process, the temperature of the hot air used to heat one side of the workpiece is higher than the temperature of the hot air used to heat the other side of the workpiece. The method for manufacturing an electrode assembly described in claim 3, wherein, in the drying process, the dew point of the hot air heating one side of the workpiece is lower than the dew point of the hot air heating the other side of the workpiece.