Multilayer electrode for secondary battery and fabrication method thereof
The present invention provides a fabrication method of a multilayer electrode for a secondary battery including: (a) preparing two or more electrode slurries each containing an electrode active material, a binder, and a solvent and heating at least one electrode slurry selected from the prepared two or more electrode slurries to a temperature lower than a boiling point (T b ) of the solvent contained in the selected electrode slurry; (b) coating the two or more electrode slurries on a current collector; and (c) cooling the coated two or more electrode slurries.
1. A fabrication method of a multilayer electrode for a secondary battery, comprising:
(a) preparing two or more electrode slurries each containing an electrode active material, a binder, and a solvent and heating at least one electrode slurry selected from the prepared two or more electrode slurries to a temperature lower than a boiling point (T b ) of the solvent contained in the selected electrode slurry;
(b) coating the two or more electrode slurries on a current collector; and
(c) cooling the coated two or more electrode slurries,
wherein the selected electrode slurry satisfies the following Relational Equations 2 and 3, and a viscosity (A1) of the electrode slurry before being heated is 20,000 cp or more, and a viscosity (A2) of the heated electrode slurry is 7,000 to 9,800 cp,
1.3
≤
A
1
/
A
2
≤
12
[
Relational
Equation
2
]
1.1
≤
A
3
/
A
2
≤
10
[
Relational
Equation
3
]
wherein A1 is a viscosity of the selected electrode slurry before being heated, A2 is a viscosity of the heated electrode slurry of the selected electrode slurry, and A3 is a viscosity of the cooled electrode slurry of the selected electrode slurry.
2. The fabrication method of a multilayer electrode for a secondary battery of claim 1 , wherein contents of binders with respect to slurry solids in the two or more electrode slurries are different from each other.
3. The fabrication method of a multilayer electrode for a secondary battery of claim 2 , wherein an electrode slurry in which a content of a binder with respect to the slurry solid is higher, of the two or more electrode slurries is coated on a place close to the current collector.
4. The fabrication method of a multilayer electrode for a secondary battery of claim 1 , wherein in the coating (b) of the two or more electrode slurries, the two or more electrode slurries are simultaneously or sequentially coated on the current collector.
5. The fabrication method of a multilayer electrode for a secondary battery of claim 1 , further comprising (d) drying the cooled two or more electrode slurries.
6. The fabrication method of a multilayer electrode for a secondary battery of claim 5 , wherein the drying is performed at a temperature of 90° C. or more and less than 180° C. for 45 seconds to 5 minutes.
7. The fabrication method of a multilayer electrode for a secondary battery of claim 1 , wherein a heating temperature (T) of the heating satisfies the following Relational Equation 1:
0.3
T
b
<
T
<
0
.
9
T
b
[
Relational
Equation
1
]
wherein T b is the boiling point of the solvent contained in the selected electrode slurry.
8. The fabrication method of a multilayer electrode for a secondary battery of claim 1 , wherein the cooling is performed at a temperature of 10 to 30°° C. for 1 to 60 seconds.
9. The fabrication method of a multilayer electrode for a secondary battery of claim 1 , wherein a content of a solid of each of the two or more electrode slurries is more than 50 wt % and 80 wt % or less.