Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Agitating or moving electrolyte during coating
Reexamination Certificate
2001-03-16
2002-05-07
Wong, Edna (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Agitating or moving electrolyte during coating
C205S333000
Reexamination Certificate
active
06383358
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for forming a thin film, particularly to a method for forming a thin film suitable for a secondary battery field usable for mobile electronic device and electric automobiles.
2. Related Art Statement
So far, a sol-gel method, a CVD method or a PVD method is employed as a thin film-forming method. These methods require a firing process after a molding process, a high vacuum condition, or a high energy condition accompanied with a substrate-heating process or a plasma-generating process. Therefore, those methods require large scale and complicate apparatus, resulting in large cost and complicate operationality in use.
Moreover, the above high energy condition runs counter to global environmental protection, resource saving and energy saving. Therefore, a new thin film-forming method without the above high energy condition has been desired.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new thin film-forming method not including a high energy condition due to firing, heating or plasma generation.
This invention relates to a method for forming a thin film comprising the steps of:
setting a porous base material in between a pair of electrodes,
flowing a first reactive solution in between one electrode of the pair of electrodes and the base material,
flowing a second reactive solution in between the other electrode of the pair of electrodes and the base material, and
applying a given voltage between the pair of electrodes, thereby to synthesize a compound thin film including the components of the first reactive solution and the second reactive solution on the porous base material.
The inventors related to the present invention have been intensely studied for developing a new thin film-forming method not including a high energy process. As a result, they have found out surprisingly that when a porous base material is set in between an anode electrode and a cathode electrode to which a given voltage is applied and a first reactive solution and a second reactive solution, which are different each other, are flown in between the cathode electrode and the base material and in between the anode electrode and the base material at their predetermined flow rates, respectively, a compound thin film including the components of the first reactive solution and the second reactive solution is directly synthesized on the base material.
FIG. 1
is a conceptual view showing the state in which the compound thin film is synthesized directly on the porous base material.
In this case, the first reactive solution is made of a water solution with a melted LiOH.H
2
O in a distilled water, and the second reactive solution is made of a water solution with a melted CoSO
4
.7H
2
O in a distilled water.
The first reactive solution is flown in between a cathode electrode
1
and a porous base material
3
at its given flow rate, and the second reactive solution is flown in between an anode electrode
2
and the porous base material
3
at its given flow rate. When a given voltage is applied between the cathode electrode
1
and the anode electrode
2
, the first and the second reactive solutions are dissociated, and thus, Li
+
ion particles exist in between the cathode electrode
1
and the porous base material
3
and Co
3+
ion particles exist in between the anode electrode
2
and the porous base material
3
.
Then, these ion particles arrive at the porous base material, and the Li
+
ion particles and the Co
3
+ion particles pass through the surface inter-connecting holes of the base material
3
and arrive at the opposite surfaces
3
B and
3
A thereof, respectively. The Li
+
ion particles on the surface
3
B react with a large amount of Co
3+
ion particles and oxide elements in the water solution to form a Co-based oxide thin film, made of LiCoO
2
or the like, on the surface
3
B of the porous base material
3
.
Moreover, the Co
3+
ion particles on the surface
3
A react with a large amount of Li
+
ion particles and oxide elements in the water solution to form a Co-based oxide thin film, made of LiCoO
2
or the like, on the surface
3
A of the porous base material
3
. As a result, a compound oxide thin film such as the Co-based oxide thin film is directly synthesized and stabilized on the porous base material.
In this case, if the difference in the flow rates and/or the pressures between the first and the second reactive solutions is controlled appropriately, the compound oxide thin film may be formed on either of the surfaces
3
A and
3
B or in the porous base material
3
.
In the thin film-forming method of the present invention, since the reactive solutions are flown constantly, the component particles such as the Co
3+
ion particles and the Li
+
ion particles to constitute the compound thin film always exist at their constant ratio. Therefore, the compound thin film can be formed uniformly, and a particulate compound or a powdery compound is not formed.
According to the thin film-forming method of the present invention, the crystalline compound thin film can be formed on the porous base material without a firing process after a thin film-forming process and a high energy condition including a substrate-heating process and a plasma generation
REFERENCES:
patent: 3520780 (1970-07-01), Findl et al.
patent: 4731168 (1988-03-01), MacIntyre
patent: 5597661 (1997-01-01), Takeuchi et al.
Yoshimura et al. “Direct Fabrication Of Thin-Film Linio2Electrodes In Lioh Solution By Electrochemical-Hydrothermal Method.” Solid State Ionics 106 (1998) pp. 39-44. No month available.
Han et al. “Simultaneous And Direct Fabrication Of Lithium Cobalt Oxide Film And Powder Using Soft Solution Processing At 100° C.” Electromechanical and Soli-State Letters. 2(2) Feb. 1999. pp. 63-66.
Fujiwara Takeshi
Han Kyoo-Seung
Song Seung-wan
Teranishi Ryo
Watanabe Tomoaki
Knobbe, Martens Olson, and Bear, LLP.
Tokyo Institute of Technology
Wong Edna
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