Electrode for secondary battery and manufacturing method thereof
The present invention relates to a battery technology, and more particularly, to a current collector that may be widely used in secondary batteries and an electrode employing the same. The current collector includes a conductive fiber layer including a plurality of conductive fibers. Each of the conductive fibers includes a conductive core consisting of a plurality of metal filaments; and a conductive binder matrix surrounding the outer circumferential surfaces of the conductive core.
1. A method of fabricating an electrode for a secondary battery comprising:
providing, into a plasma reactor, a non-woven fabric current collector comprising metal fibers which form a porosity;
providing, into the plasma reactor, a sputtering target comprising a metal, a metalloid, an oxide thereof, or a mixture thereof comprising an active material; and
depositing an active material layer of a non-radial shape on the metal fibers through the porosity using a plasma-based sputtering operation,
wherein a cross-section of the metal fiber and the active material deposited on the metal fiber, taken in a direction which is perpendicular to a longitudinal axis of the metal fiber, has a circularity from 0.2 to 0.8 as defined by Equation 1 below;
Circularity
=
2
π
A
P
[
Equation
1
]
(A denotes an entire area of a cross-section of the metal fiber and the active material layer formed on the metal fiber, and P denotes circumferntial length of the cross-section), and
wherein the circularity of the active material layer is controlled by a straight movement of clusters, neutral species, or ion species of the active material desorbed from the sputtering target.
2. The method of claim 1 , wherein the non-woven fabric current collector is disposed between an anode and a cathode inside the plasma reactor, such that an upper surface and a lower surface of the non-woven fabric current collector are exposed to plasma.
3. The method of claim 1 , wherein the active material layer is deposited from a surface of the non-woven fabric current collector to an interior of the non-woven fabric current collector.
4. The method of claim 1 , wherein an interior of the plasma reactor comprises an oxidizing atmosphere or a reducing atmosphere.
5. The method of claim 1 , wherein a pore size of the porosity is equal to or larger than that of a sheath of the plasma.
6. The method of claim 1 , wherein a pore size of the porosity is within a range from about 0.01 mm to about 2 mm.
7. The method of claim 1 , wherein a diameter of the metal fiber is within a range from about 1 μm to about 200 μm.
8. The method of claim 1 , wherein the metal or the metalloid is any one selected from a group consisting of tin (Sn), silicon (Si), antimony (Sb), zinc (Zn), germanium (Ge), aluminum (Al), copper (Cu), bismuth (Bi), cadmium (Cd), magnesium (Mg), cobalt (Co), arsenic (As), gallium (Ga), lead (Pb), and iron (Fe) or an inter-metallic compound.
9. The method of claim 1 , wherein the metal fiber is formed of a stainless steel, iron, aluminum, copper, nickel, chromium, titanium, vanadium, tungsten, manganese, cobalt, zinc, ruthenium, lead, iridium, antimony, platinum, silver, gold, or an alloy thereof.
10. The method of claim 1 , wherein in response to linearity of the straight movement increasing, the circularity decreases, and in response to linearity of the straight movement decreasing, the circularity increases.
11. A method of fabricating an electrode for a secondary battery comprising:
providing, into a plasma reactor, a non-woven fabric current collector comprising metal fibers which form a porosity;
providing, into the plasma reactor, a sputtering target comprising a metal, a metalloid, an oxide thereof, or a mixture thereof comprising an active material; and
depositing an active material layer of a non-radial shape on the metal fibers through the porosity using a plasma-based sputtering operation,
wherein a cross-section of the metal fiber and the active material deposited on the metal fiber, taken in a direction which is perpendicular to a longitudinal axis of the metal fiber, has a circularity which is less than 1 as defined by Equation 1 below;
Circularity
=
2
π
A
P
[
Equation
1
]
(A denotes an entire area of a cross-section of the metal fiber and the active material layer formed on the metal fiber, and P denotes circumferential length of the cross-section).