Positive electrode for lithium-air battery and method for preparing the same

1. A lithium-air battery comprising:

a positive electrode; and

a negative electrode disposed opposite to the positive electrode, and receiving and releasing lithium ions; and

an electrolyte provided between the negative electrode and the positive electrode,

wherein said positive electrode comprises:

a positive electrode collector formed with a porous metal; and

a positive electrode active layer provided on the positive electrode collector, and including a conductive material and a catalyst for oxygen reduction,

wherein the porous metal is metal foil, and

wherein the porous metal has a porosity of 50% or less.

2. The lithium-air battery of claim 1 , wherein the porous metal has a pore diameter greater than or equal to 20 nanometers and less than or equal to 1 millimeter.

3. The lithium-air battery of claim 1 , wherein the porous metal includes any one, or an alloy of two or more, selected from the group consisting of groups IA to VA elements and groups IB to VIIIB elements in the periodic table.

4. The lithium-air battery of claim 1 , wherein the porous metal includes any one, or an alloy of two or more, selected from the group consisting of iron, stainless steel, aluminum, copper, nickel, zinc, magnesium, tin, titanium, manganese, chromium, indium, platinum, ruthenium, rhodium, palladium, osmium, iridium, gold and silver.

5. The lithium-air battery of claim 1 , wherein a thickness of the positive electrode collector is greater than or equal to 10 micrometers and less than or equal to 50 micrometers.

6. The lithium-air battery of claim 1 , wherein a thickness of the positive electrode active layer is greater than or equal to 10 micrometers and less than or equal to 100 micrometers.

7. The lithium-air battery of claim 1 , wherein the conductive material includes one, or a mixture of two or more, selected from the group consisting of carbon materials, conductive polymers, conductive fibers and metal powder.

8. The lithium-air battery of claim 1 , wherein the conductive material includes one, two or more selected from the group consisting of mesoporous carbon, graphite, graphene, carbon black, acetylene black, denka black, ketjen black, carbon nanotubes, carbon fibers, fullerene, active carbon, polyaniline, polythiophene, polyacetylene, polypyrrole, carbon fibers, metal fibers, fluorocarbon powder, aluminum powder and nickel powder.

9. The lithium-air battery of claim 1 , wherein the catalyst for oxygen reduction includes one, two or more selected from the group consisting of precious metals, nonmetals, metal oxides and organic metal complexes.

10. The lithium-air battery of claim 1 , wherein the catalyst for oxygen reduction includes one, two or more selected from the group consisting of platinum, silver, boron, nitrogen, sulfur, ruthenium oxides, metal porphyrins and metal phthalocyanines.

11. A method for preparing a lithium-air battery, the method comprising:

forming a positive electrode active layer by coating a positive electrode material including a conductive material and a catalyst for oxygen reduction on a surface of a positive electrode collector formed with a porous metal,

wherein the porous metal is metal foil, and

wherein the porous metal has a porosity of 50% or less.

12. The method for preparing a lithium-air battery of claim 11 , wherein the coating is carried out using a filtration method under reduced pressure, a dipping method or a screen printing method.

13. The lithium-air battery of claim 1 , wherein the negative electrode includes a material selected from the group consisting of lithium metal, lithium metal-based alloys, lithium compounds and lithium intercalation materials.

14. The lithium-air battery of claim 1 , further comprising:

a separator between the positive electrode and the negative electrode.

15. A battery module comprising the lithium-air battery of claim 1 as a unit battery.

16. The lithium-air battery of claim 1 , wherein the porous metal has a porosity of 40% or less.