Cable-type secondary battery

1. A cable-type secondary battery, comprising:

an inner electrode;

a separation layer surrounding an outer surface of the inner electrode to prevent a short circuit between electrodes; and

a sheet-form outer electrode helically wound to surround the separation layer, wherein the sheet-form outer electrode is helically wound so that it does not overlap itself.

2. The cable-type secondary battery according to claim 1 , wherein the sheet-form outer electrode is in the form of a uniaxially extended strip.

3. The cable-type secondary battery according to claim 1 , wherein the sheet-form outer electrode is helically wound so that each pass of its helical winding is separated by a space.

4. The cable-type secondary battery according to claim 1 , wherein the sheet-form outer electrode comprises an outer current collector, an outer electrode active material layer formed on one surface of the outer current collector, and a supporting layer formed on another surface of the outer current collector.

5. The cable-type secondary battery according to claim 1 , wherein the sheet-form outer electrode comprises an outer current collector in the form of a mesh and an outer electrode active material layer formed on one surface of the outer current collector.

6. The cable-type secondary battery according to claim 1 , wherein the outer electrode comprises an outer current collector, an outer electrode active material layer formed on one surface of the outer current collector, and a first porous supporting layer formed on the outer electrode active material layer.

7. The cable-type secondary battery according to claim 6 , wherein the first supporting layer is a mesh-form porous membrane or a non-woven fabric.

8. The cable-type secondary battery according to claim 6 , wherein the first supporting layer is made of any one selected from the group consisting of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, and a mixture thereof.

9. The cable-type secondary battery according to claim 6 , wherein the outer electrode further comprises a conductive material coating layer comprising a conductive material and a binder on the first porous supporting layer.

10. The cable-type secondary battery according to claim 9 , wherein the conductive material comprises any one selected from the group consisting of carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube, graphene and a mixture thereof.

11. The cable-type secondary battery according to claim 9 , wherein the binder is selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene fluoride-co-trichloroethylene, polybutyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, styrene-butadiene rubber, acrylonitrile-styrene-butadiene copolymer, polyimide and a mixture thereof.

12. The cable-type secondary battery according to claim 9 , wherein the conductive material and the binder are present in a weight ratio of 80:20 to 99:1 in the conductive material-coating layer.

13. The cable-type secondary battery according to claim 6 , wherein the outer electrode further comprises a porous coating layer formed on the first porous supporting layer and comprising a mixture of inorganic particles and a binder polymer.

14. The cable-type secondary battery according to claim 6 , wherein the outer electrode further comprises a second supporting layer formed on another surface of the outer current collector.

15. The cable-type secondary battery according to claim 14 , wherein the second supporting layer is a polymer film.

16. The cable-type secondary battery according to claim 15 , wherein the polymer film is made of any one selected from the group consisting of polyolefin, polyester, polyimide, polyamide and a mixture thereof.

17. The cable-type secondary battery according to claim 6 , wherein the outer electrode further comprises a conductive layer between the outer electrode active material layer and the first supporting layer, the conductive layer comprising a conductive material and a binder.

18. The cable-type secondary battery according to claim 17 , wherein the conductive layer is formed from a mixture of the conductive material and the binder in a weight ratio of 1:10 to 8:10.

19. The cable-type secondary battery according to claim 17 , wherein the conductive layer has a pore size of 0.01 to 5 μm and a porosity of 5 to 70%.

20. The cable-type secondary battery according to claim 17 , wherein the conductive material comprises any one selected from the group consisting of carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube, graphene and a mixture thereof.

21. The cable-type secondary battery according to claim 17 , wherein the binder is selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene fluoride-co-trichloroethylene, polybutyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, styrene-butadiene rubber, acrylonitrile-styrene-butadiene copolymer, polyimide and a mixture thereof.

22. The cable-type secondary battery according to claim 4 , wherein the outer current collector further comprises a primer coating layer consisting of a conductive material and a binder.

23. The cable-type secondary battery according to claim 1 , wherein the inner electrode is an anode or a cathode, and the outer electrode is a cathode or an anode corresponding to the inner electrode.

24. The cable-type secondary battery according to claim 1 , wherein when the inner electrode is an anode and the outer electrode is a cathode,

the inner electrode active material comprises any one selected from the group consisting of natural graphite, artificial graphite, or carbonaceous material; lithium-titanium complex oxide (LTO), and metals (Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of the metals; an oxide (MeOx) of the metals; a complex of the metals and carbon; and a mixture thereof, and

the outer electrode active material comprises any one selected from the group consisting of LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiCoPO 4 , LiFePO 4 , LiNiMnCoO 2 , LiNi 1−x−y−z Co x M1 y M2 z O 2 (wherein M1 and M2 are each independently selected from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently an atomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5, 0≦z<0.5, and x+y+z≦1), and a mixture thereof.

25. The cable-type secondary battery according to claim 1 , wherein when the inner electrode is a cathode and the outer electrode is an anode,

the inner electrode active material comprises any one selected from the group consisting of LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiCoPO 4 , LiFePO 4 , LiNiMnCoO 2 , LiNi 1-x-y-z Co x M1 y M2 z O 2 (wherein M1 and M2 are each independently selected from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently an atomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5, 0≦z<0.5, and x+y+z≦1), and a mixture thereof, and

the outer electrode active material comprises any one selected from the group consisting of natural graphite, artificial graphite, or carbonaceous material; lithium-titanium complex oxide (LTO), and metals (Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of the metals; an oxide (MeOx) of the metals; a complex of the metals and carbon; and a mixture thereof.

26. The cable-type secondary battery according to claim 1 , wherein the separation layer is laminated on the outer electrode to form a sheet-form laminate of separation layer-outer electrode, and the laminate of separation layer-outer electrode is helically wound to surround the inner electrode.

27. A cable-type secondary battery, comprising:

two or more inner electrodes arranged in parallel to each other;

a separation layer surrounding outer surfaces of the two or more inner electrodes to prevent a short circuit between electrodes; and

a sheet-form outer electrode helically wound to surround the separation layer, wherein the sheet-form outer electrode is helically wound so that it does not overlap itself.