Case for batteries and preparation method thereof

1. A battery casing, comprising one or more sub-layers as constitutional elements, wherein at least one region selected from the group consisting of a surface of the casing and the sub-layers of the casing is coated partially or totally with a metal having a grain size of 50 nm or less.

2. The battery casing according to claim 1 , which is a can-shaped or a pouch-shaped casing.

3. The battery casing according to claim 2 , wherein the pouch comprises: (a) an outer coating layer; (b) a barrier layer comprising metal foil; and (c) an inner sealant layer.

4. The battery casing according to claim 3 , wherein the metal foil in the barrier layer (b) is coated with the metal having a grain size of 50 nm or less.

5. The battery casing according to claim 3 , wherein the metal foil in the barrier layer (b) is comprised of aluminum or aluminum alloy, and has a thickness of 20˜150 μm.

6. The battery casing according to claim 1 , wherein the metal having a grain size of 50 nm or less comprises nickel or nickel-containing alloy.

7. The battery casing according to claim 6 , wherein the nickel-containing alloy comprises at least one metal selected from the group consisting of Fe, Mn, In, Ag, Ge and Co.

8. The battery casing according to claim 1 , wherein the metal film obtained by coating the metal with a grain size of 50 nm or less has a thickness of about 0.05 to about 100 μm.

9. The battery casing according to claim 1 , wherein the metal film obtained by coating the metal with a grain size of 50 nm or less has a strength of 800 Mpa or more.

10. The battery casing according to claim 1 , wherein the metal film obtained by coating the metal with a grain size of 50 nm or less is formed before or after manufacturing a battery.

11. A battery comprising:

(a) a unit cell formed by assembling a cathode, an anode and a separator interposed between both electrodes;

(b) an electrolyte; and

(c) a battery casing as defined in claim 1 , which receives the unit cell and the electrolyte.

12. A method for manufacturing a battery casing, coated with a metal having a grain size of 50 nm or less, which comprises the steps of:

(a) dissolving a nickel precursor compound or a nickel-containing alloy precursor compound into a solvent;

(b) dipping a battery casing or metal foil forming the casing into the solution so that the casing is coated with the solution; and

(c) drying the coated casing or metal foil.

13. The method according to claim 12 , which further comprises a step (d) of adhering an outer coating layer comprising a polymer film, a barrier layer comprising the metal film, and an inner sealant layer, successively, in case of coating the metal foil.

14. The method according to claim 12 , wherein coating step (b) is performed via plating by positioning a positive electrode and a negative electrode with an interval between both electrodes, and dipping the both electrodes into the solution, followed by application of electric current.

15. The method according to claim 14 , wherein the negative electrode is the casing or the metal foil forming the casing, and the positive electrode is a nickel plate or a non-soluble substrate.

16. The method according to claim 12 , wherein the solution used in step (b) further comprises at least one additive selected from the group consisting of coumarin, thiourea, saccharin and boric acid.

17. The method according to claim 14 , wherein the electric current applied ranges from 5 A/cm 2 to 50 A/cm 2 .

18. The method according to claim 14 , wherein the metal grains coated onto the negative electrode upon plating has a deposition rate of about 1 to about 10 μm/min.

19. The method according to claim 12 , which further comprises a step of heat treating the casing at a temperature of 270° C. or less.