Pouch type secondary battery comprising safety member

1. A pouch-type secondary battery comprising: an electrode assembly including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte solution,

wherein the electrode assembly and the electrolyte solution are received in an internal pouch such that electrode leads are drawn from the internal pouch, the internal pouch formed by a pouch sheet that includes a heat fusion layer, a metal layer, and an outer layer in a sequential order, wherein the outer layer of the internal pouch consists of oriented nylon film,

the internal pouch is received in an external pouch such that the electrode leads are drawn from the external pouch,

wherein a first lead tape is attached to first positions on respective electrode leads at an internal pouch sealing part, and a second lead tape is attached to second positions on the respective electrode leads different from the first positions and to an external pouch sealing part, and

a safety member is included in a space between the internal pouch and the external pouch, wherein the safety member is absent from the internal pouch,

wherein the electrolyte solution is not included in the space between the internal pouch and the external pouch.

2. The pouch-type secondary battery according to claim 1 , wherein the safety member is one selected from the group consisting of nitrogen gas, alkylene glycol, 1,3-propenediol, ferrocene derivatives, organic acid-based compounds, dodecafluoro-2-methylpentan-3-one, decafluoro-2-methylbutan-3-one, 1,1,1,3,3,4,4,5,5,5-decafluoropentan-2-one, 1,1,1,2,2,4,4,5,5,5-decafluoropentan-3-one, 1,1,1,4,4,5,5,5-octafluoro-3-bis(trifluoromethyl)-pentan-2-one, dodecafluoro-4-methylpentan-2-one, dodecafluoro-3-methylpentan-2-one, dodecafluoro-3,3-(dimethyl)butan-2-one and dodecafluorohexan-3-one, or mixtures thereof.

3. The pouch-type secondary battery according to claim 1 , wherein a volume of the space between the internal pouch and the external pouch is 5 vol % or more and less than 10 vol % on the basis of the total volume of the pouch-type secondary battery fabricated in the end.

4. The pouch-type secondary battery according to claim 1 , wherein the internal pouch sealing part is folded up or down except at an end part from which electrode terminals are drawn, and the internal pouch is received in the external pouch.

5. A method for fabricating the pouch-type secondary battery defined in claim 1 , comprising:

(S1) receiving the electrode assembly in the internal pouch such that the electrode leads are drawn from the internal pouch, and hermetically sealing edges of the internal pouch;

(S2) receiving the internal pouch in the external pouch such that the electrode leads are drawn from the external pouch, and hermetically sealing edges of the external pouch except an electrode lead draw part and an inlet through which the safety member is to be introduced;

(S3) introducing the safety member into a space between the internal pouch and the external pouch through the inlet; and

(S4) completely hermetically sealing the inlet.

6. The pouch-type secondary battery according to claim 1 , wherein the safety member is in a solid state.

7. The pouch-type secondary battery according to claim 6 , wherein the solid safety member is a film.

8. The pouch-type secondary battery according to claim 6 , wherein the solid safety member is in an envelope made of an insulating non-woven fabric.

9. A method for fabricating the pouch-type secondary battery defined in claim 6 , comprising:

(S1) receiving the electrode assembly in the internal pouch such that the electrode leads are drawn from the internal pouch, and hermetically sealing edges of the internal pouch;

(S2) receiving the internal pouch in the external pouch such that the electrode leads are drawn from the external pouch, and hermetically sealing edges of the external pouch except an electrode lead draw part and an inlet through which the safety member is to be introduced;

(S3) introducing the safety member into a space between the internal pouch and the external pouch through the inlet; and

(S4) completely hermetically sealing the inlet.

10. The method according to claim 9 , wherein the step (S3) is performed before steps (S1) and (S2).

11. The method according to claim 10 , wherein the step (S3) includes:

attaching the solid safety member in the form of a film to an outer surface of the internal pouch or an inner surface of the external pouch.

12. The method according to claim 10 , wherein the step (S3) includes:

putting the solid safety member in an envelope made of an insulating non-woven fabric,

sealing the envelope, and

placing the envelope on or attaching the envelope to an outer surface of the internal pouch or an inner surface of the external pouch.

13. The pouch-type secondary battery of claim 1 , wherein a material of the first lead tape is different from a material of the second lead tape.

14. The pouch-type secondary battery according to claim 1 , wherein edges of the internal pouch are hermetically sealed.

15. The pouch-type secondary battery according to claim 1 , wherein the safety member is nitrogen gas.

16. The pouch-type secondary battery according to claim 1 , wherein the outer layer of the internal pouch is 10-120 micrometers thick.

17. A pouch-type secondary battery comprising: an electrode assembly including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte solution,

wherein the electrode assembly and the electrolyte solution are received in an internal pouch such that electrode leads are drawn from the internal pouch, the internal pouch formed by a pouch sheet that includes a heat fusion layer, a metal layer, and an outer layer in a sequential order, wherein the outer layer of the internal pouch consists of polyethyleneterephthalate,

the internal pouch is received in an external pouch such that the electrode leads are drawn from the external pouch,

wherein a first lead tape is attached to first positions on respective electrode leads at an internal pouch sealing part, and a second lead tape is attached to second positions on the respective electrode leads different from the first positions and to an external pouch sealing part, and

a safety member is included in a space between the internal pouch and the external pouch, wherein the safety member is absent from the internal pouch,

wherein the electrolyte solution is not included in the space between the internal pouch and the external pouch.