Secondary battery having vent portion on insulation film and method for manufacturing the same

A method for manufacturing a secondary battery, the method comprising the steps of:

• (a) preparing at least one positive electrode and at least one negative electrode each having a structure comprising an electrode active material layer formed on a current collector having a tab formed on at least one side thereof;
• (b) interposing a separator between the positive electrode and the negative electrode;
• (c) transferring a non-adhesive material to at least one of a positive electrode insulation film and a negative electrode insulation film through a roll pressing process by using a roll including the non-adhesive material corresponding to a shape of a vent portion, thereby forming the vent portion;
• and
• (d) connecting a positive electrode lead electrically to the positive electrode tab and connecting a negative electrode lead electrically to the negative electrode tab, and attaching the positive electrode insulation film and the negative electrode insulation film to the positive electrode lead and the negative electrode lead, respectively,
• wherein the vent portion is interposed at least between the positive electrode lead and the portion to which the positive electrode insulation film is attached or between the negative electrode lead and the portion to which the negative electrode insulation film is attached;
• and
• wherein the vent portion is configured to provide an unadhered interface between the at least one of the positive electrode insulation film or the negative electrode insulation film and the corresponding positive electrode lead or the negative electrode lead for discharging gas through at least one of the positive electrode insulation film or the negative electrode insulation film.