Secondary battery and method for producing the same

A method for producing a secondary battery including an electrode plate group in which a positive electrode plate and a negative electrode plate are wound or stacked with a separator interposed therebetween and a battery case in which the electrode plate group and an electrolyte are contained, the method comprising the steps of:

• a) forming a positive electrode active material layer on a surface of a current collector core material of a positive electrode and a negative electrode active material layer on a surface of a current collector core material of a negative electrode;
• b) forming a porous protective film on a surface of at least one of the positive electrode active material layer and the negative electrode active material layer to form a positive electrode plate and a negative electrode plate;
• c) forming, after the step b), a plurality of grooves at least in a surface of the porous protective film;
• d) forming, after the step c), an electrode plate group by winding or stacking the positive electrode plate and the negative electrode plate with a separator interposed therebetween;
• and
• e) placing and injecting, after the step d), the electrode plate group and the electrolyte in the battery case, and sealing the battery case,
• wherein in the step c), the plurality of grooves are formed simultaneously in the surface of the porous protective film and in a surface of the at least one of the active material layers.