Button-type secondary battery and method for manufacturing the same

A method for manufacturing a button-type secondary battery, the method comprising:

• preparing a lower can having a recessed lower insertion groove, an upper can having a recessed upper insertion groove, and a gasket disposed between the lower can and the upper can;
• accommodating an electrode assembly, in which a first electrode, a separator, and a second electrode are alternately stacked, in the lower can;
• disposing the gasket on an upper portion of the lower can, wherein the gasket comprises an outer part supported on an outer circumferential surface of the lower can, an inner part supported on an inner circumferential surface of the lower can, and a connection part connecting the outer part to the inner part;
• and
• clamping the upper can with the lower can by disposing the upper can on an upper portion of the lower can, thereby manufacturing the button-type secondary battery,
• wherein, in the preparation process, the lower insertion groove formed in the lower can and the upper insertion groove formed in the upper can are disposed to be spaced apart from each other so as not to face each other when the lower can and the upper can are coupled to each other.