Rechargeable battery

A rechargeable battery comprising:

• a first case accommodating an electrode assembly and having a first opening;
• a second case having a second opening smaller than the first opening, the second case covering the electrode assembly and an outer surface of the second case being coupled to an inner surface of the first case;
• an insulating material interposed between the first case and the second case to form an electrically insulating state;
• a plurality of protruded parts protruding from the outer surface of the second case;
• and
• a plurality of accommodating parts formed in the first case and coupled to the plurality of protruded parts,
• wherein the first case and the second case are coupled together to form a closed state in which the plurality of protruded parts extend into the plurality of accommodating parts, and
• wherein each of the plurality of accommodating parts is an opening at an intermediate portion of the first case spaced apart from the first opening,
• wherein a portion of the insulating material extends into the plurality of accommodating parts and is interposed between the plurality of protruded parts and the plurality of accommodating parts.