Cylindrical secondary battery

A secondary battery comprising:

• an electrode assembly that has a positive electrode plate, a separator, and a negative electrode plate;
• a cylindrical can that has the electrode assembly accommodated therein and a lower end thereof open, and is electrically connected to the negative electrode plate;
• a positive electrode terminal that penetrates an upper surface part of the cylindrical can to be electrically connected to the positive electrode plate;
• a cap plate that seals the lower end of the cylindrical can;
• and
• an insulation sheet between a lower part of the positive electrode terminal and a lower surface of the upper surface part of the cylindrical can, the insulation sheet including a first sheet of a first material, the insulation sheet further including a second sheet on a first surface of the first sheet and on a second surface of the first sheet opposite to the first surface, wherein the second sheet is of a second material different from the first material, wherein a first portion of the second sheet on the first surface is adhered to the lower surface of the upper surface part and a second portion of the second sheet on the second surface is adhered to the lower part of the positive electrode terminal to seal the inside of the cylindrical can.