Secondary battery

A secondary battery, comprising:

• an electrode assembly including a first electrode plate, a second electrode plate, and a separator between the first electrode plate and the second electrode plate;
• a can housing the electrode assembly, the can having a long axis and a short axis, and an opening at a side thereof through which the electrode assembly is inserted;
• and
• a cap plate that seals the opening of the can,
• wherein the can includes:
• a first side surface and a second side surface that face each other and extend in a first direction of the short axis of the can, the first side surface and the second side surface each having a first thickness in a second direction of the long axis of the can,
• a third side surface and a fourth side surface that face each other and extend along the second direction of the long axis of the can, the third side surface and the fourth side surface each having a second thickness, the first thickness being greater than the second thickness in the first direction, and
• a bottom surface that is located opposite the opening of the can and contacts the first through fourth side surfaces, the bottom surface having a third thickness in a third direction perpendicular to the first direction and the second direction, the first direction, the second direction, and the third direction being orthogonal to each other, wherein the third thickness of the bottom surface is greater than either of the first thickness and the second thickness, wherein:
• the can further includes a second connection part where the bottom surface is connected to the first side surface and the second side surface, and a third connection part where the bottom surface is connected to the third side surface and the fourth side surface, and
• a thickness of the second connection part and a thickness of the third connection part increase or decrease in a continuous manner in the third direction, and wherein:
• the thickness of the second connection part and the thickness of the third connection part are straightly tapered in an inner side of the can along the short and long axes, respectively, in the third direction.