Secondary battery structure

A secondary battery structure comprising:

• a can;
• an electrode assembly accommodated in the can, the electrode assembly comprising a cathode tab and an anode tab;
• a cap plate sealing an opened upper end of the can;
• and
• an upper insulator disposed between the can and the cap plate, the upper insulator having one or more than one cathode tab hole for the cathode tab, one or more than one anode tab hole for the anode tab, and one or more than one injection/impregnation hole for injecting and impregnating,
• wherein each of the cathode tab hole, the anode tab hole, and the injection/impregnation hole extends in a length direction of the upper insulator to be symmetrical with respect to a line (a) that equally divides the upper insulator in a width direction, extends in the width direction of the upper insulator to be symmetrical with respect to a line (b) that equally divides the upper insulator in the length direction, or extends in both the length and width directions of the upper insulator to be symmetrical with respect to the lines (a) and (b).