What is claimed is:
1. A lithium secondary battery, comprising:
an electrode assembly;
a can accommodating the electrode assembly;
a cap assembly coupled with the can, the cap assembly being positioned at a topmost part of the can and having an upper cap including gas discharge holes therein; and
a washer coupled with the upper cap, the washer including
a body part, the body part having a flat plate shape and having a centrally disposed connection hole; and
insertion parts, the insertion parts insertably extending respectively through the gas discharge holes toward a center of the connection hole from the body part so as to be arranged in the gas discharge holes, the insertion parts including respective extension parts extending inwardly from the body part and respective locking parts, the locking parts being at distal ends of the respective extension parts, the locking parts having widths greater than minimum widths of their respective extension parts.
2. The lithium secondary battery as claimed in claim 1 , wherein the locking parts and a portion of the respective extension parts adjacent thereto each have a width smaller than a width of one of the gas discharge holes.
3. The lithium secondary battery as claimed in claim 1 , wherein each locking part has a circular shape.
4. The lithium secondary battery as claimed in claim 1 , wherein each locking part has a rectangular shape.
5. The lithium secondary battery as claimed in claim 1 , wherein each locking part has a funnel shape.
6. The lithium secondary battery as claimed in claim 1 , wherein each locking part has a triangular shape.
7. The lithium secondary battery as claimed in claim 1 , wherein the locking part protrudes upwardly toward the upper cap from the body part.
8. The lithium secondary battery as claimed in claim 1 , wherein the washer has a lid portion extending along an outer periphery of the body part and covering an upper surface of the can.
9. The lithium secondary battery as claimed in claim 8 , wherein an inner diameter of the lid portion is greater than an outer diameter of the upper cap.
10. The lithium secondary battery as claimed in claim 1 , further comprising a heat shrinkable tube on an exterior of the can.
11. The lithium secondary battery as claimed in claim 10 , wherein the heat shrinkable tube covers the coupled washer and upper cap.
12. The lithium secondary battery as claimed in claim 1 , wherein the washer is formed of an insulator.
13. The lithium secondary battery as claimed in claim 1 , wherein a gap exists between each of the insertion parts and an edge of the gas discharge hole through which each insertion part passes.
14. The lithium secondary battery as claimed in claim 1 , further comprising a gasket including an upper portion, a mid-portion, and a lower portion, wherein the upper portion contacts a top surface and a side surface of the cap assembly, the mid-portion horizontally extends from a bottom end of the upper portion, the mid-portion having a top surface contacting a bottom surface edge of the cap assembly, and the lower portion extends downwardly from a bottom end of the mid portion and prevents the can from contacting a lower portion of the cap assembly.
15. The lithium secondary battery as claimed in claim 1 , wherein the upper cap includes:
a protruding part extending from a center of the upper cap,
a connection part extending downwardly from an outer periphery of the protruding part, the connection part including the gas discharge holes, and
a flange part extending outwardly from the connection part.
16. The lithium secondary battery as claimed in claim 15 , wherein the upper cap includes at least three gas discharge holes and the washer includes at least three insertion parts.
17. The lithium secondary battery as claimed in claim 15 , wherein the locking parts form a partial barrier between the protruding part of the upper cap and an interior of the secondary battery.
18. A lithium secondary battery, comprising:
an electrode assembly;
a can accommodating the electrode assembly;
a cap assembly coupled with the can, the cap assembly being positioned at a topmost part of the can and having an upper cap, the upper cap including
gas discharge holes therein,
a protruding part extending from a center of the upper cap,
a connection part extending downwardly from an outer periphery of the protruding part, the connection part including the gas discharge holes, and
a flange part extending outwardly from the connection part; and
a washer coupled with the upper cap, wherein the washer includes:
a body part, the body part having a flat plate shape and having a centrally disposed connection hole; and
insertion parts, the insertion parts extending toward a center of the connection hole from the body part and being arranged in the gas discharge holes, and each of the insertion parts including
an extension part extending inwardly from the body part, and inserted into and extending through the gas discharge holes, and
a locking part formed at an end of the extension part, the locking part protruding upwardly toward the protruding part from the body part and having a width greater than a minimum width of the extension part,
wherein a gap exists between each of the insertion parts and an edge of the gas discharge hole through which each insertion part passes, and the locking part and a portion of the extension part adjacent thereto each have a width smaller than a width of one of the gas discharge holes.