| CPC H01M 50/578 (2021.01) [H01M 50/152 (2021.01)] | 20 Claims |

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1. A secondary battery comprising:
an electrode assembly having a structure in which electrodes and separators are alternately disposed;
a battery can configured to accommodate the electrode assembly and having an open upper portion;
a top cap coupled to the open upper portion of the battery can;
a CID filter positioned below the top cap;
a CID gasket positioned in close contact with a side portion of the CID filter; and
an electrode tab protruding from the electrode assembly, the electrode tab being electrically connected to the CID filter at a first connection area of the CID filter,
wherein the CID filter comprises a body part defining a main body,
the body part comprising:
a plurality of main though-holes disposed along a circumferential direction of the body part, each of the main through-holes having a first width (W1); and
an auxiliary through-hole having a second width (W2) less than the first width (W1); and
wherein the body part includes a plurality of second connection areas, each of the second connection areas defined by an area connecting any one of the main through-holes to an adjacent one of the main through-holes along the circumferential direction of the body part, and wherein the auxiliary through-hole is defined in at least one of the second connection areas.
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