| 摘要 |
Provided is a lithium ion secondary battery to allow whether an electrolyte solution is leaked or not to be ascertained visually, thereby improving the safety of a battery and the efficiency of a battery assembling process. The lithium ion secondary battery comprises an electrode assembly which comprises a first electrode plate, a second electrode plate, and a separator interposed between the two electrode plates; a case where the electrode assembly is accommodated; a cap plate(310) which is combined with the upper part of the case and is provided with a terminal penetration hole and an electrolyte solution injection hole(312); and a washer(430) which is combined with the upper part of the cap plate, wherein the washer has a transparent part(450) whose some part is transparent. |
