SQUARE SECONDARY BATTERY

PROBLEM TO BE SOLVED: To obtain a square secondary battery the orientation of the positive electrode side and negative electrode side of which can be confirmed from the can bottom side.SOLUTION: A square secondary battery C1 including a battery can having a rectangular can bottom surface, a battery lid for sealing an opening facing the can bottom surface of the battery can, and a positive electrode external terminal and a negative electrode external terminal provided on the battery lid, is further provided with an insulation layer 13 covering the outer surface of the battery can 1. The insulation layer 13 is provided with a can exposing parts 51, 52 for exposing a part of the can bottom surface 21, and the can exposing parts 51, 52 have an asymmetric shape with reference to a center line C1 orthogonal to the long side of the can bottom surface. 【課題】缶底側から電池の正極側と負極側の向きを確認できる角形二次電池を得ること。【解決手段】本発明は、矩形の缶底面を有する電池缶と、電池缶の缶底面と対向する開口部を封口する電池蓋と、電池蓋に設けられた正極外部端子および負極外部端子とを有する角形二次電池Ｃ１において、電池缶１の外表面を被覆する絶縁層１３を有し、絶縁層１３には、缶底面２１の一部を露出させる缶露出部５１、５２が設けられており、缶露出部５１、５２が缶底面の長辺に直交する中心線ＬＣ１を基準として非対称な形状を有することを特徴としている。【選択図】図６Ａ