| 摘要 |
PROBLEM TO BE SOLVED: To improve safety during over-charge. SOLUTION: This secondary battery comprises a battery element having a positive electrode and a negative electrode, closed in a case formed of an exterior material, the case having a wrapping portion for wrapping the battery element with side walls and upper and lower bottoms and junction piece portions for joining at least parts of the peripheral edges of the exterior material. At least parts of the junction piece portions are bent along the side walls of the wrapping portions. In the case that fastening strength test is performed, the bent junction piece portions are fastened to the side walls at such a strength that they can sustain angles of 45 deg. or less to the side walls: the fastening strength test involves continuous charge of the battery having a voltage of 3 V in an upper limit voltage range of 10 V at a current of 1.8C for 200 minutes, where 1C is a current value for one-hour discharge of a capacity obtained by charging the battery at a constant voltage of 2.7 V to 4.2 V until the current value is zero. |
