| 摘要 |
PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery which enables the reduction of the influence of gas generation in charging and discharging the battery, and the achievement of superior cycle stability over a long period of time.SOLUTION: A lithium ion secondary battery is obtained by: enclosing, in an outer sheath formed by a laminate film, a battery element arranged by winding or laminating together at least one positive electrode and at least one negative electrode with a separator interposed therebetween; filling a nonaqueous electrolyte in the outer sheath; and thereafter hermetically sealing the outer sheath by heat seal. The lithium ion secondary battery has a space, which will make a gas pocket 2, provided adjacently to a space 1 for enclosing the battery element. In the lithium ion secondary battery, there are four easy-to-peel positions partially in a heat seal portion between the spaces, where the peel strength is 1/10-1/20 of that of its surroundings. |
