| abstract |
(57) [Problem] To provide a lithium ion secondary battery having high capacity and excellent safety. SOLUTION: As a positive electrode active material, Li X MO 2 (however, M is one or more transition metals, preferably Mn, Co, N An electrode body is used in which a positive electrode sheet coated with i) and a negative electrode sheet coated with a carbon material capable of occluding and releasing lithium ions as a negative electrode active material are stacked so as to overlap each other while maintaining a continuous state. A lithium ion secondary battery, wherein the current collector length l of the positive electrode sheet (M) and a thickness S (μm) satisfying a specific relational expression. |