| 摘要 |
PROBLEM TO BE SOLVED: To provide a high capacity lithium secondary battery exhibiting excellent safety under extremely high temperatures.SOLUTION: In the lithium secondary battery, the positive electrode active material contains a lithium-containing composite oxide which contains Ni, Co and Mn in a specific composition, where the molar composition ratio of the total amount of Ni to all metals excluding Li in the total positive electrode active material is 0.05-0.5. The negative electrode active material contains a material which contains Si and O as constituent elements (atomic ratio x of O to Si is 0.5≤x≤1.5), and a graphite carbon material. In a side surface of a battery case, a cleavage groove which cleaves when the pressure in the battery case exceeds a threshold is provided to intersect a diagonal in the side view from a wide surface. |
